System for generating Brown Gas and uses thereof

Field of the invention

The present invention relates to a system for generating Brown gas and uses thereof for different applications.

Background of the invention

Natural gas is commonly used for domestic and industrial purposes. However, there is growing concern on the use of natural gas as a source of fuel to meet the increasing needs, such as heating, of households and factories. Greenhouse emissions from the combustion of natural gas include carbon dioxide, sulphur dioxide, nitrous oxide and water vapour. In fact, the combustion of natural gas is deemed to be one of the main environmental factors contributing to global warming. Another problem with natural gas is its long-term economic viability and availability due to increased global demand compared to the global shortage of supply of natural gas. A further problem is that not all countries have their own source of natural gas and, accordingly, rely heavily on other countries to obtain natural gas. It is also essential that there be an extensive infrastructure network to support the supply, storage and distribution of natural gas to the end users. A network of exposed pipelines and terminals over a vast area is not only costly to build and maintain, but also highly vulnerable to external influence such as natural disaster or terrorist threats.

Several alternative fuel sources have been proposed instead of natural gas. One example is using solar power and transforming it into a viable source of energy. Another example is Brown gas, as described in US 4,081,656, the contents of which are incorporated herein by reference. Brown gas was described as being a suitable source of energy for pure industrial welding and cutting applications. In particular, US 4,081,656 describes a process of generating a mixture of oxygen and hydrogen gases from the electrolysis of

water. The product, Brown gas, has remarkable characteristics such as high calorific value and is capable of reactive combustion with selected metal and low pollutant emissions.

Several patents describe the uses of Brown gas. For example, US 6,761,558 describes a heating apparatus using thermal reaction of Brown gas, the contents of which are incorporated herein by reference. It further describes a method of trapping heat from the reactive burning of Brown Gas after it has passed through hexane liquid. US 6,443,725 describes a method to burn Brown gas cyclically in a burner to heat up a heat generating unit, the contents of which are incorporated herein by reference.

In view of the above, it can be seen that there is a need in the state of the art for a reliable and safe system to supply energy for domestic and industrial use, which can cater to an increase in the demand of energy, and with minimum impact on the environment. Further, this shows for a range of new technologies capitalising on these advantages.

For instance, incineration is the most common process to destroy pathogens, viruses, and toxic organics found in most domestic and industry waste. However, conventional incinerator is increasingly faced with several problems. For example, an incineration plant consumes large amounts of fuel to burn waste. The fuel may include natural gas, propane or light fuel oil. Due to the increased global demand for natural gas and the global shortage of supply of natural gas, traditional thermal incineration is a very expensive means for waste management. To mitigate the impact, new incineration plants are sited further away from populous areas, resulting in high transportation cost of waste, fuel and other supplies which are required for the operation of the incineration plant over the extended distance.

A further problem is that the discharge of dioxins and furans to the atmosphere as a result of incomplete combustion during incineration of domestic and

industry waste poses a serious health threat to the community. This has led to increasing pressure from environmentalists to impose stringent control and regulations over the disposal of dioxin- and furan-producing waste. High combustion temperatures of more than 1200°, with high turbulent mixing (using force draft air) of waste and high dwelling time of flue gas for at least 2 seconds can effectively destroy dioxins and furans in the combustion chamber during the incineration process. Therefore, one way of ensuring the complete combustion of waste and minimising the formation of dioxins and furans during combustion is to modify the existing incineration process to substantially raise the temperature of the furnace in order to enhance the combustion efficiency. However, this will lead to an increase in operation costs as fuel consumption will increase.

Several alternative approaches have been proposed to attain high combustion temperature. One example is to switch to a fluidized bed propane incinerator. Another example is using the thermal plasma incinerator that uses high energy, high intensity plasma jet for waste destruction. These approaches, however, cannot be directly incorporated into existing incineration facilities. Another approach is to use alternative fuel sources that are inexpensive, high in calorific value and have minimal environmental impact.

In another example airborne particulate matter emissions and flue gas emissions are still a prevalent problem. It is also widely known that such emissions pose a significant environmental and health risk. Such emissions may be produced by industrial processes, coal firing and incineration plants from the burning of waste, just to name a few. As a result of the processes, the constituents of the emissions may be harmful to the environment if discharged into the atmosphere without further treatment.

Existing measures to control and treat the emissions and flue gas include the use of cyclones, electrostatic precipitators (ESPs), settling chambers, wet

scrubbers and fabric filter systems. However, to a large extent, these only aid in reducing particulate matter within the emissions and flue gas and partially treat the constituents of the flue gas and emissions. Therefore, when the "treated" emissions and flue gas is discharged into the atmosphere, the emissions and flue gas may still contain harmful constituents which may be hazardous to the environment.

For example, cyclones have a low overall particulate collection efficiency, especially for particulate sizes below 10 mm. In the case of ESPs, though effective in treating the emissions and flue gas, these are very expensive to install and maintain. They also require a large space for installation. Also, ozone may be produced by the negatively charged electrodes of the ESPs during gas ionization, which adds to the environmental problems. Highly trained personnel may also be required to operate the ESPs. Fabric filter systems are also expensive in that costly refractory mineral or metallic fabric is required when operated at temperatures in excess of about 290 ⁰ C. There also exists an explosion and fire hazard of certain dusts at certain concentrations in the presence of accidental sparks or flames.

With this in mind, an environmentally sound and energy efficient means to address those issues would be advantageous.

Summary of the invention

According to a first aspect, the present invention provides a system for the generation, storage and use of Brown gas comprising:

at least one Brown gas generator, in communication with an electricity supply and water supply;

at least one first storage chamber, in fluid communication with the generator, for storing the Brown gas generated from said generator; and

Brown gas application means in communication with said at least one first storage chamber,

wherein said generator and first storage chamber are located proximate the Brown gas application means.

It will be appreciated that "proximate" makes reference to the intended application of the invention. For example, an application for use within a building would necessarily require a definition of "proximate" to fall within the building premises, such as a plant room as with a conventional boiler, roof mounting similar to industrial air conditioning or adjacent an external housing of the building as with an electrical distribution box.

In a different application, such as for a residential development, "proximate" may include a central location within the residential development. This is compared to, and differentiated from, conventional energy supply, such as mains electricity, whereby generation may occur several kilometres away from the development. Thus, in this case, "proximate" will be defined as within a usable location, not requiring substantial infrastructure before the final distribution for use, as compared to conventional energy supply which is "remote" in terms of generation and/or storage and so requiring substantial infrastructure for distribution. Accordingly, in the present invention, one advantage of having the generator and first storage chamber located proximate the Brown gas application means is to increase the efficiency of the system. Such an arrangement would also reduce the costs for providing less infrastructure when compared to relying on external sources for energy.

Brown gas has been shown to have high calorific value and negligible pollution emission when compared to other forms of natural gas. Accordingly, it would be advantageous to use Brown gas for domestic and industrial purposes. For example, the Brown gas generated may be used for the provision of piped gas for cooking and space heating or for industry heat treatment in production

processes, for producing hot water for use in laundry, sanitary and washing, for producing chilled water for use in space cooling and for providing fuel for an incineration unit to decompose garbage, refuse and other domestic or industrial waste.

In a second aspect, the invention provides a boiler and burner unit for producing hot water, the boiler and burner unit comprising:

- a first inlet for receiving feed water;

- a second inlet for receiving Brown gas from a Brown gas generator; and

- an outlet for discharging hot water produced,

According to a further embodiment, the application means may comprise at least one first chamber for producing hot water, wherein heat for heating said hot water is derived from combustion of Brown gas, with the Brown gas obtained from the at least one first storage chamber. In particular, the at least one first chamber may be a boiler and burner unit. The at least one first chamber may comprise:

a first inlet for receiving Brown gas from the at least one first storage chamber;

a second inlet for receiving water;

- a gas burner; and

an outlet for discharging the hot water produced,

wherein the Brown gas from the first inlet may be burnt by the gas burner, thereby heating the water from the second inlet and wherein the heated water may be discharged from the outlet.

The second inlet for receiving water may be connected to an outlet of at least one heat exchanger contained within the at least one Brown gas generator.

The second inlet for receiving water may also be connected to an outlet of at least one solar thermal collector.

There may be provided at least one flash arrestor before the first inlet. The flash arrestor may include devices commonly used on the supply line of volatile gases such as hydrogen, acetylene and other fuel gases to prevent a flame from propagating to the source of the supply such as a pressurized gas storage tank or gas generator. For the purposes of the present invention, a flash arrestor may be installed at various junctions of Brown gas supply to prevent flash back from torching the Brown gas storage tank that is partially filled with the liquefied hydrocarbon as a flame coolant.

The at least one first chamber may further comprise a reactive metal element. For example, the reactive metal element which may be used in the at least one first chamber may include, but is not limited to, any of the following: platinum, steel, nickel-chromium alloy or other high temperature nickel alloys. The reactive metal element may be in the form of a singly curved or doubly curved shell with perforation on the shell surface to maximise the contact area between the metal element and the Brown gas flame. The nickel-chromium alloy may be in the form of a nichrome wire. The reactive metal element may be placed in the path of the Brown gas flame to effect reactive combustion to further elevate the flame temperature in the first chamber.

The system of the present invention may further comprise at least one second storage chamber for storing the hot water produced from the at least one first chamber. Accordingly, the at least one second storage chamber may be connected to the outlet of the at least one first chamber. The hot water produced may be stored in a storage chamber for future space heating, use in laundry, sanitary and washing.

According to a further embodiment, the application means may further comprise at least one second chamber for producing chilled water. In particular, the at least one second chamber may be an absorptive chiller unit.

The at least one second chamber may comprise:

a first inlet for receiving an absorbent;

a second inlet for receiving a refrigerant;

a third inlet for receiving coo! water;

a fourth inlet for receiving warm water;

a first heat exchanger;

- a second heat exchanger;

a first outlet for discharging warm water; and

a second outlet for discharging chilled water produced,

wherein the third inlet and first outlet may be connected to the first heat exchanger, and the fourth inlet and second outlet may be connected to the second heat exchanger.

The absorbent may be lithium bromide (LiBr), ammonia (NHa), or other suitable absorbents such as desiccants or dehumidifiers as would be clear to the skilled addressee. The refrigerant may be water. Other suitable refrigerants may also be used for the purposes of the present invention.

The at least one second chamber may utilise the heat produced from a heat exchanger running hot water from the at least second storage chamber or produced directly from the at least one first chamber from the combustion of Brown gas to vapourise the refrigerant and the absorber to effect a cooling

cycle. As a result of the cooling cycle, water from the at least one second chamber is chilled. The chilled water produced may be stored in at least one third storage chamber. The chilled water may be used for various applications. For example, for space cooling applications. In particular, the chilled water from the at least one third storage chamber may flow into an air handling unit, which comprises a heat exchanger with a blower, to provide space cooling.

According to a further embodiment, the application means of the present invention may further comprise at least one third chamber for burning waste. In particular, the at least one third chamber is an incinerator unit. The at least one third chamber may comprise:

a combustion unit for burning waste by combusting Brown gas;

a first inlet connected to the combustion unit for receiving waste;

a second inlet connected to the combustion unit for receiving Brown gas from the at least one first storage chamber; and

an outlet connected to the combustion unit for discharging flue gas produced from the combustion unit.

The waste may be separated into solid and liquid waste. The waste may be treated prior to being fed into the combustion unit to reduce the moisture content in the waste.

The system according to the present invention may also comprise a heat exchanger connected to the outlet for discharging flue gas with a lower temperature. Alternatively, the system according to the present invention may comprise a wet scrubber connected to the outlet connected to the combustion unit to quench the temperature of-the flue gas discharging from the outlet and/or to remove particulates and fly ash in the flue gas. A wet scrubber is a device for treating gas streams to remove sub-micron or larger fly ash. A wet scrubber

may have a series of high volume, water spraying nozzles to provide rapid quenching of the flue gas discharging from the outlet. For example, the flue gas may be quenched to 200 ⁰ C to 300 ⁰ C. This may prohibit the reformation of dioxins and furans in the atmosphere. The outlet may also be connected to an air filter system. Having an incinerator within the system is advantageous so that harmful waste may be treated without delay and accordingly, harmful emissions to the environment are avoided. The incinerator may also be configured as a waste-to-energy incinerator whereby the heat of combustion of waste is recovered for steam or power generation.

According to a second aspect, the present invention provides a boiler and burner unit for producing hot water, the boiler and burner unit comprising:

a first inlet for receiving feed water;

a second inlet for receiving Brown gas from a Brown gas generator; and

an outlet for discharging hot water produced,

wherein the Brown gas is burnt to produce heat which heats the feed water to produce hot water.

The outlet for discharging hot water produced may be connected to a storage tank for storing the hot water produced. The first inlet of the boiler and burner unit may be connected to: the outlet of a first heat exchanger of the Brown gas generator; the outlet of at least one solar thermal collector, and/or the storage tank for storing the hot water produced.

In a third aspect the invention provides a system for recovering heat generated by burning of combustion material comprising:

- at least one Brown gas generator, in communication with an electricity supply and water supply;

- at least one first storage chamber, in fluid communication with the generator, for storing the Brown gas generated from the generator;

- at least one combustion chamber, in communication with the at least one first storage chamber, for burning the combustion material; and

- at least one heat-extracting chamber adapted to receive heat produced by the combustion chamber from the burning of the combustion material,

wherein the generator and the first storage chamber are located proximate the combustion chamber and the heat-extracting chamber.

In a fourth aspect the invention provides a method of recovering heat generated by the burning of combustion material, the method comprising the steps of:

- burning combustion material in at least one combustion chamber by combusting Brown gas; and

- receiving flue gas produced by the combustion chamber for recovering heat therein.

The at least one Brown gas generator takes in electricity to dissociate water into oxygen and hydrogen gases in an electrolysis process. The at least one Brown gas generator may include an electrolysis chamber. The mixture of oxygen and hydrogen gases is piped to the at least one first storage chamber. The at least one first storage chamber may contain a pre-determined quantity of a liquefied hydrocarbon that may act as a flame coolant. For example, the liquefied hydrocarbon may be selected from the group consisting of: hexane, heptane, methanol, ethanol and a combination thereof. The liquefied hydrocarbon may be maintained at a low temperature, for example at a temperature below the

boiling point of the hydrocarbon. The skilled addressee will appreciate suitable storage temperatures for the applicable hydrocarbon, as these are a matter of common general knowledge. For example, the temperature may be between 20 ⁰ C to 100 ⁰ C. In particular, the temperature may be between 10 ⁰ C to 20 ⁰ C. In particular, the temperature may be 20 ⁰ C when the hydrocarbon used is hexane. The liquefied hydrocarbon serves as a catalyst to moderate the flame temperature of the Brown gas. In particular, the liquefied hydrocarbon may be hexane.

According to a further embodiment, the waste is burnt in the at least one combustion chamber. The at least one combustion chamber uses Brown gas as fuel. The Brown gas may be obtained from the at least one first storage chamber. In particular, the combustion chamber may be an incineration unit. The combustion chamber may be of a single-stage or a multiple-stage configuration. The at least one combustion chamber may comprise:

- a combustion unit for burning combustion material by combusting Brown gas;

- a first inlet connected to the combustion unit for receiving combustion material;

- a second inlet connected to the combustion unit for receiving Brown gas from the at least one storage chamber; and

- an outlet connected to the combustion unit for discharging flue gas produced by the combustion unit.

The combustion material may be waste, refuse garbage and other domestic or industrial waste. The combustion chamber may further comprise a pre- treatment unit for pre-treating combustion material prior to being fed into the combustion unit. The combustion material may be separated into solid and liquid combustion material. The combustion material may be sorted to remove

recyclable, non-combustible material and hazardous combustion material. The combustion material may be compacted and/or dried to reduce the moisture content in the combustion material.

Combustion material is burnt in the combustion unit. Combustion material is fed into the combustion unit by any suitable method. For example, the combustion material may be fed into the combustion unit by gravitational or mechanical means. The combustion unit may comprise a Brown gas burner to project a high temperature flame into the combustion unit to burn the combustion material. The combustion unit may also comprise a further inlet to allow fresh air to be supplied to the combustion unit to achieve more complete burning of the combustion material. The combustion unit may be lined with a refractory material to maintain a high temperature within the combustion unit. The burnt combustion material and charred non-combustible material may be collected within the combustion unit and removed from the combustion unit for disposal. The burnt combustion material and charred non-combustible material may undergo further treatment before being disposed.

The combustion chamber may also comprise a re-oxidation chamber in addition to the combustion unit. The re-oxidation chamber may be a means for thermal scrubbing of flue gas produced in the combustion unit before the flue gas is discharged into the atmosphere. For example, the flue gas produced from the burning of combustion material in the combustion unit may be oxidised in the re- oxidation chamber to further decompose or oxidise the flue gas into a form which is less harmful to the environment. The re-oxidation chamber may also use Brown gas for its operation. The re-oxidation chamber may therefore comprise a Brown gas burner to heat the flue gas to a suitable temperature. For example, the temperature to which the flue gas is heated may be the reduction reaction temperature of the flue gas constituents. The temperature may be between 1000 ⁰ C and 2000 ⁰ C. In particular, the temperature may be between about 1000 ⁰ C and 1500 ⁰ C.

To further reduce the emission of nitrous oxide, the Brown gas burner in the re- oxidation chamber may use a mixture of pure oxygen and Brown gas for burning instead of fresh air. The high nitrogen content in fresh air may react to form nitrous oxides under high temperature, which may be harmful to the environment.

The re-oxidation chamber may comprise a mesh-grid block. The mesh-grid block may be positioned such that it is in direct contact with the Brown gas flame in the re-oxidation chamber to attain a high temperature. The mesh-grid block may be supported on metal frames. The mesh-grid block may be of any suitable material. For example, the mesh-grid block may be made of platinum, stainless steel, nickel-chromium alloy or aluminium-chromium alloy. Incoming flue gas from the combustion unit may be made to pass through the heated glowing mesh-grid block to effect thermo-chemical reaction that completely oxidises the flue gas constituents such as carbon monoxide, nitrous oxides and other particulates in the flue gas. The treated flue gas may be used for other applications in the system of the invention, or be further treated before being discharged into the atmosphere.

In a multiple-stage configuration of the combustion chamber, for example a two- stage combustion chamber, the combustion material may be burnt in the combustion unit with insufficient air conditions to produce flue gas comprising carbon dioxide gas, water vapour, carbon monoxide gas, hydrogen gas and gases of hydrocarbon compounds. The flue gas may then be ducted to a re- oxidation chamber. The re-oxidation chamber may be supplied with sufficient air and oxygen-enriched conditions to further oxidise the components of the flue gas.

To ensure that the flue gas produced is ducted out of the combustion unit, the combustion unit and re-oxidation chamber are maintained at a suitable negative pressure. For example, the pressure may be -50 Pa. The negative pressure

may be maintained by installing a suction fan at the outlet of the combustion unit.

As mentioned above, the burning of the combustion material in the combustion chamber produces flue gas. The heat from the flue gas is used in other applications within the system. For example, the flue gas produced may be ducted to the at least one heat-extracting chamber. In particular, the at least one heat-extracting chamber may be a boiler unit or a dryer.

The boiler unit may be for producing steam, such that the heat for producing the steam is derived from the flue gas ducted to the boiler unit from the combustion chamber. Any suitable boiler unit may be used. The boiler unit may be designed so as to take in flue gas not exceeding a pre-determined temperature and to admit in flue gas at a pre-determined minimum volumetric flow rate. In this case, a blower may be installed at the inlet of the boiler unit to reduce the temperature of the incoming flue gas and to increase the volumetric flow rate of the incoming flue gas. For example, the boiler unit may be in the form of a metallic-tube counter flow heat exchanger boiler unit. The at least one heat-extracting chamber may comprise:

- a water inlet;

- a flue gas inlet for receiving flue gas produced from the combustion unit;

- a first outlet for discharging the steam produced, and

- a second outlet for discharging flue gas,

such that water from the water inlet is heated by flue gas from the flue gas inlet, thereby producing steam and wherein the steam is discharged from the first outlet and flue gas is discharged from the second outlet. Accordingly, the flue gas inlet of the at least one heat-extracting chamber may be connected to the outlet of the at least one combustion chamber.

The feed water into the heat-extracting chamber may be obtained from a water supply within the system. The feed water in the heat-extracting chamber absorbs the heat from the flue gas produced by the combustion chamber to form steam. The steam may rise to a steam drum for further heating at elevated pressure to produce superheated steam.

The feed water to the at least one heat-extracting chamber may be pre-heated at the combustion chamber. For example, tubes of feed water may run at the roof and along the walls of the combustion chamber, such that the tubes are exposed to the heat from the flue gas produced by the combustion chamber or the heat within the combustion chamber. The feed water within the tubes may be heated by convection and radiation heat. The volumetric flow rate of the feed water in the tubes may be controlled such that the water is heated to approximately 9O ⁰ C or less. The heated feed water may then be pumped into the at least one heat-extracting chamber for steam production.

According to a further embodiment, the system of the present invention may further comprise a means for generating electricity in communication with the at least one first chamber. The means for generating electricity may comprise:

- at least one steam turbine adapted to receive steam produced by the at least one first chamber;

- at least one generator, in communication with the at least one steam turbine, for generating electricity; and

- means for discharging the electricity generated from the generator.

The steam from the at least one heat-extracting chamber, for example boiler unit, turns the turbine producing mechanical energy which is converted into electrical energy in the at least one generator, thereby generating electricity and wherein the generated electricity is discharged. Any suitable steam turbine may be used. For example, the steam turbine may be a single-stage or multiple-

stage steam turbine. The supply of steam or superheated steam to the steam turbine may be regulated by a control system. For example, the supply of steam to the steam turbine may be regulated by varying the flow rate of feed water into the boiler unit.

The electricity generated may be supplied to the at least one Brown gas generator for generating Brown gas and/or to an electricity grid. Therefore, one of the advantages of the system of the present invention is that by generating electricity from steam, reliance on an external source of electrical power may be reduced.

The system may further comprise a heat exchanger in communication with the at least one steam turbine. In particular, the heat exchanger may be a cooling unit. The heat exchanger may comprise:

- a steam inlet for receiving steam from the steam turbine; and

- a water outlet,

wherein the heat exchanger cools the steam received from the steam inlet, thereby condensing the steam to produce water and wherein the water is discharged from the water outlet. The water discharged from the heat exchanger may be recycled within the system. For example, the water discharged from the heat exchanger may be used as feed water into the boiler unit.

The heat exchanger may also be in communication with the at least one heat- extracting chamber. In particular, when the steam turbine has reached maximum capacity, the steam produced in the boiler unit may be ducted to the heat exchanger to be cooled into water. Accordingly, the heat exchanger may comprise a second inlet adapted for receiving steam produced by the at least one heat-extracting chamber when the steam turbine has reached its maximum capacity.

According to a further embodiment, the at least one heat-extracting chamber may comprise a dryer for drying combustion material before it is burnt in the combustion chamber. For example, the at least one heat-extracting chamber may be part of the pre-treatment unit of the combustion chamber as described above. In particular, the dryer reduces the moisture content of the combustion material before the combustion material is burnt in the combustion unit. Heat for drying the combustion material in the at least one heat-extracting chamber may be derived from flue gas discharged from the combustion chamber. Accordingly, flue gas from the combustion chamber may be ducted to the dryer. Flue gas from the boiler unit may also be ducted to the dryer for drying the combustion material. The dried combustion material is fed into the combustion chamber for burning in the combustion chamber.

The system of the present invention may also comprise a post-treatment unit for treating flue gas before it is discharged into the atmosphere. Accordingly, flue gas from the combustion chamber, dryer and/or boiler unit may be ducted into the post-treatment unit. The post-treatment unit may comprise at least one re- oxidation chamber, a wet scrubber and/or a quencher. A re-oxidation chamber, such as that described above, thermally scrubs flue gas by combusting Brown gas. A wet scrubber is a device for treating gas streams to remove sub-micron or larger fly ash. A wet scrubber may have a series of high volume, water spraying nozzles to provide rapid quenching of the flue gas discharging from the outlet. For example, the flue gas may be quenched to 200 ⁰ C to 300 ⁰ C. This may prohibit the reformation of dioxins and furans in the atmosphere. The outlet may also be connected to an air filter system. The quencher reduces the temperature of the flue gas discharging from the outlet and/or to remove particulates and fly ash in the flue gas.

According to a second aspect, the present invention provides a method of recovering heat generated by the burning of combustion material, the method comprising the steps of:

- burning combustion material in at least one combustion chamber by combusting Brown gas; and

- receiving flue gas produced by the combustion chamber for recovering heat therein.

The method may further comprise the step of producing steam in a boiler, wherein the heat for producing the steam is derived from the flue gas produced by the combustion chamber. The steam may be fed into a steam turbine, in communication with a generator for generating electricity.

The method may further comprise the step of drying combustion material before burning in the at least one combustion chamber such that the heat for drying the combustion material is derived from the flue gas produced by the combustion chamber.

In a fifth aspect the invention provides an assembly for treating flue gas before discharging into the atmosphere comprising:

- at least one processing chamber for receiving and heating flue gas;

- means for combusting Brown gas to supply heat for heating flue gas; and

- a portion for discharging heated flue gas.

In a sixth aspect the invention provides a method for treating flue gas before being discharged into the atmosphere comprising the steps of:

- providing flue gas to the at least one processing chamber;

- providing Brown gas to a means for combusting Brown gas; and

- heating the flue gas to a pre-determined temperature by combusting the Brown gas.

The means for combusting Brown gas may be a Brown gas burner. Any suitable Brown gas burner may be used for the purposes of the present invention. The Brown gas burner may project a high temperature flame into the processing chamber to heat the flue gas. The processing chamber may also comprise a further inlet to allow fresh air to be supplied to the processing chamber. The processing chamber may be supplied with sufficient air and oxygen-enriched conditions to further oxidise the flue gas constituents. The processing chamber may be lined with a refractory material to maintain a high temperature within the processing chamber. When the flue gas is heated, the flue gas may be oxidised in the processing chamber to further decompose or oxidise into a form which may be less harmful to the environment. For example, the flue gas may be heated to a suitable temperature. The flue gas may be heated to the ignition temperature. The temperature to which the flue gas is heated may be greater than 700 ⁰ C. In particular, the flue gas may be heated to a temperature from 800 ⁰ C to 1600 ⁰ C.

The assembly may further comprise at least one member within the at least one processing chamber, wherein heating the flue gas in proximity to the at least one member achieves a greater heating efficiency of the flue gas. For example, the at least one member may comprise a mesh, steel wool, rods, metal plates or a combination thereof. The member may be made of any suitable material. In particular, the member comprises a mesh-grid block, wherein the mesh-grid block is housed within the at least one processing chamber. The mesh-grid block may be made of platinum, steel, nickel-chromium alloy, aluminium- chromium alloy or a combination thereof. The member may be positioned such that it is in direct contact with the Brown gas flame projected in the processing chamber to attain a high temperature. The member may be supported on supporting means. For example, the rnesh-grid block may be supported on metal frames. Incoming flue gas into the processing chamber may be made to pass through the heated member for better heating efficiency. In particular, the

incoming flue gas may be made to pass through the heated glowing mesh-grid block to effect thermo-chemical reaction that completely oxidises the flue gas constituents such as carbon monoxide, nitrous oxides and other particulates in the flue gas. The treated flue gas may be used for other applications, or be further treated before being discharged into the atmosphere.

There may be one or more processing chambers comprised in the assembly. For example, there may be one, two, three, four, five or six processing chambers. In particular, there are three processing chambers. The advantage of having more processing chambers is that the residence time of the flue gas being heated increases and therefore, complete oxidation of flue gas constituents may be achieved. When there is more than one processing chamber, a possible way of arranging the processing chambers is in a series arrangement, such that flue gas passes through each of the three processing chambers sequentially.

The heated flue gas may be used in other applications. Accordingly, the assembly may further comprise a heat-extracting chamber adapted to receive the heated flue gas from the at least one processing chamber. In particular, the heat-extracting chamber may comprise a boiler unit. Even more in particular, the heat-extracting chamber comprises a steam boiler unit.

The heat-extracting chamber may comprise a boiler unit for producing steam, such that the heat for producing the steam is derived from the heated flue gas ducted to the boiler unit from the at least one processing chamber. Any suitable boiler unit may be used. For example, the boiler unit may be in the form of a metallic-tube or plate-type counter flow heat exchanger boiler unit. The heat- extracting chamber may comprise:

- a water inlet;

- a steam outlet; and

- a flue gas outlet,

the heat-extracting chamber arranged to permit the flue gas to heat the water to produce steam. In particular, the water from the water inlet is heated by the flue gas from the at least one processing unit, thereby producing steam and wherein the steam and flue gas are discharged from the steam outlet and flue gas outlet respectively.

The feed water into the boiler unit may be obtained from a water supply. The feed water in the boiler unit absorbs the heat from the flue gas produced by the at least one processing chamber to form steam. The steam may rise to a steam drum for further heating at elevated pressure to produce superheated steam. The feed water to the boiler unit may be pre-heated. For example, tubes of feed water may run at the roof and along the walls of the at least one processing chamber, such that the tubes are exposed to the heat from the flue gas fed into the processing chamber(s) or the heat within the processing chamber(s). The feed water within the tubes may be heated by convection and radiation heat. The volumetric flow rate of the feed water in the tubes may be controlled such that the water is heated to approximately 9O ⁰ C or less. The heated feed water may then be pumped into the boiler unit for steam production.

According to a further embodiment, the assembly may further comprise a means for generating electricity in communication with the heat-extracting chamber. The means for generating electricity may comprise:

- at least one steam turbine adapted to receive steam produced by the heat-extracting chamber;

- at least one generator, in communication with the at least one steam turbine, for generating electricity; and

- means for discharging the electricity generated from the generator.

The steam from the heat-extracting chamber, in particular the boiler unit, turns the turbine produping mechanical energy which is converted into electrical energy in the at least one generator, thereby generating electricity and wherein the generated electricity is discharged. Any suitable steam turbine may be used. For example, the steam turbine may be a single-stage or multiple-stage steam turbine. The supply of steam or superheated steam to the steam turbine may be regulated by a control system. For example, the supply of steam to the steam turbine may be regulated by varying the flow rate of feed water into the boiler unit. The electricity generated may be supplied to an electricity grid. The electricity may be used for other applications within the system. Therefore, one of the advantages of the system of the present invention is that by generating electricity from steam, reliance on an external source of electrical power may be reduced.

The assembly may further comprise a heat exchanger in communication with the at least one steam turbine. In particular, the heat exchanger may be a cooling unit. The heat exchanger may comprise:

- a first inlet for receiving steam from the steam turbine; and

- a water outlet,

wherein the heat exchanger is capable of condensing the steam to produce water and wherein the water is discharged from the outlet. The water discharged from the heat exchanger may be recycled within the assembly. For example, the water discharged from the heat exchanger may be used as feed water into the boiler unit. Accordingly, the water outlet of the heat exchanger may be connected to the water inlet of the heat-extracting chamber.

The heat exchanger may also be in communication with the heat-extracting chamber. In particular, when the steam turbine has reached maximum capacity, the steam produced in the boiler unit of the heat-extracting chamber may be

ducted to the heat exchanger to be cooled into water. Accordingly, the heat exchanger may comprise a second inlet adapted for receiving steam produced by the heat-extracting chamber when the steam turbine has reached its maximum capacity.

The assembly of the present invention may also comprise a post-treatment unit for further treating flue gas before it is discharged into the atmosphere. For example, the post-treatment unit may be a scrubbing assembly. The scrubbing assembly may comprise means for scrubbing flue gas. The scrubbing assembly is adapted to receive flue gas from the portion for discharging heated flue gas and/or the flue gas outlet of the heat-extracting chamber. In particular, the means for scrubbing flue gas is a scrubber. Any suitable scrubber may be used. For example, the scrubber may be a wet scrubber, a venturi scrubber, an impingement plate scrubber or a spray tower scrubber. The means for scrubbing flue gas may comprise gravity settling chambers and mechanical collectors.

It is important that the means for scrubbing flue gas is able to transfer particles from the flue gas to the liquid stream to reduce the amount of particulates in the flue gas. This reduces the amount of particulate matter in the flue gas before the flue gas is discharged into the atmosphere. The means for scrubbing flue gas may be able to remove particulate matter having an average diameter of about 3 //m or more. The means for scrubbing flue gas may be able to simultaneously collect particulate matter and gaseous pollutants from the flue gas. The gases may be removed by absorption or chemical reaction. For example, in a scrubber, particle-laden flue gas is forced to contact liquid droplets, sheets of liquid on a packing material, or jets of liquid from a plate. The ability of a particulate wet scrubber, for example, to remove particles from a gas stream depends on the following variables:

- the size, i.e. aerodynamic diameter, of the particle;

- the velocity of the particle; and/or

- the velocity of the droplet, sheet or jet.

The means for scrubbing flue gas may further comprise pre-fliters or final filters to further remove particulate matter within the flue gas. For example, pre-filters may be installed upstream of a scrubber intended to catch particulate matter with a larger average diameter. While the scrubber itself would be able to remove this larger particulate matter as well, the removal of the larger particles before the gas stream passes through a scrubber allows the scrubber to focus more keenly and effectively on particulate matter with a smaller average diameter. A final filter may be installed downstream of the scrubber. The final filter is intended to catch particles that were not removed during the scrubbing process.

A wet scrubber may treat gas streams by removing sub-micron or larger fly ash from the gas stream. In addition to removing particulate matter from gas streams, a wet scrubber may also rapidly quench flue gas. For example, a wet scrubber may have a series of high Volume, water spraying nozzles to provide rapid quenching of the flue gas.

The scrubbing assembly may further comprise a means for cooling the flue gas before being discharged into the atmosphere. Any suitable means for cooling the flue gas may be used. For example, the means for cooling the flue gas is a quencher. The means for cooling the flue gas may cool the flue gas to a temperature of less than 300 ⁰ C. The advantage of cooling the flue gas prior to being discharged into the atmosphere is that this may prohibit the reformation of dioxins and furans in the atmosphere. The means for cooling may be connected to an air filter system to further remove particulates and fly ash in the flue gas.

According to a second aspect, the present invention provides a method for treating flue gas before being discharged into the atmosphere comprising the steps of:

- providing flue gas to the at least one processing chamber;

- providing Brown gas to a means for combusting Brown gas; and

- heating the flue gas to a pre-determined temperature by combusting the Brown gas.

The heating step may comprise heating the flue gas in the presence of at least one member for achieving a higher heating efficiency. The pre-determined temperature may be greater than 700 ⁰ C. The means for combusting Brown gas may be a Brown gas burner.

According to a particular embodiment, flue gas is provided to three processing chambers, the flue gas passing through each of the three processing chambers sequentially. In particular, the method may comprise the steps of:

- providing flue gas to a first processing chamber;

- heating the flue gas in the first processing chamber to a first predetermined temperature by combusting Brown gas;

- ducting the heated flue gas from the first processing chamber to a second processing chamber;

- heating the flue gas in the second processing chamber to a second predetermined temperature by combusting Brown gas;

- ducting the heated flue gas from the second processing chamber to a third processing chamber; and

- heating the flue gas in the third processing chamber to a third predetermined chamber by combusting Brown gas.

For example, the first pre-determined temperature may be about 800 ⁰ C. The second pre-determined temperature may be about 1000 ⁰ C. The third pre- determined temperature may be greater than 1200 ⁰ C. In particular, the third pre-determined temperature may be about 1600X.

The method may further comprise a step of producing steam in a heat- extracting chamber, wherein heat for producing the steam is derived from the heated flue gas. The steam produced may be fed into at least one steam turbine, in communication with a generator for generating electricity.

The method may further comprise steps to further treat the heated flue gas. For example, the method may comprise the steps of.

- scrubbing the heated flue gas in a means for scrubbing flue gas; and/or

- cooling the heated flue gas in a means for cooling flue gas.

The flue gas may be cooled to a suitable temperature. For example, the flue gas is cooled to a temperature of less than 300 ⁰ C.

Brief description of the figures

It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible, and consequently the particularity of the accompanying drawings is not intended to be limiting of the present invention.

Figure 1 is a schematic diagram of the system according to one embodiment of the present invention.

Figure 2 is a schematic diagram of an absorptive chiller, according to a further embodiment of the present invention.

Figure 3 is a schematic diagram of an incinerator unit, according to a further embodiment of the present invention.

Figure 4 is a schematic diagram of a localized production, storage and delivery system for piped Brown Gas and hot and chilled water to a multi-storey building, according to a further embodiment of the present invention.

Figure 5 is a schematic diagram of the system according to a further embodiment of the present invention.

Figure 6 is a schematic diagram of a system utilising the heat from the flue gas produced by a combustion chamber according to a further embodiment of the present invention.

Figure 7 is a schematic diagram of a system utilising the heat from the flue gas produced by a combustion chamber according to a further embodiment of the present invention.

Figure 8 is a schematic diagram of the assembly according to a further embodiment of the present invention.

Detailed description of the invention

Figure 1 shows a part of the isolated system of one embodiment of the present invention. In particular, Figure 1 shows the generation of Brown gas and the use of Brown gas in a boiler and burner unit in an isolated system. Brown gas is generated in a Brown gas generator 116, one form being described in US

Patent No. 4,081 ,656. The generator 116 may include an electrolysis chamber.

An electricity supply 104 is connected to a control panel 106 which monitors and controls the operating parameters such as electricity supply to the

generator 116 via power lines 114. There is also provided a water supply 102. The water supply 102 may be in the form of a water storage tank. Water from the water supply 102 is passed through a reverse osmosis (RO) water filter 108 and the filtered RO water is stored in a RO water tank 110. Water from the RO water tank 110 is fed into the generator 116 by means of a pump 112.

Consequently, the generator 116 takes in the RO water and electricity to dissociate oxygen and hydrogen gases in an electrolysis process. The mixture of the generated oxygen and hydrogen gases are piped to a Brown gas storage tank 122 via pipe 121. The generator 116 further comprises a heat exchanger 118. The immediate by-product of the electrolysis process is heat from the dissociation of water into its constituents. The heat exchanger 118 is water cooled. Water is supplied to the heat exchanger 118 from the water supply 102 through pipe 152. Subsequently, pre-heated water is piped out of the heat exchanger 118 by pipe 154.

The Brown gas storage tank 122 is partially filled with a liquefied hydrocarbon. In this case, the liquefied hydrocarbon is hexane 124. There is also provided a hexane storage tank 126. Hexane 124 from the hexane storage tank 126 is pumped into the Brown gas storage tank 122 by means of a pump 127. The mixture of oxygen and hydrogen gas mix with the hexane vapours 124 to form Brown gas 120. The Brown gas storage tank 122 is further equipped with a relief valve 128.

The control panel 106 also monitors and controls other operating parameters such as the RO water supply to the generator 116 from the RO water tank 110, hexane 124 supply to the Brown gas storage tank 1.22, gas pressure within the generator 116 and the Brown gas storage tank 122, operating temperature of the generator 116, and flow rate of the mixture of oxygen and hydrogen gases from the generator 116.

The Brown gas 120 from the Brown gas storage tank 122 may be supplied directly to end users via a piping network 130. The pipes may be equipped with at least one check valve 132 to ensure that the flow of the gas proceeds in one direction only. The pipe 130 further comprises a pressure regulator 133, control valve 134 and a flash arrestor 136. In addition to supplying the Brown gas 120 directly to end users, the Brown gas 120 may also be supplied to a boiler and burner unit 146 for producing hot water.

In particular, the Brown gas 120 is supplied to the burner 148 of the boiler and burner unit 146 by pipe 138. The pipe 138 comprises a check valve 140, a pressure regulator 141, a control valve 142 and a flash arrestor 144. The burner 148 is a standard industrial gas burner with means for gas ignition, means for flame shape and pattern control and means to detect flame. The burner 148 operates on Brown gas 120 and has a motor driven blower, gas supply solenoid valve and a gas nozzle. The burner 148 is configured to produce a flame at a temperature of up to 100O ⁰ C. The burner 148 projects a flame into the boiler.

The boiler 150 is a cylindrical structure with space within to house water-tube bundles (not shown) to store feedwater supplied to the boiler 150 to be heated to produce hot water. In addition, within the boiler 150, there is a layer of reactive metal element which is placed in the path of the flame burning the Brown gas 120 to effect reactive combustion that helps to further elevate the flame temperature. Hot gas produced from the combustion of Brown gas 120 in the burner 148 comes into contact with the tube bundles and consequently, the feedwater within the tubes get heated. To retain the heat of combustion as much as possible, the exterior of the boiler 150 is clad in a layer of thermal insulation materials. The heat from the combustion of Brown gas 120 in the burner 148 is used to heat the feedwater supplied to the boiler 150 in order to produce hot water.

Feedwater to the boiler 150 comes from three sources. Firstly, as make-up water from the water supply 102. The water is pumped into the boiler by pump 158 along pipe 156. Secondly, as pre-heated water in pipe 154 discharged from the heat exchanger 118 in the Brown gas generator 116. Thirdly, as pre-heated water in pipe 157 discharged from at least one solar thermal collector 159. The at least one solar thermal collector 159 takes in water from the water supply 102 and discharges pre-heated water to be fed into the boiler and burner unit 146 via pipe 157. In particular, the water from pipes 154, 156 and 157 is combined and pumped into the boiler and burner unit 146 by pump 158. The hot water produced by the boiler 150 may be used for space heating, sanitary and washing applications. The hot water produced by the boiler 150 may be mixed with water from the water supply 102 through a blender valve to achieve a temperature of about 50 ⁰ C to 70 ⁰ C, depending on the applications, before using the water for space heating, sanitary and washing applications. The hot water produced may be stored in a hot water storage tank.

Figure 2 shows a further unit which is included in the system of the present invention. In particular, Figure 2 shows the arrangement of an absorptive chiller 200. The absorptive chiller 200 produces chilled water, which may be used for space cooling applications. The absorptive chiller 200 is divided into four sections: condenser 202, generator 204, evaporator 206 and absorber 208. The absorptive chiller 200 operates on a thermochemical process of evaporating a refrigerant at near vacuum to absorb heat from its surroundings.

The evaporator 206 and the absorber 208 sections are maintained at near vacuum conditions. In particular, the conditions at the evaporator 206 are as follows: the evaporator 206 is maintained at a vacuum state to effect evaporation at a lower temperature. For example, the pressure may be about 1 kPa and the temperature may be about 4°C.The absorptive chiller 200 is heated by a heat exchanger 205 running hot water from the hot water tank 201. In addition, to supplement the heat, it may be placed in close proximity to a burner

148 of the boiler and burner unit 146. Lithium bromide (LiBr) 210, an absorber, and water 212, a refrigerant, is fed into the generator section 204 of the absorptive chiller 200. The heat produced from the hot water produced by the boiler and burner unit 146, or from the burning of the Brown gas 120 by the burner 148, vapourises the water content in the LiBr solution 210 in the generator section 204. The refrigerant vapour in the form of water vapour 214 circulates to the condenser section 202 and gives up its latent heat to the cooling water 242 in a heat exchanger 216 in the condenser section 202. In the process, the water vapour 214 condenses back into refrigerant water 212.

The refrigerant water 212 flows through the pipe 218 which comprises an expansion valve 220 to form a refrigerant spray 222 in the evaporator section 206. The water from the spray 222 is sprayed on a bundle of chilled water tubes 224 in the evaporator section 206. The water from the spray 222 is partly absorbed by the concentrated LiBr 230 in the absorber section 208 and partly collected at 223 of the evaporator section 206 and recycled back to the condenser section 202 though pipe 218 with the help of pump 238. The temperature of the water of the refrigerant spray 222 is cool and therefore the water of the refrigerant spray 222 absorbs the heat from the warm water 246 in the chilled water tubes 224 and evaporates (under vacuum). Consequently, chilled water is discharged from the chilled water tubes 224. The refrigerant vapour produced in the process is absorbed by the concentrated LiBr 230 in the absorber section 208. This rapid absorption of the refrigerant vapour creates a vacuum state at the evaporator 206, as the evaporator 206 and the absorber 208 are interconnected. In particular, there is a pump (not shown) connected to the evaporator 206 and absorber 208. The pump creates a high vacuum of less than 1.0% of atmospheric pressure. Concentrated LiBr is produced in the generator section 204. When the water content in the LiBr solution evaporates in the generator section 204, concentrated LiBr is formed. The concentrated LiBr flows to the absorber section 208 through pipe 226, which comprises an

expansion valve 228, to form a LiBr spray 230. The LiBr from the LiBr spray 230 is collected at the bottom of the absorber section 208 to form a pool of diluted LiBr solution 232 as it combines with the refrigerant vapour from the evaporator 206, which is recycled back to the LiBr pool 210 in the generator section 204 by a pump 236. The LiBr spray 230 sprays LiBr on a heat exchanger 215 in the absorber section 208. The heat exchanger 215 has cooling water 240 of temperature of approximately 25°C being fed into the heat exchanger from a cooling tower 250, while water of a slightly higher temperature 242 is discharged from the heat exchanger 215 and fed into heat exchanger 216 in the condenser section 202. Consequently, high temperature water 244 is discharged from the heat exchanger 216 after absorbing the heat from the refrigerant vapour 214 in the condenser section 202, and fed into the cooling tower 250.

The chilled water 248 produced in the evaporator section 206 is piped to a storage tank or directly to the end users for use in various applications, such as space cooling applications. For example, the chilled water 248 can flow to an air handling unit (a heat exchanger with a blower) of respective households to provide for space cooling application.

The system of the present invention also includes an incinerator unit 300. The arrangement of the incinerator unit 300 is shown in Figure 3. In particular, the incinerator unit 300 uses Brown gas 120 generated by the Brown gas generator 116 as fuel. The incinerator unit 300 oxidises domestic and industrial waste on site of the system. The incinerator unit 300 operates on Brown gas 120, which is obtained from the Brown gas storage tank 122. The Brown gas 120 is piped from the storage tank 122 to a combustion chamber 312 and a re-oxidation chamber 314 by pipe network 302. The pipe network 302 further comprises a pressure regulator 304, a check valve 303 at the outlet of the Brown gas storage tank 122 and a multivalve 306 to split the flow of Brown gas 120 into the combustion chamber 312 and the re-oxidation chamber 314. The pressure

regulator 304 controls and maintains a uniform outlet Brown gas 120 pressure in pipe network 302. Each of the combustion chamber 312 and the re-oxidation chamber 314 is equipped with a Brown gas burner 313 and 315 respectively. The Brown gas burners 313 and 315 are standard industrial gas burners with means for gas ignition, means for flame shape and pattern control and means to detect a flame. The Brown gas burners 313 and 315 operate on Brown gas 120 and also have a motor driven blower, a gas supply solenoid valve and a gas nozzle. The burners 313 and 315 are configured to produce a flame at a temperature of up to 1500 ⁰ C in the combustion chamber 312 and re-oxidation chamber 314. There is also provided a flash arrestor 308 and 310 and control valve 305 and 307 at the inlet of each of the combustion chamber 312 and the re-oxidation chamber 314 respectively.

The incinerator unit 300 also comprises pre-treatment units 316 and 318. Pre- treatment unit 316 is for the pre-treatment of solid waste, while pre-treatment unit 318 is for the pre-treatment of liquid waste. Pre-treatment unit 316 comprises a collection unit 320, a sorter 322 and a dryer 324. The collection unit 320 collects the solid waste, while the sorter 322 sorts the waste. The solid waste may be sorted physically through visual means by manual sorters to remove glass, grit, metal and other bulky items. Moisture content of the waste is reduced in the dryer 324, where the waste is heated. The waste is heated by tubular bundles. The tubular bundles have steam passing through the tubes of bundle to heat the bundles, and therefore heating the waste. The waste from the dryer 324 is then fed into the combustion chamber 312. Similarly, for the pre-treatment of liquid waste, there is provided in the pre-treatment unit 318 a collection unit 326 for collecting the liquid waste, a filter 328 to remove sludge from the liquid waste and an evaporator 330 to remove the water content from the sludge. The filter 328 may be any suitable filter. For example, the filter may be a fabric or membrane filter. Alternatively, filter presses or centrifugal filters may also be used. The pre-treatment process for liquid waste may include a

solid-water separation to filter out sludge from raw water. The sludge may be collected in an evaporator for dewatering. The filtered raw water may then be chemically treated before discharging to a drainage system. The treated waste is then fed into the combustion chamber 312.

The combustion chamber 312 is heated up by the burning of the Brown gas 120 to reach a temperature of up to 1500 ⁰ C, which is above the flash point of most solid waste. Once the combustion chamber 312 attains a temperature of about 1000 ⁰ C from the burning of waste and Brown gas 120, the Brown gas burner 313 ceases operation. The Brown gas burner 313 only re-ignites when the temperature of the combustion chamber 312 drops to below 1000 ⁰ C. The combustion chamber 312 may also have a heat exchanger 338 within itself. The heat exchanger 338 may maximise heat recovery. For example, circulating water contained in the tube bundle of the heat exchanger 338 absorbs the heat of combustion from the combustion chamber 312 and releases the heat at the waste dryer 324, where the heat may be used in removing the moisture from the solid waste. A circulatory system is also included in the incinerator unit 300 to provide feed water to the heat exchangers in the incinerator unit 300. The circulatory system comprises multivalves 348, 350, 352, a steam settling tank 344, a pump 346 and piping network 342.

Flue gas 332 which is produced as a result of the burning of the waste in the combustion chamber 312 is fed into a re-oxidation chamber 314 to completely decompose any waste remaining in the flue gas 332 by further oxidising the organic material and other harmful materials.

The re-oxidation chamber 314 is maintained at temperatures of 1000 ⁰ C or above by the combustion of flue gas 332 and supplementary burning of Brown gas 120 by burner 315. The re-oxidation chamber 314 is equipped with a means to be supplied fresh air for oxygen enriched burning of the flue gas 332. The re-oxidation chamber is heated up by the burner 315 to reach a

temperature of about 1000 ⁰ C, which is the auto-ignition temperature of flue gas constituents such as carbon monoxide (CO), hydrogen (H ₂ ) and methane (CH ₃ ). Once the re-oxidation chamber 314 attains a temperature of about 1000 ⁰ C from the burning of the flue gas 332 and supplementary burning of Brown gas 120, the burner 315 stops operating. The burner 315 starts burning Brown gas 120 when the temperature of the re-oxidation chamber 314 drops to below 1000°C. The re-oxidation chamber 314 is further equipped with a mesh-grid block 311 supported on a metal frame within the re-oxidation chamber 314. The highly permeable perforated mesh-grid block 311 may be made of platinum, steel, nickel-chromium alloy or other nickel alloys. The cell of the mesh-grid block 311 can be of any suitable shape such as square, triangle or polygonal shape. The mesh-grid block 311 may be constructed as an interlaced, multi-layer structure to maximise contact with the incoming flue gas 332, and its exposure to Brown gas flame produced by the burner 315.

The orientation of the direction of flow of the flue gas 332 and the Brown gas flame produced by the burner 315 in relation to the mesh-grid block 311 is such that they are perpendicular to each other or parallel to one another. The mesh- grid block 311 is positioned such that it is in line with the Brown gas flame produced by the burner 315. The flue gas 332 from the combustion chamber 312 is channelled to pass through the mesh-grid block 311. Upon direct exposure to the Brown gas flame produced by the burner 315, the mesh-grid block 311 glows and attains a temperature capable of reacting with the incoming flue gas 332. In this process, the flue gas constituents such as carbon monoxide (CO), hydrogen (H2) and other gaseous hydrocarbon compounds are oxidised into forms which are less harmful to the environment, such as carbon dioxide (CO ₂ ), water and other less harmful gases.

The resulting flue gas 335 from the re-oxidation chamber 314 is passed through a chamber 334 comprising a wet scrubber 336 before it is discharged into the atmosphere as exhaust gas 340. The wet scrubber 336 treats the resulting flue

gas 335 to remove sub-micron or larger fly ash. The wet scrubber 336 may have a series of high volume, water spraying nozzles to provide rapid quenching of the flue gas 335 to a temperature of about 200 ⁰ C to 300 ⁰ C before it is released as exhaust gas 340 to prohibit the re-formation of dioxins and furans in the atmosphere. Feed water to the wet scrubber 336 is obtained from the water supply 102. The exhaust gas 340 released from the chamber 334 may be connected to an air filer system.

Figure 4 shows an example of the arrangement of the various units of the system as described above. In particular, Figure 4 shows how the units, such as the Brown gas generator 116, the boiler and burner unit 146, the absorptive chiller 200 and the incinerator unit 300 can be used in an isolated system for producing Brown gas, storing the Brown gas and delivering the Brown gas for various applications in a multi-storey building.

Figure 5 shows a genera! isolated system of one embodiment of the present invention. In particular, Figure 5 shows the generation of Brown gas and the use of Brown gas in a combustion chamber in an isolated system. Brown gas is generated in a Brown gas generation system 1113, wherein the Brown gas generation system 1113 comprises a Brown gas generator 1114, a heat exchanger 1116 and a Brown gas storage tank 1122. In particular, Brown gas is generated in the Brown gas generator 1114, one form being described in US Patent No. 4,081 ,656. The generator 1114 may include an electrolysis chamber. An electricity supply 1104 is connected to a control panel 1106 which monitors and controls the operating parameters such as electricity supply to the generator 1114 via power lines 1112. There is also provided a water supply 1102. The water supply 1102 may be in the form of a water storage tank. Water from the water supply 1102 is passed through a reverse osmosis (RO) water filter 1108 by means of a pump 1110 and the filtered RO water is fed into the electrolysis chamber of the generator 1114.

Consequently, the generator 1114 takes in the RO water and electricity to dissociate oxygen and hydrogen gases in an electrolysis process. The mixture of the generated oxygen and hydrogen gases are piped to a Brown gas storage tank 1122 via pipe 1121. The Brown gas generation system 1113 further comprises a heat exchanger 1116. The immediate by-product of the electrolysis process is heat from the dissociation of water into its constituents. The heat exchanger 1116 is water cooled. Cool water is circulated to the heat exchanger 1116 from a cooling tower 1118 through pipe 1117. Subsequently, warm water is piped out of the heat exchanger 1116 by pipe 1119 and returned to the cooling tower 1118.

The Brown gas storage tank 1122 is partially filled with a liquefied hydrocarbon. In this case, the liquefied hydrocarbon is hexane 1124. There is also provided a hexane storage tank 1126. Hexane 1124 from the hexane storage tank 1126 is pumped into the Brown gas storage tank 1122 by means of a pump (not shown). The mixture of oxygen and hydrogen gases mix with the hexane vapour to form Brown gas 1120. The Brown gas storage tank 1122 is further equipped with a relief valve 1128. A relief valve is a valve that is set to open at a certain pressure level to prevent the pressure in a container or system from reaching unsafe levels.

The Brown gas 1120 from the Brown gas storage tank 1122 may be supplied directly to a combustion chamber 1142 via a piping network 1130. The pipes of piping network 1130 may be equipped with at least one check valve 1132 to ensure that the flow of the Brown gas 1120 proceeds in one direction only. The piping network 1130 further comprises at least one pressure regulator 1134, at least one control valve 1136 and at least one flash arrestor 1138. A pressure regulator is a device used for controlling and maintaining a uniform outlet gas pressure to a piping, while a flash arrestor is a device which prevents "flashback" from an external fire through an open safety faucet.

In particular, the Brown gas 1120 is supplied to at least one burner 1140 of combustion chamber 1142 by piping network 1130. Burner 1140 is a standard industrial gas burner with means for gas ignition, means for flame shape and pattern control and means to detect flame. Burner 1140 operates on Brown gas 1120 and has a motor driven blower, gas supply solenoid valve and gas nozzle. Burner 1140 is configured to produce a flame at a temperature of more than 1200 ⁰ C. Burner 1140 may be located at the side of combustion chamber 1142 and projects a flame into combustion chamber 1142. When waste is burnt in combustion chamber 1142, flue gas is produced. The heat from the flue gas may be utilised for generating electricity, as will be described in detail below.

Figure 6 shows the arrangement of the system of the present invention in which the heat from the flue gas produced by combustion chamber 1142 is utilised in various further applications. The combustion chamber shown in Figure 6 comprises a single-stage combustion unit 1142a. The combustion unit 1142a uses Brown gas 1120 generated by the Brown gas generation system 1113 as fuel to burn combustion material. The combustion material may be waste, which may include domestic and industrial waste. The Brown gas 1120 from the Brown gas generation system 1113 is piped to combustion unit 1142a by piping network 1130 as described in Figure 5 above. Pressure regulator 1134 controls and maintains a uniform outlet Brown gas pressure suitable for combustion unit 1142a in piping network 1130. For example, the gas pressure may be about 11 inches of water (i.e. about 2738 Pa).

The inner wall of combustion unit 1142a is lined with a refractory material to contain the heat of combustion within the combustion unit 1142a and to protect the structure of the combustion unit 1142a. For example, the refractory material may include hard, heat resistant materials capable of working in an acidic environment. Examples of refractory material include, but are not limited to, alumina, silicon carbide, fire clay, bricks and silica. Intermittent jets of compressed air are supplied to combustion unit 1142a through perforations at

the side or the base of combustion unit 1142a. The compressed air serves to enhance turbulence mixing of waste that is to be burnt in the combustion unit 1142a with air. The intermittent jets of compressed air help to prevent choking of the perforations supplying compressed air to the combustion unit 1142a. A grating (not shown) at the base of combustion unit 1142a separates dry solid waste from ashes. Bottom ash 1201 from the combustion of the waste in the combustion unit 1142a is collected through a hopper (not shown) at the base of the combustion unit 1142a for disposal.

Flue gas 1202 is produced as a result of the burning of the waste in the combustion unit 1142a. Some of the flue gas 1202 is ducted from the combustion unit 1142a to a water tube steam boiler 1204. Water is pumped into the steam boiler 1204 by a pump 1212. In the steam boiler 1204, the water circulates in tubes 1206 which are heated externally by the flue gas 1202 ducted to the steam boiler 1204 from the combustion unit 1142a. For example, the flue gas may be at 900 ⁰ C. As the water-filled tubes 1206 comprised in the steam boiler 1204 are exposed to the high temperature flue gas 1202, the temperature of the water in the tubes 1206 rises, and due to thermosiphon effect, hot water rises to steam drum 1208 in steam boiler 1204. Further heating of hot water in steam drum 1208 by flue gas 1202 produces steam 1214. Steam 1214 is drawn off the top of steam drum 1208 and optionally further heated in a superheater (not shown) to produce superheated steam. Flue gas 1202 is then ducted to a post-treatment unit 1230 via channel 1228a for treating flue gas 1202 before it is discharged into the atmosphere as exhaust gas 1236. Post- treatment unit 1230 is described in more detail below.

Steam 1214 or superheated steam is then used to drive steam turbine 1216. For example, the superheated steam may be at 390 ⁰ C or higher. Steam turbine 1216 may be a single-stage or multiple stage steam turbine. Steam turbine 1216 is connected to a generator 1220 for generating electricity by shaft 1218. Steam 1214 is fed under high pressure of about 23 bar (2.3 x 10 ⁶ Pa) to the

steam turbine 1216. Steam turbine 1216 spins, causing shaft 1218 to spin as well. As a result of the spinning of shaft 1218, a magnet comprised in generator 1220 is also turned. The magnet has wires coiled around it. As the magnet inside generator 1220 turns, an electric current is produced in the wires. Generator 1220 converts the mechanical energy into electrical energy. The electricity generated by generator 1220 is then transmitted to a series of electrical devices for adjusting the voltage and current for use by the Brown gas generation system 1113 to generate Brown gas 1120, or to an electricity grid located within the system which is the electricity supply 1104 for the system.

Steam 1214 or superheated steam passing through steam turbine 1216 is then channelled to a heat exchanger 1222. Steam 1214 is cooled in heat exchanger 1222 to condensate into water. The condensed water is then pumped back into tubes 1206 of steam boiler 1204 by pump 1212 for absorbing heat from flue gas 1202 for the production of steam 1214. Feed water flowing into heat exchanger 1222 for cooling the steam 1214 or superheated steam from steam turbine 1216 is obtained from water supply 1102 by pipe network 1224. Heat exchanger 1222 also cools excess superheated steam or excess steam 1214. Steam 1214 is considered excess when steam turbine 1216 has reached its maximum capacity and is unable to take in any more steam 1214 or superheated steam. When this happens, the excess steam 1214 or excess superheated steam is channelled to heat exchanger 1222 via bypass pipe 1226. As described above, the excess steam 1214 and excess superheated steam is cooled and condensed into water in heat exchanger 1222. The water is then pumped back into tubes 1206 of steam boiler 1204 by pump 1212 for absorbing heat from flue gas 1202 for the production of steam 1214.

The combustion chamber 1142 also comprises a pre-treatment unit 1242. In particular, pre-treatment unit 1242 is for the pre-treatment of solid waste. Pre- treatment unit 1242 comprises a dryer to reduce the moisture content of the waste before it is fed into the combustion unit 1142a for burning. The waste is

heated by tubular bundles 1243 found within the dryer. Tubular bundles 1243 have flue gas 1202 passing through the tubes of the bundles which externally heat the waste. In particular, the tubes of the tubular bundles 1243 are highly conductive. Some flue gas 1202 from combustion unit 1142a is ducted to tubular bundles 1243 via channel 1229. Flue gas 1202 from steam boiler 1204 is also ducted to tubular bundles 1243 via channel 1228b. Flue gas 1202 passing through the tubular bundles 1243 is then ducted into post-treatment unit 1230 via channel 1244 for treating flue gas 1202 before it is discharged into the atmosphere as exhaust gas 1236. Post-treatment unit 1230 is described in more detail below.

Flue gas 1202 from steam boiler 1204 and pre-treatment unit 1242 is ducted into post-treatment unit 1230 via channels 1228a and 1244 respectively. Post- treatment unit 1230 comprises wet scrubber 1232 and quencher 1234. Flue gas 1202 from steam boiler 1204 and pre-treatment unit 1242 is washed down in wet scrubber 1232. Wet scrubber 1232 may be a chemical wet scrubber. For example, the chemical used in the chemical wet scrubber may be aqueous slurry formed from calcium hydroxide or sodium hydroxide. Wet scrubber 1232 may be an enclosure with multiple interconnected chambers. Each chamber may be formed by perforated plates to slow down the passage of flue gas 1202 passing though wet scrubber 1232. Wet scrubber 1232 treats flue gas 1202 to remove sub-micron or larger fly ash, dust and particulates. Wet scrubber 1232 may have a series of high pressure, fluid spraying nozzles. For example, the fluid may be an alkaline solution such as sodium hydroxide or calcium hydroxide. The alkaline solution neutralises flue gas 1202 which may be acidic. The alkaline solution also washes away fly ash and large particulates in flue gas 1202.

After flue gas 1202 passes through wet scrubber 1232, the semi-treated flue gas 1202 is then washed down in quencher 1234 for rapid quenching. Quencher 1234 has a series of high volume, water spraying nozzles to provide

the rapid quenching of flue gas 1202 to a temperature of about 200 ⁰ C to 300°C before flue gas 1202 is released as exhaust gas 1236 to prohibit the reformation of dioxins and furans in the atmosphere. Quenching also reduces the odour of the semi-treated flue gas 1202. Feed water to quencher 1234 is obtained from water supply 1102. The water from water supply 1102 is pumped to quencher 1234 by pump 1239 via pipe network 1238. Fluid containing fly ash and large particulates collected at the base of post-treatment unit 1230 may pass though a filter system before being recycled back to the spraying nozzle of wet scrubber 1232 via pump 1233. At regular intervals, the fluid at the base of post-treatment unit 1230 may be discharged to treatment unit 1240 where it is chemically treated. The chemically treated fluid may be recycled back into wet scrubber 1232 or be discharged to a drainage system.

Optionally, exhaust gas 1236 released from quencher 1234 may be connected to an air filter system for further treatment before being discharged to the atmosphere. Exhaust gas 1236 may also comprise saturated water vapour. Therefore, an evaporator may be installed at the gas outlet of quencher 1234 to remove the saturated vapour in exhaust gas 1236 so as to prevent the formation of plume in the atmosphere. As a further option, the treated flue gas 1202 may also be passed through a gas filtration system before being discharged into the atmosphere to remove submicron sized particles.

A further arrangement of the system of the present invention in which the heat from the flue gas produced by the combustion chamber 1142 is utilised in various further applications is shown in Figure 7. The system of Figure 6 and that of Figure 7 is essentially the same, with the exception of the combustion chamber 1142. The combustion chamber 1142 shown in Figure 7 comprises a two-stage combustion chamber. In particular, the combustion chamber 1142 of Figure 7 comprises combustion unit 1142a and re-oxidation chamber 1302. Re- oxidation chamber 1302 may be a thermai re-oxidation chamber. As with combustion unit 1142a, re-oxidation chamber 1302 also uses Brown gas 1120

generated by the Brown gas generation system 1113 as fuel. Accordingly, Brown gas 1120 is piped from the Brown gas generation system 1113 to the re- oxidation chamber 1302 by pipe network 1130. Pipe network 1130 may comprise a multivalve 1303 to split the flow of Brown gas 1120 into the combustion unit 1142a and re-oxidation chamber 1302. Pipe network 1130 further comprises check valve 1304, pressure regulator 1306, control valve 1308 and flash arrestor 1310. Pressure regulator 1306 controls and maintains a uniform Brown gas pressure in pipe network 1130.

Re-oxidation chamber 1302 is equipped with a Brown gas burner 1312. Brown gas burner 1312 is a standard industrial gas burner with means for gas ignition, means for flame shape and pattern control and means to detect a flame. Brown gas burner 1312 operates on Brown gas 1120 and also has a motor driven blower, a gas supply solenoid valve and a gas nozzle. Brown gas burner 1312 may be configured to produce a flame at a temperature of more than 1200 ⁰ C in the re-oxidation chamber 1302. In particular, the re-oxidation chamber 1302 is maintained at a temperature of about 1000 ⁰ C, which is the reduction reaction temperature of flue gas constituents such as carbon monoxide (CO), hydrogen (H2) and methane (CH ₄ ).

At the start up of the incineration (burning) process, the Brown gas burners 1140 and 1312 of the combustion unit 1142a and re-oxidation chamber 1302 respectively fire Brown gas 1120 to heat up the furnace space within the combustion unit 1142a and re-oxidation chamber 1302. The flow rate and duration of firing of the Brown gas 1120 are controlled to attain a preset temperature in the combustion unit 1142a. Typically, in the absence of waste, the combustion unit 1142a can attain a temperature of more than 1000 ⁰ C. During the incineration process, dry waste is constantly fed to the combustion unit 1142a to be burnt. At steady state, with the constant supply of waste, the combustion unit 1142a can reach temperatures of more than 1200°C. In the burning process, flue gases rich in carbon monoxide, gaseous hydrocarbon

compounds and oxides of nitrogen (NO _x ) are produced. The flue gas 1202 generated is carried to the re-oxidation chamber 1302 for further treatment. The re-oxidation chamber 1302 may be of an elongated structure to allow for a minimum of two seconds of dwelling time for the complete combustion of flue gas 1202. Alternatively, the re-oxidation chamber 1302 may be made of two or more interconnected small furnaces of similar or different construction for a more complete treatment of the flue gas 1202 by increasing the exposure time of the flue gas 1202 to treatment.

The re-oxidation chamber 1302 is equipped with a mesh-grid block 1313 supported on a metal frame within re-oxidation chamber 1302. The highly permeable perforated mesh-grid block 1313 may be made of platinum, steel, nickel-chromium alloy or nickel alloys. The mesh-grid block 1313 reacts positively with the Brown gas flame produced by Brown gas burner 1312 to attain a high temperature within the re-oxidation chamber 1302. The cell of the mesh-grid block 1313 can be of any suitable shape such as square, triangle or polygonal shape. In particular, the mesh-grid block 1313 can be constructed as an interlaced, multi-layer structure to maximize contact with the incoming flue gas 1202, and its exposure to Brown gas flame produced by Brown gas burner 1312.

The orientation of the direction of flue gas flow and the Brown gas flame produced by the Brown gas burner 1312 with regards to the mesh-grid block 1313 is such that they are perpendicular to each other or parallel to one another. The mesh-grid block 1313 is positioned such that it is in line with the Brown gas flame produced by the Brown gas burner 1312. The flue gas 1202 from the combustion unit 1142a is channelled to pass through the mesh-grid block 1313. Upon direct exposure to the Brown gas flame produced by the Brown gas burner 1312, the mesh-grid block 1313 glows and attains a temperature capable of reacting with the incoming flue gas 1202. In the process, flue gas constituents such as CO, H2 and other gaseous hydrocarbon

compounds are oxidised into forms which are less harmful to the environment, such as carbon dioxide (CO ₂ ), water and other less harmful gases. In particular, the nitrogen-containing flue gas 1202 reduces into elemental constituents of nitrogen and oxygen before the oxygen further reacts with the hydrogen in the Brown gas 1120, thereby producing nitrogen and water vapour.

As described in Figure 6 above, a portion of flue gas 1314 from the re-oxidation chamber 1302 is ducted to steam boiler 1204 for the production of steam (or superheated steam) for driving steam turbine 1216 and generator 1220 to generate electricity. A portion of flue gas 1314 from re-oxidation chamber 1302 is also ducted to tubular bundles 1243 via channel 1315 for drying the waste in pre-treatment unit 1242.

Throughout the incineration process, both the combustion unit 1142a and the re-oxidation chamber 1302 are maintained at a negative pressure to ensure a correct draught is created for the flow of flue gas 1202 from the combustion unit 1142a and re-oxidation chamber 1302 to steam boiler 1204 and pre-treatment unit 1242. For example, the pressure may be about -50 Pa. The negative pressure in the combustion unit 1142a and re-oxidation chamber 1302 may be achieved via a suction fan installed either at the flue gas discharge end of combustion unit 1142a (in the case of the system shown in Figure 6), at the flue gas discharge end of re-oxidation chamber 1302 (in the case of the system shown in Figure 7), or at the exhaust end of the post-treatment unit 1230.

Figure 8 shows a general assembly of one embodiment of the present invention. In particular, Figure 8 shows the treatment of flue gas emitted from a flue gas emitter before the flue gas is released into the atmosphere. Flue gas 2103 from flue gas emitter 2102 is ducted into first processing chamber 2104. Flue gas emitter 2102 may be any system which emits flue gas. For example, flue gas emitter 2102 may be an incineration unit, a coal fired kiln and the like. Flue gas 2103 may be rich in carbon monoxide, gaseous hydrocarbon

compounds and oxides of nitrogen (NO _x ). Flue gas 2103 typically has a temperature of about 300 ⁰ C or more. In first processing chamber 2104, flue gas 2103 is further heated. For example, flue gas 2103 is further heated to about 800 ⁰ C in first processing chamber 2104. The heated flue gas 2103 is then ducted into second processing chamber 2106 for further heating. For example, flue gas 2103 may be heated to a temperature of about 1000 ⁰ C in second processing chamber 2106. The heated fiue gas 2103 from second processing chamber 2106 is ducted into third processing chamber 2108 to be heated to a temperature of greater than 1200 ⁰ C. In particular, the temperature in third processing chamber 2108 is about 1600 ⁰ C.

Flue gas 2103 is heated in first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 by combusting Brown gas. Brown gas may be generated in a Brown gas generator, one form being described in US Patent No. 4,081,656. Brown gas may be supplied directly to processing chambers 2104, 2106 and 2108 from a Brown gas storage tank 2110 by pipe network 2112. Brown gas storage tank 2110 may be equipped with a relief valve 2111. A relief valve is a valve that is set to open at a certain pressure level to prevent the pressure in a container or system from reaching unsafe levels. Pipe network 2112 may be equipped with at least one check valve 2114. Pipe network 2112 may further comprise multivalve 2116 to split the flow of Brown gas to each processing chamber 2104, 2106 and 2108. For example, the flow of Brown gas may be split such that Brown gas is supplied to first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 by pipe networks 2118, 2120 and 2122 respectively. Each pipe network 2118, 2120, 2122 may comprise at least one pressure regulator 2124, 2132, 2140, at least one control valve 2126, 2134, 2142 and at least one flash arrestor 2128, 2136, 2144, respectively. A pressure regulator is a device used for controlling and maintaining a uniform outlet gas pressure to a piping, while a flash arrestor is a device which prevents "flashback" from an

external fire through an open safety faucet. Pressure regulators 2124, 2132 and 2140 control and maintain a uniform outlet Brown gas pressure suitable for processing chambers 2104, 2106 and 2108 in pipe networks 118, 2120 and 2122 respectively. For example, the gas pressure may be about 11 inches of water (i.e. about 2738 Pa).

In particular, Brown gas is supplied to burners 2130, 2138 and 2146 of first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 respectively. Burners 2130, 2138 and 2146 may be standard industrial burners with means for gas ignition, means for flame shape and pattern control and means to detect flame. Burners 2130, 2138 and 2146 operate on Brown gas and have a motor driven blower, gas supply solenoid valve and gas nozzle. Burners 2130, 2138 and 2146 are configured to produce a flame at a temperature of more than 1200 ⁰ C. Burners 2130, 2138 and 2146 may be located so as to project a flame into processing chambers 2104, 2106 and 2108 respectively.

Brown gas burners 2130, 2138 and 2146 are configured to produce a flame at a temperature of about 800 ⁰ C, 1000°C and 1200°C in first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 respectively. In particular, the auto-ignition temperature of flue gas constituents such as carbon monoxide (CO), hydrogen (H ₂ ) and methane (CH ₄ ) is between about 800 ⁰ C and 1600 ⁰ C. Once the desired temperature is attained in processing chambers 2104, 2106 and 2108 from the burning of flue gas 2103 and supplementary burning of Brown gas, Brown gas burners 2130, 2138 and 2146 stop operating. Brown gas burners 2130, 2138 and 2146 start burning Brown gas when the temperature of first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 drop below 800°C, 1000°C and 1200 ⁰ C respectively. At the start-up of the treatment process, Brown gas burners 2130, 2138 and 2146 fire Brown gas to heat up the furnace space within first processing chamber 2104, second processing

chamber 2106 and third processing chamber 2108 respectively. The flow rate and duration of firing of Brown gas are controlled to attain a preset temperature in each of processing chambers 2104, 2106 and 2108.

First processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 may be of an elongated structure to allow for a minimum of two seconds of dwelling time for the complete combustion of flue gas 2103. Alternatively, each first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 may be made of two or more interconnected small furnaces of similar or different construction for a more complete treatment of flue gas 2103 by increasing exposure time of flue gas 2103 to treatment. At least one of first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 may be further equipped with a mesh-grid block (not shown).

The mesh-grid block may be supported on a metal frame within the at least one first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108. The highly permeable perforated mesh-grid block may be made of platinum, steel, nickel-chromium alloy, nickel alloy, or a combination thereof. The mesh-grid block reacts positively with the Brown gas flame produced by Brown gas burners 2130, 2138 and 2146 to attain a high temperature within first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108. The cell of the mesh-grid block may be of any suitable shape and size. For example, the shape of the cell of the mesh-grid block may be square, triangle or polygonal. In particular, the mesh- grid block can be constructed as an interlaced, multi-layer structure to maximise contact with incoming flue gas 2103, and its exposure to the Brown gas flame produced by Brown gas burners 2130, 2138 and 2146.

The orientation of the direction of flue gas flow and the Brown gas flame produced by the Brown gas burners 2130, 2138 and 2146 with regards to the

mesh-grid block is such that they are perpendicular to each other or parallel to one another. The mesh-grid block is positioned such that it is in line with the Brown gas flame produced by the Brown gas burners 2130, 2138 and 2146. The flue gas 2103 from the flue gas emitter 2102, first processing chamber 2104 or second processing chamber 2106 is channelled to pass through the mesh-grid block in first processing chamber 2104, second processing chamber 2106 or third processing chamber 2108 respectively. Upon direct exposure to the Brown gas flame produced by the Brown gas burners 2130, 2138 and 2146, the mesh-grid block glows and attains a temperature capable of reacting with the incoming flue gas 2103. In the process, flue gas constituents such as CO, H ₂ and other gaseous hydrocarbon compounds are oxidised into forms which are less harmful to the environment, such as carbon dioxide (CO ₂ ), water and other less harmful gases. In particular, the nitrogen-containing flue gas 2103 dissociates into elemental constituents before reacting with the hydrogen in the Brown gas, thereby producing nitrogen.

Some of the heated flue gas 2103 from each first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 may be ducted into a post-treatment unit. The post-treatment unit may be a scrubbing assembly 2176 which will be described in more detail below. Alternatively, some of the heated flue gas from the processing chambers, in particular, third processing chamber 2108, is ducted to a water tube steam boiler 2148. Water is pumped into steam boiler 2148 by pump 2170. In steam boiler 2148, water circulates in tubes 2150, which are heated externally by the heated flue gas 2103 ducted to steam boiler 2148 from third processing chamber 2108. As the water-filled tubes 2150 comprised in steam boiler 2148 are exposed to the high temperature flue gas 2103, the temperature of the water in the tubes 2150 rises, producing steam 2154 which then rises to steam drum 2152 in steam boiler 2148. Steam 2154 is drawn off the top of steam drum 2152 and optionally further heated in a superheater (not shown) to produce superheated steam.

Flue gas 2103 is then ducted to a post-treatment unit for treating flue gas 2103 before it is discharged into the atmosphere as exhaust gas 2194. The post- treatment unit may be scrubbing assembly 2176, which will be described in more detail below.

Steam 2154 or superheated steam is then used to drive steam turbine 2156. For example, the superheated steam may be at 250 ⁰ C or higher. Steam turbine 2156 may be a single-stage or multiple stage steam turbine. Steam turbine 2156 is connected to a generator 2158 for generating electricity by a shaft 2160. Steam 154 is fed under high pressure to steam turbine 2156. Steam turbine 2156 spins, causing shaft 2160 to spin as well. As a result of the spinning of shaft 2160, a magnet comprised in generator 2158 is also turned. The magnet has wires coiled around it. As the magnet insider generator 2158 turns, an electric current is produced in the wires. Generator 2158 converts the mechanical energy into electrical energy. The electricity generated by generator 2158 is then transmitted to an electricity grid 2168.

Steam 2154 or superheated steam passing through steam turbine 2156 is then channelled to heat exchanger 2166. Steam 2154 is cooled in heat exchanger 2166 to condensate into water. The condensed water is then pumped back into tubes 2150 of steam boiler 2148 by pump 2170 for absorbing heat from flue gas 2103 for the production of steam 2154. Feed water flowing into heat exchanger 2166 for cooling the superheated steam from steam turbine 2156 is obtained from water supply 2172 by pipe network 2174. Heat exchanger 2166 also cools excess superheated steam or excess steam 2154. Steam 2154 is considered excess when steam turbine 2156 has reached its maximum capacity and is unable to take in any more steam 2154 or superheated steam. When this happens, the excess steam 2154 or excess superheated steam is channelled to heat exchanger 2166 via bypass pipe 2162. As described above, the excess steam 2154 and excess superheated steam is cooled and condensed into water in heat exchanger 2166. The water is then pumped back into tubes 2150 of

steam boiler 2148 by pump 2170 for absorbing heat from flue gas 2103 for the production of steam 2154.

Flue gas 2103 from steam boiler 2148, first processing chamber 2104, second processing chamber 2106 and/or third processing chamber 2108 is ducted into scrubbing assembly 2176. Scrubbing assembly 2176 comprises wet scrubber 2178 and quencher 2188. Flue gas 103 from steam boiler 2148, first processing chamber 2104, second processing chamber 2106 and/or third processing chamber 2108 is washed down in wet scrubber 2178. Wet scrubber 2178 may be a chemical wet scrubber. Wet scrubber 2178 may be an enclosure with multiple interconnected chambers. Each chamber may be formed by perforated plates to slow down the passage of flue gas 2103 passing though wet scrubber 2178. Wet scrubber 2178 treats flue gas 2103 to remove sub-micron or larger fly ash, dust and particulates. Wet scrubber 2178 may have a series of high pressure, fluid spraying nozzles 2180. For example, the fluid may be an alkaline fluid such as sodium hydroxide or calcium hydroxide. The alkaline fluid neutralises flue gas 2103 which may be acidic. The alkaline fluid also washes away fly ash and large particulates in flue gas 2103.

After flue gas 2103 passes through wet scrubber 2178, the semi-treated flue gas 2103 is then washed down in quencher 2188 for rapid quenching. Quencher 2188 has a series of high volume, water spraying nozzles 2190 to provide the rapid quenching of flue gas 2103 to a temperature of about 200 ⁰ C to 300 ⁰ C before flue gas 2103 is released as exhaust gas 2194 into the atmosphere to prohibit the re-formation of dioxins and furans in the atmosphere. Quenching also reduces the odour of semi-treated flue gas 2103. Feed water to quencher 2188 is obtained from water supply 2172. The water from water supply 2172 is pumped to quencher 2188 by pump 2192 via pipe network 2196. Fluid 2182 containing fly ash and large particulates collected at the base of scrubbing assembly 2176 may pass though a filter system before being recycled back to the spraying nozzle 2180 of wet scrubber 2178 via pump 2184.

At regular intervals, the fluid 2182 at the base of scrubbing assembly 2176 may be discharged to treatment unit 2186 where it is chemically treated. The chemically treated fluid may be recycled back into wet scrubber 2178 or be discharged to a drainage system.

Optionally, exhaust gas 2194 released from scrubbing assembly 2176 may be connected to an air filter system for further treatment before being discharged to the atmosphere. Exhaust gas 2194 may also comprise saturated water vapour. Therefore, an evaporator may be installed at the gas outlet of scrubbing assembly 2176 to remove the saturated vapour in exhaust gas 2194 so as to prevent the formation of plume in the atmosphere. As a further option, the treated flue gas 2103 may also be passed through a gas filtration system before being discharged into the atmosphere to remove submicron sized particles.

Throughout the treatment process, the first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 are maintained at a negative pressure to ensure a correct draught is created for the flow of flue gas 2103 from the processing chambers 2104, 2106 and 2108 to steam boiler 2148 and scrubbing assembly 2176. For example, the pressure may be about - 50 Pa. The negative pressure in the first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108 may be achieved via a suction fan installed either at the flue gas discharge end of first processing chamber 2104, second processing chamber 2106 and third processing chamber 2108, or at the exhaust end of the scrubbing assembly 2176.