OF SOLID WASTE

FIELD OF THE INVENTION

This invention relates to an apparatus and method for the treatment of solid waste. More particularly, but not exclusively, this invention relates to an apparatus and method for the treatment of solid, carbonaceous waste such as municipal solid waste, industrial waste, food waste, bio waste, wood waste, medical waste, coal or tyre waste, or any other solid-state waste. BACKGROUND TO THE INVENTION

There are various methods for the treatment of carbonaceous waste products. A particular type of thermal treatment is done by means of pyrolysis, whereby carbonaceous material is combusted. Russian Federation patent number RU 2180950, describes a method of combustion of solid waste, wherein the waste contains halogens, sulphur and phosphorus, in this method, a mixture of waste, air and fuel is supplied to a reactor and combusted. Neutralizing additives are also supplied to the reactor by means of two streams. The first stream is an alkaline earth reagent stream, which is supplied to a combustion zone where the temperature is 800-1500 °C. The second stream is an alkaline reagent stream, which is supplied to a secondary combustion chamber for the secondary combustion of high temperature gaseous products. The secondary combustion chamber is a swirled cyclonic torch with the temperature of 1200-1500 °C. A disadvantage of the above mentioned method, however, is that it does not provide high efficiency combustion in the secondary combustion chamber. Further, the high temperature levels (1200 - 1500 °C) lead to a sharp increase in the concentration of NO _x . The long length of the combustion zone in the cyclonic torch also leads to an increase in residence time of the combustion products in the high temperature combustion zone, thereby also increasing NO _x levels. These high NO _x levels necessitate an increase of chemical reagents for its neutralization. Further to the above disadvantages, direct burning in the cyclonic torch requires the use of a protective wall in the secondary combustion chamber. The linear flow in the cyclonic torch does not assist in increasing the quality of carburetion, combustion and chemical reactions. The process is therefore not effective in reducing emissions.

Another known method for solid waste treatment is described in Russian Federation patent number RU 2249766. In this method, waste is separated and the organic portion of the waste is ground to a size of 100 mm, whereafter it is mixed with the air (300 - 400 °C). Thereafter, the waste-air mixture is delivered to a cyclonic oven, tangentially, with the velocity not lower than 28 m/sec. The combustion process takes place at a temperature of 1320 - 1350 °C. Gaseous waste from this step is then combusted in a secondary catalytic combustion chamber at a temperature of 1320 - 1500 °C. A cleanup process for HCi, Cl ₂ and HF takes place in a de-carbonisation chamber with limestone powder, and Ca(OH) ₂ is produced. Disadvantages of the above method for the treatment of municipal solid and industrial waste, is that it does not provide high efficiency combustion, or subsequent cleanup of combustion products at a temperature of 1300 - 1500 °C. The mentioned temperature range and the structure of the stream, leads to a sharp increase in the concentration of NO _x , especially in light of the long length of the combustion zone in the cyclonic torch, which, in turn, leads to an increase in residence time of the combustion products in the high temperature combustion zone. The increase of the NO _x , necessitates that chemical reagents used for neutralization of NO _x be increased. Apart from the foregoing, the secondary combustion and cleanup processes have to take place in two different devices, namely the secondary combustion chamber and decarbonisation chamber respectively.

Another known method, namely "PIROXEL technology", is described in an article "Technology of municipal solid, medical and industrial waste disposal", published in the magazine "Building and urban development in Sankt- Petersburg and Leningrad region" (Edition 1(123) 2011 , pg 111 - 113). In this technology, waste is delivered to a pyrolysis chamber, where the waste is heated and dried. The dried waste undergoes dry pyrolysis and gasification processes in the pyrolysis chamber. Gaseous combustion products are combusted in the secondary combustion chamber. A cleanup process of the gaseous combustion products takes place, whereby Na ₂ C0 ₃ is supplied at a temperature of 1100 X in order to clean up dioxins, furans, acids and anhydrides in a neutralisation chamber. A cleanup process of NO _x takes place in the recovery chamber, at a temperature 1050 °C, by supplying CO(NH ₂ )2 to the chamber Heat recovery of flue gases then takes place in the recovery boiler. Disadvantages of the above method, however, are that it does not enable high efficiency combustion and cleanup processes. Long residence times of combustion products at a high temperature zone leads to the sharp increases in concentration of the NO _x . These NO _x increases requires increases supplies of CO(NH ₂ )2 in the recovery chamber. The particular arrangement in structure of the processes in the secondary combustion, neutralisation and recovery chambers respectively, is not capable of enhancing the quality of combustion and cleanup. This is due to the fact that heat and mass transfer, as well as the chemical and physical processes are reliant on the structure and configuration of the streams.

Russian Federation patent number RU 2135895, describes an apparatus used for the combustion of solid waste. The apparatus includes a waste drying device, a reactor and a post combustion chamber. The reactor is in the form of a pyrolysis chamber joined to a furnace. The post combustion chamber and cleanup device for flue gases are located along the flow of the gases in front of a scrubber-cooler, and is in the form of a thermo-chemical reactor in which its shell is divided into three chambers by means of vertical partitions. The first chamber is connected via a gas exhaust to the inner volume of the pyrolysis chamber. An oxidizer inlet is located above the post-combustion chamber inlet. The first chamber is connected, via an aperture in the upper part of the partition, to the second chamber, where the reagent supplying device is located for cleaning acids and anhydrides. The second chamber is connected, via the aperture in the lower part of the partition, to the third chamber. The reagent supplying device, for NO _x recovery, is located on the third chamber. The third chamber is also connected to a heat exchanger.

A disadvantage of the above mentioned apparatus is its big size. Also, as a result of the configuration of the streams, heat transfer and chemical-physical processes are not efficient.

A further, known apparatus for solid waste treatment is described in Russian Federation patent number RU 2249766. This apparatus includes a cyclonic combustion chamber with a tangential inlet for shredded waste and heated air, a catalytic post combustion chamber (which works on a principal of flameless combustion), a lime supplier, an air heater, a heat exchanger and a wet gases cleanup device. The lime de-carbonisation chamber is a vertical chamber, wherein hot gases move from a lower zone to an upper zone and lime, initially dispersed in the upper zone, moves to the lower zone. A disadvantage of this apparatus is its big size and low efficiency.

OBJECT OF THE INVENTION

It is accordingly an object of the present invention to provide an apparatus and method for the treatment of solid waste, with which the above disadvantages may be overcome or minimised, or which may provide a useful alternative to existing technologies.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided an apparatus for the treatment of substantially solid or carbonaceous waste including:

- a housing defining a chamber within the housing, the housing having a first end and a second end;

- at least one solid waste inlet for receiving substantially solid or carbonaceous waste;

- at least one reagent inlet for receiving reagents;

- at least one ash outlet; and

- at least one gas outlet; wherein the at least one gas outlet is adapted to be in fluid flow communication with at least one gas-treatment apparatus.

The chamber defined within the housing may be pyrolysis chamber.

The substantially solid waste may be selected from the group including municipal waste, industrial waste, food waste, bio waste, wood waste, tyre waste, medical waste or any other solid or carbonaceous waste. The substantially solid waste may include moisture.

The reagents may be chemical reagents. The gas from the gas outlet may be a synthetic gas selected from the group including carbon monoxide, carbon dioxide and hydrogen, or pyrolysis gas which is produced by pyrolysis of the carbonaceous material. The gas outlet may be in the form of an annular passage.

The apparatus may have at least two gas conduits (or pipes) leading from the gas outlet, a first and a second gas conduit. The first gas conduit is adapted to be in fluid flow communication with a first gas treatment apparatus and the second gas conduit is adapted to be in fluid flow communication with a second gas treatment apparatus.

The apparatus may have at least two additional reagent inlets located at the first and second gas conduits respectively.

The solid waste inlet is positioned to the first side of the housing. The solid waste inlet in the housing further is connected to a waste loading device, including a hopper adapted to receive the solid or carbonaceous waste. The waste loading device may include an actuator for feeding the waste into the chamber. The actuator of the waste loading device may be an electric gear actuator or alternatively a pneumatic or hydro-pneumatic actuator.

The two gas conduits and two additional reagent inlets are also positioned to the first side of the housing. The ash outlet is positioned at an opposite, second end of the housing. Each of the reagent inlets may be connected to a respective dosing device, for purposes of regulating the flow of reagents from said dosing devices.

The apparatus further includes a primary gasifying agent inlet, located towards the second end of the housing. The primary gasifying agent inlet includes a rotating device, in the form of a plurality of radial ribs, with apertures defined between each pair of ribs. The rotating device, with its plurality of radial ribs, is rotatable within the housing by means of a device actuator. The device actuator may be an electrical motor gear.

The plurality of radial ribs ensures that the primary gasifying agent is rotated as it enters the pyroiysis chamber. The rotation of the primary gasifying agent, in turn, serves to rotate the waste in the pyroiysis chamber. The primary gasifying agent inlet is in fluid flow communication with a hot air inlet, for purposes of ensuring that both hot air and primary gasifying agent enter the pyroiysis chamber as an air-gasifying agent mixture.

The primary gasifying agent and/or hot air may be supplied from external sources.

The ash outlet may be an annular ash outlet and may lead to an ash collection chamber. The ash outlet may be defined around the primary gasifying agent inlet by means of radial blades, located on the lateral cylindrical surface of the primary gasifying agent inlet. The radial blades serve to direct ash from the lower part of the pyrolysis chamber to the ash collection chamber. The apparatus may further include at least one secondary gasifying agent inlet. Preferably, the apparatus may include two secondary gasifying agent inlets. Each secondary gasifying agent inlet may be provided with one or more burners. The burners operate in a pulsating manner and are connected to an external fuel source. The fuel source may be liquid waste.

The apparatus may further include at least one heater or heat-exchanger. These heaters may be air heaters, in fluid flow communication with an external air source via one or more air inlets. The air heaters may also have one or more air outlets, which lead to the hot air inlet located at the primary gasifying agent inlet. The apparatus also includes thermo couples or temperature sensors.

The apparatus also may include mesh filter positioned in the pyrolysis chamber.

The apparatus may be cylindrical.

The first and second gas treatment apparatus, or afterburners, each include a housing having an outer wall and an inner wall, an annular passage defined between the outer wall and inner wall of the housing, through which air is flowabie; a combustion chamber; supplementary fuel inlets, a gas inlet, an air inlet and an outlet; the gas inlet leading to a primary fuel distributor consisting of a plurality of hollow blades, each hollow blade defining an internal compartment within the blade, which internal compartments are in fluid flow communication with the air inlet via respective blade entrances; the blades further defining inter-blade passages between them, which passages are in fluid flow communication with the gas inlet and the combustion chamber; and each blade further having an aperture in fluid flow communication with the combustion chamber, through which air in the internal compartment can exit the blades.

The gas inlet of each gas treatment apparatus is in fluid flow communication with the respective gas conduits of the apparatus for the treatment of solid waste. Each gas conduit extends from the annular gas outlet in the pyrolysis chamber of the apparatus.

Each gas treatment apparatus may include a boiler, more specifically a recovery boiler, for purposes of heat recovery. The recovery boiler may contain heat exchangers. The heat exchangers may be modular and interchangeable.

According to a second aspect of the invention, there is provided a method for the treatment of substantially solid or carbonaceous waste, which method includes the steps of:

- providing a waste treatment apparatus including a housing defining a chamber within the housing and the housing having a first end and a second end;

- allowing waste to be received into a hopper, leading to a waste loading device;

- feeding the waste into the chamber of the apparatus via at least one waste inlet;

- providing reagents to the chamber via at least one reagent inlets;

- allowing a mixture of gasifying agent and air to enter the chamber via one or more gasifying agent inlets;

- allowing the waste in the chamber to be heated and dried;

- allowing the dried waste to be ignited and combusted by means of burners;

- allowing ash produced during the combustion to pass through an ash outlet and be collected in an ash collection chamber; and

- allowing outlet gas to move through a mesh filter and be removed from the apparatus via a gas outlet leading to gas conduits, whereafter the outlet gas is fed via the gas conduits to one or more gas-treatment apparatus.

The chamber defined within the housing may be pyrolysis chamber. The substantially solid waste may be selected from the group including municipal waste, industrial waste, food waste, bio waste, wood waste, tyre waste, medical waste or any other solid or carbonaceous waste. The substantially solid waste may include moisture. The reagents may be chemical reagents.

The outlet gas may be a synthetic gas selected from the group including carbon monoxide, carbon dioxide and hydrogen, or pyrolysis gas which is produced by pyrolysis of carbonaceous material.

The gas outlet may be in the form of an annular passage.

The apparatus may have at least two gas conduits (or pipes) leading from the at least one gas outlet, a first and a second gas conduit. The first gas conduit is adapted to be in fluid flow communication with a first gas treatment apparatus and the second gas conduit is adapted to be in fluid flow communication with a second gas treatment apparatus.

The apparatus may have two additional reagent inlets located at the first and second gas conduits respectively.

The solid waste inlet is positioned to a first side of the housing. The solid waste inlet in the housing further is connected to the waste loading device, which includes the hopper adapted to receive the solid or carbonaceous waste. The waste loading device may include an actuator for feeding the waste into the chamber. The actuator of the waste loading device may be an electric gear actuator or alternatively a pneumatic or hydro-pneumatic actuator.

The two gas conduits and two additional reagent inlets are also positioned to the first side of the housing. The ash outlet is positioned at an opposite, second end of the housing. Each of the reagent inlets may be connected to a respective dosing device, for purposes of regulating the flow of reagents from said dosing devices.

The apparatus further includes a primary gasifying agent inlet, located towards the second end of the housing. The primary gasifying agent inlet includes a rotating device, in the form of a plurality of radial ribs, with apertures defined between each pair of ribs. The rotating device, with its plurality of radial ribs, is rotatable within the housing by means of a device actuator. The device actuator may be an electrical motor gear. The plurality of radial ribs ensures that the primary gasifying agent is rotated as it enters the pyrolysis chamber. The rotation of the primary gasifying agent in turn serves to rotate the waste in the pyrolysis chamber.

The primary gasifying agent inlet is in fluid flow communication with a hot air inlet, for purposes of ensuring that both hot air and primary gasifying agent enter the pyrolysis chamber as an air-gasifying agent mixture. The primary gasifying agent and/or hot air may be supplied from external sources. The ash outlet may be an annular ash outlet and may lead to an ash collection chamber. The ash outlet may be defined around the primary gasifying agent inlet by means of radial blades, located on a lateral cylindrical surface of the primary gasifying inlet. The radial blades serve to direct ash from the lower part of the pyrolysis chamber to the ash collection chamber.

The apparatus may further include at least one secondary gasifying agent inlet. Preferably, the apparatus may include two secondary gasifying agent inlets. Each secondary gasifying agent inlet may be provided with one or more burners. The burners operate in a pulsating manner and are connected to an external fuel source. The fuel source may be liquid waste.

The apparatus may further include at least one heater or heat-exchanger. These heaters may be air heaters, in fluid flow communication with an external air source via one or more air inlets. The air heaters may also have one or more air outlets, which lead to the hot air inlet located at the primary gasifying agent inlet. The apparatus also includes thermo couples or temperature sensors.

The apparatus also may include mesh filter positioned in the gasification chamber.

The apparatus may be cylindrical. The first and second gas treatment apparatus, or afterburners, each include a housing having an outer wall and an inner wall, an annular passage defined between the outer wall and inner wall of the housing, through which air is flowable; a combustion chamber; supplementary fuel inlets, a gas inlet, an air inlet and an outlet; the gas inlet leading to a primary fuel distributor consisting of a plurality of hollow blades, each hollow blade defining an internal compartment within the blade, which internal compartments are in fluid flow communication with the air inlet via respective blade entrances; the blades further defining inter-blade passages between them, which passages are in fluid flow communication with the gas inlet and the combustion chamber; and each blade further having an aperture in fluid flow communication with the combustion chamber, through which air in the internal compartment can exit the blades.

The gas inlet of each gas treatment apparatus is in fluid flow communication with the respective gas conduits of the apparatus for the treatment of solid waste, via a gas passage or pipe. Each gas conduit extends from the annular gas outlet in the pyrolysis chamber of the apparatus.

Each gas treatment apparatus may include a boiler, more specifically a recovery boiler, for purposes of heat recovery. The recovery boilers may contain heat exchangers. The heat exchangers may be modular and interchangeable. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further by way of non-limiting examples with reference to the accompanying drawings wherein:

Figure 1 is a longitudinal cross sectional view of the waste treatment apparatus of the invention;

Figure 2 is a top view of the apparatus of Figure 1 ;

Figure 3 is a radial cross sectional view along line ΙΙΙ-ΙΙ of the apparatus of Figure 1 ;

Figure 4 is a front view of the apparatus of Figure 1 according to a first embodiment of the invention;

Figure 5 is a longitudinal cross sectional view of a gas treatment apparatus according to a first embodiment;

Figure 6 is a cross sectional view along line VI-VP;

Figure 7 is a is a partial cross sectional view of a gas treatment apparatus and recovery boiler according to a second embodiment of the invention; and

Figure 8 is a front view of the apparatus of Figure 1 according to a second embodiment of the invention. DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to the drawings, an apparatus for the treatment of substantially solid or carbonaceous waste according to the invention is generally designated by reference numeral 10.

The apparatus 10 includes a housing 12 defining a chamber 14 within the housing 12, at least one solid waste inlet 16, at least one reagent inlet 18, at least one ash outlet 20 and at least one gas outlet 22 (shown on figure 3), wherein the at least one gas outlet 22 is adapted to be in fluid flow communication with at least one gas-treatment apparatus 24.

The chamber 14 defined within the housing 12 is a pyrolysis chamber 14.

The apparatus also has two gas conduits 23, leading from the gas outlet 22, namely a first and a second gas conduit (23a and 23b). The first gas conduit 23a is adapted to be in fluid flow communication with a first gas treatment apparatus 24a and the second gas conduit 23b is adapted to be in fluid flow communication with a second gas treatment apparatus 24b. The apparatus has two additional reagent inlets 19, a first and a second reagent inlet (19a and 19b), at the first and second gas conduits (23a, 23b) respectively. A further reagent inlet is also provided for the gas treatment apparatus 24. The solid waste inlet 16 is positioned to a first side of the housing 12. The solid waste inlet 16 in the housing further is connected to a waste loading device 28, including a hopper 30 adapted to receive the solid or carbonaceous waste. The waste loading device 28 includes an actuator with a reducer 48 for feeding the waste into the chamber 14. The actuator 48 of the waste loading device 28 is an electric gear actuator or a pneumatic or hydro-pneumatic actuator. The waste loading device 28 (figure 1) functions in an automatic manner and has two gate-valves (50 and 52), namely an inlet gate-valve 50 and an outlet gate- valve 52. The two gate valves function in a pulsating manner, i.e. the open in an alternating manner to ensure that no heat losses occur from the chamber 14. The automatic waste loading device 28 (figure 1) is in fluid flow communication with the inner volume of the gasification chamber 14 via the inlet 16. The two gas conduits (23a and 23b) and two additional reagent inlets (19a and 19b) are positioned to the first side/end of the housing. The ash outlet 20 is positioned at an opposite, second end of the housing 12. Each conduit (23a, 23b) connects tangentially to the respective gas treatment apparatus (24a, 24b).

Each of the reagent inlets are connected to respective dosing devices (for example dosing device 32 for reagent inlet 18), for purposes of regulating the reagents entering the pyrolysis chamber 14. The reagent inlet 18 has dosing device 32. The dosing devices for the additional reagent inlets are not shown in the drawings.

The apparatus 10 further includes a primary gasifying agent inlet 34, located towards the second end of the housing. The primary gasifying agent inlet 34 includes a rotating device, in the form of a plurality of radial ribs 36, with apertures defined between each pair of ribs 36. The rotating device, in the form of a plurality of radial ribs 36, is rotatable within the housing 12 by means of an actuator 35. The plurality of radial ribs 36 ensures that the primary gasifying agent is rotated as it enters the pyrolysis chamber 14. The rotation of the primary gasifying agent in turn serves to rotate the waste in the pyrolysis chamber 14.

The primary gasifying agent inlet 34 is in fluid flow communication with a hot air inlet 37, for purposes of ensuring that both hot air and primary gasifying agent enter the pyrolysis chamber 14 as an air-gasifying agent mixture.

The primary gasifying agent and/or hot air is supplied from external sources. The ash outlet 20 is an annular ash outlet and leads to an ash collection chamber 26. The ash outlet 20 is defined around the primary gasifying agent inlet 34 by means of radial blades 41 , located on a lateral cylindrical surface of the primary gasifying inlet 34. The radial blades 41 serve to direct ash from the lower part of the pyrolysis chamber 14 to the ash collection chamber 26. The apparatus further includes at least one secondary gasifying agent inlet 38. Preferably, the apparatus includes two secondary gasifying agent inlets (38a, 38b). Each secondary gasifying agent inlet (38a, 38b) is provided with one or more burners (not shown). The burners operate in a pulsating manner and are connected to an external fuel source. The fuel source is a liquid waste. The secondary gasifying agent is a mix of air and fuel from external sources. The apparatus also include at least one heater 42 or heat-exchanger. These heaters 42 are air heaters, in fluid flow communication with an external air source via one or more air inlets 44. The air heater 42 is built into a middle part of the wall of the housing 12. The air heaters have one or more air outlets (not shown), which lead to the hot air inlet 37 at the primary gasifying inlet 34. The apparatus also includes thermo couples or temperature sensors (not shown).

The apparatus further includes a mesh filter 46 (figure 3) positioned in the chamber 14. In a preferred embodiment of the present invention, the apparatus 10 is cylindrical.

The primary gasifying agent inlet 34 ensures a consistent supply of the gasifying agent via apertures defined in-between the sparger-like radial ribs 36. Due to the positioning of the radial ribs 36 and blades 41 , and the rotation thereof, the constant feed of gasifying agent and/or air mixture into the pyrolysis chamber 14 ensures that waste in the chamber 14 is constantly being rotated around a central axis of the chamber 14. The radial blades 41 of the ash outlet 20 guide ash to the ash collection chamber 26.

The secondary gasifying agent inlets (38a, 38b) are located on a lateral wall of the apparatus 10. The secondary or supplementary gasifying agent is air and/or products of the combustion of the air and fuel supplied from an external source. The gasifying agent inlets (38a, 38b) each includes burners (not shown).

The secondary gasifying agent inlets (38a, 38b) is connectable to a liquid waste tank and are adapted utilise liquid waste, which includes a hydrocarbon components, as fuel.

The waste loading device 28 (figure 1) functions in an automatic manner and includes the hopper 30, an electric gear with a reducer 48, and gate-valves (50, 52) in association with the electric gear, namely an inlet gate-valve 50 and an outlet gate-valve 52. The automatic waste loading device 28 (figure 1 ) is in fluid flow communication with the inner volume of the pyrolysis chamber 14 via the inlet 16. The combustion products outlets 22 (figure 3) is located in the upper part of the pyrolysis chamber 14 (figure 1) above the inlet 16. The combustion products are in the form of a steam-gas mixture. The outlet 22 (figure 3) includes an annular passage 54, defined between an inner lateral cylindrical surface of the pyrolysis chamber 14 and its conical shell 56, which tapers towards the first, operative top end of the apparatus 10.

A mesh filter 46 (figure 1 and 3) is located in between the inner lateral cylindrical surface of the gasification chamber 14 and the conical shell 56, perpendicular to a central axis of the pyrolysis chamber 14.

The annular passage 54 (figure 3) is connected tangentially to the one or more gas conduits, or piped outlets (23a, 23b). The outlets 23 tangentially lead to the respective gas treatment apparatus 24, also referred to as "afterburners" (figure 5).

The additional chemical reagent inlets (19a, 19b) are located on each of these conduits (23a, 23b). The chemical reagents are supplied not only to the pyrolysis chamber 14 of the apparatus 10, but also to the gas treatment apparatus 24 via these additional reagent inlets.

Referring to figure 5, the gas treatment apparatus 24, includes a housing having an outer wall 58, an inner wall 60 and an annular passage 62 being defined between the outer wall 58 and inner wall 60, through which air is flowable, as well as a combustion chamber 64 and supplementary fuel inlets 66.

The gas treatment apparatus 24 also includes a solid-fraction separation device 68 and a solid fraction collector 70, located at an opposite end to the supplementary fuel inlets 66.

Referring to figure 6, each gas treatment apparatus 24, includes a primary fuel distributor 71 consisting of a plurality of hollow blades 72 (figure 6), each hollow blade 72 defining an internal compartment 74 within the blade, which internal compartments 74 are in fluid flow communication with an air inlet 88 (figure 3) via respective blade entrances (not shown); the blades 72 further defining inter-blade passages 76 between them, which passages 76 are in fluid flow communication with the outlet 22 (figure 3) of the apparatus 10, and are also in fluid flow communication with the combustion chamber 64; and each blade 72 further having an aperture 78 in fluid flow communication with the combustion chamber 64, through which air in the internal compartments 74 can exit the blades. The gas treatment apparatus 24 includes one or more gas-treatment reagent inlets 80 and an ignition source in the form of a burner (not shown).

The outlet gas from the pyrolysis chamber 14 is fed to the gas treatment apparatus 24. This outlet gas will function as primary fuel for the gas treatment apparatus and is in the form of combusted products (steam-air mixture or gaseous waste). The gaseous waste could be a synthetic gas selected from the group including carbon monoxide, carbon dioxide and hydrogen, or pyrolysis gas which is produced by pyrolysis of carbonaceous material. The gas treatment apparatus 24 has an inlet 84 for this primary fuel (outlet gas from the apparatus 10 via conduits 23).

The primary fuel inlet 84 and combustion products outlet 86 (figure 6) are located at the first end of the gas treatment apparatus 24. The gas treatment apparatus 24 further contains a second end, opposite to the primary fuel inlet 84 and the combustion products outlet end.

The air inlet 88 (figure 3) is located towards the second end. The air inlet 88 is further provided tangentially to the outer wall 58 of the gas treatment apparatus 24 (figure 5). The air inlet 88 is in the flow communication with the annular passage 62 of the gas treatment apparatus 24. The annular passage 62 serves as a cooling jacket as it provides insulation.

A solid fraction outlet is located at the second end of the gas treatment apparatus 24. A solid fraction, that is solid residue, is removed via apertures in the operative lower end of the solid fraction separation device 68, from where it moves to the collector 70. Flue gases are withdrawn to a recovery boiler 90, which boiler 90 serves to produce energy via a heat recovery step. The recovery boilers 90 contain heat exchangers, which could be modular and interchangeable.

In the present embodiment of the invention, where a water/air heat exchanger is used, flue gas is withdrawn via the outlet channel 86 to the recovery boiler 90, where it passes through a heat exchanger 100. In the heat exchanger 100, cold water enters via cold water inlet 101. The flue gas is cooled and exists via flue gas outlet 102. During the heat exchange process, the cold water is heated and hot water exists via hot water outlet 104. The cooled flue gas from the flue gas outlet 102, finally exits via a chimney (not shown). The above constitutes the heat-recovery step.

In one embodiment of the invention, as per figure 4, the gas treatment apparatus 24 and recovery boiler 90 are separate from each other and are provided in succession of each other.

In an alternative embodiment of the invention, as per figures 7 and 8, the gas treatment apparatus 24 is provided within the recovery boiler 90.

The method for treating solid waste is as follows: Waste is delivered to the pyrolysis chamber 14, where it is combusted. The gaseous combustion products are flown to the gas treatment apparatus 24, which serves as a secondary combustion chamber 24, for secondary combustion and clean-up, while energy production takes place in the recovery boiler 90. The combustion process and cleanup process are performed sequentially in several stages, namely heating, followed by thermal decomposition and gasification of the waste. Gasification of the waste take place at a temperature of 700 - 900 °C in the presence of a mixture of chemical reagents, Ca(OH)2 and/or CaC03, which serve to clean up HCi, Cl ₂ , HF, SO2 and P4O-10 present.

During the above heating and thermal decomposition process, CaCi ₂ , CaF ₂ , CaS0 ₄ and Ca ₃ (P0 ₄ )2 are formed. These compounds are subsequently removed from the pyrolysis chamber 14, together with any other solid residue, via the ash removing device 26.

The gasifying agent used in the process could be air, or combustion products in the form of an air-fuel mixture provided from an external sources. The gasifying agent is supplied in a pulsating manner. These pulsations of gasifying agent, contributes to the intensity of the chemical reactions taking place during gasification and neutralisation (of HCi, Ci ₂ , HF, S0 ₂₎ P ₄ Oio) respectively.

The temperature of between 700 and 900 °C in the pyrolysis chamber, allows the waste to dry and decompose. It further assists with gasification and the creation of a steam-gas mixture (gaseous waste or primary fuel) with a high calorific value. The calorific value is an important factor in ensuring that the maximum possible temperature is obtained in the combustion zone of the secondary combustion chamber or gas treatment apparatus 24. The air and steam-gas mixture are divided into a number of individual and alternating jet streams, which is delivered to one, or a number of, the gas treatment apparatus 24 for the secondary combustion process, which takes place at temperatures of between 1350 and 1800 °C. The gas-treatment apparatus 24 includes a counter current, vortex combustion chamber 64.

In this part of the process, Ca(OH) ₂ or CaC0 ₃ firstly are supplied to clean the rest of the HCt, Cl ₂ , HF, S0 ₂ , P ₄ O ₁₀₎ CO, C _x H _y and CH ₄ . Produced neutral salts are then removed. CO(NH ₂ )2 secondly is supplied in order to clean NO and NO ₂ and reduce CO ₂ . The N ₂ and H ₂ O that are produced, are removed with the flue/outlet gases.

The separation of the air and combustion products into a number of alternate jet streams, its acceleration in a primary fuel distributor 71 (where the air is an ejecting jet stream and the combustion products is an ejected jet stream) leads to increased combustion efficiency. The combustion efficiency is linked to the maximum velocity of the ejecting air, which provides a specified ejection coefficient. Therefore, the amount of waste combusted, and the combustion efficiency, can be pre-determined according to the velocity of the ejecting air.

The use of all the accelerated air jets as an ejecting stream, facilitates in obtaining a maximum kinetic energy at the outlet 86 (primary fuel distributor outlet 86) and provides a specific ejection co-efficient for the burning of the combustion products. This ensures the reduction of the pyrolysis gas pressure to below atmospheric, without requiring an increase of energy consumption which conventionally would be needed to increase the pressure of the supplied air. A reduction of the gas pressure in the gas treatment apparatus inlet 84, to below atmospheric, leads to the creation of a vacuum in the chamber. This vacuum prevents any leakage of gaseous products to the atmosphere.

In the gas treatment apparatus 24, a strong swirling stream, or vortex, is formed. This external peripheral vortex flows from the primary fuel distributor 71 , along the walls of the combustion chamber 64, towards the second end of the combustion chamber 64, which is in counter flow to the internal central axial stream, flowing in the centre of the combustion chamber 64 towards the outlet channel 86. This two counter current streams swirl in the same direction. The prepared primary fuel-air mixture is ignited by the burner (not shown). The high temperature in the combustion zone leads to the decomposition of all organic compounds of the gaseous waste, and oxidation of CO to CO ₂ .

The relatively short residence time of the gaseous waste in the combustion chamber 64 prevents excessive levels of NO and NO2. Two or more gas treatment apparatus 24 with combustion chambers 64, facilitate in the reduction of the combustion zone lengths which, in turn, reduces the residence time of the combustion products in the chambers 64. This restricts the formation of NO and NO ₂ . Delivery of the alternate accelerated air and primary fuel jets tangentially to the combustion chamber 64, leads to the formation of the strong vortices of the fuel-air mixture. The external peripheral vortex is in counter flow to the internal central stream of the fuel-air mixture flowing in the centre of the combustion chamber 64, with both counter current streams swirling in the same direction. Due to the two streams flowing in a counter-current manner, high radial and axial gradients of static pressure is created. The configuration of the streams lead to fully developed anisotropic turbulence, which prevails in the radial direction, and the generation of both low and high frequency acoustic waves. This, in turn, facilitates lower emission rates, so as to meet environmental standards.

A reduction in emissions levels are attributed to the following:

- Increase efficiency of carburetion, combustion and clean up of CO, C _x H _y , CH ₄ , hydrocarbons, residual Cl, Cfe, HF, SO ₂ and P ₄ Oi ₀ ;

- Reduction of NO ₂ and CO ₂ levels; and

- The formation of N ₂ and H ₂ O in the secondary combustion chamber.

Due to a reduction in diameter of the external peripheral vortex (which flows from the primary fuel distributor 71 ) and the supply of Ca(OH) ₂ and/or CaCO ₃ , followed by CO(NH ₂ ) ₂ , the formation and concentration of neutral salts are increased. These neutral salts are removed from the secondary combustion chamber 64 with the external peripheral stream. To stabilize the combustion process of any diluted gaseous products (i.e. gas with a low calorific value), a high calorific value supplementary fuel is delivered from an external source. The supplementary fuel may be a liquid waste with carbonaceous components.

In use, solid, carbonaceous waste from the waste loading device 28 is delivered to the pyrolysis chamber 14. The inlet gate-way valve 50 and outlet gate-way valve 52 (with its electric engine) seal the inner volume of the waste loading device 28 and the inner volume of the combustion chamber 14. By means of an electric gear (or pneumatic or hydro-pneumatic means) acting as actuator at the reducer 48 of the device 28, the waste is delivered to the pyrolysis chamber 14 via inlet 16. From the chemical reagents inlet 18, by means of its associated dosing device 32, the chemical reagents are delivered to the pyrolysis chamber 14. The pyrolysis chamber 14 is filled with a mixture of the waste and the chemical reagents from the lower end of the chamber 14 up to inlet 16. Supplementary air and fuel are delivered to the secondary gasifying agent inlets (38a, 38b). The prepared air-fuel mixture is ignited by the burners, associated with the secondary gasifying agent inlets (38a, 38b). The start up of the pyrolysis chamber 14 and the combustion chamber 64 occur simultaneously.

Temperature sensors provide an indication that the process is active. The air from the external source is delivered via the air inlet 44 to the air-heater 42. From there, the heated air (from outlet 45 and connected to pipe 37) is delivered to a gasification zone of the pyrolysis chamber 14 consistently and evenly via apertures in-between the ribs 36 of the primary gasifying agent inlet 34. The radial ribs 36 act as spargers. The combustion process in the gasification chamber 14 includes (a) waste heating (b) waste drying (c) pyrolysis and (d) gasification. The burners of the secondary gasifying agent inlets (38a, 38b) operate in a pulsating mode or manner, which intensifies the combustion process. The secondary gasifying agent inlets (38a, 38b) are connected to a liquid-waste external source where liquid waste (with organic components) is used as a supplementary fuel source. The use of the supplementary fuel serves to increase the temperature in the pyrolysis chamber, in cases where the solid waste fed into the chamber 14 has a too low calorific value or the solid waste has a high moisture content. The radial ribs 36 on the outer wall of inlet 34, aid the waste in mixing and rotating around the central axis of the chamber 14 in the gasification zone. This also serves to intensify combustion. Further, the radial blades 41 guide ash into the ash collection device 26. The steam-air mixture flows through the mesh filter 46, whereafter it is delivered to the annular passage 54. Through one or more apertures (figurel) in the wall of the pyrolysis chamber 14, the steam-air mixture flows to the gas outlet 22 (figure 3) and then to the gas conduits 23. The gas conduits 23 are tangentially connected to the annular passage 54 of the pyrolysis chamber 14. This leads to the formation of strong vortices in the annular passage 54 and reduces the loss of pressure of the steam-air mixture at the outlet 22. Each gas conduit 23 is tangentially connected to respective gas treatment apparatus 24. This also aids in the reduction in pressure loss of the steam-air mixture at the inlet 84 of each gas treatment apparatus 24.

Chemical reagents are then delivered to the combustion chamber 64 of each gas treatment apparatus 24 via reagent inlets 19. The secondary combustion chamber 64 is adapted to function simultaneously as a neutralisation chamber and a recovery chamber. The manufacturing process is, therefore, simplified, as one chamber can perform multiple functions. Less manufacturing material (metal) is needed, the overall apparatus is smaller and costs are saved.

Outlet gas from the apparatus 10, in the form of a mixture of gas or primary fuel (the steam-gas mixture), and chemical reagents, are delivered to the gas treatment apparatus 24 via outlet 22 (leading to conduits 23a and 23b), from where it moves onto inter-blade passages 76. This gas mixture is ignited by the burner (not shown). The process of combustion of the primary fuel-air mixture forms a combustion zone, an intermediary zone and dilution zone and is carried out in the central axial stream. Flue/outlet gas is withdrawn via outlet channel 86 to the recovery boiler 90, from where heat recovery takes place.

The reagent inlet 80 for the gas treatment apparatus 24, is in the form at least one injector 80, which is connected to a supplementary chemical reagent dosing device. Solid fractions are separated in the separation device 68 and moves to collector 70.

Flue gas is withdrawn from the apparatus 24 via the outlet channel 86 to the recovery boiler 90, where it passes through a heat exchanger 100. In the heat exchanger 100, cold water enters via cold water inlet 101. The flue gas is cooled and exists via flue gas outlet 102. During the heat exchange process, the cold water is heated and hot water exists via hot water outlet 104. The cooled flue gas from the flue gas outlet 102, finally exits via a chimney. The above constitutes the heat-recovery step.

In one embodiment of the invention, as per figure 4, one part of the gas treatment apparatus 24, namely the part including the combustion chamber, and a second part of the gas treatment apparatus, namely the recovery boiler 90 are separate from each other and are provided in succession of each other. In an alternative embodiment, the gas treatment apparatus is located within the recovery boiler.

The purpose of the injection of supplementary fuel to the combustion chamber 64 is to ensure a high temperature in the combustion zone (of no less than 1 600 °C).

A solid material fraction (following the combustion process in the combustion chamber 64) is separated in the solid fraction separation device 68 and is removed via the end aperture in the lower part of the device 68 to the collector

70.

This invention can be implemented in any waste treatment combustion systems, furnaces or gas generators.

Various components of the present invention may be modular and interchangeable. The invention also provides for the apparatus 10 to generate electricity, either via a steam to electricity step (if used in conjunction with a steam turbine) or a syngas to electricity step (if used in conjunction with a gas engine).

EXAMPLE OF THE INVENTION

To illustrate the method of the present invention, municipal solid waste will be used as an example.

The municipal solid waste, in an unsorted state, is conventionally provided at a rate of 12 500 kg/day. The composition of the waste, in mass percentage, is as follows:

Paper and Cardboard: 31.00 %;

Leather, Rubber: 1.00 %:

Glass: 3.00 %; Polymers, Plastics: 7.00 %;

Wood: 2.00 %;

Textiles: 5.00 %;

Food Waste: 34.00 %;

Inert Waste (Slag): 2.00 %;

Miscellaneous Small Matter: 9.00 %;

Metals: 6.00 %.

Total: 100.00 %

During a separation step, prior to the waste being fed to the waste treatment apparatus 10, all non organic waste components (metals, ceramics, glass etc.) are removed. Normally these components constitute 20 % of the waste. Consequently, of the initial 12,500 kg/day municipal solid waste, 10 000 kg/day is fed to the apparatus, with its composition, in mass percentage, as follows:

Paper and Cardboard: 3 875.00 kg/day (38,75 %);

Leather, Rubber: 125.00 kg/day (1 ,25 %);

Wood: 250.00 kg/day (2,50 %);

Textile: 625.00 kg/day (6,25 %);

Food Waste: 4250.00 kg/day (42,50 %);

Polymers, Plastic: 875.00 kg/day (8,75 %).

Total: 10 000.00 kg/day (100 %) The average calculated moisture of the organic waste after the initial separation step is 42 - 43 %. In the chamber 14 of the apparatus 10, the waste is dried. The weight of the municipal solid waste in an absolute dry state is 5776.00 kg.

The average composition of the dried municipal solid waste, in mass percentage, is as follows: Carbon 51.20 %;

Hydrogen 6.90 %;

Oxygen 31.42 %;

Sulphur 0.22 %;

Chlorine 0.35 %;

Nitrogen 2.71 %;

Ash 7.20 %.

Consequently, the mass of the individual components of the 5776.00 kg of dried waste, is as follows:

Carbon 2957.31 kg

Hydrogen 398.54 kg

Oxygen 1814.82 kg

Sulphur 12.71 kg Chlorine 20.22 kg

Nitrogen 156.53 kg

Ash 415.87 kg

After the drying step, the gasifying agent (in the form of air and/or combustion products - i.e. an air-fuel mixture) is provided at 10.30 ton/day.

An outlet gas is then produced by the treatment process of the municipal solid waste, the gas having a wet and a dry fraction. The amount of wet outlet gas produced is 19.12 ton/day (19,025 thousand nm ³ /day), while the amount of dry outlet gas produced is 13.96 ton/day (12,6 thousand nm ³ /day).

The specification of outlet gas produced in this example, is as follows:

Density of the Dry gas: 1.2 kg/nm ³ ;

Temperature at the chamber outlet: 600 - 700 °C;

Calorific value of the Wet gas: 4.27 MJ/kg (4.4 MJ/nm ³ ); and

Moisture of the gas: 5160.4 kg (27,0 %).

Dry gas content (before gas clean-up process) (mass %):

CO ₂ 12,2 %;

CO 22.27 %; CH ₄ 3.15 %;

C ₂ H ₄ 0.55 %;

H ₂ 0.53 %;

H ₂ S 0.07 %;

N ₂ 57.16 %;

CI 0.03 %;

Resin Vapour 4.06 %.

Ash output is 922.0 kg.

The following step in the process is the gas clean-up step, which takes place in three stages.

The first stage of gas clean-up takes place as follows: · CaC0 ₃ or Ca(OH) ₂ is supplied to the pyrolysis chamber 14 to cleanup HCl, Ct _2> HF, S0 ₂ , P4O10;

• CaC½, CaF ₂ , CaS0 ₄ , Ca ₃ (P0 ₄ ) ₂ is formed and removed from the chamber 14;

• The average amount of chemical reagent supplied to the chamber 14 is 70 -165 kg/day, the amount being dependent on the percentage of harmful substances present; The average diameter of the chemical reagent particles are 0.15 mm;

From the chamber 14, the outlet gas proceeds to the gas treatment apparatus 24, for a combustion process in the presence of air;

The air flow rate in the combustion chamber of the gas treatment apparatus is 75,706 ton/day (58,5 thousand nm ³ /day).

The second stage of gas clean-up takes place as follows: · CaC0 ₃ or Ca(OH)2 is supplied to the combustion chamber to clean up the remaining Ct, Cl ₂ , HF, S0 ₂ , P ₄ O _m CO, C _x H _y , CH ₄ etc;

• The amount of reagent supplied is 10 - 20 kg/day, the amount again being dependent on the amount of harmful substances present; · The total daily amount of Ca(OH) ₂ is 80 - 185 kg/day.

The third stage of gas clean-up takes place as follows:

• CO( H2)2 is supplied to the combustion chamber to clean up NO and NO ₂ and to reduce CO ₂ gases; · N ₂ and H ₂ O is formed during this stage;

• The amount of reagent supplied is 20 - 35 kg/day. The combustion products output is 94,817 ton/day.

Wet gas (combustion products) composition:

C0 ₂ 9 804.08 kg (10.34 % of the mass); Water vapour (H ₂ 0) 7357.80 kg (7.76 % of the mass);

0 ₂ 11 899.53 kg (12.55 % of the mass);

N ₂ 65 755.59kg (69.35 % of the mass).

The temperature in the secondary combustion chamber is 1350 °C to 1800 °C. The temperature of the combustion products at the combustion chamber outlet is 800 °C - 1000 °C.

Table 1 below sets out the results of an emission test conducted after performing the method of the present invention:

(Note that the below results were obtained without the supply of CO(NH ₂ ) ₂ to the combustion chamber 64 of the gas treatment apparatus 24 for the reduction of NO and CO). Table 1

1*. PCDD and PCDF - Polychlorinated dibenzo-p-dioxins and dibenzofurans

2*. DIRECTIVE 2000 76 EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL 4 December 2000 on the incineration of waste

3*. Air Quality Act, 2004 (Act No. 39 of 2004) Ambient Air Quality Standards, South Africa

It will be appreciated that various alternative embodiments are also possible in

10 accordance with the present invention.