The present invention relates to apparatus and a method for gasifying carbonaceous material. In particular, but not exclusively, the present invention relates to an apparatus for gasifying carbonaceous material that is configured in use to define two physically separate and distinct reduction zones and two physically separate and distinct oxidation zones which enables the calorific value of produced syngas to be increased relative to known apparatus.

Apparatus which can be used for gasifying carbonaceous materials have been known for many decades. Such an apparatus is commonly referred to as a gasifier. Gasifiers are used to produce flammable synthesis gases via thermochemical pyrolysis (i.e., thermal decomposition of organic molecules), oxidation and reduction (or gasification) of combustible organic materials such as biomass materials and combustible domestic and industrial waste. The resulting gases produced in the gasifier can then be cooled and cleaned and utilised for the production of energy in the form of electrical power and heat by means of gas engine generators, dual fuel converted diesel engine generators, gas turbines, high temperature fuel cells or the like. The cooled and cleaned gasses can also be converted to liquid fuels such as methanol, ethanol, ammonia and FT-diesel or the like by means of processing the raw gases in catalytic converters. The resulting raw gases produced can also be directly utilised and combusted in swirl burners retrofitted to a boiler (e.g., a thermal oil or steam boiler) to generate energy in the form of electrical power and heat by means of organic Rankine cycle (ORC) turbines or steam turbines. Generated power may be supplied to the national grid system via a substation transformer or utilised to produce hydrogen via an electrolysis process or the like. Electrolysis is the process of using electricity to split water into hydrogen and oxygen.

Typical gasifiers include various zones where certain reactions take place with the carbonaceous material being passed through the gasifier. One is these zones is commonly referred to as an oxidation zone. An oxidation zone is a zone in which exothermic chemical reactions predominantly occur between the carbonaceous material and at least one gaseous component (e.g., O2) to thereby oxidise the carbonaceous material and produce at least one further gaseous component (e.g., CO or CO2). Another of these zones is commonly referred to as a reduction zone (also known as a gasification zone). A reduction zone is a zone in which endothermic chemical reactions predominantly occur between the carbonaceous material and at least one gaseous component (e.g., H ₂ O or CO2) to thereby reduce the gaseous component into at least one further gaseous component (e.g., H ₂ or CO). Typical gasifiers however are limited to having only a single oxidation zone and a single reduction zone which are adjacent one another. For example, in an updraft gasifier, the single reduction zone is disposed immediately above the single oxidation zone. In a downdraft gasifier, the single reduction zone is disposed immediately below the single oxidation zone. However, having only a single reduction zone in a gasifier limits the calorific value of the gas that is produced in the gasifier, which is a measure of the heating power of the produced gas. For example, conventional air blown gasifiers produce around 4 to 6 MJ/Nm ³ calorific value syngas. This is because carbonaceous material which exits the reduction zone is thereafter removed from the gasifier even though the carbonaceous material might be capable of producing further synthesis gas. To date, there has been a technical prejudice in the art that gasifiers should be configured to only have a single oxidation zone and a single reduction zone.

Furthermore, due to high temperature operation of conventional gasifiers, clinkers can be formed, which are lumps of agglomerated carbonaceous material. Melted clinkers can fuse together to form bridges and/or channels near the base of a gasifier vessel which can cause discontinuous gas and fuel flow, as a result of which the resulting gas has a poor calorific value and high tar/particulate content. High tar/carbon particulate content gas impairs the quality of the product gas. For this reason, many conventional gasifiers are configured to operate in batch mode as a result of difficulties encountered in continuous ash/clinker removal, overheating, fuel bridging or channelling and excessive tar production. However, intermittent use of a gasifier results in increased tar content of the produced gas as a result of conditions in the start-up, ramp up and low temperature phases. This causes tar to accumulate in the gas treatment sections, pipework and in internal parts of power generators utilising the product gas, as a result of which the various parts of the gas treatment equipment and the engine power generators require frequent cleaning and maintenance, which in turn increases maintenance costs. This limits the range of materials which can be used in the gas producing process. In addition, because of the relatively high local temperatures in the oxidation region in the course of the gasification process, melted cinders cannot be fully discharged, as a result of which congestion occurs in the system. An example gasifier is disclosed in WO 2005/047435. This gasifier suffers from the disadvantage that the perforated catalytic element can become blocked with deposition of carbon soot particles at the surface of catalyst whilst raw gas is passing through, limiting the extent to which the apparatus can be used continuously. In addition, large clinkers formed due to fused ash and char in the high temperature zone accumulate in the bottom of the gasifier over a period of operation time which then causes bridge formation, blocking the continuous fuel movement in the reaction vessel and ash/char extraction from the gasifier.

Still furthermore, gasified carbonaceous materials which exit a typical gasifier are often discarded as waste as they have no further commercial use. It has to date been accepted that this is a side effect of using a gasifier.

It is an aim of the present invention to at least partly mitigate one or more of the above- mentioned problems.

It is an aim of certain embodiments of the present invention to help provide a gasifier which can produce gas with a higher calorific value than is possible using known gasifiers. In this way, the gasifier may be called an ‘intensive gasifier’.

It is an aim of certain embodiments of the present invention to help provide a gasifier which can operate continuously over longer periods of time than is possible using known gasifiers, thus helping to avoid clinker formation and thus reducing the overall tar/particulate content of the produced gas.

It is an aim of certain embodiments of the present invention to help provide a gasifier which has dual reduction zones separated by an oxidation zone.

It is an aim of certain embodiments of the present invention to help provide a gasifier which produces microporous biochar and/or activated carbon as a by-product.

It is an aim of certain embodiments of the present invention to help provide a single gasifier which can be used with a wide range of different carbonaceous materials. In this way, the gasifier may be called a ‘responsive gasifier’.

It is an aim of certain embodiments of the present invention to help provide a gasifier in which substantially no additional heat or energy needs to be provided once the gasification reactions are initiated. In this way, the gasifier may be called an ‘autothermal gasifier’.

According to a first aspect of the present invention there is provided apparatus for gasifying at least one carbonaceous material, comprising: at least one container comprising: at least one carbonaceous material inlet, at an upper end of the container, for providing carbonaceous material into an internal chamber of the container; at least one first carbonaceous material outlet, at a lower end of the container, for removing carbonaceous material from the internal chamber; and at least one gas outlet for removing gas from the internal chamber; wherein the internal chamber comprises a first carbonaceous material communication pathway between the carbonaceous material inlet and the first carbonaceous material outlet, and wherein carbonaceous material which travels along the first carbonaceous material communication pathway in use at least passes consecutively through a first reduction zone, a first oxidation zone, and a second reduction zone.

Aptly, carbonaceous material which travels along the first carbonaceous material communication pathway in use at least passes consecutively through the first reduction zone, the first oxidation zone, the second reduction zone, and a second oxidation zone.

Aptly, carbonaceous material which travels along the first carbonaceous material communication pathway in use passes consecutively through a drying zone, a pyrolysis zone, the first reduction zone, the first oxidation zone, the second reduction zone, and the second oxidation zone.

Aptly the apparatus further comprises: a moveable grate mechanism configured in use to move carbonaceous material from the first oxidation zone in a direction towards the second reduction zone.

Aptly the moveable grate mechanism is further configured in use to carry the fuel weight load and to provide agitation for uniformity in the fuel bed and to distribute oxidant evenly through the grid gaps of the grate mechanism.

Aptly, the moveable grate mechanism comprises at least one pair of grate elements, a first grate element of said pair being moveable with respect to a second grate element of said pair.

Aptly, the first grate element is reciprocally moveable relative to the second grate element.

Aptly, the first and/or second grate element comprises a plurality of substantially parallel, spaced apart elongate arm members.

Aptly, adjacent elongate arm members are spaced apart by around 1 to 6 mm. Aptly, each elongate arm member of said elongate arm members comprises a first substantially flat portion inclined at 0 to 25 degrees to a horizontal axis, a second substantially flat portion inclined at 0 to 15 degrees to a vertical axis, and a curved connection portion that connects the first substantially flat portion and the second substantially flat portion.

Aptly, the first substantially flat portion has a length of about around 50 to 250 mm.

Aptly, the second substantially flat portion has a height of about around 10 to 30 mm.

Aptly, the moveable grate mechanism is disposed at a base of the first oxidation zone.

Aptly, the moveable grate mechanism is driven by an electric or hydraulic motor disposed outside the container.

Aptly, the container comprises a first substantially upright container portion defining a first internal chamber region of said internal chamber.

Aptly, the first substantially upright container portion comprises at least one side wall comprising the carbonaceous material inlet.

Aptly, the first substantially upright container portion comprises an upper end wall comprising the gas outlet.

Aptly, the first substantially upright container portion has a substantially cylindrical or oval shape.

Aptly, in use the first internal chamber region is configured to provide a drying zone, a pyrolysis zone below the drying zone, and a first part of the first reduction zone below the pyrolysis zone.

Aptly, the container comprises a first substantially horizontal container portion defining a second internal chamber region of said internal chamber.

Aptly, the first substantially horizontal container portion comprises a first opening in an upper surface of the first substantially horizontal container portion and a second opening in a lower surface of the first substantially horizontal container portion. Aptly, the moveable grate mechanism forms part of the lower surface.

Aptly, the first substantially horizontal container portion comprises a first end wall and a second end wall, opposite the first end wall.

Aptly, the first opening in the upper surface is proximate the first end wall and the second opening in the lower surface is proximate the second end wall.

Aptly, the first end wall and/or second end wall and/or at least one side wall of the first substantially horizontal container portion comprises at least one aperture for locating an ignition element.

Aptly, the first substantially horizontal container portion is integrally formed with or connectable to the first substantially upright container portion such that the first opening mates with a first lower open end of the first substantially upright container portion.

Aptly, the first substantially horizontal container portion has a substantially cuboid shape.

Aptly, the first substantially horizontal container portion has a substantially rectangular cuboid shape.

Aptly, in use the second internal chamber region is configured to provide the first oxidation zone and a further part of the first reduction zone above the first oxidation zone.

Aptly, the container comprises a second substantially upright container portion defining a third internal chamber region of said internal chamber.

Aptly, the second substantially upright container portion comprises a first open upper end and a second open lower end.

Aptly, the second substantially upright container portion comprises an inner wall and an outer wall spaced apart from the inner wall to define a gap therebetween.

Aptly, water and/or steam is configured to flow through the gap in use. Aptly, the second substantially upright container portion is integrally formed with or connectable to the first substantially horizontal container portion such that the first open upper end mates with the second opening.

Aptly, in use the third internal chamber region is configured to provide the second reduction zone.

Aptly, the container comprises a second substantially horizontal container portion defining a fourth internal chamber region of said internal chamber.

Aptly, the second substantially horizontal container portion comprises the first carbonaceous material outlet and a third opening in an upper wall.

Aptly, the second substantially horizontal container portion comprises at least one fluid inlet nozzle.

Aptly, in use steam and/or water is provided into the second oxidation zone via the fluid inlet nozzle.

Aptly, the fluid inlet nozzle is configured to atomise water to thereby provide water mist into the second oxidation zone.

Aptly, steam and/or water is provided to the fluid inlet nozzle from the gap between the inner and outer wall of the second substantially upright container portion.

Aptly, the second substantially horizontal container portion is integrally formed with or connectable to the second substantially upright container portion such that the second open lower end mates with the third opening.

Aptly, the second substantially horizontal container portion comprises a first conveying element for conveying carbonaceous material through the fourth internal chamber region.

Aptly, the first conveying element is an auger conveyor.

Aptly, the first conveying element is driven by an electric or hydraulic motor disposed outside the container. Aptly, in use the fourth internal chamber region is configured to provide the second oxidation zone.

Aptly, the container comprises a residue removal container portion defining a fifth internal chamber region of said internal chamber.

Aptly, the residue removal container portion is disposed beneath the moveable grate mechanism.

Aptly, the residue removal container portion comprises a second conveying element for conveying carbonaceous material in the fifth internal chamber region to at least one second carbonaceous material outlet.

Aptly, the second conveying element is an auger conveyor.

Aptly, the second conveying element is driven by an electric or hydraulic motor disposed outside the container.

Aptly, the residue removal container portion comprises an inner wall and an outer wall spaced apart from the inner wall to define a gap therebetween.

Aptly, water and/or steam is configured to flow through the gap in use.

Aptly, the gap between the inner and outer wall of the residue removal container portion is fluidly connected to the gap between the inner and outer wall of the second substantially upright container portion.

Aptly, at least one fluid conduit penetrates through the inner and outer wall of the residue removal container portion and terminates within the fifth internal chamber region.

Aptly, the fluid conduit comprises at least one fluid outlet on a lower surface of the fluid conduit.

Aptly, in use air is provided into the first oxidation zone through the moveable grate mechanism via the fluid outlet of the fluid conduit. Aptly the apparatus further comprises a third conveying element for conveying carbonaceous material towards the carbonaceous material inlet.

Aptly, the third conveying element is an auger conveyor.

Aptly, the third conveying element is driven by an electric or hydraulic motor disposed outside the container.

According to a second aspect of the present invention there is provided a method for gasifying at least one carbonaceous material, comprising the steps of: providing carbonaceous material into an internal chamber of at least one container via at least one carbonaceous material inlet of the container; moving the carbonaceous material along a first carbonaceous material communication pathway between the carbonaceous material inlet and at least one first carbonaceous material outlet, wherein carbonaceous material which travels along the first carbonaceous material communication pathway at least passes consecutively through a first reduction zone, a first oxidation zone, and a second reduction zone; gasifying the carbonaceous material in at least the first reduction zone and the second reduction zone; and removing gas produced in at least the first reduction zone and the second reduction zone from the internal chamber via at least one gas outlet of the container.

Aptly, carbonaceous material which travels along the first carbonaceous material communication pathway at least passes consecutively through the first reduction zone, the first oxidation zone, the second reduction zone, and a second oxidation zone.

Aptly, carbonaceous material which travels along the first carbonaceous material communication pathway passes consecutively through a drying zone, a pyrolysis zone, the first reduction zone, the first oxidation zone, the second reduction zone, and the second oxidation zone.

Aptly, the method further comprises: in the drying zone, maintaining the carbonaceous material at a temperature of about around 100 to 200 degrees Celsius to remove moisture from the carbonaceous material.

Aptly, the method further comprises: in the pyrolysis zone, maintaining the carbonaceous material at a temperature of about around 200 to 700 degrees Celsius to pyrolyze the carbonaceous material. Aptly, the method further comprises: in the first reduction zone, maintaining the carbonaceous material at a temperature of about around 700 to 900 degrees Celsius.

Aptly, the method further comprises: in the first oxidation zone, maintaining the carbonaceous material at a temperature of about around 900 to 1200 degrees Celsius.

Aptly, the method further comprises: in the second reduction zone, maintaining the carbonaceous material at a temperature of about around 800 to 1000 degrees Celsius

Aptly, the method further comprises: in the second oxidation zone, maintaining the carbonaceous material at a temperature of about around 700 to 900 degrees Celsius.

Aptly, the method further comprises: maintaining the temperature in the drying zone, the pyrolysis zone, the first reduction zone and the first oxidation zone via heat produced from exothermic oxidation reactions in the first oxidation zone.

Aptly, the method further comprises: maintaining the temperature in the second reduction zone and second oxidation zone via heat produced from exothermic oxidation reactions in the second oxidation zone.

Aptly, the method further comprises: maintaining the temperature in the second reduction zone and second oxidation zone via heat preserved in hot char which is flowing from the first oxidation zone to the second reduction zone and via partial heat produced from exothermic oxidation reactions in the second oxidation zone.

Aptly, the method further comprises: moving the carbonaceous material along the first carbonaceous material communication pathway such that the carbonaceous material is within the internal chamber for a time period of about around 60 to 120 minutes.

Aptly, the method further comprises: moving the carbonaceous material along the first carbonaceous material communication pathway such that the carbonaceous material is within the drying zone for a time period of about around 10 to 15 minutes.

Aptly, the method further comprises: moving the carbonaceous material along the first carbonaceous material communication pathway such that the carbonaceous material is within the pyrolysis zone for a time period of about around 10 to 20 minutes. Aptly, the method further comprises: moving the carbonaceous material along the first carbonaceous material communication pathway such that the carbonaceous material is within the first reduction zone for a time period of about around 10 to 15 minutes.

Aptly, the method further comprises: moving the carbonaceous material along the first carbonaceous material communication pathway such that the carbonaceous material is within the first oxidation zone for a time period of about around 5 to 10 minutes.

Aptly, the method further comprises: moving the carbonaceous material along the first carbonaceous material communication pathway such that the carbonaceous material is within the second reduction zone for a time period of about around 10 to 15 minutes.

Aptly, the method further comprises: moving the carbonaceous material along the first carbonaceous material communication pathway such that the carbonaceous material is within the second oxidation zone for a time period of about around 20 to 25 minutes.

Aptly, the method further comprises: providing the carbonaceous material into the internal chamber via at least one auger conveyor connected to the carbonaceous material inlet.

Aptly, the method further comprises: providing at least one auger conveyor in the second oxidation zone to convey carbonaceous material in a direction towards the first carbonaceous material outlet.

Aptly, the method further comprises: removing carbonaceous material from the internal chamber via the first carbonaceous material outlet.

Aptly, the method further comprises: removing residue that passes through a moveable grate mechanism at a base of the first oxidation zone via at least one second carbonaceous material outlet.

Aptly, the method further comprises: conveying the residue that passes through the moveable grate mechanism towards the second carbonaceous material outlet via at least one auger conveyor.

Aptly, the method further comprises: providing steam and/or water into the second oxidation zone via at least one fluid inlet nozzle. Aptly, the method further comprises: providing steam and/or atomised water into the second oxidation zone.

Aptly, the method further comprises: via the steam and/or water provided into the second oxidation zone, activating the carbonaceous material and thereby producing microporous biochar and/or activated carbon.

Aptly, the method further comprises: providing the steam and/or water to the fluid inlet nozzle from a gap disposed between an inner and outer wall of at least part of the container.

Aptly, the method further comprises: providing water into the gap via at least one water inlet in the outer wall of the container; and producing steam via heat transfer from the carbonaceous material within the container to the water.

Aptly, the method further comprises: providing steam and/or water into the second oxidation zone at a location diametrically opposed to a location of the first carbonaceous material outlet such that carbonaceous material is removed from the internal chamber at a temperature of about around 100 to 150 degrees Celsius.

Aptly, the method further comprises: providing air and/or a mixture of air and exhaust gases into the first oxidation zone through a moveable grate mechanism disposed at a base of the first oxidation zone.

Aptly, the method further comprises: providing an ignition element in at least one aperture of the container; and igniting the ignition element to initially ignite the carbonaceous material in the first oxidation zone.

Aptly, the ignition element is ignited for a period of 10-30 minutes to initially ignite the carbonaceous material.

Aptly, the method further comprises: removing synthesis gas via the gas outlet.

Aptly, the method further comprises: moving carbonaceous material from the first oxidation zone in a direction towards the second reduction zone via at least one reciprocally moving grate element. Aptly, the carbonaceous material is biomass and/or biowaste and/or industrial or commercial waste and/or a fossil fuel.

According to a third aspect of the present invention there is provided use of the apparatus according to the first aspect of the present invention.

According to a fourth aspect of the present invention there is provided a moveable grate mechanism for a gasifier, comprising: at least one pair of grate elements, a first grate element of said pair being reciprocally moveable with respect to a second grate element of said pair.

According to a fifth aspect of the present invention there is provided a method of producing activated biochar in a gasifier, comprising the steps of: providing carbonaceous material into a gasifier; at least partially gasifying the carbonaceous material in the gasifier to produce biochar; and providing steam and/or atomised water into an internal region of the gasifier containing the biochar to thereby produce activated biochar.

Certain embodiments of the present invention help provide a gasifier that produces synthesis gas with a calorific value of around 7 MJ/Nm ³ to 10 MJ/Nm ³ .

Certain embodiments of the present invention help provide a methodology of gasifying carbonaceous materials, which results in a synthesis gas having a higher H2 and CO content.

Certain embodiments of the present invention help provide a method of gasifying carbonaceous materials which also results in microporous biochar and/or activated carbon being produced as a by-product.

Certain embodiments of the present invention help provide a gasifier in which carbonaceous material is gasified in physically separate reduction zones in two distinct stages.

Certain embodiments of the present invention help provide a responsive, intensive and autothermal gasifier. In this sense, responsive means that the intensive gasifier design can be operated safely and continuously utilising a variety of feedstock types without changing the design of the gasifier.

Certain embodiments of the present invention help provide a gasifier with a ratio of maximum to minimum throughput rate of 10:1 (turndown ratio) without compromising on efficiency. Certain embodiments of the present invention help provide a gasifier which is able to operate continuously over longer periods than known gasifiers, which produces syngas with a higher calorific value than known gasifiers (intensive) and that operates with different type of feedstocks without design modification (responsive) and that produces activated carbon or microporous biochar as a by-product without utilisation of external energy source (autothermal).

Embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

Figure 1 illustrates a process flow diagram of a complete gasification system;

Figure 2 illustrates a cross-sectional view of a gasifier;

Figure 3 illustrates a moveable grate mechanism usable within a gasifier;

Figure 4 illustrates a perspective view of a gasifier;

Figure 5a illustrates SEM images at various length scales of raw (un-gasified) oak wood chips;

Figure 5b illustrates SEM images at various length scales of the oak wood chips that have passed through a gasifier according to certain embodiments of the present invention;

Figure 5c illustrates SEM images at various length scales of poplar wood chips that have passed through a gasifier according to certain embodiments of the present invention; and

Figure 5d illustrates SEM images at various length scales of nut shells that have passed through a gasifier according to certain embodiments of the present invention.

In the drawings like reference numerals refer to like parts.

Figure 1 illustrates a process flow diagram 100 for a gasification system including an optional fuel preparation stage 110, a gas production and processing stage 120 and an optional electricity generation stage 190. In the fuel preparation stage, fuel to be provided into a gasifier is stored in a storage step 112. The fuel is stored in a storage device such as a bunker or a hopper. The fuel that is stored may be biomass and/or biowaste and/or industrial/commercial waste and/or a fossil fuel or the like. These are all examples of carbonaceous materials and thus the fuel may also be referred to herein as carbonaceous material. Following the fuel storage step 112 is a shredder step 114. In the shredder step, the stored carbonaceous material is provided to a shredder such that the carbonaceous material is shredded or cut into appropriate shape(s) for feeding into a gasifier. Other ways of providing the carbonaceous material into appropriate shapes may of course be utilised. Following the shredder step is a dryer step 116. In the dryer step the shredded carbonaceous material is provided into a dryer (such as a belt or rotary drum dryer or the like) in order to de-hydrate the carbonaceous material and thus reduce its water content. Optionally, this may involve heating the carbonaceous material in the dryer if necessary.

After the carbonaceous material has been optionally shredded and dried, the carbonaceous material is provided into a gasifier 130 in the gas production and processing stage 120. Carbonaceous material is transferred to the gasifier via hydraulic or electric motor driven feeders with two specially designed feeding screws located under a fuel feeding bunker. The carbonaceous material, which is discharged from the feeding spirals into a reservoir of the hydraulic or electric motor feeders, is fed into the gasifier using the feeders as hydraulic presses or electric motor screw conveyors. The pressing or squeezing applied by the feeders compresses the carbonaceous material which thus provides air and gas tightness to prevent air ingress into the gasifier or gas from escaping from the gasifier. The carbonaceous material provided into the gasifier 130 is gasified as will be described in more detail hereinbelow. During gasification of the carbonaceous material within the gasifier 130, the carbonaceous material is processed such that by the time it is output from the gasifier, it is in the form of char. As will be appreciated by those of skill in the art, char is a carbonaceous material that is principally made up of elemental carbon along with some inert minerals and metals. The activated char is extracted from the gasifier 130 via a char discharge auger 132. The char discharge auger conveys the char into a char tank 134. According to certain embodiments of the present invention, the char that is output from the gasifier is microporous. As such, it may be referred to as activated carbon or microporous biochar. The activated carbon/biochar output from the gasifier has an average pore size of around 10-20 pm.

During the gasification of the carbonaceous material in the gasifier 130, gas is also produced. The gas produced from a gasifier is commonly referred to as synthesis gas (syngas) or producer gas. Syngas is a gas which is made up principally of H ₂ and CO (other components, such as CO2 and CH ₄ , may also be included). After being produced in the gasifier, the syngas is provided into a syngas burner 135 via a gas communication channel (not shown) made of steel or the like. Optionally, the syngas may also be passed through one or more cyclones or ceramic candle filters (not shown) to remove particulates from the syngas before it enters the syngas burner. The syngas burner 135 combusts the syngas to produce high temperature byproduct combustion gases. The syngas burner 135 may be of the swirl (vortex) type as will be appreciated by a person skilled in the art. Syngas produced in the gasifier 130 may also be mixed with ambient air and/or preheated air and/or exhaust gases from a recuperator 150 before being transported to the syngas burner. In the syngas burner 135 there is a combustion chamber (not shown) and the inner surfaces of the syngas burner is covered with refractory material of appropriate thickness. The syngas burner has an inner body (not shown) made of steel material or the like. The syngas burner also has vortex pipes (not shown) that distribute the hot by-product combustion gases evenly to the thermal oil heater 140 (may also be referred to as thermal oil boiler). A gas distributor channel (not shown) is disposed around the syngas burner 135, and using this channel, preheated air can be provided homogeneously to the vortex pipes at the desired pressure. There is also a pilot burner ignition system (not shown) and flame sensor (not shown) to ignite syngas in the burner. The pilot burner is a burner of a standard type natural gas burner as will be appreciated by those of skill in the art. The pilot burner operates continuously for safety purposes.

Combustion gases produced in the syngas burner are then provided to a thermal oil heater 140. The thermal oil heater fires through a helical coil (not shown) and generates energy using the combustion gases generated in the syngas burner flame. The energy is generated by heating the coil through radiation and convection from the syngas flame and combustion gases. The coil heats the thermal oil or fluid that is pumped through the thermal oil heater using a pump (not shown). A blower 145 provides primary and secondary air to the thermal oil heater for efficient combustion of syngas and to control the emissions. The heated thermal oil can be used to heat coils in various types of heaters. The thermal oil may also be provided to an Organic Rankine Cycle (ORC) turbine 192 as discussed below. Thermal oil which is used in the ORC turbine is thereafter returned to the thermal oil boiler for re-heating. The thermal oil may be directly returned from the ORC turbine to the thermal oil boiler. Alternatively, the thermal oil may be returned to the thermal oil boiler via an economiser 145. Unlike a water or steam boiler, the heating process in the thermal oil boiler does not heavily pressurize the system. For example, the operating pressure of the thermal oil heater is between -5mBar to - 70mBar. A primary thermal oil circulating pump (not shown) which provides thermal oil circulation between the thermal oil boiler and the ORC turbine, is directly coupled to an evaporator with a special gasket suitable for thermal oil and an electric motor. The pump and the thermal oil degasser may share a common chassis. Another circulation pump may be provided for redundancy such that it may be used instead of the primary pump when the primary pump is broken or taken into maintenance.

Exhaust gases leave the convection section of the thermal oil heater 140 with a temperature of about 350°C and enter a thermal oil economiser 145. The economiser 145 may partially reheat the thermal oil being returned from the ORC turbine via heat exchange with the exhaust gases from the thermal oil boiler. The economiser includes several coils that are manufactured by bending steel drawn pipes into spirals of a certain diameter and its body is made of carbon steel. The operating pressure of the economiser is between -10 mBar and -90 mBar.

After leaving the economiser 145, the exhaust gases from the thermal oil boiler pass through an air to gas recuperator 150. The recuperator 150 is a heat exchanger. Ambient air is heated in the recuperator 150 using heat from the exhaust gases in the recuperator. The ambient air is heated to a temperature of around 120°C to 220°C. This preheated air may then be supplied to the syngas burner for use in combustion of the syngas (e.g., by combining the preheated air with the syngas or by providing the air directly into the syngas burner). The preheated air may also be provided directly into the gasifier 130 for use as an oxidising agent in an oxidation zone of the gasifier. The recuperator operates at a pressure of between -10mBar to -90mBar. The recuperator includes a smoke pipe (not shown) to help heat the air in the recuperator as will be appreciated by a person of skill in the art. The air is supplied by a fan and carried to the recuperator through air ducts. Airflow capacity adjustment can be provided with the help of an inverter.

The fluid communication pathways within the economiser 145 and/or the recuperator 150 may be cleaned intermittently by a soot blower using hot water and/or low grade steam generated in a water jacket surrounding part of the gasifier 130. The water jacket is described in more detail with referenced to Figure 2.

Exhaust gases that exit the recuperator then pass through an Induced Draft (ID) Fan 155 that provides sufficient pressure for the downstream suction and for the exhaust gases to flow through a Water Scrubber 160 and a Wet Electrostatic Precipitator (WESP) 165 before exiting through the stack 180. The exhaust gases leaving the ID Fan first enter the water scrubber 160. Water droplets in the scrubber react with acid gases such as HCI, HF and SOx and these pollutants are effectively removed from the exhaust gas stream. The water scrubber also has the feature of holding any ash particles in the exhaust gases. The pH value of the washing water can be increased by dosing caustic NaOH or Ca(OH)2 to control the acid gases. The chemical dosing system can ensure the desired pH value in the washing water. Some amount of process water may be discharged to a sewer after appropriate water filtration and treatment from the wet scrubber water circulation unit (not shown). The water scrubber body is made of high-grade stainless-steel material to help prevent corrosion. The water scrubber operates at a pressure of between +10mBar and +50mBar.

The Wet Electrostatic Precipitator (WESP) 165 has several perforated plates to ensure even distribution of exhaust gases entering from the bottom of the WESP tower across its entire cross-section. This arrangement provides smooth speed and flow maximizing performance in the collector section. The exhaust gases flow upwards through the electrically grounded pipes (collector electrodes). An ionizer electrode held at a high negative DC potential is mounted concentrically to each collector electrode. The high voltage difference between the ionizer and collector electrodes produces an intense electrostatic field (corona). Particles passing through this field are negatively charged and attracted to the collector electrode. Particles reaching the collector wall are caught in a film of water and discharged into a sump. The collector section is cleaned continuously (fogging) and periodically (washing) with a spray system using industrial water or rinsing acid. Washing systems are located above and below the collector. The water supply should be provided at around 2 to 3 bar (fogging) and 4 to 5 bar (washing). Wash frequency and cycle time are determined by process conditions and operator experience. Dust characteristics, concentration, organic material, and processing conditions can greatly affect the frequency and duration of cleaning. The cleaned gases then exit from the top of the WESP and are emitted via a stack 180. Both the WESP and the water scrubber operate at a pressure of between +15mBar and +100mBar.

The Dissolved Air Filtration (DAF) component 170 is a component that uses a water treatment process that clarifies wastewaters by the removal of suspended matter such as oil, tar or solids. The removal is achieved by dissolving air in the wastewater under pressure and then releasing the air at atmospheric pressure in a flotation tank basin. The released air forms tiny bubbles which adhere to the suspended matter causing the suspended matter to float to the surface of the water where it may then be removed by a skimming device. A water recirculation tank 165 holds certain amounts of process water (e.g., 5m3) and water that is used in the water scrubber and the WESP is provided from the recirculation tank by means of a water circulation pump (not shown). Processed water from the water scrubber and the WESP return to the recirculation tank after the DAF process. Some of the process water is discharged from the recirculation tank to a water treatment station or a sewer to keep process water clean enough to be recirculated. Top up clean water is added to the recirculation tank when the water level drops to a certain level in the recirculation tank.

The heat obtained by the combustion of the syngas is transferred to the ORC Turbine 192 in the electricity generation stage 190 by means of a thermal oil circuit. That is to say that the heat generated from syngas combustion heats thermal oil in the thermal oil heater 140 and this heated thermal oil is then provided to the ORC turbine 192. The ORC turbine generates power and produces low-temperature waste heat through a closed thermodynamic cycle which follows the principle of the Organic Rankine Cycle (ORC). The low-temperature heat generated in the turbine is discharged through an air-cooled condenser (ACC) (not shown) to allow heat to be dissipated to the atmosphere. In the ORC process, designed as a closed cycle, the organic working medium is preheated in a regenerator, then heated and vaporized through heat exchange with the thermal oil loop in an evaporator (not shown). The generated vapour is expanded in a turbine that drives an electric generator 194 to produce electricity. After leaving the turbine, the organic working medium (still in the vapour phase) passes through the regenerator that is used to pre-heat the organic liquid before vaporizing, therefore, increasing the electric efficiency through internal heat recovery. The organic vapour then condenses by discharging low-temperature heat to the atmosphere through an ACC. After the condenser, the working medium is brought back to the pressure level required (for turbine operation) by the working fluid pump and then preheated by internal heat exchange in the regenerator.

Figure 2 illustrates a gasifier 200. The gasifier is an example of an apparatus that can be used for gasifying carbonaceous material. The gasifier is an updraft gasifier. This means that carbonaceous material within the gasifier moves in a downwards direction from an inlet at an upper end of the gasifier to an outlet at a lower end of the gasifier, whereas gas produced in the gasifier (producer gas or syngas) moves in an upwards direction through the gasifier to an outlet at the upper end of the gasifier. Thus, in all regions of the gasifier where carbonaceous material is present, the carbonaceous material flows in the gasifier in a counter-current with respect to the flow of gas produced in the gasifier. As discussed above, the carbonaceous material may be biomass and/or biowaste and/or industrial/commercial waste and/or a fossil fuel or the like. The gasifier includes a container 210 which has an upper end 211 and a lower end 216. The container 210 is manufactured from a pressure and heat resistant steel material. However, it will be appreciated that other materials could be used according to certain other embodiments of the present invention. During use, carbonaceous material within the container 210 is heated to an operating temperature of up to around 1200°C and has an operating pressure of around +1 Ombar to -50mbar. However, the exact operating temperature within the container varies with the feedstock (carbonaceous material) composition, moisture content, ash melting temperature and heating value. Thermocouples (not shown) are located at various locations on inner side walls of the container 210 to measure temperature at various levels within the container. An inside of the container 210 may be covered with high-temperature resistant refractory material (not shown) to control endothermic gasification reaction temperatures and to prevent excessive heat loss and to protect the gasifier steel body. At the upper end of the container there is at least one carbonaceous material inlet 212 which enables carbonaceous material to be provided into an internal chamber 220 of the container. Connected to the inlet 212 is an auger conveyor 213 (an example of a conveying element) which conveys carbonaceous material towards the inlet 212 from a hopper 214. The auger conveyor is air-tight. The auger conveyor is controlled by means of a hydraulic motor 215 although it will be appreciated that other motors (e.g., electric) may be used according to certain other embodiments of the present invention. The motor has a variable speed-control which enables the throughput of carbonaceous material passing through the container to be controlled. At the lower end of the container there is at least one carbonaceous material outlet 217 which enables carbonaceous material to be removed from the internal chamber. A moveable gate 218 enables the outlet to be selectively opened or closed. The container also has at least one gas outlet 219 (i.e., synthesis gas discharge pipes) in an upper end of the container. It is noted that according to certain other embodiments of the present invention, the gas outlet may not be situated at the upper end of the container. The gas outlet 218 also has a moveable gate 221 which enables the outlet to be selectively opened or closed. During use of the gasifier, a negative pressure is formed at the synthesis gas outlet using a gas suction fan (not shown). This fan enables gases to be removed from the container whilst enabling entry of air into the container. The syngas produced in the gasifier leaves the gasifier via the gas outlet 219 at the upper end of the container. The gasifier normally operates under slight vacuum conditions by using airlocked double screw feeders and gate valves. However, it will be appreciated that under certain circumstances the gasifier may be operated under slight positive pressure according to certain other embodiments of the present invention.

The container 210 includes several distinct portions. A first substantially upright container portion 230, a first substantially horizontal container portion 240, a second substantially upright container portion 250, a second substantially horizontal container portion 260 and a residue removal container portion 270. The first substantially upright container portion is a top portion of the container and defines a first internal chamber region 231 of the internal chamber. The first substantially upright container portion includes a first open lower end 232 and an upper end wall 233 which includes the gas outlet 219. The first substantially upright container portion also includes at least one side wall which includes the carbonaceous material inlet 212. The first substantially upright container portion is upright in the sense that the side wall(s) is substantially aligned with a vertical axis. The first substantially upright container portion has a generally cylindrical or oval shape, however it will be appreciated that other shapes may be used according to certain other embodiments of the present invention. A cylindrical or oval shape provides the advantage of a stronger structure and simplified construction, thereby reducing its cost, whilst also reducing the formation of fuel bridges and dead zones, thereby enabling the gasifier to be operated continuously for longer periods, thereby increasing the efficiency of operation of the gasifier. In addition, by enabling the gasifier to be operated continuously for longer periods, this reduces the tar/particulate content of the resulting gas, as a result of which maintenance costs of gas and water clean-up of downstream equipment and prime mover power generator using the resultant gas can be reduced.

The first substantially horizontal container portion 240 sits directly beneath the first substantially upright container portion. The first substantially horizontal container portion defines a second internal chamber region 241 of the internal chamber. The first substantially horizontal container portion includes a first opening 242 in an upper surface 243 and a second opening 244 in a lower surface 245. The first opening 242 is located near an end wall 246i and the second opening 244 is located near an opposing end wall 2462 in the first substantially horizontal container portion. The first opening mates with the open lower end 232 of the first substantially upright container portion. These two portions may be integrally formed with one another (e.g., welded) or may be connectable to each other (e.g., via a flange). In the end wall 2462 there is located an aperture in which an ignition element 247 (i.e., a burner) may be located. It will however be appreciated that this ignition element may be provided in a side wall or the end wall 246i of the first substantially horizontal container portion. The ignition element (which may be referred to as a start-up burner) is used to bring the temperature within the gasifier to the desired level during the first commissioning (i.e., initialisation) of the system. This may take around 10-30 minutes. The first substantially horizontal container portion is horizontal in the sense that the upper surface and lower surface are substantially aligned with a horizontal plane and at least one linear dimension of the upper and lower surface is more than twice the distance between the upper and lower surface. The first substantially horizontal container portion has a generally cuboid shape (optionally a rectangular cuboid shape) although it will be appreciated that other shapes may be used according to certain other embodiments of the present invention. A moveable grate mechanism 280 (described in more detail below) forms part of the lower surface of the first substantially horizontal container portion.

The second substantially upright container 250 portion sits directly beneath the first substantially horizontal portion. The second substantially upright container portion defines a third internal chamber region 251 of the internal chamber. The second substantially upright container portion includes a first upper open end 252 and a second lower open end 253. The upper open end mates with the second opening in the lower surface of the first substantially horizontal container portion. These portions may be integrally formed with one another (e.g., welded) or may be connectable to each other (e.g. via a flange). The second substantially upright container portion includes at least one side wall 254. The side wall includes an inner wall and an outer wall which are spaced apart and thus define a gap between them. The gap can be used to circulate fluid around the outside of the second substantially upright container portion. This arrangement may be referred to as a water jacket. The outer wall includes at least one fluid outlet 255 which allows fluid to be provided out of the gap. The provision of fluid out of the gap is controlled by gate valve 256. In use, fluid that is provided into the gap is heated via heat exchange from the carbonaceous material within the container. The fluid that is provided into the gap is water and this is heated to a temperature of around 70-100°C or above to thereby produce steam. The circulating fluid helps to cool the carbonaceous material and thus control the exit temperature of the carbonaceous material when it exits the container via the carbonaceous material outlet 217. The fluid that is circulated is also used an oxidising agent for provision into the second substantially horizontal container portion 260. The second substantially upright container portion is upright in the sense that the side wall(s) is substantially aligned with a vertical axis. A primary axis which extends in a vertical direction through the centre of the second substantially upright container portion is offset from a primary axis which extends in a vertical direction though the centre of the first substantially upright container portion. The offset is around 1 -4 m. The second substantially upright container portion has a generally cuboid shape (optionally a rectangular cuboid shape) although it will be appreciated that other shapes may be used according to certain other embodiments of the present invention.

The second substantially horizontal container portion 260 sits directly beneath the second substantially upright container portion. The second substantially horizontal container portion defines a fourth internal chamber region 261 of the internal chamber. The second substantially horizontal container portion includes the carbonaceous material outlet 217 and a third opening 262 in an upper wall of the second substantially horizontal container portion. The third opening mates with the open lower end of the second substantially upright container portion. These portions may be integrally formed with one another (e.g., welded) or may be connectable to each other (e.g., via a flange). The second substantially horizontal container portion is horizontal in the sense that the upper wall and lower wall are substantially aligned with a horizontal plane and at least one linear dimension of the upper and lower wall is more than twice the distance between the upper and lower wall. The second substantially horizontal container portion has a generally cuboid shape although it will be appreciated that other shapes may be used according to certain other embodiments of the present invention. Part of the upper wall has an inner wall and outer wall defining a gap in between. The gap is fluidly connected to the gap around the second substantially upright container portion. In the upper wall, there is at least one fluid inlet nozzle 263. The fluid nozzle is disposed at a location diametrically opposite to the location of the first carbonaceous material outlet. This enables the carbonaceous material to be rapidly cooled as it exits the container. The fluid inlet nozzle is in fluid communication with the fluid outlet 255 such that fluid in the gap (hot water and/or steam) can be provided into the second substantially horizontal container portion via the nozzle. This enables the gasifier to be efficient by making use of the heat generated by the gasifier. It will be appreciated that according to certain other embodiments of the present invention water and/or steam can be provided to the nozzles from an external source. The nozzles are configured such that water being provided through them is atomised and generates mist which enters the fourth internal chamber region. The mist may include droplets having an average diameter of between 1 micron and 50 microns, for example 3 to 20 microns, or 5 to 15 microns. This misting is achieved by using nozzles with at least one fluid exit aperture having a diameter of 0.05 mm - 1.00 mm, for example 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, or 0.70 mm. The choice of diameter depends on the droplet size desired. The nozzles are high pressure water nozzles which are used to atomise water and spray in mist to the hot char bed. The tip of the nozzle is very small and twisted so that it increases the pressure and causes turbulence to create very small water droplets (mist). Such nozzles will be appreciated by one of skill in the art. The nozzles may additionally or alternatively inject steam into this region. Injecting steam or providing atomised water (mist) through nozzles causes the carbonaceous material within the container which has been partially gasified to be ‘activated’, increasing the pore size of the carbonaceous material and thus produces activated carbon or microporous biochar. Within the second substantially horizontal container portion there is also an auger conveyor 264 (an example of a conveying element) which in use conveys carbonaceous material through the fourth internal chamber region in a direction from the lower open end of the second substantially upright container portion towards the carbonaceous material outlet. The auger conveyor is driven by a hydraulic motor 265 although it will be appreciated that other motors (e.g. electric) can be used according to certain other embodiments of the present invention. The motor is a variable speed-controlled motor which thus helps to enable the carbonaceous material throughput to be controlled. Enabling carbonaceous material to be removed continuously and variably also enables the gasifier to operate continuously for longer periods which thus helps to reduce the maintenance needed and the tar/particulate content of the syngas.

The residue removal container portion 270 is located immediately below the moveable grate mechanism 280 forming part of the lower surface of the first substantially horizontal container portion. The residue removal container portion defines a fifth internal chamber region 271 of the internal chamber. The residue removal container portion may be integrally formed with (e.g., welded) to the first substantially horizontal container portion or may be connectable (e.g. via a flange) to the first substantially horizontal container portion. The residue removal container portion collects carbonaceous material residue which falls through the moveable grate mechanism. Within this portion there is an auger conveyor 272 (an example of a conveying element) which conveys residue carbonaceous material to at least one second (residue) carbonaceous material outlet 273. A moveable gate 274 is selectively openable and closable in the outlet 273. The residue may for example be char fines and/or ash particles. By having the ability to remove residue, the gasifier may be used continuously for longer periods. The auger conveyor 272 is driven by a hydraulic motor 275 although other motors (e.g., electric) may be used according to certain other embodiments of the present invention. A cross-section of the residue removal container portion decreases as it extends away from the grate mechanism such that residue is directed towards the auger conveyor. The residue removal container portion has a generally inverted pyramidal shape or funnel shaped. The residue removal container portion has at least one side wall that also has an inner and outer wall with a gap therebetween. This may be referred to as a water jacket. The gap is in fluid communication with the gap surrounding the second substantially upright container portion and the gap of the second substantially horizontal container portion. The outer wall includes a fluid inlet 276 and a fluid outlet 277. The fluid inlet enables water to be provided into the gap. The fluid outlet enables fluid to be provided from the gap into the second substantially horizontal container portion via the fluid inlet nozzles. The provision of fluid from the gap is controlled via a gate valve 278. A fluid conduit 279 penetrates through the side wall from a region outside the container. The fluid conduit terminates within the fifth internal chamber region. At an end of the fluid conduit in the fifth internal chamber region, there is at least one fluid outlet on a side wall of the conduit. In other words, the fluid conduit is perforated. These fluid outlets are on a lower surface of the conduit opposed to the moveable grate mechanism. This is so that the fluid conduits do not get blocked by residue falling through the grate. During use, air is provided along the conduit and this air exits via the fluid outlets. The air then enters the first oxidation zone through the moveable grate mechanism. Providing air in this way enables a more miniaturised construction of the gasifier and more efficient operation of the gasifier. The air acts as an oxidising agent. The air may be enriched with oxygen or steam and also mixed with exhaust gases from the ID Fan 155. The air may be provided as preheated air from a recuperator 150 as discussed above. The sub-stoichiometric air provided via the fluid conduit is supplied by a fan and is fed to the first oxidation zone through air ducts in the fluid conduit and through air vents in the moveable grate mechanism. Airflow adjustment can be provided using an inverter drive on the fan.

Within the container there is also a moveable grate mechanism 280. That is to say there is a grate mechanism within the container that has at least one part that is moveable relative to the container (which essentially remains stationary throughout a gasification process). The motion of the moveable grate is a translational motion relative to the walls of the container (i.e., no rotation takes place). In particular, the parts of the grate mechanism that are moveable move reciprocally in a plane that is perpendicular (or that is within 10 or 20 degrees of being perpendicular) to a vertical axis of the gasifier (e.g., a vertical axis extending through the centre of the first substantially upright container portion). That is to say, all points of the plane are perpendicular (or within 10 or 20 degrees of) to that vertical axis. The plane may be aligned with a support surface (that supports the carbonaceous material on the grate) of the moveable part of the grate. In this way, the moveable part of the grate (e.g., one of a pair of grate elements) moves reciprocally in this plane such that a support surface of the grate element that supports the carbonaceous material on the grate always remains in that same plane regardless of where the grate element has moved to. The moveable grate mechanism is controlled by means of a hydraulic motor 281 . However, it will be appreciated that other motors (e.g., electric) may be used according to certain other embodiments of the present invention. The moveable grate mechanism is configured to move carbonaceous material that is within the gasifier in use from the first oxidation zone in a direction towards the second reduction zone. This is achieved via moving the moveable parts of the grate mechanism in a reciprocal motion in a specific plane (which is a horizontal plane or is 10 or 20 degrees from a horizontal plane). This results in the carbonaceous material being urged from one end of the first substantially horizontal container portion to the other end of the same container portion, where the carbonaceous material can then fall into the second substantially upright container portion. This movement of material is helped by providing a grate which is not flat across its support surface. Instead, the moveable grate has a step-like structure provided by a multitude of grate elements each having a different average height when measured from the lowermost point of the container. Each of these grate elements provides part of the support surface. At least one step or level of the grate (e.g., one grate element) can move reciprocally with respect to another step or level of the grate (e.g., another grate element). In this way, a leading face of the step or level of the grate (e.g., grate element) that is moving can provide an urging force to the carbonaceous material in a desired direction, such as in the direction of the second reduction zone. The speed of the motor can be controlled which allows the rate at which carbonaceous material is moved towards the second reduction zone to be adapted. The moveable grate mechanism holds and supports carbonaceous material that is present within the container. The moveable grate mechanism also agitates the carbonaceous material and thus can mechanically reduce the size of carbonaceous material particles in the container. This helps reduce the likelihood of material blockage by way of bridging or channelling in the container which thus enables the gasifier to be operated continuously for longer periods. This in turn reduces the tar/particulate content of the resulting syngas. The moveable grate mechanism also enables air to be provided therethrough which thus allows air to be uniformly distributed to the first oxidation zone (i.e., not distributed via a single opening in a wall of the container). The moveable grate mechanism is described in more detail with reference to Figure 3.

The internal chamber has a carbonaceous material communication pathway which carbonaceous material travels along during use of the gasifier. An example track 290 that carbonaceous material may pass along when traveling along this pathway is shown in Figure 2. When travelling along this pathway during use of the gasifier, the carbonaceous material passes through certain zones within the internal chamber. That is to say that the carbonaceous material passes consecutively through a drying zone, a pyrolysis zone (which is immediately adjacent to the drying zone), a first reduction zone (or first gasification zone), which is immediately adjacent to the pyrolysis zone, a first oxidation zone (which is immediately adjacent to the first reduction zone), a second reduction zone (or second gasification zone), which is immediately adjacent to the first oxidation zone, and a second oxidation zone (which is immediately adjacent to the second reduction zone). An oxidation zone is a zone in which exothermic chemical reactions predominantly occur between the carbonaceous material and at least one gaseous component (e.g., O2) to thereby oxidise the carbonaceous material and produce at least one further gaseous component (e.g., CO or CO2). A reduction zone is a zone in which endothermic chemical reactions predominantly occur between the carbonaceous material and at least one gaseous component (e.g., H ₂ O or CO ₂ ) to thereby reduce the gaseous component into at least one further gaseous component (e.g., H ₂ or CO). These zones are generally defined by the boundaries shown in Figure 2 within the internal chamber although the exact boundaries may be subject to some fluctuation during use of the gasifier. Even though these fluctuations exist, at all times the reduction zone and oxidation zone can be defined as above. To put these zones in more simple terms, the reduction zone may be considered to be the zone where the rate of reduction of CO ₂ exceeds the rate of its formation (endothermic reactions are predominant), and the oxidation zone may be considered to be the zone where the rate of formation of CO ₂ exceeds the rate of its reduction (exothermic reactions are predominant). The boundary between these zones may be considered to be where these rates are essentially equal. The drying zone, pyrolysis zone and part of the first reduction zone are located within first internal chamber region 231 . A further part of the first reduction zone and the first oxidation zone are located within the second internal chamber region 241 . The second reduction zone is located within the third internal chamber region 251 . The second oxidation zone is located in the fourth internal chamber region 261 . The internal chamber also includes a carbonaceous residue communication pathway which residue travels along during use of the gasifier. When travelling along this pathway, residue (generated in the pyrolysis zone, first reduction zone or first oxidation zone) travels through the fifth internal chamber region (which may be referred to as a residue collection zone).

During use of the gasifier, carbonaceous material enters the internal chamber via the carbonaceous material inlet and becomes located in the drying zone. In the drying zone, the carbonaceous material is heated and maintained at a temperature of around 100°C to 200°C. In the drying zone, excess moisture is removed from the carbonaceous material. This causes an approximate weight loss of the carbonaceous material of around 10-30% depending on moisture content of feedstock. The temperature of the carbonaceous material is maintained within this zone via reactions occurring in other zones of the gasifier. The residence time of the carbonaceous material in the drying zone is around 10 to 15 minutes. Essentially, in this zone raw carbonaceous feedstock is converted to dry carbonaceous feedstock and H ₂ O. The H ₂ O is removed via the gas outlet and the dry carbonaceous material moves downwards through the container under the influence of gravity into the pyrolysis zone while preventing formation of fuel voids.

The pyrolysis zone is itself made up of two zones, a pure pyrolysis zone and a flaming pyrolysis zone. In the pure pyrolysis zone, hemicellulose present within the carbonaceous material is degraded causing volatiles to be released from the carbonaceous material. The volatiles are removed from the container via the gas outlet. The carbonaceous material in this pure pyrolysis zone is heated and maintained at a temperature of around 200°C to 500°C. The residence time in the pure pyrolysis zone is around 5 to 10 minutes. There is no free oxygen in the pure pyrolysis zone and so the carbonaceous material is heated in the absence of any free oxygen. In this zone, the weight of the carbonaceous material is reduced by around 20%. After leaving the pure pyrolysis zone, the carbonaceous material falls under gravity to the flaming pyrolysis zone. In this zone, the carbonaceous material is heated and maintained at a temperature of around 500 to 700 degrees Celsius. In this zone, cellulose and lignin decomposes and the weight loss of the carbonaceous material is around 45 wt%. Produced volatiles are also removed via the gas outlet. The residence time in this zone is around 5 to 10 minutes. Some free oxygen is present in the flaming pyrolysis zone which can cause the volatile gases being produced from the carbonaceous material to combust. This is why this zone is referred to as ‘flaming’. Significant weight loss was not observed to occur above 700 degrees Celsius in the pyrolysis zones, indicating that a temperature at this level or above might be preferable for preparation of activated biochar. This is believed to be because all the volatiles in the carbonaceous material is evaporated into gaseous state up to 700 degrees Celsius. After the completion of flaming pyrolysis, remaining material is char (fixed carbon and inert) which does not gasify in the absence of oxygen up to 700 degrees Celsius. Therefore, significant weight loss is not observed above this temperature in the pyrolysis zone. Further weight loss can only be observed when char residue enters the reduction zone followed by oxidation zone in the presence of oxygen which consumes some of the char residue. In the pyrolysis zones, carbonaceous material is essentially converted to char, volatiles (including tars) and gases. The total weight loss in the drying and pyrolysis zone is approximately 75 wt%. To heat the drying zone and the pyrolysis zones to their required temperatures, heat generated in the first oxidation zone (via exothermic reactions) is used. This heat is passed upward through the container via radiation and convection.

After leaving the pyrolysis zone, the carbonaceous material (which is now char) moves downward under gravity into the first reduction zone. In the first reduction zone, various chemical reactions occur. The main reactions that occur are the endothermic reactions C + CO2 = 2CO (Boudouard reaction) and C + H2O = CO + H2 (water gas reaction). However, due to the fluidic nature of the gasifier, other reactions also occur although these will be less common. For example, C + 2H2 = CH4 (methane formation), CO + H2O = CO2 + H2 (water gas shift reaction), CH4 + H2O = CO + 3H2 (reforming reaction), 2CO + 2H2 = CH4 + CO2 (methane formation) and CO2 + 4H ₂ = CH ₄ + 2H ₂ O (methane formation). The key components of syngas (CO + H ₂ ) are principally generated in the first reduction zone (and the second reduction zone). In the first reduction zone, the carbonaceous material is heated and maintained at a temperature of around 700 to 900 degrees Celsius. The residence time is around 10 to 15 minutes. The carbonaceous material is at least partly gasified in the first reduction zone. At least some of the gas generated in this zone may travel upwards through the pyrolysis zone and drying zone and exit the container via the gas outlet at the upper end of the container. The temperature is maintained in the first reduction zone via exothermic reactions taking place in the first oxidation zone.

After the first reduction zone, the carbonaceous material then enters the first oxidation zone. In this zone, the main reactions that take place are the following exothermic reactions. C + 2O2 = CO, CO + 2O2 = CO2, C + O2 = CO2 and H ₂ + 2 O2 = H ₂ O. Other reactions may also occur to a lesser extent. These exothermic reactions produce the energy needed to maintain the temperature at the required levels in the drying zone, the pyrolysis zone, the first reduction zone and the first oxidation zone itself. The first oxidation zone is heated and maintained at a temperature of around 900 to 1200 degrees Celsius. The residence time in this zone is around 5 to 10 minutes. At least some of the gas generated in this zone may travel upwards through the first reduction zone, pyrolysis zone and drying zone and exit the container via the gas outlet at the upper end of the container.

The moveable grate mechanism 280 moves the carbonaceous material from the first oxidation zone towards the second reduction zone. Once the carbonaceous material reaches the upper open end of the second substantially upright container portion, the material falls through the second reduction zone under the influence of gravity. In the second reduction zone, water and/or steam which is provided via the fluid inlet nozzles 263 reacts with the carbonaceous material such that a principal reaction in this zone is the endothermic reaction C + H ₂ O = CO + H ₂ . This zone enables the H ₂ and CO content of the syngas to be significantly increased which increases the calorific value of the syngas. Other reactions of course take place in this zone such as C + CO2 = 2CO, C + 2H2 = CH4, CO + 3H2 = CH4 + H2O. In this zone, the carbonaceous material is heated and maintained at a temperature of around 700 to 900 degrees Celsius. The residence time in this zone is around 10 to 15 minutes. The second reduction zone thus further gasifies the carbonaceous material. At least some of the gas generated in this zone may travel upwards through the first oxidation zone, first reduction zone, pyrolysis zone and drying zone and exit the container via the gas outlet at the upper end of the container. After leaving the second reduction zone under the effects of gravity, the carbonaceous material enters the second oxidation zone. In this zone, the carbonaceous material is gradually moved towards the carbonaceous material outlet via the auger conveyor. Opposite the outlet, the fluid inlet nozzles provide atomised water at a temperature of around 70 to 100 degrees Celsius and/or inject steam. The water/steam strikes the hot carbonaceous material to generate super-heated steam in this zone which has two effects. It causes the carbonaceous material that is about to leave via the outlet to be rapidly cooled to a temperature of around 120 to 150 degrees Celsius. This makes the material easier to handle when it exits the gasifier compared to known gasifiers. The temperature difference between the water/steam and the carbonaceous material also causes the H ₂ to dissociate from the O (for the H ₂ O molecules of the steam/water). This provides free oxygen that is able to drive the principal exothermic reactions (e.g., C + ¹ Z> O ₂ = CO, C + O ₂ = CO ₂ ) in this zone which provides heat energy to the second reduction zone to drive the endothermic reactions. Other reactions also take place in the second oxidation zone such as C + H ₂ O = H ₂ + CO, C + 2H ₂ O = 2H ₂ + CO ₂ and C + CO ₂ = 2CO. Not all H ₂ O molecules are dissociated which is why these are able to react with the carbonaceous material in this zone and which is why a principal reaction in the second reduction zone is C + H ₂ O = CO + H ₂ . At least some of the gas generated in this zone may travel upwards through the second reduction zone, first oxidation zone, first reduction zone, pyrolysis zone and drying zone and exit the container via the gas outlet at the upper end of the container. This zone is heated and maintained at an average temperature of around 700 to 900 degrees Celsius. However, local to the carbonaceous material outlet where steam/water is introduced the temperature may be significantly lower than this. The residence time in this zone is around 20 to 25 minutes. During the dual reduction and dual oxidation zones, there is a weight loss of around 10%. Thus, a total weight loss is approximately 85 wt% between the carbonaceous material inlet and outlet. Providing two reduction zone enables the calorific value of the syngas to be increased by around at least 15% compared to known gasifiers with only a single reduction zone.

By providing steam and/or atomised water (mist) directly into the second oxidation zone which contains partially gasified carbonaceous material, not only does this enable the calorific value of the syngas to be increased, but it also enables the production of microporous biochar or activated carbon as a by-product of the gasification process. Microporous biochar or activated carbon can be used in CO ₂ adsorption, soil remediation, water filtration and air pollution removal. The biomass fed into the gasifier passes through several zones and is converted into syngas and biochar is produced as a by-product. The biomass passes through the drying, pyrolysis, reduction and oxidation zones in the gasifier and is converted into biochar at elevated temperatures (500-1200°C). The amount of biochar produced depends on the biomass type and the operational conditions. Approximately 10-20% of the biomass fed to the reactor is converted into biochar. The introduction of water/steam in the second reduction zone however enables the biochar to be specifically ‘activated’. Particularly, the introduction of water/steam causes three outcomes: (a) removal of any excess volatiles and tars from biochar; (b) formation of new micropores; and (c) expansion of existing pores. Utilising the gasifier 200, it is thus possible to convert biochar by-product into activated carbon (or microporous biochar), which is a widely used valuable product. Whilst known gasifiers may produce syngas and non-microporous biochar, the gasifier 200 produces higher quality and quantity syngas as well as activated carbon (microporous biochar) without going through any excessive energy consuming other extra processes. The average pore diameter of the microporous biochar/activated carbon leaving the gasifier is around 10-20 pm. Figure 5a illustrates Scanning Electron Microscope (SEM) images at various length scales of oak wood chips (an example of biomass) prior to being passed through the gasifier 200. Figure 5b illustrates SEM images at various length scales of the oak chips of Figure 5a after passing through the gasifier 200. It can be seen that the material exiting the gasifier 200 is microporous with an average pore diameter of around 10-20 pm. Figure 5c and 5d show SEM images at various length scales of poplar chips and nut shells, respectively, after being passed through gasifier 200. These images also illustrate that the material exiting the gasifier 200 is microporous with an average pore diameter of around 10-20 pm.

Turning to Figure 3, this illustrates a moveable grate mechanism 300. The moveable grate mechanism may be the mechanism 280 from Figure 2. As discussed above in relation to Figure 2, the grate mechanism is configured to move carbonaceous material from the first oxidation zone in a direction towards the second reduction zone. The moveable grate mechanism can move carbonaceous material at a predetermined rate. The mechanism also provides agitation in the reaction bed to break bridge or channels when formed. The grate mechanism 300 includes a first grate element 310 and a second grate element 320 which together form a pair of grate elements. The grate elements are formed of heat resistant cast steel although it will be appreciated that other materials may be used according to certain other embodiments of the present invention. The grate elements are arranged to form a staircase-like structure. Whilst in Figure 3 only one pair of grate elements is illustrated, it will be appreciated that according to certain embodiments of the present invention that multiple pairs of grate elements may be utilised to form an extended staircase-like structure. The first grate element is moveable in a reciprocal fashion indicated by arrow 330 with respect to the second grate element. In Figure 3, the second grate element is held in a fixed position although according to certain other embodiments of the present invention both (or all) grate elements may be reciprocally moveable. The first grate element includes multiple substantially parallel, spaced apart elongate arm members 340i - 340 _n . The second grate element also includes multiple substantially parallel, spaced apart elongate arm members 350i - 350 _n . Each of the arm members have an overall length of around 200 - 400 mm indicated by 360. Aptly, the length of the arm members is around 250 mm. The arm members have overall height of around 100-150 mm indicated by 370. The arm members have a thickness of around 10 to 30 mm indicated by 380. Aptly the thickness is 22 mm.

Adjacent elongate arm members are spaced apart from one another by around 1 to 6 mm. That is to say that a gap between adjacent elongate arm members is around 1 to 6 mm. Aptly, elongate arm members are spaced apart by around 3 mm. This spacing enables air to pass upwards through the grate elements so that air can be uniformly provided to the first oxidation zone. The air also provides a cooling effect for the grate mechanism. This spacing also enables fine char particles or ash to fall through the grate elements and enter the residue removal container portion. Each of the arm members has a first substantially flat portion 342, a second substantially flat portion 344, and a curved connecting portion 346. A void or gap is provided between the first substantially flat portions of two adjacent arm members. This void/gap is around 3mm. The first substantially flat portion has a length of around 50 to 250 mm. The second substantially flat portion has a height of around 10 to 30mm. When used in a gasifier, the first substantially flat portion of an elongate arm member is inclined at around 0 to 25 degrees to a horizontal axis. That is to say that an end of the first substantially flat portion which meets the curved connecting portion is at a lower location than the opposite end of the first substantially flat portion. This helps to facilitate the movement of carbonaceous from into the second reduction zone. The second substantially flat portion is inclined at an angle of around 0 to 15 degrees to a vertical axis. This enables the second substantially flat portion to act as a pushing surface which applies force to the carbonaceous material upon movement of the grate element. The second substantially flat portion of one grate element abuts with a first substantially flat portion of an adjacent grate element. In this way, movement of the grate element causes the second substantially flat portion to slide along a surface of the adjacent first substantially flat portion. A gap between adjacent arm members varies in the region between adjacent connecting portions. That is to say that a size of the gap continuously increases between an end of the curved connecting portion which connects to the second substantially flat portion and an end of the curved portion which connects to the first substantially flat portion. The gap varies from 1 to 6 mm. The varying sized gap enables smooth movement of the grids at different operating temperatures due to expansion and contraction. As can be seen in Figure 2, this moveable grate mechanism is disposed at a base of the first oxidation zone. By utilising such a grate mechanism, multiple benefits are provided. As air enters via the grate, this enables the first oxidation zone to be provided with a uniform stream of air which thus helps to provide uniform reaction kinetics in the first oxidation zone. The air also cools the grate. Furthermore, as the grate mechanism moves back and forth, the carbonaceous material is agitated and the size of particulates is mechanically reduced. When the particulates are small enough, they fall through the grate and are removed from the gasifier. This prevents blockage of the gasifier and helps to ensure continuous operation over longer periods. This in turn helps to increase the quality of the syngas.

Figure 4 illustrates a perspective view of a gasifier 400. The gasifier is similar to the gasifier shown in Figure 2. The gasifier 400 includes a container 410 including a first substantially upright container portion 430, a first substantially horizontal container portion 440, a second substantially upright container portion 450, a second substantially horizontal container portion 460 and a residue removal container portion 470. Figure 4 helps to illustrate the configuration of these portions in more detail than Figure 2. The gasifier of Figure 4 also has at least one gas outlet 419, at least one carbonaceous material inlet 412 and at least one carbonaceous material outlet 417.

Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to” and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and/or steps are mutually exclusive. The invention is not restricted to any details of any foregoing embodiments. The invention extends to any novel one, or novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.