AU2021106888A4

AU2021106888A4 - A system and a method for pyrolysing biomass

Info

Publication number: AU2021106888A4
Application number: AU2021106888A
Authority: AU
Inventors: Adam Christopher Carson; Steven John HILL
Original assignee: Sda Eng Pty Ltd
Current assignee: Sda Engineering Pty Ltd
Priority date: 2021-08-24
Filing date: 2021-08-24
Publication date: 2021-11-25
Anticipated expiration: 2029-08-24

Abstract

The present disclosure relates to a system and a method for pyrolysing biomass to create biochar in a continuous process. The system and method comprising firstly introducing the biomass to an inlet of a primary zone of a reaction chamber, and subsequently conveying the biomass from the first end to a second end of the primary zone, and using an oxidant injection assembly to controllably inject oxidant into lower ports located in a lower portion of the primary zone to release combustible gases. Further, using the oxidant injection assembly to controllably inject oxidant into upper ports located in an upper portion of the primary zone to partially combust the released combustible gases resulting in: heat generation that pyrolyses the biomass, and providing and maintaining sub-stoichiometric conditions. 1/4 CD, ru I-O cu ell I CI) ICIn LO in (03 I In I Ia

Description

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A SYSTEM AND A METHOD FOR PYROLYSING BIOMASS TECHNICAL FIELD

[0001] The present disclosure relates to the field of pyrolysis. In a particular form, the present disclosure relates to a system and a method for pyrolysing biomass to create biochar.

BACKGROUND

[0002] Pyrolysis is the thermochemical decomposition of materials at high temperatures, which generally occurs in an oxygen (or reactive gas) deficient environment. An example of a typical pyrolysis process is one that utilises a reaction chamber having a mechanism that feeds in carbon containing material, which within the scope of the present disclosure may be referred to as "biomass", at an inlet and exposing the biomass to high temperatures to yield three distinct products: a solid carbon-rich char (often referred to as "biochar"), a gaseous volatiles (often referred to as "syngas"), and a mixture of tars and oils that may also contain water (often referred to as "product liquid"). The produced carbon-rich char has a range of uses including (but not limited to) as a fuel for generating energy, use as a soil amendment agent, and others. The product gaseous volatiles may also be used to generate energy.

[0003] Gasification and combustion are related processes that often occur within the reaction chamber during pyrolysis, however they are two distinct processes. Gasification occurs at a higher temperature than pyrolysis, requires a gasification agent (typically air, oxygen or steam) to react with the biomass to yield the gaseous volatiles and the carbon-rich biochar. Gasification must occur in limited oxygen conditions so as to not combust the produced gaseous volatiles, as under excess oxygen conditions, combustion occurs where the product yield is a flue gas and ash as the only solid product. Pyrolysis, gasification and combustion are all processes that may take place to some extent inside the reaction chamber, however their relative rates and locations must be properly controlled to ensure that the overall pyrolysis process functions as desired.

[0004] Presently available pyrolysis processes, such as the example provided above used for pyrolysing biomass, typically bum all or part of the gaseous volatile products ("syngas product") and use the resulting heat to supply the required energy to sustain the pyrolysis reaction. This is typically done using either of two processes. The first process is to flow this wholly or partially combusted syngas product back through the biomass still undergoing pyrolysis within the reaction chamber, thereby maximizing convective heat transfer to the biomass to create biochar. The second process is to combust the gaseous volatile products in a separate chamber, and subsequently transfer the heat to the feedstock via conduction through a process chamber wall. There are several problems with either of these presently utilised pyrolysis processes. Problems with the first method include that it often leads to burning the biomass resulting in a suboptimal biochar product with poor properties, and that the requirement for gas flow through the feedstock for convective heat transfer limits the size and shape of feedstock particles that can be used, as the feedstock must be relatively porous in bulk to allow paths for the gas flow. Problems with the second process include that processes utilising conductive heat transfer are difficult to commercially upscale due to square-cube law, such that when upscaling the reaction chamber utilising conductive heat transfer isometrically, the volume of the reaction chamber (and thus the amount of biomass contained therein) increases with the cube of scale, while the surface area available for conductive heat transfer increases with the square of scale. As with the first method, the requirement for direct contact between the process chamber wall and the biomass for conductive heat transfer again limits the size and shape of biomass particles, and this direct contact requirement also often causes heat exchange surfaces within the reaction chamber to foul requiring maintenance.

[0005] It is against this background and the problems and difficulties associated therewith, that the present invention has been developed.

[0006] Throughout this disclosure, the term "pyrolysis" should be understood to mean thermal decomposition (or thermochemical decomposition) of materials at elevated temperatures in the absence of or with limited supply of an oxidising agent such as oxygen. The main products of pyrolysis are gaseous volatiles (such as synthesis gases that are also referred to as "syngas"), product liquids and carbon-rich char (may be referred to as "biochar", when derived from a biomass feedstock, or referred to simply as a "pyrolysed product"). Typically the product synthesis gas (also referred to herein as "syngas product") may include carbon monoxide, carbon dioxide, hydrogen, and hydrocarbons. Typically the product liquids may include water, tars, oils and other hydrocarbons (for example, acidic water based liquids often referred to as "wood vinegar").

[0007] Additionally, within the scope of this disclosure, the terms "feedstock", "biomass", "carbon containing material" or "organic material" may be interchangeable and should be understood to mean a material having a relatively high carbon content. This includes biomass, i.e. living or formerly living organic matter that may be used as fuel, but could also include chemically organic solids, such as coal or other fossil fuel derivatives. Specific biomass products may include, by way of example only, agricultural products and residual products such as straw, forestry products such as wood chips or timber residue, biomass derived/produced in aquatic environments such as algae, nut shells, animal wastes, pits and seeds of fruit/vegetables. Other types of non-biomass feedstock may include, again by way of example only, plastics, coals, municipal and industrial residues. Biomass, on its own, may be used as a renewable source of fuel to produce heat or electricity, but also be employed by pyrolysis processes as a feedstock for producing other fuels including the production of syngas.

[0008] Furthermore, the process, system and method disclosed herein may also be described as partial gasification, as well as pyrolysis. That is to say, the process, system and method disclosed may be applied or referred to as a gasification process, a gasification system and a gasification method. Those skilled in the art will understand that pyrolysis describes the release of gas from heating the biomass, whereas gasification generally requires a reaction of oxidant (e.g. air or high temperature steam) with the fixed carbon content of the biomass and generally utilises higher temperatures when compared to pyrolysis. Since the gasification consumes the carbon content of the biomass, the emphasis of gasification is on the gas produced rather than a biochar product.

SUMMARY

[0009] Embodiments of the present disclosure relate to a system and a method for pyrolysing biomass to create biochar. The system and method being particularly intended for pyrolysing biomass by introducing the biomass into a primary zone of a reaction chamber via an inlet and conveying it through said primary zone toward a second end thereof, using an oxidant injection assembly to controllably inject oxidant into a lower portion of the primary zone to generate heat proximal to the biomass and thereby release combustible gases into the primary zone, subsequently using the oxidant injection assembly to controllably inject oxidant into an upper portion of the primary zone to partially combust the released combustible gases resulting in heat generation that pyrolyses the biomass, and providing and maintaining sub-stoichiometric conditions, producing biochar discharged at an outlet adjacent to the second end, and further using the oxidant injection assembly to controllably inject oxidant into a secondary zone of the reaction chamber downstream from the primary zone to further combust the partially combusted gases.

[0010] According to a first aspect of the present disclosure, there is provided a system for pyrolysing biomass. The system comprising: a reaction chamber comprising a first end, a second end, a primary zone, and a secondary zone downstream from the primary zone; and an oxidant injection assembly comprising a plurality of flow injectors; the primary zone comprising: an upper portion comprising one or more upper primary ports; and a lower portion comprising an inlet for the biomass proximal to the first end, an outlet for a biochar product adjacent to the second end, and one or more lower ports disposed between the inlet and the outlet; the secondary zone comprising: one or more secondary ports and a flue; and wherein each flow injector is connectable to respective upper primary, lower and secondary ports to control discharge of oxidant into the reaction chamber; and wherein, in use, oxidant injected into the one or more lower ports results in heat generated proximal to the biomass resulting in the release of combustible gases into the primary zone, oxidant injected into the one or more upper primary ports results in partial combustion of the released combustible gases to provide and maintain sub-stoichiometric conditions resulting in heat generation that pyrolyses the biomass.

[0011] In one embodiment, the system further comprises a means for controlling draft within the primary zone, and the reaction chamber further comprises at least one pressure sensor, wherein, in use, the means for draft control is arranged to control the draft within the reaction chamber in response to inputs from at least the pressure sensor(s).

[0012] In one embodiment, the system further comprises one or more extraction means comprising at least one extraction line in fluid communication with the reaction chamber, wherein, in use each extraction line is arranged to extract gases from the biomass prior to pyrolysis and/or the biochar prior to discharging the biochar.

[0013] In one embodiment, the one or more extraction means comprises a first extraction line proximal to and in fluid communication with the inlet for the biomass, and a second extraction line proximal to the secondary conveyor mechanism is in fluid communication with the outlet for the biochar.

[0014] In one embodiment, in use, the first extraction line extracts gases from the biomass prior to pyrolysis and the second extraction line extracts gases from the biochar prior to discharging the biochar.

[0015] In one embodiment, in use, the first and second extraction lines remove water vapour from the biomass and excess gas (or leaked air) from the biochar.

[0016] In one embodiment, a first end of the first extraction line is in fluid communication with the inlet for the biomass, and a second end of the first extraction line is in fluid communication with the, or each, upper injection ports. In an alternative embodiment, the second end of the first extraction line is in fluid communication with the, or each secondary injection port.

[0017] In one embodiment, a first end of the second extraction line is in fluid communication with the outlet for the biochar, and a second end of the second extraction line is in fluid communication with the, or each secondary injection port.

[0018] In one embodiment, the reaction chamber comprises one or more temperature sensors arranged to provide temperature measurements in the primary zone, and the system further comprises a control system arranged to control the flow injector(s) connected to the upper primary, lower and secondary port(s) in response to inputs from at least the temperature sensor(s), wherein, in use, the control system controls the resulting partial combustion of the combustible gases in the primary zone to result in heat generation to pyrolyse the biomass and provide and maintain the sub-stoichiometric conditions.

[0019] In one embodiment, the heat generated comprises a combination of radiant and convective heat that pyrolyses the biomass.

[0020] In one embodiment, the control system injects oxidant into the upper primary ports to further provide a reducing atmosphere within the primary zone of the reaction chamber.

[0021] In one embodiment, each of the flow injectors are individually controllable via the control system.

[0022] In one embodiment, each of the flow injectors are controlled to maintain a hierarchy of pressures between the primary and secondary zones to prevent leakage of injected or produced gases or oxidants. In this embodiment, the hierarchy of pressures is achieved via control of draft, or via the ejector effect at the injection points, or via a combination thereof.

[0023] In one embodiment, the system further comprises a conveying mechanism extending between the inlet and outlet of the lower portion of the primary zone.

[0024] In one embodiment, the conveying mechanism comprises a feed hopper proximal to the first end or inlet of the lower portion of the primary zone. In this embodiment, the feed hopper provides for supply of biomass into the system for pyrolysis.

[0025] In one embodiment, the conveying mechanism comprises a screw conveyor extending between the inlet and outlet of the lower portion of the primary zone, wherein in use, the screw conveyor conveys and agitates the biomass from the inlet to the outlet. In this embodiment, the screw conveyor may be connected to a drive mechanism.

[0026] In one embodiment, the system further comprises a char chute connected to the outlet proximal to the second end of the reaction chamber, whereby in use, the pyrolysed product is transported through the char chute into an inlet of a secondary conveying mechanism for conveying and agitating the pyrolysed product from the inlet to a char exit of the secondary conveying mechanism.

[0027] According to a second aspect of the present disclosure, there is provided a method for pyrolysing biomass to produce biochar. The method comprising: (a) introducing the biomass to an inlet at a first end of a primary zone of a reaction chamber; (b) conveying the biomass from the first end to a second end of the primary zone; (c) using an oxidant injection assembly to controllably inject oxidant into one or more lower injection ports located in a lower portion of the primary zone to generate heat proximal to the biomass and release combustible gases into the primary zone; (d) using the oxidant injection assembly to controllably inject oxidant into one or more upper injection ports located in an upper portion of the primary zone to partially combust the released combustible gases to provide and maintain sub-stoichiometric conditions that result in heat generation to pyrolyse the biomass; (e) using the oxidant injection assembly to controllably inject oxidant into one or more secondary injection ports located in a secondary zone of the reaction chamber downstream from the primary zone to further combust the partially combusted gases; and (f) discharging biochar at an outlet adjacent to the second end.

[0028] In one embodiment, at step (d) the oxidant injection assembly controllably limits the injection of the oxidant to provide and maintain a reducing atmosphere within the primary zone of the reaction chamber, whereby the heat generated comprises a combination of radiant and convective heat that pyrolyses the biomass.

[0029] In one embodiment, the oxidant injection assembly of steps (c) to (e) comprises a plurality of flow injectors, wherein each flow injector is connectable to respective lower, upper primary and secondary ports to control discharge of oxidant into the primary and secondary zones of the reaction chamber, and are controlled by a control system to maintain temperatures within the primary and secondary zones of the reaction chamber.

[0030] In one embodiment, the method comprises a further step (g) whereby one or more extraction means comprising at least one first extraction line is used extract gases from the biomass at step (a) as it is introduced at the inlet, and a further extraction line that is used to extract gases at step (f) as the produced biochar is discharged at the outlet.

BRIEF DESCRIPTION OF DRAWINGS

[0031] Embodiments of the present disclosure will be discussed with reference to the accompanying drawings wherein:

[0032] Figure 1 is a schematic flow diagram illustrating a system and method for pyrolysing biomass, within a typical application wherein a reaction chamber comprises both primary and secondary zones and an extraction means to extract gas from the biomass and a produced biochar;

[0033] Figure 2 is a schematic flow diagram illustrating an alternate system and method for pyrolysing biomass, wherein a secondary conveyor mechanism comprises a water injection point;

[0034] Figure 3 is a schematic flow diagram illustrating a further alternate system and method for pyrolysing biomass, wherein a reaction chamber comprises syngas offtake outlets and a controllable throttle or damper disposed between a primary zone and a secondary zone of the reaction chamber; and

[0035] Figure 4 is a schematic flow diagram illustrating a further alternate system and method for pyrolysing biomass, wherein the system is a rotary kiln comprising a reaction chamber comprising a primary zone and a secondary zone.

[0036] In the following description, like reference characters designate like or corresponding parts throughout the figures.

DESCRIPTION OF EMBODIMENTS

[0037] Referring to anyone of the Figures, there is illustrated a system (100) and a method for pyrolysing biomass (200). The system (100) and method is directed to be used in a continuous process, rather than a batch process, however it will be apparent in the disclosure below that the system (100) and method may also be considered a semi-batch process (for example whereby the biomass (200) is periodically fed into the system (100)). The system (100) and method are particularly configured with the aim to produce two distinct products, namely: a carbon-rich char (hereinafter referred to as "a pyrolysed product" or "a biochar" or "a biochar product" interchangeably), a synthetic gas (hereinafter referred to as "a syngas product" or "a product syngas" or "a combusted syngas" interchangeably). It will be appreciated by those skilled in the art that the system (100) and method of the disclosure below may also produce a third product, namely a liquid by-product (often comprising bio-oils, tars and water), however it is not the intent of the system (100) and method to produce said by-product. It will be further appreciated by those skilled in the art that the system (100) and method of the disclosure below aims to create biochar by slow pyrolysis, without extracting the syngas product for use as a separate fuel product. Rather, the syngas product is completely combusted to yield a substantial amount of heat as a potentially useful by-product, which may, for example, be utilised downstream of the system (100) as a hot exhaust gas.

[0038] Particularly, the present disclosure relates to a method for pyrolysing biomass (200) to produce biochar. The method comprising:

(a) introducing the biomass (200) to an inlet (11) at a first end (12) of a primary zone (13) of a reaction chamber (10);

(b) conveying the biomass (200) from the first end (12) to a second end (14) of the primary zone (13), in this way creating a biomass bed extending between the first and second ends (12 and 14);

(c) using an oxidant injection assembly (30) to controllably inject oxidant into one or more lower ports (15) located in a lower portion of the primary zone (13) to generate heat proximal to the biomass (200), and thereby the biomass bed, and release combustible gases into the primary zone (13);

(d) using the oxidant injection assembly (30) to controllably inject oxidant into one or more upper primary ports (16) located in an upper portion of the primary zone (13) to partially combust the released combustible gases to provide and maintain sub-stoichiometric conditions that result in heat generation to pyrolyse the biomass (200);

(e) using the oxidant injection assembly (30) to controllably inject oxidant into one or more secondary ports (18) located in a secondary zone (19) of the reaction chamber (10) downstream from the primary zone (13) to further combust the partially combusted gases; and

(f) discharging biochar at an outlet adjacent to the second end.

[0039] It will be appreciated that the partial combustion of the released combustible gases (i.e. the partially combusted gases), may be partially combusted syngas.

[0040] In one embodiment, step (d) of the method above, oxidant injection assembly (30) controllably limits the injection of the oxidant to provide and maintain a reducing atmosphere within the primary zone (13) of the reaction chamber (10). It will be appreciated in this embodiment, that the heat generated by the partial combustion of the released combustible gases in the primary zone (13) comprises a combination of radiant and convective heat that is then used to pyrolyse the biomass (200).

[0041] In one embodiment, the oxidant injection assembly of steps (c) to (e) of the above method comprises a plurality of flow injectors (31), wherein each flow injector (31) is connectable to respective lower (15), upper primary (16) and secondary (18) ports to control discharge of oxidant into the primary (13) and secondary (19) zones of the reaction chamber (10), and are controlled by a control system to maintain temperatures within the primary (13) and secondary (19) zones of the reaction chamber (10).

[0042] In one embodiment, the above method comprises a further step (g), whereby one or more extraction means comprising at least one t extraction line (50) (or first extraction line) that is used to extract gases from the biomass (200) at step (a) as it is introduced at the inlet (11) of the reaction chamber (10), and a further extraction line (51) (or second extraction line) that is used to extract gases at step (f) as the produced biochar is discharged at the outlet (17). It will be understood that the extracted gases may be gases originating from within the biomass (200) fed at the inlet (11), or water vapour within the biomass (200) fed in at the inlet (11), or may be oxidants from the primary zone (13) that have been transported to the outlet (17) (i.e. leaked gas). It will be appreciated that when it is water vapour within the biomass (200) that is extracted by the, or each extraction means, the extraction means is in effect drying or de-watering the biomass (200) prior to it entering the reaction chamber (10) via the inlet (11).

[0043] Additionally, the present disclosure also relates to the system (100) for pyrolysing the biomass (200). The system comprising: the reaction chamber (10) comprising the first end (12), the second end (14), the primary zone (13) (may be considered a primary combustion zone), and the secondary zone (19) (which may be considered a secondary combustion zone) downstream from the primary zone (13). The system (100) additionally comprises the oxidant injection assembly (30) comprising a plurality of flow injectors (31). The primary zone (13) comprising the upper portion (may also be referred to as an upper section or upper primary portion) comprising the one or more upper primary ports(16). The primary zone (13) further comprising the lower portion (may also be referred to as a lower section) comprising the inlet (11) for the biomass (200) proximal to the first end (12), the outlet (17) for a pyrolysed product (or biochar product) adjacent to the second end (14), and the one or more lower ports (15) disposed between the inlet (11) and the outlet (17). The secondary zone (19) comprising the one or more secondary ports (18) and a flue (20) (or exhaust port or outlet port). Each flow injector (31) is connectable to respective upper primary (16), lower (15) or secondary (18) ports to control discharge of oxidant into the reaction chamber (10). It will be appreciated that the flow injector(s) (31) connected to the upper primary port(s) (16) may be referred to as the upper primary flow injector(s) (31), the flow injector(s) (31) connected to the lower port(s) (15) may be referred to as the lower flow injector(s) (31), and the flow injector(s) (31) connected to the one or more secondary ports (18) maybe referred to as the secondary flow injector(s) (31). The system (100) in use, has oxidant injected into the one or more lower ports (15) that results in heat generated proximal to the biomass (200) (or the biomass bed) resulting in the release of combustible gases into the primary zone (13), oxidant injected into the one or more upper primary ports (16) results in partial combustion of the released combustible gases further resulting in heat generation that pyrolyses the biomass (200), and providing and maintaining sub-stoichiometric conditions.

[0044] In one embodiment, the system (100) further comprises a means for controlling draft. Such control may be effected via a damper (70) as, best illustrated in Figure 3, within the primary zone (13). In this embodiment, the reaction chamber (10) may further comprise at least one pressure sensor/transmitter (PT), whereby, in use, the means for draft control (70) is arranged to control the draft within the reaction chamber (10) in response to inputs from the at least one pressure sensor(s) (PT). Alternatively, draft may be controlled via the oxidant injection assembly (30), injecting oxidant into the flue (20) via an additional injection port (31), as shown in any one of Figures 1 or 3. As illustrated, the additional port (31) is proximal to the flue (20), and is connectable to the oxidant injection assembly (30). Alternatively, draft may be controlled via a combination of the above methods, or via other methods known to those skilled in the art.

[0045] In one embodiment, referring to either one of Figures 1 or 3, the system (100) comprises the one or more extraction means, the first extraction line (50) is proximal to and in fluid communication with the inlet (11) for the biomass (200), and the second extraction line (51) proximal to the secondary conveyor mechanism (45) is in fluid communication with the outlet (17) for the biochar (or pyrolysed product). In use, the first (50) and second (51) extraction lines extract gases from the biomass (200), for example by removing water vapour, and remove excess gases from the biochar product prior to discharging the biochar.

[0046] In one embodiment, a first end of the first extraction line (50) is in fluid communication with the inlet (11) for the biomass (200), and a second end of the first extraction line (50) is in fluid communication with the, or each, upper primary ports (16), as illustrated by the solid line in Figures 1 and 3. In an alternative embodiment, the second end of the first extraction line (50) may be in fluid communication with one of the secondary ports (18), as illustrated by the dashed line in Figures 1 and 3.

[0047] In one embodiment, a first end of the second extraction line (51) is in fluid communication with the second conveyor mechanism (45) at the outlet (17) for the biochar (or pyrolysed product), and a second end of the second extraction line (51) is in fluid communication with one of the secondary ports (18), or alternatively in fluid communication directly with the secondary zone (19).

[0048] In one embodiment, the reaction chamber (10) further comprises one or more temperature sensors (32) arranged to provide temperature measurements. In this embodiment, the system (100) further comprises a control system arranged to control the flow injectors(s) connected to the upper primary (16), lower (15) and secondary (18) port(s) in response to inputs from at least the temperature sensor(s) (32). The control system, in use, controls the release of combustible gases into the primary zone (13) and partial combustion thereof to result in heat generation to pyrolyse the biomass (200) and provide and maintain the sub-stoichiometric conditions. Therefore, it will be understood that the control system, in effect, controls oxidant injection into the system (100).

[0049] Referring to anyone of the Figures, there is illustrated the reaction chamber (10) comprising the features of the system (100) and method disclosed above. With particular reference to Figures I to 3, the reaction chamber (10) may further comprise a conveying mechanism (40) comprising a screw conveyor (41), wherein the screw conveyor (41) substantially extends between the inlet (11) and the outlet (17) of the lower portion of the primary zone (13). Whereby, in use, the screw conveyor (41) conveys and agitates the biomass (200) from the inlet (11) to the outlet (17). It will be appreciated that the conveying mechanism (40) functions so as to "feed" and continuously provide fresh biomass (200) into the reaction chamber (10) to discharge/output/eject/produce biochar at the outlet (17), thus making the system (100) and method continuous. The screw conveyor (41) may be connected to a drive mechanism (42), whereby in use, the drive mechanism (42) imparts mechanical drive to allow the screw conveyor (41) to convey the biomass (200) from the inlet (11) to the outlet (17).

[0050] In one embodiment, the screw conveyor (41) maybe any suitable means such as a moving floor, a centerless screw conveyor, or the like that are well known in the art for mechanically conveying and agitating feedstock such as the biomass (200) to create the moving biomass bed. In an alternative embodiment, such as illustrated in Figure 4 in particular, the biomass (200) may be conveyed through the reaction chamber mechanically by situating the reaction chamber (10) within a rotary kiln (300). It will be appreciated that in a preferred embodiment of the present disclosure, the biomass (200) is agitated as it is conveyed from the inlet (11) to the outlet (17), as agitation is beneficial in ensuring even mixing and heating of the biomass (200). It will be further appreciated that agitation of the biomass (200) serves to turn over the biomass (200) and expose different portions of the biomass (200) to the heat generated by partial combustion of the released combustible gases (noting that the heat generated may comprise one or more of a radiant and convective heat), thereby advantageously providing more uniformity to the temperature through the depth of the conveyed biomass (200).

[0051] In one embodiment, best illustrated by any one of Figures I to 3, the conveyor mechanism (40) may further comprise a feed hopper (43). The feed hopper (43) is preferably located proximal to the first end (12) or the inlet (11) of the lower portion of the primary zone (13), as illustrated. The feed hopper (43) provides for supply of biomass (200) into the system (100) for pyrolysis, and may be considered the feed inlet for the conveyor mechanism (40). In this embodiment, the screw conveyor (41) extends from the feed hopper (43) to the outlet (17) at the second end (14) of the reaction chamber (10). In this particular embodiment, biomass (200) is introduced at the feed hopper (43), subsequently conveyed and agitated by the screw conveyor (41) through the inlet (11) at the first end (12), through the reaction chamber, and to the outlet (17) proximal to the second end (14) of the reaction chamber where the produced biochar is discharged. Further, in this embodiment, the inlet (11) may feature a means for air leakage control, however is not essential as any air introduced unintentionally at this point will not come into contact with any of the biomass (200) that is undergoing pyrolysis. It will be appreciated that provided the feed hopper (43) is proximal to the inlet (11) of the reaction chamber (10), advantageously, this arrangement minimises the risk of air unintentionally leaking into the system (100) at the inlet (11).

[0052] In one embodiment, still referring to any one of Figures I to 3, the system (100) may further comprise a char chute (44) proximal and connected to the outlet (17) and the second end (14) of the reaction chamber (10). The char chute (44) being particularly arranged to transport the produced/discharged biochar at the outlet (17) to an inlet of a secondary conveyor mechanism (45). It will be appreciated that the secondary conveyor mechanism may be considered a char discharge screw. The secondary conveying mechanism (45) comprises a secondary drive mechanism (46) connected to a secondary screw conveyor (47), in use, the secondary drive mechanism (46) imparts drive to the secondary screw conveyor (47) to convey and agitate the biomass (200) from the inlet of the secondary conveyor mechanism (45) to a char exit (48). It will be appreciated by those skilled in the art that the secondary conveyor mechanism (45) may be used for a number of purposes, such as but not limited to:

- Providing a reasonable seal at the outlet (17) of the lower portion of the primary zone (13)

and thus the reaction chamber, to prevent air unintentionally drafting into the reaction chamber via the outlet (17) or the char exit (48);

- Remove the produced biochar from the system (100) once the biochar (200) has undergone pyrolysis, and if required, cool the produced biochar which may be achieved via direct or indirect heat transfer, or by a water injection port (49) illustrated in Figures 1, 2, 3 and 4 injecting a cooling liquid (preferably water) to ensure that the biochar is sufficiently cooled and passivated before being discharged at the char exit (48). It will be appreciated that other cooling methods are envisaged, such as via a cooling jacket (not shown) on the secondary screw conveyor (45), or other solid coolers, and not limited to only those discussed herein.

[0053] In anyone of the above embodiments, the primary zone (13) (which may also be referred to as combustion zone 1 or the primary combustion zone) may be particularly arranged to partially combust the released combustible gases from the biomass (200). The released combustible gases may also be considered or referred to as pre-combusted syngas, as it is released from the biomass (200) as the biomass (200) is introduced at the inlet (11) of the reaction chamber (10), whereby the control system or the oxidant injection assembly (30) controls the flow injector(s) connected to the one or more lower ports (15) of the oxidant injection assembly (30) to controllably inject oxidant into lower portion of the primary zone (13). The one or more lower ports (15) may extend into the lower portion of the primary zone (13) toward the first end (12) of the reaction chamber (10), and inject the oxidants that causes the release of combustible gases from the biomass (200) into the primary zone (13). The released combustible gases subsequently travel to the upper portion of the primary combustion zone (13), whereby it will be appreciated from any one of Figures I to 3, is physically distant from the lower portion. The physical distance between the upper and lower portions of the primary zone (13) is an appropriate distance that is designed or determined by the dimensions of the reaction chamber (10). As illustrated, it will be appreciated that the one or more lower ports (15) are spaced and positioned such that they do not inject gas directly into the biomass (200) (or biomass bed) as it is conveyed from the inlet (11) to the outlet (17). This advantageously avoids burning the biomass (200) and thus the produced biochar comprises better properties.

[0054] It will be appreciated that the lower ports (15) may serve mainly for process start-up, that is, to commence the pyrolysis of the biomass (200). That is to say, the lower ports (15) maybe utilised to inject oxidant so as to increase the temperature of the biomass (200) proximal to the first end (12) of the reaction chamber, after which injection via these ports (15) may be turned off so as to not burn the biomass (200). It will be understood, in this way, each of the lower ports (15) may be individually controllable such that, for example, ports (15) proximal to the first end (12) could be injecting oxidant, but the ports (15) proximal to the second end (14) (or closer to the second end) could be turned off, which may advantageously help to force the heat generated toward the biomass (200) proximal to the inlet (11). It will be appreciated that this is particularly advantageous with biomass (200) that has a high moisture content, where higher heat (or a flame) near the biomass (200) inlet (11) effectively dries the incoming biomass, but oxidant is not injected at points toward the outlet (17) so as to avoid burning the produced biochar. It will be appreciated that flames may occur in the hot combustible gas atmosphere, when oxidant (such as air) is injected via the ports (15, 16 and 18).

[0055] It will be appreciated that the physical distance between the upper and lower portions of the primary zone (13) advantageously minimises (or mitigates) the partially combusted gases from making contact with the biomass (200) being pyrolysed via the heat generated. The partially combusted gases is instead directed or flowed toward the secondary zone (19) downstream of the first zone (13). It will also be appreciated that between the upper and lower portions of the primary zone (13) is sufficient area for generated heat from partial combustion of the released combustible gases to transfer radiative and convective heat to the biomass (200) being conveyed from the inlet (11) to the outlet (17).

[0056] It will further be appreciated that within the primary zone (13), the oxidant controllably injected via the control system and the upper primary flow injector(s) (31) to the upper primary port(s) (16) to provide sub-stoichiometric conditions. That is to say, that the primary zone (13) is injected with oxidant without enough oxygen to completely combust the combustible gases released from the biomass(200). In this way, the control system injects oxidant into the upper primary ports (16) to further provide and maintain a reducing atmosphere within the primary zone (13) of the reaction chamber (10), thus advantageously avoiding oxidation of the biomass (200). It will be appreciated that if excess oxidant or air were to be injected into the primary zone (13), the released combustible gases from the biomass (200) would be completely combusted resulting in complete combustion of gases (or syngases) and the atmosphere within the primary zone (13) of the reaction chamber (10), further resulting to burning of and a reduction in the yield of the produced biochar. Accordingly, it is an advantage of the present disclosure to inject oxidant only containing enough oxygen into the primary zone (13) of the reaction chamber (10) so as to increase temperatures within the reaction chamber (10) as needed for heat to be generated for radiative heat transfer to pyrolyse the biomass (200) being conveyed.

[0057] In anyone of the above embodiments, the oxidant injected into the primary zone (13) of the reaction chamber (10) may be controlled via the flow injectors (31) and thus the control system to produce the required temperature within the reaction chamber (10), whereby preferably the one or more upper primary ports (16) comprise low-velocity jets that minimise recirculation of the oxidant injected into the lower portion of the primary zone (13).

[0058] In any one of the above embodiments, the secondary zone (19) (which may also be referred to as combustion zone 2 or the secondary combustion zone) is particularly arranged to complete combustion of the partially combusted gases (or syngases) received from upstream primary zone (13). It will be understood that within the secondary zone (19), the oxidant injection assembly (30) is used to controllably inject oxidant comprising excess oxygen (i.e. excess air conditions) via the one or more secondary ports (18) into the secondary zone (19) to further combust the partially combusted gases, to ensure that all combustible products (such as CO and others) are destroyed from the gas, before it is directed for use as heat and/or vented to the atmosphere via the flue (20). Each of the secondary ports (18) within the secondary zone (19) may comprise a number of independently controllable jets, whereby the jets are at different angles (e.g. pointing in the direction of the flue, tangentially to the flue, or back toward the primary zone (13) of the reaction chamber). It will be appreciated that these controllable jets may be advantageously modulated independently to control the draft of the incoming partially combusted gas and the completely combusted gas produced within the secondary zone (19).

[0059] It will also be appreciated that it is possible to utilise alternate syngas offtake points (such as and 61 illustrated on Figure 3) at particular locations within the reaction chamber (10), which can be used in combination with, or without the secondary zone (19). The gases extracted from the offtake points (60 and 61) may comprise different properties dependant on the balance of flows and operating conditions within the reaction chamber (10), and the position (60 or 61) in the reaction chamber (10) from which the gases are taken from. It will be appreciated that alternate locations within the reaction chamber (10) where syngas offtake points could exist are envisaged beyond those illustrated. The gases taken from the offtake points (60 or 61) may be used directly or cooled, and filtered before being used in other equipment or processes (such as in an engine or a syngas-fuelled boiler).

[0060] In any one of the above embodiments, it will be appreciated that any one of the lower ports (15), the upper primary ports (16) or the secondary ports (18) may comprise independently (or regionally) controllable and directed jets. In particular, at the upper primary ports (16) and the secondary ports (18) where combustion occurs, the independently controllable and directed jets advantageously provide for improved process control through controlling the temperatures of each of the upper portion of the primary zone (13) and secondary zone (19). In the upper portion of the primary zone (13) and the secondary zone (19), flames occur where the oxidant injection occurs (as illustrated in any one of the Figures). It would be appreciated that rates of oxidant injection via any one of the ports (15, 16 and 18) are adjustable, and are adjusted to control the temperature within each of the primary (13) and secondary (19) zones. Whereby, while the oxidant is limited to maintain sub- stoichiometric conditions, the higher oxidant injection rates provide higher temperatures, and lower oxidant injection rates provide lower temperatures.

[0061] It will be appreciated that in anyone of the above embodiments, that each of the flow injectors (31) of the oxidant injection assembly are individually controllable via the control system, or by manual means such as valves or other known variable physical inputs (not illustrated). Further, the flow injectors (31) are controlled by the control system in response to inputs from temperature sensors (32) that provide temperature measurements throughout the system (100).

[0062] In the above embodiments, wherein the system (100) comprises the extraction means, it will be appreciated that it is advantageous to pre-dry, or remove water vapour (i.e. de-watering) from the biomass (200) before it enters the inlet (11) of the reaction chamber (10). The water vapour may be sucked off the biomass (200) at a location of the first extraction line (50), as illustrated in Figures 1 and 3, and directed to the secondary zone (19) of the reaction chamber (10) for destruction of any combustibles in the removed water vapour during the combustion process that occurs within the secondary zone (19) to further combust the partially combusted gas. In an alternative embodiment to the systems (100) illustrated in the Figures, a blower, a separate suction fan, or a separate zone may be provided for extracting gases (such as the water vapour) from the biomass (200) material prior to pyrolysis within the reaction chamber (10).

[0063] It will be appreciated that each of the flow injectors (31) are controlled by the control mechanism such that the injection of oxidant into the primary (13) and secondary zones (19) of the reaction chamber (10) is regulated to maintain a hierarchy of pressures between the primary (13) and secondary (19) zones to prevent leakage of injected oxidants or produced gases.

[0064] A method for air sealing or controlling the draft within the system (100) disclosed herein is also be specified, using a combination of the features of the above embodiments, which relies on maintaining pressures within the primary (13) and secondary (19) zones of the reaction chamber (10). It will be appreciated that maintenance of these pressures may advantageously avoid using a physical seal to prevent leakage of injected oxidants or produced gases (such as a rotary valve or airlock as used in existing prior art systems). Examples of ways the pressures within the zones (13 and (19) are given below:

a. In a preferred example, the pressure hierarchy may be Pi > PATM > P 2 , wherein Pi is the pressure in the primary zone (13), PATM is atmospheric pressure, and P 2 is the pressure in the secondary zone (19), such that no external or unwanted gas/air drafts into the reaction chamber (10), and none of the produced combustible gases (or syngas) escapes the reaction chamber (10) into the environment. It will be appreciated that in this example, the system (100) comprises the extraction means and extraction lines (50 and 51).

b. Alternatively, the pressure hierarchy may be PATM > 1 >=P 2, whereby only the first extraction line (50) is required. It will be appreciated that this arrangement is simpler, but does allow air to draft into the reaction chamber (10) via the biomass (200) feed end at the inlet (11).

c. Use of a means of controlling the gas/air draft in the flue (20), such as an air ejector (directed and individually controlled air jets in the secondary zone (19)), or dilution air via additional injection port (31) into the flue (20) (shown in figures 1 and 3), or flue damper (70), to control the draft or suction pressure provided by the flue (20), so as to maintain the desire relative pressure within the reaction chamber (10).

d. Use of a damper (such as 70 in Figure 3), baffle or restriction between primary zone (13) and secondary zone (19) to maintain a pressure differential between the two zones (13 and 19). It will be appreciated that a restriction such as the damper (70) may be combined with the first extraction line (50), wherein a first end of the first extraction line (50) is in fluid communication with the inlet (11) for the biomass (200), and a second end of the first extraction line (50) is in fluid communication with the secondary injection port (18) (as illustrated by the dashed line in Figures 1 and 3), where the secondary zone (19) is under negative pressure due to the draft in the flue (20) so as to ensure that any combusted syngas is pushed out of the reaction chamber (10) and into the biochar outlet (17) is then sucked into the secondary zone (19) for burning or combustion, rather than being vented into the atmosphere. The first extraction line (or suction line 50) may be combined with an ejector nozzle and adjustable air injection to control suction pressure such that a small but positive flow is achieved from the primary zone (13) into the secondary zone (19). It will be appreciated that if the primary zone (13) is operated at positive pressure, the secondary extraction line (or suction line 51) can be added to the biomass (200) inlet (11) to prevent syngas venting to atmosphere. Alternatively, the primary zone (13) maybe operated at slight negative pressure (with the secondary zone (19) under a stronger negative pressure) to ensure that the air drafts into the reaction chamber (10) at the biomass (200) feed end (i.e. inlet 11), rather than syngas flowing out, this air would effectively just add to the air to the primary zone (13).

It will be appreciated that other examples than those disclosed here for maintaining pressures (or draft control) within the zones (13 and 19) of the system (100) are envisaged, and are known to those skilled in the art. Accordingly, other methods may be applied to the system (100) or method disclosed.

[0065] In any one of the above embodiments, it will be appreciated that generally the temperature within the primary zone (13) of the reaction chamber (10) is higher at the second end (14) than the first end (12). That is, at or near the inlet (11) the temperature within the lower portion of the primary zone (13) may be at its lowest, and the temperature at or near the outlet (17) adjacent to the second end (12) of the lower portion of the primary zone (13) may be near or at its highest. Accordingly, it will be appreciated, that the inlet (11) may be considered a cold end of the reaction chamber (10), and the outlet (17) maybe considered a hot end of the reaction chamber (10). Furthermore, it will be appreciated that the secondary zone (19), as it is downstream from the primary zone (13), may thus be downstream from the hot end of the reaction chamber (10).

[0066] It will be appreciated that the system (100) and method disclosed above for pyrolysing biomass (200), that a novel and unique combination of continuous (or semi-batch) slow pyrolysis that does not extract the produced syngas (i.e. the completely combusted combustible gases in the secondary zone) for use as a separate product is disclosed. Whereby the biomass (200) is introduced into a primary zone (13) of the reaction chamber (10) to undergo pyrolysis by; first increasing temperature within the primary zone (13) and releasing combustible gases from the biomass (200), second partially combusting the released combustible gases to create partially combusted gas and generate a combination of radiant and convective heat which pyrolyses the biomass (200) to create biochar, and thirdly further combust the partially combusted gases in the secondary zone (19) downstream from the first zone (13) exhausting the resultant combusted syngas to yield heat as a by product that may be used by subsequent processes. Although not discussed in detail, it will be appreciated that the heat by-product is a substantial amount that may, for example, be utilised downstream of the system (100) as a hot exhaust gas or other uses. It will also be appreciated that the disclosed system (100) and method achieves this novel and unique combination may be achieved using a screw type or fluidized bed reaction chamber (10), as illustrated in any one of Figures I to 3, or alternatively, the novel and unique combination may also be achieved using a rotary kiln reaction chamber (10), as illustrated in Figure 4.

[0067] In any one of the above embodiments, the oxidant injection assembly (30) may be considered an air injection assembly. That is to say, the air injection assembly injects/supplies air rather than oxidant, and this will be understood to be interchangeably applicable to any one of the above embodiments where reference is made to 'oxidant injection assembly (30)' and the 'oxidant' injected. Where, in use, the air injection assembly (30) injects air via the plurality of flow injectors (31) into any one of the upper (16), lower (15) or secondary (18) ports.

[0068] It will be appreciated that in anyone of the above embodiments, the system (100) and method utilises radiant heat transfer in order to pyrolyse the biomass (200) to create biochar, as opposed to conductive or predominantly convective heat transfer used in prior art pyrolysis systems and methods. Prior art pyrolysis systems and methods commonly use conductive heat transfer through a wall of a process chamber in order to transfer heat from burning syngas to biomass to be pyrolysed. Other prior art systems and methods utilise alternative means of heating to achieve pyrolysis, such as electric heating. Additionally, prior art systems and methods commonly burn all or part of the syngas products to subsequently flow this back through the biomass being pyrolysed within the reaction chamber to maximize convective heat transfer to pyrolyse the biomass to create biochar. It will be appreciated that in any one of the above embodiments, not one of the partially combusted gas or the further combusted syngas product are flowed back through the biomass (200) being pyrolysed, as it is an aim of the present disclosure to minimise the contact between the oxidant gas (i.e. the gas injected by the oxidant injection assembly) and the biomass (200) or produced biochar, which advantageously minimises the burning of the produced biochar and minimises (or mitigates) convective heat transfer in favour of radiative heat transfer during pyrolysis in the primary zone (13) of the reaction chamber (10).

[0069] An additional advantage of the present disclosure, in any one of the embodiments, is that in the upper portion of the primary zone (13) where the released combustible gases are partially combusted to create the partially combusted gases and generate heat (i.e. where the flame or ignition of the released combustible gases occur), the upper injection ports (16) may operate via the oxidant injection assembly (30) at higher flame temperatures in order to enhance radiative heat transfer via the generated heat while minimising (or mitigating) burning of the produced biochar. That is, contact between the flame or ignition and the biochar being produced is avoided, as the flame or ignition occurs in the upper portion of the primary zone (13) while the biomass (200) being pyrolysed to produce the biochar is in the lower portion of the primary zone (13), and it is only the generated heat from the partially combusted syngas that radiates down to the lower portion of the primary zone (13) to pyrolyse the biomass (100).

[0070] It will be appreciated that the system (100) and method of the present disclosure produces biochar with better properties than prior art systems, as none of the released combustible gases or the partially/further combusted syngases are required to flow back through the biomass (200) being pyrolysed to create biochar, which would otherwise limit size and shape of the biomass (200) particles. This does not preclude that in certain embodiments, gases may also flow through the biochar or biomass, while maintaining the other advantages of the system (100) disclosed herein.

[0071] A further advantage of the present disclosure, and the feature of any one of the above embodiments utilising/maximising radiant heat transfer to pyrolyse the biomass (100), is that the reaction chamber (10) is easier to upscale for commercial viability when compared to prior art systems or methods that target convective heat transfer. Prior art systems or methods utilising conductive heat transfer are difficult to upscale due to square-cube law, such that when upscaling the prior art reaction chamber isometrically, the volume of the prior art reaction chamber (and thus the amount of biomass contained therein) increases with the cube of scale, while the surface area available for conductive heat transfer increases with the square of scale. The present disclosure, in contradistinction, maximises radiative heat transfer to pyrolyse the biomass (200) which scales with the 4 power of absolute temperature, and is therefore very significant as high flame temperatures (at the upper portion of the primary zone (13) via the one or more upper ports) is capable of being achieved as there the risk of burning the produced biochar is minimised. Advantageously, this offers the present disclosure with the ability of transferring a large amount of energy (i.e. via radiant heat transfer resultant of partially combusting the released combustible gases in the upper portion of the primary zone) within a small physical space (i.e. the primary zone), and within a short period of time, which allows for the potential of higher throughput within a given size of the reaction chamber (10). Also in any one of the above embodiments, the reaction chamber (10) may be an insulated reaction chamber (10), whereby the reaction chamber is insulated so as to maximize temperatures above the biomass (200) being conveyed from the inlet (11) to the outlet (17). The reaction chamber (10) can be constructed with insulating and high temperature rated materials exposed to the heat allowing primary zone (13) temperatures in excess of 1200 degrees Celsius, and well above what high temperature steels or metal alloys can withstand.

[0072] It will also be understood that a further advantage of the disclosed system (100) and method is that any one of the above embodiments are easier to upscale (i.e. provide better scalability), when compared to existing prior art pyrolysis systems or methods. The system (100) is easier to upscale for the reasons provided above, but also due to temperature within the primary zone (13) can be increased by fine-tuning the injected oxidant (via any one of the lower (15) or upper (16) ports) to biomass (200) ratio (i.e. air to fuel ratio), which advantageously allows for higher heat generation and transfer rates (resultant of partially combusting the released combustible gases in the upper portion of the primary zone (13)) as the volume of biomass (200) conveyed through the lower portion of the primary zone

(13) increases, and thereby compensating for the limitations of the square-cube law (which hinders scalability of prior art systems that maximise conductive heat transfer to achieve pyrolysis).

[0073] Finally, it will be appreciated that the fundamental principle of the system (100) and method disclosed in any one of the above embodiments is to provide a conveying, agitated biomass (200) which receives radiant heat from the upper portion of the primary zone (13), in which, released combustible gases are partially combusted, under sub-stoichiometric conditions, to generate heat. The generated heat is then received (or transferred or radiantly transferred) to the biomass (100), to pyrolyse the biomass (100) and result in the further release of combustible gases for partial combustion in the upper portion of the primary zone (13), thereby fuelling the system (100) (or process). The conveyor mechanism continuously introduces biomass (200) into the system (100) and outputs biochar, thereby making the system (100) and method disclosed herein continuous.

[0074] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.

[0075] It will be understood that the terms "comprise" and "include" and any of their derivatives (e.g. comprises, comprising, includes, including) as used in this specification, and the claims that follow, is to be taken to be inclusive of features to which the term refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied.

[0076] In some cases, a single embodiment may, for succinctness and/or to assist in understanding the scope of the disclosure, combine multiple features. It is to be understood that in such a case, these multiple features may be provided separately (in separate embodiments), or in any other suitable combination. Alternatively, where separate features are described in separate embodiments, these separate features may be combined into a single embodiment unless otherwise stated or implied. This also applies to the claims which can be recombined in any combination. That is a claim may be amended to include a feature defined in any other claim. Further a phrase referring to "at least one of' a list of items refers to any combination of those items, including single members. As an example, "at least one of: a, b, or c" is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.

[0077] It will be appreciated by those skilled in the art that the disclosure is not restricted in its use to the particular application or applications described. Neither is the present disclosure restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the disclosure is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope as set forth and defined by the following claims.

Claims

1. A system for pyrolysing biomass, the system comprising: a reaction chamber comprising a first end, a second end, a primary zone, and a secondary zone downstream from the primary zone; and

an oxidant injection assembly comprising a plurality of flow injectors; the primary zone comprising: an upper portion comprising one or more upper primary ports; and a lower portion comprising an inlet for the biomass proximal to the first end, an outlet for a biochar product adjacent to the second end, and one or more lower ports disposed between the inlet and the outlet; the secondary zone comprising: one or more secondary ports and a flue; and wherein each flow injector is connectable to respective upper primary, lower and secondary ports to control discharge of oxidant into the reaction chamber; and wherein, in use, oxidant injected into the one or more lower ports results in heat generated proximal to the biomass resulting in the release of combustible gases into the primary zone, oxidant injected into the one or more upper primary ports results in partial combustion of the released combustible gases resulting in: heat generation that pyrolyses the biomass, and providing and maintaining sub-stoichiometric conditions.

2. The system of claim 1, wherein the system further comprises a means for controlling draft within the primary zone, and the reaction chamber further comprises at least one pressure sensor, wherein, in use, the means for draft control is arranged to control the draft within the reaction chamber in response to inputs from at least the pressure sensor(s).

3. The system of any one of claims 1 or 2, wherein the system further comprises one or more extraction means comprising at least one extraction line in fluid communication with the reaction chamber, wherein, in use each extraction line is arranged to extract gases from the biomass prior to pyrolysis and/or the biochar prior to discharging the biochar.

4. The system of any one of the preceding claims, wherein the reaction chamber comprises one or more temperature sensors arranged to provide temperature measurements in the primary zone, and the system further comprises a control system arranged to control the flow injector(s) connected to the upper primary, lower and secondary port(s) in response to inputs from at least the temperature sensor(s), wherein, in use, the control system controls oxidant injection.

5. A method for pyrolysing biomass to produce biochar, the method comprising: (a) introducing the biomass to an inlet at a first end of a primary zone of a reaction chamber; (b) conveying the biomass from the first end to a second end of the primary zone; (c) using an oxidant injection assembly to controllably inject oxidant into one or more lower injection ports located in a lower portion of the primary zone to generate heat proximal to the biomass and release combustible gases into the primary zone; (d) using the oxidant injection assembly to controllably inject oxidant into one or more upper injection ports located in an upper portion of the primary zone to partially combust the released combustible gases to provide and maintain sub-stoichiometric conditions that result in heat generation to pyrolyse the biomass; (e) using the oxidant injection assembly to controllably inject oxidant into one or more secondary injection ports located in a secondary zone of the reaction chamber downstream from the primary zone to further combust the partially combusted gases; and (f) discharging biochar at an outlet adjacent to the second end.