Improved method of producing activated carbon material

Abstract

The present invention relates to an improved method and apparatus of producing activated carbon material from carbonaceous feedstock material with enhanced energy recovery processes.

Description

Improved method of producing activated carbon materialTechnical Field

[0001] The present invention relates to an improved method and apparatus of producing activated carbon material. In particular, but not exclusively, the present invention relates to a method of self-sustaining steam activated carbon material production from carbonaceous feedstock material with enhanced energy recovery processes.Background of Invention

[0002] Activated carbon material is typically produced by the activation of charcoal, a carbonaceous compound, i.e. carbonised material, derived from any carbon-based material. Charcoal is traditionally produced through the heating of a carbon-based feedstock material (traditionally wood, coconut husk, or coal) in an environment with little or no oxygen, which results in the partial decomposition of the chemical structure of the original feedstock. This produces charcoal; a carbonaceous compound consisting of large amounts of elemental carbon of differing allotropes. When the feedstock consists of non-traditional plant or animal matter, the carbonised material is often referred to as "biochar".

[0003] Activated carbon material is typically produced using one of three following processes. Firstly, it may be produced by chemical activation of a carbon containing material using an acid, a strong base, or a salt. Secondly, it may be produced by physical activation of a carbon containing material by heating the material to high temperatures in an oxidising or partially oxidising environment, such as by inputting steam or carbon dioxide into a heated rotary kiln or fluidised bed reactor. Finally, it may be produced by a combination of the first and second activation processes.

[0004] The production of a carbonised material is typically produced on a small batch scale or on a large continuous scale in reactors, such as kilns, drums, etc., in an energy intensive manner. In an existing process for producing carbonised material such as charcoal or biochar, a carbon containing feed material is inputted into a rotary kiln or fluidized bed in an environment substantially without oxygen and is heated to py rolytica I ly convert the feedmaterial to biochar. This method requires external heating to sustain, but typically results in a higher quality product.

[0005] Another common method of producing carbonised material includes using small throughput batch reactors, such as pits, stationary kilns, stationary drums, etc., in a poorly controlled manner. In an existing process for producing carbonised material such as charcoal or biochar, for example, a carbon containing feed material is inputted into a stationary kiln or drum, in an environment with limited oxygen, and is ignited to pyrolytically convert the feed material to charcoal or biochar. This method uses energy from the partial combustion of the feedstock within the reactor to sustain the process, but typically results in a lower quality product as the environment cannot be kept totally free of oxygen.

[0006] The production of activated carbon is also produced on either a small batch scale or a large continuous scale in reactors, such as kilns, drums, etc., in an energy intensive manner. In an existing process for producing activated carbon material, for example, a carbonised feed material, such as the above-described biochar, is inputted into a fixed-bed in an environment with some oxygen (e.g. 5%) and heated to convert the feed material to activated carbon.

[0007] The heat typically required for the pyrolysis process described above is at least 250°C, but more commonly 400 to 1000°C. For heating, a fuel such as propane or natural gas is typically combusted to heat the kilns, resulting in an energy intensive process. Where the process does not require external heating, a lower quality, higher ash product is obtained, resulting in an inefficient process. Both of the methods exemplified above also result in significant toxic and / or harmful emissions from the process, which include, but are not limited to toxic gasses from the pyrolysis process and / or particulate matter from inefficient combustion, which must be treated before being emitted to the atmosphere; thus adding further complexity to the process.

[0008] Further, the temperature typically required for the activation process listed above is 400-600°C, if low levels of oxygen gas are used, or greater than 800°C if steam, or carbon dioxide, ora combination of the latter two are used. Thus, for higher temperature reactors in particular, the existing processes for producing activated carbon are energy and resourceintensive, requiring greater volumes of fuel to provide the higher temperatures and often requiring emissions and resource recovery, adding further complexity to the processes.

[0009] In an existing activation process, pyrolysis gasses are at least partially combusted in the activator reactor to produce activated carbon to minimise the volume of fuel required. But, as these gasses are not sufficient to provide the high temperatures required for the activation process without further treatment, their use adds complexity to the process without eliminating the need for external fuel.

[0010] The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing context for the present invention. It is not suggested or represented that any of these matters formed part of the common general knowledge relevant to the prevent invention as it existed before the priority date of each claim of this application.Summary of Invention

[0011] According to one aspect of the present invention, there is provided a method of producing activated carbon material, comprising: inputting a feed material into a first reactor; pyrolytically producing a carbonised material in the first reactor from the feed material using heat produced by a carbonisation furnace, and producing volatile gas from the first reactor; routing at least part of the volatile gas to an activation furnace configured to provide heat for a second reactor to produce activated carbon material from the carbonised material; heating air using waste heat from the carbonisation furnace in a heat exchanger located adjacent to and connected to the first reactor; routing the heated air to the activation furnace to provide preheated air for the activation furnace; combusting the volatile gas with the preheated air in the activation furnace; inputting the carbonised material from the first reactor into the second reactor; producing the activated carbon material in the second reactor from the carbonised material, and producing further volatile gas from the second reactor; combusting the further volatile gas with the preheated air in the activation furnace; and outputting the activated carbon material from the second reactor.

[0012] In an embodiment, the method further comprises the heat exchanger preheating the air via conductive heat transfer of waste heat from the carbonisation furnace in the first reactor to a series of tubes in the heat exchanger. The tubes aid in the conductive heat transfer of the waste heat from the carbonisation furnace to the air in the tubes. The method may further comprise drawing air through the tubes in the heat exchanger via a fan to heat the air. For example, the method further comprises the heat exchanger heating the air to 150-250°C.

[0013] The method further comprises producing exhaust gas from the carbonisation furnace. Preferably, energy, in the form of waste heat, in the exhaust gas is also recovered.

[0014] In an embodiment, the method further comprises: producing exhaust gas from the activation furnace; routing at least part of the exhaust gas to a waste heat boiler; producing steam in the waste heat boiler; routing the steam to the second reactor; and producing the activated carbon material in the second reactor from the carbonised material using at least in part the steam from the waste heat boiler. For example, the steam is produced by the waste heat boiler at between 1 and 5 bar and 100-200°C.

[0015] In an embodiment, the method further comprises routing at least part of the exhaust gas to the first reactor.

[0016] In an embodiment, further exhaust gas is produced from the carbonisation furnace and the method further comprises routing at least part of the further exhaust gas to the waste heat boiler. That is, waste heat in the exhaust gas of the activation furnace, generated predominantly by combusting the volatile gas and the further volatile gas in the activation furnace, along with waste heat from the exhaust gas of the carbonisation furnace, is recovered to generate steam to more efficiently and effectively produce activated carbon material.

[0017] In an embodiment, the method further comprises the heat exchanger using the exhaust gas from the carbonisation furnace and / or the activation furnace to preheat the air.

[0018] In an embodiment, the method further comprises routing at least part of the exhaust gas and / or the further exhaust gas adjacent to the carbonisation furnace to heat the first reactor

[0019] In an embodiment, the method further comprises routing at least part of the exhaust gas and / or the further exhaust gas adjacent to the activation furnace to heat the second reactor.

[0020] In an embodiment, the method further comprises the activation furnace heating the second reactor to 900-1200°C. In an embodiment, the second reactor is a kiln and the carbonised material is retained in the kiln for 45-200min to produce the activated carbon material.

[0021] That is, the invention preferably uses high-temperature steam of 100-200°C and high temperatures within the second reactor of 900-1200°C for the activation of the carbonised material. In some examples, the temperature is 900-1000°C. In other examples, the temperature is greater than 1100°C. To achieve the high temperatures, the invention does not rely on external fuel to generate these temperatures. Instead, the volatile gasses, including the pyrolysis process volatiles, are combusted at very high temperatures with the preheated air. The preheated air enables these volatile gasses to be combusted at sufficiently high temperatures to provide the heat required for the activation process to be self-sustaining and for generating high-temp steam to be self-sustaining.

[0022] The pre-heated air thus enables the volatile gasses produced from the first reactor, i.e. the pyrolysis process volatiles, and the second reactor to be combusted at higher temperatures. These temperatures are sufficient for the second reactor to optimally produce activated carbon and to generally eliminate the need for external fuel to be used in the process.

[0023] It will be appreciated by those persons skilled in the art that steam works better than Oxygen for producing activated carbon for some material, such as very hard / dense feedstocks.

[0024] In an embodiment, the method further comprises the carbonisation furnace heating the first reactor to 600-900°C. In an embodiment, the first reactor is a kiln and the feed material is inputted into the kiln until the kiln is 20% full. In other embodiments, the kiln is partially filled up to a maximum of 35%.

[0025] In an embodiment, the method further comprises a variable speed drive controlling residence time of the feed material in the kiln.

[0026] In an embodiment, the method further comprising combusting LPG, diesel or natural gas to provide start-up heat for the carbonisation furnace and / or the activation furnace.

[0027] According to another aspect of the present invention, there is provided an apparatus for producing activated carbon material, the apparatus comprising: a first reactor for pyrolytically producing a carbonised material, comprising: an input port of the first reactor for receiving a feed material; an output port of the first reactor for outputting a carbonised material pyrolytically produced in the first reactor from the feed material; and a volatile gas outlet for outputting volatile gas produced in the first reactor; a carbonisation furnace configured to provide heat for the first reactor to pyrolytically produce the carbonised material; and a second reactor for producing an activated carbon material, comprising: an input port of the second reactor for receiving the carbonised material from the output port of the first reactor; an output port of the second reactor for outputting an activated carbon material produced in the second reactor from the carbonised material; a volatile gas outlet for outputting further volatile gas produced in the second reactor; a heat exchanger, located adjacent to and connected to the first reactor, configured to heat air using waste heat from the carbonisation furnace to provide preheated air for the activation furnace; an activation furnace configured to provide heat for the second reactor to produce the activated carbon material by combusting at least the volatile gas and the further volatile gas with the preheated air.

[0028] In an embodiment, the heat exchanger comprises a series of tubes and heats the air via conductive heat transfer of waste heat from the carbonisation furnace to the series oftubes. The apparatus may further comprise a fan configured to draw air through the series of tubes in the heat exchanger to heat the air. As mentioned, the preheated air is 150-250°C.

[0029] In an embodiment, the first reactor is a kiln reactor. The kiln reactor may be configured as a single tube kiln where the input port is located at a proximal end of the reactor for receiving the feed material and the output port is located at the distal end of the reactor for outputting the carbonised material. Similarly, the second reactor may be a kiln reactor configured as a single tube kiln where the input port is located at a proximal end of the reactor for receiving the carbonised material and the output port is located at the distal end of the reactor for outputting the activated carbon material.

[0030] Alternatively, the kiln reactor of the first and / or second reactor is configured as a double tube kiln where the input port of the reactor and the output port are located at the send end of the reactor.

[0031] In the second reactor kiln, the activation furnace heats the second reactor to 900-1200°C and the carbonised material is retained in the second reactor kiln for 45-200min to produce the activated carbon material.

[0032] In the first reactor kiln, the carbonisation furnace heats the first reactor kiln to 600-900°C and the residence time in the kiln is controlled by a variable speed drive. The feed material is inputted into the kiln until the kiln is 20% full.

[0033] In an embodiment, the apparatus further comprises a waste heat boiler configured to produce steam, wherein exhaust gas is produced from the activation furnace and at least part of the exhaust gas is routed to the waste heat boiler. The steam is routed to the second reactor, and the second reactor produces the activated carbon material from the carbonised material using at least in part the steam from the waste heat boiler.

[0034] In an embodiment, further exhaust gas is produced from the carbonisation furnace and at least part of the further exhaust gas is routed to the waste heat boiler.

[0035] In an embodiment, the apparatus further comprises a supplemental air input configured to input supplemental air to the preheated air to cool the preheated air to adesired temperature range and below the maximum working temperature of the fan. For example, the desired temperature is 150 to 250°C.

[0036] In an embodiment, the apparatus further comprises a first fan configured to draw the volatile gas from the volatile gas outlet of the first reactor and a first water spray quench configured to cool the volatile gas to below the maximum working temperature of the first fan.

[0037] In an embodiment, the apparatus further comprises a second fan configured to draw the further volatile gas from the volatile gas outlet of the second reactor and a second water spray quench configured to cool the further volatile gas to below the maximum working temperature of the second fan.Brief Description of Drawings

[0038] In order that the invention can be more clearly understood, examples of embodiments will now be described with reference to the accompanying drawings, in which:

[0039] Figure 1 shows a flow chart of a method of producing activated carbon material, according to an embodiment of the invention;

[0040] Figure 2 shows a flow chart of a method of producing activated carbon material, according to another embodiment of the invention;

[0041] Figure 3A shows part of a schematic of an apparatus for producing activated carbon material, according to an embodiment of the invention; and

[0042] Figure 3B shows another part of the schematic of an apparatus for producing activated carbon material of Figure 3A.Detailed Description

[0043] A summary of a flow chart of a method 10 of producing activated carbon material is shown in Claim 1. The method 10 comprises the steps of: inputting 12 a feed material into a first reactor; pyrolytically producing 14 a carbonised material in the first reactor from the feed material using heat produced by a carbonisation furnace, and producing volatile gasfrom the first reactor; routing 16 at least part of the volatile gas to an activation furnace configured to provide heat for a second reactor to produce activated carbon material from the carbonised material; heating 18 air using waste heat from the carbonisation furnace in a heat exchanger located adjacent to and connected to the first reactor; routing 20 the heated air to the activation furnace to provide preheated air for the activation furnace; combusting 22 the volatile gas with the preheated air in the activation furnace; inputting 24 the carbonised material from the first reactor into the second reactor; producing 26 the activated carbon material in the second reactor from the carbonised material, and producing further volatile gas from the second reactor; combusting 28 the further volatile gas with the preheated air in the activation furnace; and outputting 30 the activated carbon material from the second reactor.

[0044] Exhaust gas is produced from the carbonisation furnace and the method further comprises: routing at least part of the exhaust gas to a waste heat boiler; producing steam in the waste heat boiler; routing the steam to the second reactor; and producing the activated carbon material in the second reactor from the carbonised material using at least in part the steam from the waste heat boiler. This process is shown in Figure 2.

[0045] More specifically, Figure 2 shows a flow chart where raw feed material is inputted into the first reactor and the raw material undergoes carbonisation to produce a carbonised material, such as biochar, using heat produced by the carbonisation furnace. As mentioned, at least part of the exhaust gas from the carbonisation furnace is routed to the waste heat boiler to produce steam which is, in turn, routed to the second reactor where the biochar undergoes steam activation to produce activated carbon, which is outputted as the final product for bagging.

[0046] Figures 3A and 3B shows a schematic of part of an apparatus 34 for producing activated carbon material. The apparatus 34 comprises a first reactor 36 for pyrolytica lly producing a carbonised material. The first reactor 36 comprises a carbonisation furnace 38 configured to provide the heat for the feed material within the first reactor 36 to pyrolytica I ly produce the carbonised material, such as biochar, from the feed material.

[0047] The first reactor 36 comprises an input port 39, connected to a screw feeder 40, for receiving the feed material from a hopper and an output port 42 for outputting thecarbonised material, such as biochar, pyrolytica I ly produced in the first reactor 38 from the feed material. The carbonised material is outputted at 400-800°C.

[0048] The first reactor 36 also comprises a volatile gas outlet 44 for outputting volatile gas produced in the first reactor 36 and an exhaust gas outlet 47 so that exhaust gas produced by the carbonisation furnace 38 can be routed to a waste heat boiler 46 to produce steam to produce activated carbon material in a second reactor 48. That is, the steam from the waste heat boiler 46 is routed to the second reactor 48 that is configured to produce the activated carbon material from the carbonised material from the first reactor 36. The exhaust gas outlet 47 is connected to a cyclone dust collector 49 intermediate the waste heat boiler 46 to filter dust from the exhaust gas.

[0049] The apparatus 34 comprises an activation furnace 50 configured to provide heat to the second reactor 48 to produce the activated carbon material. The second reactor 48 comprises the activation furnace 50. The activation furnace 50 produces an exhaust gas, which is outputted via an exhaust gas outlet 65, which is routed to the first reactor 36 and then to the waste heat boiler 46 to produce the steam.

[0050] In the embodiment of Figure 3, the first reactor 36 and the second reactor 48 are kilns comprises a bed for the material and the carbonisation furnace 38 and the activation furnace 50, respectively.

[0051] The second reactor 48 further comprises an input port 52 for receiving the carbonised material from the output port 42 of the first reactor 38, which is connected to a water cooled screw feeder 53 to cool the carbonised material upon entry to the second reactor 48. The second reactor 48 also comprises an output port 54 for outputting activated carbon material produced in the second reactor 48 from the carbonised material. The activated carbon material is outputted at 600-800° and is cooled before undergoing further processing before being bagged for shipping. The second reactor 48 also comprises a volatile gas outlet 56 for outputting volatile gas produced in the second reactor 48.

[0052] The apparatus 34 further comprises a heat exchanger 58, located adjacent to and connected to the first reactor 36, configured to heat air using waste heat from the carbonisation furnace 38 to provide preheated air for the activation furnace 50. To do so,the heat exchanger 58 comprises a series of tubes located in the first reactor 36 and heats the air via conductive heat transfer of waste heat from the carbonisation furnace 38 in the first reactor 36 to the series of tubes. A fan 59 is connected to the heat exchanger 58 so that air is drawn through the series of tubes in the heat exchanger 58 to heat the air.

[0053] The activation furnace 50 is further configured to provide heat for the second reactor 48 to produce the activated carbon material by combusting at least the volatile gas from the first reactor 36 and the further volatile gas from the second reactor 48, which has combustible volatiles, with the preheated air to improve the efficiency of the activation furnace 50. Fans 6163 are connected to the volatile gas outlet 44 and the further volatile gas outlet 56, respectively, to force the volatile gasses to the burners of the activation furnace 50.

[0054] As mentioned, start-up heat for the burners of the carbonisation furnace 38 and the activation furnace 50 in is provided by either LPG, diesel, of natural gas. In the embodiment of Figure 3, the activation furnace 50 has 3 burners: one dedicated for start-up fuel, such as LPG, diesel, of natural gas, one dedicated to volatile gas from the first reactor 36 and one dedicated to further volatile gas from the second reactor 48. The carbonisation furnace 38 has one burner dedicated to using start-up fuel, such as LPG, diesel, of natural gas.

[0055] Raw feed materials are initially stored in either a hopper or some other suitable feedstock storage device, which acts as an intermediate storage to ensure constant supply of feed material to the first reactor 36. The size of raw materials in the hopper 40 to be used as feed material is approximately <3 cm and moisture content of <50%.

[0056] The hopper / feeder 40 will feed raw material on to a continuous weigh feeder belt and the feed material will pass through a metal detector to remove any metal before the feed material drops to a bucket elevator which feeds a screw feeder of the first reactor 36 adjacent the input port 39. The screw feeder feeds the raw materials through a double-layer pneumatic discharge valve at the input port 39, which ensures that no air enters the first reactor 36, to carry out the pyrolysis reaction.

[0057] The carbonisation furnace 38 heats up the biomass of feed material to approximately 600 - 900°C and ensures correct residence time in the first reactor 36 for the biomass to produce good quality carbonised material for the activation process.

[0058] As mentioned, the first reactor 36 and the second reactor 48 are kilns. The residence time in the first reactor kiln 36 is controlled via a variable speed drive (VSD). The filling percentage of the kiln / reactor is kept below 20% to ensure effective heat transfer via indirect heating method, that's hot gasses are in an external chamber to the biomass. This temperature range is chosen as it limits tar formation, cracks the tars that are formed, and enables a high fixed carbon content in the biochar that is produced.

[0059] During the carbonisation process, combustible volatiles are generated by the biomass in the first reactor 36. These volatiles are collected using an induced draft fan and directed to the burners of the activation furnace 50, which are used to heat up the furnace. In another embodiment, these combustible volatiles may be directed to the burners of the carbonisation furnace 38 too.

[0060] The exhaust gas, also known as flue gas, from the activation furnace 50, and in some embodiments the carbonisation furnace 38, is used by the waste heat boiler 46 before it gets treated and exhausted to the atmosphere. The temperature of the piping between the pyrolysis volatile gas outlet 44 and the burners of the activation furnace 50 is insulated to ensure it does not drop below 350°C as tar condensation occurs at this temperature.

[0061] That is, the waste heat boiler 46 is used to generate steam using the hot flue gasses that are generated by predominantly the activation furnace 50. The activation furnace 50 is hotter than the carbonisation furnace 38 and is self-sustaining as it predominantly combusts volatile gasses from the first reactor 36 and the second reactor 48.

[0062] The steam that is generated by the waste heat boiler 46 is used in the steam activation kiln second reactor 48 for the carbon activation process. The steam is generated at between 1 and 5 bar and 100 - 200°C. The steam is outputted from the waste heat boiler 46 via a steam outlet 45 and routed to the second reactor 48 via a steam inlet 51. Waste steam may be vented to atmosphere.

[0063] During the activation process, combustible volatiles are generated by the biomass like the carbonisation furnace, these volatiles are collected using an induced draft fan and directed to the burners which heat up the furnaces.

[0064] The steam produced from the waste heat boiler can either be fed into the second reactor 48 via the feeding end or the product discharge end (depending on reactor configuration).

[0065] As mentioned, the air that is used to combust the volatile gasses from the volatile gas outlet 44 is pre-heated via the heat exchanger 58 that utilises waste heat from the carbonisation furnace 38. This allows the air to be heated to between 150 and 250°C. This enables the combustion temperature to reach > 950°C in the activation furnace 50. In some examples, the combustion temperatures are > 1100°C, which is achieved by combusting the volatile gasses with the pre-heated air. The apparatus 34 achieves this using waste heat to pre-heat the combustion air in the activation furnace 50 by affixing an air supply line to the activation furnace 50 of the second reactor 48.

[0066] That is, the pre-heated air is used to combust both the carbonization volatiles (which include CO, CO2, H2, CH4, and tar) and the activation volatiles (which contain H2 and CO). If pre-heated air is not used to achieve higher temperatures, such as > 1100°C, moisture and tar needs to be removed from the volatile gases. Pre-heating the air therefore eliminates this need and engineering complexity from the apparatus 34.

[0067] In order to avoid having the air getting too hot and damaging the fan 59, supplemental make-up air may be used by the apparatus 34, as shown in Figure 3B. This basically dilutes the pre-heated air supplied to the furnace 50 to reduce the temperature to the maximum working temperature of the fan 59 that supplies the pre-heated air.

[0068] In order to protect the fans 6163 that suck the volatile gases out of the first and second reactors 3848, and move the volatile gases to the burners of the furnaces, there is a water spray quench 55 to cool the volatile gases to below the maximum working temperature of the fans 6163, as shown in Figure 3B.

[0069] In the embodiment, if the heat exchanger 58 heats the air greater than 250°C, further supplemental air can be inputted to the air stream after the heat exchanger 58 tokeep the pre-heated air in the desired temperature range of 150 and 250°C. This cools the pre-heated air to below the maximum working temperature of the fan 59, as shown in Figure 3B.

[0070] By pre-heating the air, the apparatus 34 greatly increases pyrolysis and activation volatile gas mixture combustion efficiency, which essentially allows a temperature cascade throughout the process in order to ensure that both the minimum target activation and pyrolysis temperatures are met. Without such a process, the combustion temperature would not be sufficiently high to heat both the pyrolysis and activation reactors without further fuel. That is, by preheating the air, the apparatus 34 can produce activated carbon material in a self-sustaining manner.

[0071] In addition, by using waste heat from the pyrolysis step, with the heat exchanger 36 sitting either on top or side by side with the first reactor 36, this avoids the need for supplementary heating. In this configuration, heat from the carbonisation furnace 38 also heats the heat exchanger 58 and, in turn, the air that is drawn through via conduction and convection.

[0072] The table below shows a typical carbonization volatile gas mixture produced at 800C in the first reactor 36.

[0073] Typically, LHV's for such a gas mixture range from 10 - 20 MJ / kg.

[0074] As mentioned, this volatile gas mixture is combusted in the activation furnace 50 and the carbonisation furnace 38 to generate heat for the first 36 and second reactors 48, respectively. The waste heat from combustion of the volatile gasses is thus used to generate steam in the waste heat boiler 46, heat air in the heat exchanger 58, and heat the activation furnace 50 and the carbonisation furnace 38.

[0075] As mentioned, the second reactor 48 performs steam activation of the carboned material in either a rotary kiln or other suitable reactor. This kiln is required to be heated up to roughly 900-1000°C and the activation furnace 50 combusts the volatiles with the preheat air to achieve this temperature range.

[0076] The carbonised material is then retained in the kiln for roughly 45-200 min subject to these temperatures. This ensures that the steam inputted into the kiln and the gasses generated by the kiln open the micropores of the carbonised material to achieve the desired surface area of the activated carbon.

[0077] The hot activated carbon material produced by the second reactor kiln 48 goes through two steps of cooling before it goes through the sizing and bagging process. The cooling is achieved by using the water-cooled conveyors and a drum cooler which will cool down to the product <40°C. A cooling tower is used to cool the closed-circuit water that is used by these processes.

[0078] Once the activated carbon is cooled, using a bucket elevator the activated carbon goes through a crusher and a mechanical sieve process to sperate different sizes of activated carbon. Using the crusher the activated carbon is sized to meet the specification of granular activated carbon. To produced powdered activated carbon the granular activated carbon out of the sieve will be conveyed to a grinder where the product will be further reduced in size to meet the specification.

[0079] After the product is sized to the desired specification the packing line is consists of two lines, one line is dedicated to produce 20kg bags of product and second line is dedicated for 1 tonne bulk bags.

[0080] Table 1 shown below depicts results and experimental conditions for the pyrolysis and activation of multiple biomass samples. Where specified, the pyrolysis was concluded with the injection of 1.0 stoichiometric equivalent of steam and maintained at the activation temperature range specified above. Surface areas were then determined by iodine titration method (ASTM D4607). It should be noted that surface areas correlate 1:1 with iodine number and is a commonly used industry metric for activated carbon surface area tests.

[0081] Table 1. Comparative results / conditions of steam activation with pre-heated air.Temp Pyrolysis Pyrolysis Activation Overall Final 12 Code Biomass (C) time (min) mass loss mass loss yield (mg / g)1 Acacia 1000 60 81% 16% 16% 7632 Acacia 1000 60 89% 18% 9% 1330 Macadamia3 shell 1000 60 91% 42% 5% 8014 Eucalyptus 1000 60 76% 23% 18% 4915 Eucalyptus 1000 60 80% 18% 16% 8146 Walnut shell 900 90 80% 11% 18% 10287 Almond shell 1000 60 81% 20% 15% 1048

[0082] In addition, it will be appreciated by those persons skilled in the art that further aspects of the method will be apparent from the above description of the apparatus 34. Further, the persons skilled in the art will also appreciate that at least part of the method 10 could be embodied in software (e.g. program code) that is implemented by a controller (not shown) configured to control the apparatus 34 for producing activated carbon material. The software could be supplied in a number of ways, for example of a tangible computer readable medium, such as a disc or a memory.

[0083] Those skilled in the art will also appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications.

[0084] Where any or all of the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.

Claims

The claims defining the invention are as follows1. A method of producing activated carbon material, comprising:inputting a feed material into a first reactor;pyrolytically producing a carbonised material in the first reactor from the feed material using heat produced by a carbonisation furnace, and producing volatile gas from the first reactor;routing at least part of the volatile gas to an activation furnace configured to provide heat for a second reactor to produce activated carbon material from the carbonised material;heating air using waste heat from the carbonisation furnace in a heat exchanger located adjacent to and connected to the first reactor;routing the heated air to the activation furnace to provide preheated air for the activation furnace;combusting the volatile gas with the preheated air in the activation furnace; inputting the carbonised material from the first reactor into the second reactor; producing the activated carbon material in the second reactor from the carbonised material, and producing further volatile gas from the second reactor;combusting the further volatile gas with the preheated air in the activation furnace; andoutputting the activated carbon material from the second reactor.

2. A method as claimed in claim 1, further comprising the heat exchanger heating the air via conductive heat transfer of waste heat from the carbonisation furnace in the first reactor to a series of tubes in the heat exchanger.

3. A method as claimed in claim 2, further comprising drawing the air through the series of tubes in the heat exchanger via a fan to heat the air.

4. A method as claimed in any one of claims 1 to 3, further comprising:producing exhaust gas from the activation furnace;routing at least part of the exhaust gas to a waste heat boiler;producing steam in the waste heat boiler;routing the steam to the second reactor; andproducing the activated carbon material in the second reactor from the carbonised material using at least in part the steam from the waste heat boiler.

5. A method as claimed in claim 4, further comprising producing further exhaust gas from the carbonisation furnace and routing at least part of the further exhaust gas to the waste heat boiler.

6. A method as claimed in claim 5, further comprising routing at least part of the exhaust gas to the first reactor.

7. A method as claimed in any one of claims 1 to 6, further comprising the activation furnace heating the second reactor to 900-1200°C.

8. A method as claimed in claim 7, wherein the second reactor is a kiln and the carbonised material is retained in the kiln for45-200min to produce the activated carbon material.

9. A method as claimed in any one of claims 1 to 8, further comprising the carbonisation furnace heating the first reactor to 600-900°C.

10. A method as claimed in claim 9, wherein the first reactor is a kiln and the feed material is inputted into the kiln until the kiln is 20% full.

11. A method as claimed in claim 10, further comprising a variable speed drive controlling residence time of the feed material in the kiln.

12. A method as claimed in any one of claims 1 to 11, further comprising the heat exchanger heating the air to 150-250°C.

13. A method as claimed in any one of claims 1 to 12, further comprising the waste heat boiler producing the steam at 1-5 bar and 100-200°C.

14. A method as claimed in any one of claims 1 to 13, further comprising combusting LPG, diesel or natural gas to provide start-up heat for the carbonisation furnace and or the activation furnace.

15. An apparatus for producing activated carbon material, the apparatus comprising:a first reactor for pyrolytica I ly producing a carbonised material, comprising:an input port of the first reactor for receiving a feed material;an output port of the first reactor for outputting a carbonised material pyrolytically produced in the first reactor from the feed material; anda volatile gas outlet for outputting volatile gas produced in the first reactor; a carbonisation furnace configured to provide heat for the first reactor to pyrolytically produce the carbonised material; anda second reactor for producing an activated carbon material, comprising:an input port of the second reactor for receiving the carbonised material from the output port of the first reactor;an output port of the second reactor for outputting an activated carbon material produced in the second reactor from the carbonised material;a volatile gas outlet for outputting further volatile gas produced in the second reactor;a heat exchanger, located adjacent to and connected to the first reactor, configured to heat air using waste heat from the carbonisation furnace to provide preheated air for the activation furnace;an activation furnace configured to provide heat for the second reactor to produce the activated carbon material by combusting at least the volatile gas and the further volatile gas with the preheated air.

16. An apparatus as claimed in claim 15, wherein the heat exchanger comprises a series of tubes and heats the air via conductive heat transfer of waste heat from the carbonisation furnace to the series of tubes.

17. An apparatus as claimed in claim 16, further comprising a fan configured to draw air through the series of tubes in the heat exchanger to heat the air.

18. An apparatus as claimed in any one of claims 15 to 17, further comprising a waste heat boiler configured to produce steam, wherein exhaust gas is produced from the activation furnace and at least part of the exhaust gas is routed to the waste heat boiler.

19. An apparatus as claimed in claim 18, wherein the steam is routed to the second reactor and the second reactor produces the activated carbon material from the carbonised material using at least in part the steam from the waste heat boiler.

20. An apparatus as claimed in claim 18 or 19, wherein further exhaust gas is produced from the carbonisation furnace and at least part of the further exhaust gas is routed to the waste heat boiler.

21. An apparatus as claimed in any one of claims 15 to 20, wherein the activation furnace heats the second reactor to 900-1200°C.

22. An apparatus as claimed in claim 21, wherein the second reactor comprises a kiln and the carbonised material is retained in the kiln for 45-200min to produce the activated carbon material.

23. An apparatus as claimed in any one of claims 15 to 22, wherein the carbonisation furnace heats the first reactor to 600-900°C.

24. An apparatus as claimed in any one of claims 15 to 23, wherein the first reactor comprises a kiln and the feed material is inputted into the kiln until the kiln is 20% full.

25. An apparatus as claimed in claim 24, further comprising a variable speed drive controlling residence time of the feed material in the kiln.

26. An apparatus as claimed in any one of claims 15 to 25, wherein the preheated air is 150-250°C.

27. An apparatus as claimed in any one of claims 15 to 26, when dependent on claim 17, further comprising a supplemental air input configured to input supplemental air to the preheated air to cool the preheated air to a desired temperature range and below the maximum working temperature of the fan.

28. An apparatus as claimed in any one of claims 15 to 27, further comprising a first fan configured to draw the volatile gas from the volatile gas outlet of the first reactor and a firstwater spray quench configured to cool the volatile gas to below the maximum working temperature of the first fan.

29. An apparatus as claimed in claim 28, further comprising a second fan configured to draw the further volatile gas from the volatile gas outlet of the second reactor and a second water spray quench configured to cool the further volatile gas to below the maximum working temperature of the second fan.

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