WO2022029313A1

WO2022029313A1 - Process for producing activated charcoal and the activated charcoal produced thereby

Info

Publication number: WO2022029313A1
Application number: PCT/EP2021/072056
Authority: WO
Inventors: Lukas RENDL
Original assignee: Rendl Lukas
Priority date: 2020-08-06
Filing date: 2021-08-06
Publication date: 2022-02-10
Also published as: DE102020120741A1

Abstract

The invention relates to a process for producing an activated charcoal from a residue material obtained in a wood gasification process, wherein the starting material used is a wood gasification charcoal obtained in a staged process of gasification of organic fuels and wood with spatial separation of the individual process steps such as pyrolysis, oxidation and reduction, wherein the reduction is conducted in a moving bed reactor, by means of which a fine-grain carbon-rich charcoal is produced, and the wood gasification charcoal thus produced is subsequently sent to activation, wherein the wood gasification charcoal is activated chemically and/or physically, and to an activated charcoal produced by the process, wherein the activated charcoal, after physical activation, has a BET surface area between 500 m2/g and 950 m2/g and, after chemical activation, has a BET surface area between 475 m2/g and 1150 m2/g.

Description

Process for the production of activated charcoal and the activated charcoal produced therewith

The invention relates to a method for producing activated charcoal and the activated charcoal produced therewith.

Activated carbon is a fine-grained carbon in the form of a microcrystalline, heavily disturbed graphite with a large internal surface area, thanks to which it is used as an adsorbent in chemistry, medicine, water and waste water treatment, and ventilation and air conditioning technology. It is used as granules, as a powder, in pellet form or pressed into tablets (charcoal compacts).

Activated carbon consists mainly of carbon (usually > 90%) with a highly porous structure. Like a sponge, the pores are connected to each other with open pores. The inner surface area is between 300 and 2000 m ² /g carbon, so the inner surface area of four grams of activated carbon corresponds roughly to the area of a soccer field. The density of activated carbon is in the range of 0.2 to 0.6 g/m ³ . The pore size distribution of the micropores (<2 nm), mesopores (2 - 50 nm) and macropores (> 50 nm) determines the adsorption properties.

Macropores are access routes for fluids into the interior of the coals and play a key role in diffusion and mass transport processes into deeper-lying areas of the grain. Most of the adsorption takes place on the surface of the micropores. The size of this area determines the effective surface and thus the adsorption properties of an activated carbon.

The size of the effective surface is characterized by the so-called BET measurement, named after the inventors Stephen Brunauer, Paul Hugh Emmett and Edward Teller. In this analysis method, a gas (adsorptive), often liquid nitrogen, is passed over the material to be examined (adsorbent) and due to the cooling of the liquid nitrogen, a normal pressure device is used to below the saturation vapor pressure of the material measuring gas determines the adsorbed quantity (adsorption). The saturation vapor pressure of the sample gas must not be reached during the analysis process, otherwise condensation would occur, which would falsify the measurement result. Subsequent heating of the sample releases part of the adsorbed amount of gas from the surface, allowing an adsorption-desorption isotherm to be determined. The measured amount of adsorbed or released gas is proportional to the surface.

Activated carbon is obtained from plant, animal, mineral or petrochemical substances. Wood, peat, nut shells, coconut fibre, lignite or hard coal are used as the starting material.

When the activated carbon is extracted, so-called polycyclic aromatic hydrocarbons (PAHs) are produced as a result of the incomplete combustion processes of the starting material. These are solid, mostly colorless, lipophilic compounds that are carcinogenic. Accordingly, it is of interest to keep these values low in the activated carbon.

Three methods can be used for the production and activation of activated carbon. Chemical activation by acid, a strong base, or a salt. The physical activation by heating the material to high temperatures in an oxidizing or partially oxidizing environment, which is steam or carbon dioxide, in a heated rotary kiln or fluidized bed reactor. Or a process method that is a combination of the first two.

WO 2019 104 382 A1 discloses a method for producing activated carbon, in which the starting material made of wood, coconut shells or coal is placed in a first reactor and pyrolytically carbonized material and volatile gas are produced. Part of the volatile gas is diverted to a first combustor to provide heat for the first reactor. Part of the resulting fuel gas from the first combustion chamber is diverted to a second reactor in order to provide the fuel gas for converting carbonizing material into activated carbon.

CN 109 569 512 discloses a process for producing a modified activated carbon adsorbent, in which the starting material made of wood, apricot shells, coconut shells and palm shells is crushed, ground, sieved, washed with deionized water and then dried. Then the material with Microwave radiation treated under a nitrogen atmosphere and finally impregnated with an aqueous 1-5% citric acid solution to obtain modified activated carbon.

US 2016 005 92 11 describes a method for improving, characterizing and testing activated carbon. Activated carbon based on coconut shells is used as the starting material and activated by various treatments to become more mesoporous. The starting material used has 95% micropores and 5% mesopores. A catalyzed impregnated activated carbon is produced by treatment with an aqueous calcium-based catalyst, which is heated at a pyrolysis temperature until a structure of 10% mesopores is formed.

Known manufacturing processes have the disadvantage that the starting material consists of coconut shells, which are usually transported to the production site from the Philippines and thus the production of activated carbon creates a large CCh footprint. In addition, the process steps are often not coordinated in such a way that the environment is relieved.

The object of the invention is to provide a method for producing activated charcoal, the starting materials of which are locally available, are produced from a residue and so plant material does not have to be applied separately for the production of activated charcoal, and whose production process steps have recycling steps in order to relieve the burden on the environment .

The object is achieved with the method having the features of claim 1.

Advantageous developments are characterized in the subclaims dependent thereon.

Another object of the invention is to produce a corresponding activated carbon that is produced more effectively and sustainably and has an increased BET surface area and low PAH values.

The object is achieved with the features of claim 17. The inventors have recognized that a residue that occurs in a wood gasification process for the production of biogas to generate electricity and heat, namely the residual coal, which is normally mixed with water at the end of the process to avoid dust and filled into big bags, as a Starting material can be used for the production of activated carbon and thus this residue can be fed to an upgrading.

The production of the residual coal is based on a staged gasification process with a spatial and control-technical separation of the individual process steps such as pyrolysis, oxidation and reduction. The separation enables individual controllability of the process conditions.

In the first step of the process, dried biomass from organic plant material such as wood chips, shrubbery, forest residues and waste wood is burned in a pyrolysis process by adding air at temperatures of approx. 450 - 500 °C. Due to the high temperatures, the introduced biomass is broken down into its solid, liquid and gaseous components. The gas produced during pyrolysis still has a high proportion of tars.

The pyrolysis products are then fed into a reduction reactor, the so-called fluidized bed reactor. This reactor is a special floating fixed bed technology. In classic fixed-bed reactors, gravity and the gas flow act downwards, causing the reactor contents to become increasingly compacted.

In the floating bed reactor, these forces act in opposite directions. As a result, the biochar heap in the gasifier always remains ideally loosened and well permeable, regardless of the previous structure of the wood chips. This type of gasification produces almost no tar and foreign bodies in the gasified coal. Due to the upward operation, slag deposits can be easily removed at the foot of the floating bed reactor. In addition, instead of ash, high-quality wood gasification charcoal or biochar is produced as a by-product, in which more CO2 remains stored in the biochar than in conventional wood gasification processes due to the special treatment. As a result, the wood gasification charcoal has a high carbon content and can be modified to activated charcoal by direct activation.

The oxidation takes place at the entrance of the reduction reactor. In the oxidation zone, the components from the pyrolysis are partially burned by adding more air. Due to the resulting high temperatures of up to 900°C, almost the entire tar content from the pyrolysis is split (cracked). As a result, a significant part of the gas cleaning already takes place in the oxidation zone.

The actual gasification of the biomass takes place in the reduction zone. The solid carbon from the pyrolysis process forms a stable, suspended fixed bed in the reduction reactor. The gas heated by the oxidation flows through this fixed bed. As it flows through, the product gas cools down to around 700°C due to endothermic reactions and exits at the top of the reactor. This product gas is enriched with the carbon particles that are separated out in the downstream filter process.

The separated carbon particles are the starting material for the production of activated carbon. These charcoal particles or residual charcoal are particularly suitable for the production of activated charcoal because the high temperatures in the oxidation zone of up to 900° C. mean that the accumulation of polycyclic aromatic hydrocarbons (PAH) is low.

In addition, the wood gasification charcoal used as the starting material for the activated charcoal has the advantage that the charcoal is in a homogeneous powder form after the gasification process, has relatively few volatile components (approx. 10%) and has a carbon content of 80%. Due to the relatively homogeneous powder form, the processing effort for activation to activated carbon is lower than with a conventional production process for activated carbon from a different starting material. As a result, the manufacturing process saves energy and a residue is refined that was normally only used to produce briquettes.

In the present invention, the wood gasification charcoal is refined into activated charcoal by activation processes instead of for briquette production. Thus, two already known processes such as a wood gasification process for the production of biogas and the activation of activated carbon are used and an intermediate step according to the invention is introduced. As a result, the locally available plant material is utilized even more efficiently.

In this intermediate step, the wood gasification coal is not mixed with water and bottled, but the residual heat of the coal is transferred to a raw shell heat exchanger taken away. In addition, this residual heat is at least partially used to preheat the activation means and the reactors, thus ensuring thermal feedback. This intermediate step makes available a new starting material for the production of activated carbon, which is available locally and is not burdened with high transport costs.

The coconut shells, which are usually used for the large-scale production of activated carbon, are delivered to the production site from southern countries, often from the Philippines, which leads to long transport routes and a high CO2 load. The inventor has recognized that the locally present residue from the special wood gasification process is particularly suitable for activation into activated carbon. Since today value is placed on sustainable products that have a lower environmental impact during production, the inventor has created an additional benefit in addition to the technically excellent suitability of the modified residue. Thus, the starting material of this invention does not cover a huge transport distance, instead the residual product of a wood gasification plant is recycled through a charcoal activation process.

In addition, the invention envisages treating the waste water in some process steps and feeding it back into the process, which also leads to a reduction in the burden on the environment.

CN 109 160 512 discloses a residue from biomass gasification which is used for producing activated carbon. The processing of this residue before activation to activated carbon is expensive. In the present invention, the residue used for the activated carbon activation is originally in homogeneous powder form, has relatively few volatile components (approx. 10%) and a carbon content of 80%. As a result, the existing residue can be used immediately for activation to activated carbon and can only optionally be mechanically sieved into different fractions by a screening plant and/or crushed to the required particle sizes by the grinding plant. The residue from CN 109 160 512 has to go through several preliminary process steps before it can be physically activated into activated carbon. The raw material is mixed with a high-temperature binder and an activation aid, and then kneaded. Then, a normal temperature binder is added and the whole mixture is kneaded again. After a subsequent extrusion of the mass, it is dried before being fed into the gasification reactor. All of these preparation steps are not necessary in the present invention.

In the present invention, locally available organic plant material such as wood chips, shrubbery, sawn timber from forest and landscape maintenance, windblown wood and wood infested with pests is converted in a wood gasification process and the residual heat of the resulting coal is removed in a raw shell heat exchanger. The residual material that accumulates in the wood gasification process can be directly activated by activation steps to form activated carbon.

The invention thus relates in particular to a method for producing an activated charcoal from a residue that occurs in a wood gasification process, characterized in that a wood gasification charcoal is used as the starting product, which in a staged gasification process of organic fuels and wood with a spatial separation of the individual process steps such as pyrolysis , Oxidation and reduction occurs, with the reduction being carried out in a fluidized bed reactor, whereby a fine-grained, carbon-rich char is produced and the wood gasification char produced in this way is subsequently supplied to an activation, with the wood gasification char being chemically and/or physically activated.

One embodiment provides that the carbon is chemically activated by means of ultrasound or vacuum by means of an impregnating agent, the impregnating agent being phosphoric acid, potassium hydroxide, potassium carbonate or zinc chloride.

One embodiment provides that the impregnation takes place at temperatures between 400 and 1000°C and in particular at temperatures of 405, 700, 850 and 1000°C.

One embodiment provides that the impregnating agent and deionized water are mixed in the mixing ratios of 1:1 to 1:5 and, in particular, are used in the mixing ratios of 1:1, 1:3 and 1:5.

One embodiment provides that the treatment of the impregnation takes place over a period of 0.4 to 2.5 hours, in particular 0.5 to 2 hours.

One embodiment provides that after the impregnation, the treated carbon is filtered off through a filter and dried in a dryer, with the waste water either treated in a treatment system and fed back into the process or discharged into a waste water system.

One embodiment provides that, during the physical activation, the activating agent is placed in the activation reactor and preheated by means of a heat exchanger.

One embodiment provides that the activating agents are IXh/FWCg), CO2 or COz/tWCg).

One embodiment provides that the physical activation takes place at 750 to 950°C, in particular 800 to 875°C and in particular at 850°C. The activation times are between 0.5 and 2.5 hours, in particular between 1 and 2 hours.

One embodiment provides that the wood gasification charcoal is mechanically pretreated before chemical or physical activation by one or more of the following steps: sieving, sifting, classifying, grinding.

One embodiment provides that a maximum particle size of 3 mm is preferably set.

One embodiment provides that particles above a desired maximum grain size are crushed to the required particle size.

One embodiment provides that the wood gasification charcoal is filtered from the raw gas stream at the end of the wood gasification process and before activation by a gas filter and is cooled via a lock system, which at the same time represents a transition container, and rendered inert with an inert fluid, in particular an inert gas such as nitrogen.

One embodiment provides that the wood gasification charcoal is passed through a further lock as an intermediate step before activation, which at the same time represents a raw shell heat exchanger in which the residual heat present is dissipated. One embodiment provides that the waste heat obtained in the raw shell heat exchanger is fed to subsequent or previous process steps of the method, in particular for preheating the activation means and the activation reactor.

One embodiment provides that the wood gasification charcoal is temporarily stored in a reservoir in order to ensure a uniform, continuous supply for the activation process.

A further aspect of the invention relates to an activated charcoal produced from wood gasification charcoal using a method according to claims 1 to 16, the activated charcoal having a BET surface area between 500 m ² /g and 950 m ² /g after physical activation and after chemical activation has a BET surface area between 475 m ² /g and 1150 m ² /g.

The invention is explained by way of example using a drawing. They show:

FIG. 1: Prior art and method according to the invention

At the beginning of the process, in section Sl, Figure 1 shows the current state of the art, in which, in a wood gasification process, the combustible material such as wood chips, residual forest wood, waste wood and plant material is processed in a staged process with a spatial separation of the individual process steps such as pyrolysis, oxidation and reduction is converted.

In the pyrolysis, the reduced addition of air at temperatures of 450 - 500 °C results in a partial combustion of the plant material to form coke and pyrolysis gas.

The pyrolysis products are then fed into a special floating bed reactor, with the oxidation taking place at the entrance to the reduction reactor. In the oxidation zone, the components from the pyrolysis are partially burned by adding more air. Due to the resulting high temperatures of up to 900°C, almost the entire tar content from the pyrolysis is broken down. As a result, a significant part of the gas cleaning already takes place in the oxidation zone.

The floating bed reactor represents the reduction zone in which the actual gasification of the biomass takes place. The solid carbon from the pyrolysis process forms a stable, suspended fixed bed in the reduction reactor. This fixed bed is through through the Oxidation heated gas flows through. As it flows through, the product gas cools down to around 700°C due to endothermic reactions and exits at the top of the reactor. This product gas is enriched with the carbon particles, which are separated in the gas filter 1 connected downstream. The separated carbon particles are the starting material for the production of activated carbon.

The product gas is then transported to a gas scrubber and the coal left over from the gasification process is rendered inert with nitrogen in a lock or transfer container 2 and partially cooled. As soon as it leaves the filter, the carbon has a specific BET surface area of between 200 and 300 m ² /g.

In the known state of the art, the coal is usually mixed with water in a downstream mixer 28. The wet coal powder is then filled into big bags 29 and used as fertilizer/soil treatment.

In Section 2, the process path according to the invention is listed, in which the wood gasification coal left over from the fuels preferably passes through a further lock. A raw shell heat exchanger 3 is integrated in this sluice, through which the residual heat of the wood gasification coal is dissipated.

The barrier 23 in front of the raw shell heat exchanger 3 and the barrier 24 after the raw shell heat exchanger 3 serve as safety aspects and enable a separation between the wood gasification process and the activation processes. This area can be flooded with an inert gas, such as nitrogen, on the one hand to prevent the development of fire and on the other hand to provide a liquid heat transfer medium for dissipating and passing on the thermal energy. This now modified residue is now fed into a carbon activation process.

A certain supply of coal is created in the storage tank 4 and this is continuously carried out through the activation process. Here, too, it is possible to render the system section inert with an inert gas such as nitrogen.

The resulting coal is in powder form with an existing particle size range and an existing particle size distribution. It has been found that the activation stage should preferably be started with a maximum particle size of 3 mm. about this To make sure, the upper belt can be separated by means of a screening or classifying system 5 or different fractions can also be classified. In order to enable a complete processing of the feed material, oversizes can be crushed to the required particle sizes with a grinding plant 6 . Conventional grinding systems such as ball mills, impact mills or the like can be used for this purpose. If grain size classification is not necessary, the coal stream can be transported and activated directly.

This is followed by chemical and/or physical activation of the charcoal.

Chemical activation is discussed below. The wood gasification coal is chemically impregnated in section 7 with the help of ultrasound or vacuum. Impregnation is carried out, for example, with phosphoric acid, potassium hydroxide, potassium carbonate, zinc chloride.

The impregnation takes place at temperatures between 400 and 1000 °C and in particular at temperatures of 405, 700, 850 and 1000 °C.

Impregnating agent and deionized water are mixed in the mixing ratios of 1:1 to 1:5 and are used in particular in the mixing ratios of 1:1, 1:3 and 1:5.

The treatment of the impregnation takes place over a period of 0.4 to 2.5 hours, in particular 0.5 to 2 hours. After the treatment period, the treated coal is filtered through a filter 8 and dried in a separate dryer 9 or directly in a drying zone in the activation reactor 12. The waste water is either treated in a treatment system 10 and returned to the process or fed into the waste water system.

In physical activation, the charcoal is brought into contact with an activating agent. Depending on the type of activation, the coal is either pretreated mechanically or fed directly into the activation reactor 12 (e.g. rotary kiln, fluidized bed, fixed bed pulsation reactor) for physical activation.

The activating agent is also added in the reactor (e.g. Nz/HzOfg), CO2, COz/HzOfg)), which is preheated by means of a heat exchanger 11 . The physical activation now takes place here at 750 to 950° C., in particular 800 to 875° C. and in particular at 850 °C. The activation times are between 0.5 and 2.5 hours, in particular between 1 and 2 hours.

Depending on the different process parameters, activated carbon with a wide variety of BET surface areas and pore sizes can be produced. In addition, the physical activation of the wood gasification carbon further reduces the PAH values, which makes it possible to use the activated carbon produced in the food and animal feed sector. In order to avoid uncontrolled burning in the reactor or to ensure safety technology, nitrogen can be supplied for complete inerting. The activated carbon is discharged via a sluice system rendered inert with nitrogen (shutoff 25 in front of the raw-shell heat exchanger 13 and the shut-off 26), with residual heat being dissipated here by means of a raw-shell heat exchanger 13 in order to avoid self-ignition. Depending on the filling level in the transfer container 14, the product is discharged periodically by opening the barrier 27.

With a chemical activation method, the product can be suitably upgraded by washing the chemicals from the carbon in the scrubber 15 with water. The washing water is separated off in the filter 16, and the residual moisture that remains in the coal is removed by a downstream dryer 17. Physically activated charcoal is applied directly. A subsequent screening plant 18 enables separation into different products. With this screening plant, 18 activated carbons can be produced in granulate and powder form. To reduce dust and facilitate handling, the carbon powder is optionally mixed with water in a mixer 19 . In a pelletizer 20, activated carbon pellets are produced from the powdered carbon dust.

Due to the fact that volatile components escape from the coal during the activation process, dust can also be discharged and certain gas-forming reactions take place, exhaust gas aftertreatment 21 is required (e.g. filter, catalytic converter, post-combustion). The steam contained in the exhaust gas is separated in the downstream exhaust gas condensation 22. The waste heat obtained from this and that from the raw-shell heat exchanger 3 and raw-shell heat exchanger 13 is used to partially preheat the activating agent and the reactor. The advantage of the invention is that the method is more environmentally friendly than conventional methods. No coconut shells are used as raw material for the production of the activated charcoal, which have to be delivered from southern countries like the Philippines, which leads to a reduction of the carbon footprint of this activated charcoal. In addition, a residual product, which is usually only used with a low value, is upgraded to a valuable and versatile raw material.

Furthermore, the process is preferably operated in a network in such a way that improved energy efficiency of the overall process is achieved, since in particular all waste heat can be used for the energy-requiring processes in the method. In addition, the invention provides for treating the waste water in some process steps and feeding it back into the process, which also leads to a relief of the environment.

reference sign

1 gas filter

2 transfer tanks

3 raw shell heat exchangers

4 template memory

5 screening plant

6 mill plant

7 section

8 filters

9 dryers

10 treatment system

11 heat exchanger

12 activation reactor

13 tubular shell heat exchanger

14 transfer containers

15 washers

16 filters

17 dryers

18 screening plant

19 mixers

20 pelleting

21 exhaust aftertreatment

22 flue gas condensation

23 Shut-off in front of the raw shell heat exchanger 3

24 Shut-off after the raw shell heat exchanger 3

25 Shut-off in front of the raw shell heat exchanger 13

26 Shut-off after the raw shell heat exchanger 13

27 Barrier after the transfer container

Claims

Method for producing an activated charcoal from a residue that occurs in a wood gasification process, characterized in that a wood gasification charcoal is used as the starting product, which occurs in a staged gasification process of organic fuels and wood with a spatial separation of the individual process steps such as pyrolysis, oxidation and reduction , wherein the reduction is carried out in a fluidized bed reactor, whereby a fine-grained, carbon-rich char is produced and the wood gasification char produced in this way is subsequently supplied to an activation, the wood gasification char being activated chemically and/or physically. Method according to one of the preceding claims, characterized in that the carbon is chemically activated by means of ultrasound or vacuum by means of an impregnating agent, the impregnating agent being phosphoric acid, potassium hydroxide, potassium carbonate or zinc chloride. Method according to one of the preceding claims, characterized in that the impregnation takes place at temperatures between 400 and 1000°C and in particular at temperatures of 405, 700, 850 and 1000°C. Method according to one of the preceding claims, characterized in that impregnating agent and deionized water are mixed in the mixing ratios of 1: 1 to 1:5 and are used in particular in the mixing ratios 1: 1, 1:3 and 1:5. Method according to one of the preceding claims, characterized in that the treatment of the impregnation takes place over a period of 0.4 to 2.5 hours, in particular 0.5 to 2 hours. Method according to one of the preceding claims, characterized in that after the impregnation the treated coal is filtered through a filter (8) and dried in a dryer (9), the waste water either being treated in a treatment system (10) and returned to the process or discharged into a sewage system.

7. The method according to any one of the preceding claims, characterized in that given the physical activation, the activating agent in the activation reactor (12) and is preheated by means of a heat exchanger (11).

8. The method according to claim 7, characterized in that the activating agents are N ₂ /H ₂ O(g), CO ₂ or CO ₂ /H ₂ O(g).

9. The method according to claim 7 or 8, characterized in that the physical activation takes place at 750 to 950 °C, in particular 800 to 875 °C and in particular at 850 °C. The activation times are between 0.5 and 2.5 hours, in particular between 1 and 2 hours.

10. The method according to any one of the preceding claims, characterized in that the wood gasification coal is mechanically pretreated before chemical or physical activation by one or more of the steps screening, sifting, classifying, grinding.

11. The method according to any one of the preceding claims, characterized in that preferably a maximum particle size of 3 mm is set.

12. The method according to any one of the preceding claims, characterized in that particles above a desired maximum particle size are crushed to the required particle size.

13. The method according to any one of the preceding claims, characterized in that the wood gasification coal is filtered out of the raw gas flow at the end of the wood gasification process and before activation by a gas filter (1) and cooled via a lock system, which also represents a transition container (2), and an inert fluid, in particular an inert gas such as nitrogen, is rendered inert.

14. The method according to any one of the preceding claims, characterized in that the wood gasification coal is passed as an intermediate step before activation through a further lock, which is also a raw shell heat exchanger (3) in which the residual heat present is dissipated.

15. The method according to any one of the preceding claims, characterized in that the waste heat obtained in the raw shell heat exchanger (3) is fed to subsequent or previous process steps of the method, in particular for preheating the activation means and the activation reactor (12).

16. The method according to any one of the preceding claims, characterized in that the wood gasification coal is temporarily stored in a storage tank (4) in order to ensure a uniform, continuous supply for the activation process. 17. activated carbon, produced by a method according to claims 1 to 16 from

Wood gasification charcoal, wherein the activated charcoal has a BET surface area between 500 m ² /g and 950 m ² /g after physical activation and a BET surface area between 475 m ² /g and 1150 m ² /g after chemical activation.

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