Process for gasifying biomass with tar adsorption

Abstract

A process and apparatus for gasification of biomass. Biogenic residue may be supplied to a heating zone to dry the biomass and allow the volatile constituents to escape to generate a pyrolysis gas. The pyrolysis gas is supplied to an oxidation zone and substoichiometrically oxidized to generate a crude gas. The carbonaceous residue generated in the heating zone and the crude gas is partially gasified in a gasification zone. The gasification forms activated carbon and a hot process gas. The activated carbon and the hot process gas are conjointly cooled. The adsorption process during the conjoined cooling has the result that tar from the hot process gas is absorbed on the activated carbon in the cooling zone. A pure gas which is substantially tar-free is obtained. The tar-enriched activated carbon may be at least partly burned for heating the heating zone and/or the gasification zone.

Claims

1. A process (10) for gasifying biomass (B), comprising: supplying biomass (B) to an apparatus (11) for gasification, generating a crude gas (R) and a carbonaceous residue (RK) from the supplied biomass (B) in a first process step, partially gasifying the carbonaceous residue (RK) with gas constituents of the crude gas (R) in a gasification zone (ZV) in a second process step, as a result of which activated carbon (AK) and a hot product gas (PH) are formed, removing between a minimum of 0.02 units of mass and a maximum of 0.1 units of mass of the activated carbon (AK) and the hot product gas (PH) from the gasification zone (ZV) per unit of mass of supplied biomass (B) with respect to a reference condition water-free and ash-free (waf), conveying the activated carbon (AK) and the hot product gas (PH) to a cooling zone (ZK), and conjointly cooling the activated carbon (AK) and the hot product gas (PH) in the cooling zone (ZK) in a third process step (14), so that an adsorption process takes place, wherein the activated carbon (MAK2) is enriched with tar from the hot product gas (PH) while cooling, supplying the product gas (PA, PR) that has been cleaned due to the adsorption process as fuel to an apparatus, and proportionally adapting an amount of the supplied biomass (MB) and an amount of the activated carbon (AK) removed from the gasification zone (MAK2) to performance requirements of the apparatus.

2. The process according to claim 1, wherein, in the third process step (14) for the adsorption process in the cooling zone (ZK), the product gas (PH) and the activated carbon (MAK2) are cooled together in the cooling zone (ZK) such that a temperature of the product gas remains above a lower threshold temperature that is higher than a dew point temperature of the product gas (PA, PR).

3. The process according to claim 2, wherein the lower threshold temperature is between a minimum of 10 K and a maximum of 20 K greater than the dew point temperature of the product gas (PA, PR).

4. The process according to claim 1, further comprising, during the first process step, drying the supplied biomass (B) during a first partial step (12i) in a heating zone (ZE) and heating the supplied biomass (B) in such a manner that volatile constituents of the biomass (B) escape, forming a pyrolysis gas (PY) and the carbonaceous residue (RK), and substoichiometrically oxidizing at least the pyrolysis gas (PY) during a subsequent partial step (12ii) of the first process step (12) in an oxidation zone (ZO) due to the supply of an oxygen-containing gas (L), thereby forming the crude gas (R).

5. The process according to claim 4, wherein the heating zone (ZE) and the oxidation zone (ZO) are separate from one another.

6. The process according to claim 4, further comprising substoichiometrically oxidizing of the pyrolysis gas (PY) and gasifying the carbonaceous residue (RK) in zones that are separate from one another.

7. The process according to claim 4, wherein the substoichiometric oxidation is performed in the oxidation zone (ZO) at a temperature (TO) of a minimum of 1000° C. up to a maximum of 1200° C.

8. The process according to claim 4, further comprising adjusting the temperature (TO) in the oxidation zone (ZO) by adjusting the amount of the supplied oxygen-containing gas (L).

9. The process according to claim 1, further comprising elevating a pressure at which at least one of the first, second, and third process steps are performed relative to ambient pressure.

10. The process according to claim 1, further comprising one or both of heating the crude gas (R) and the carbonaceous residue (RK) in the gasification zone (ZV) by indirect heating, and cooling the activated carbon (AK) and the hot product gas (PH) in the cooling zone (ZK) by indirect cooling.

11. The process according to claim 1, further comprising incinerating the activated carbon (AK) with adsorbed tar from the third process step (14) in a reactor (44) with air that was used in the third process step (14) for cooling the product gas (PH) and the activated carbon (AK), and heating the heating zone (ZE) using exhaust gas (G) from the incineration of the activated carbon (AK).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Advantageous embodiments of the process and the apparatus, respectively, can be inferred from the dependent patent claims, the description and the drawings. Hereinafter, preferred exemplary embodiments of the invention are explained in detail with reference to the appended drawings. They show in

(2) FIG. 1 a block diagram of an exemplary embodiment of the inventive process and the inventive apparatus, respectively,

(3) FIG. 2 a block diagram of another exemplary embodiment of the inventive process and the inventive apparatus, respectively, and

(4) FIG. 3 an exemplary embodiment of the apparatus with a separate heating chamber for drying and pyrolysis and a shared reaction chamber for an oxidation zone and a gasification zone, as well as a separate cooling zone in a separate cooling chamber.

DETAILED DESCRIPTION

(5) FIG. 1 depicts a schematic block diagram of an exemplary embodiment of the invention. The block diagram illustrates a process 10 and an apparatus 11, respectively, for gasifying a biomass B. The process comprises essentially three successive process steps 12, 13, 14. In a first process step 12 the biomass B is supplied, together with an oxygen-containing gas, to the oxidation zone ZO. The oxygen-containing gas used in the exemplary embodiment is air L. The amount of supplied air L is adjusted as a function of the demand of a product gas to be generated. Furthermore, it is possible to adjust a temperature TO in the oxidation zone ZO via the amount of air L.

(6) In this first process step 12, the biomass B oxidizes substoichiometrically in the oxidation zone ZO. In so doing, a crude gas R and a carbonaceous residue RK are formed. The temperature TO in the oxidation zone is adjusted below—but as close as possible to—the ash melting point or at the ash softening point of the ash of the carbonaceous residue RK. This avoids that the ash of the carbonaceous residue melts or softens in the oxidation zone ZO and that an agglutination in the region of the oxidation zone ZO occurs. On the other hand, due to an extremely high temperature TO in the oxidation zone ZO, a reduction of the tar content in the crude gas R is already achieved. The crude gas R and the carbonaceous residue RK are subsequently partially gasified in a second process step 13 in a gasification zone ZV. The gasification zone ZV can be indirectly heated with the aid of a heating arrangement 15. Otherwise, the temperature TV in the gasification zone ZV can be adjusted, for example, by transferring heat from the oxidation zone ZO, in particular by introducing hot carbonaceous residue RK, as well as hot crude gas R. In at least one preferred embodiment, the heating arrangement 15 may comprise at least one burner 16.

(7) The temperature TV in the gasification zone ZV can be adjusted via the heating arrangement 15, independently of the temperature in the oxidation zone ZO. In the exemplary embodiment of the invention, the temperature TV in the gasification zone ZV is a minimum of 800° C. and a maximum of 1000° C. The carbonaceous residue RK is partially gasified in the gasification zone ZV with gas constituents of the crude gas, wherein, in the exemplary embodiment, up to approximately 75% of the carbonaceous residue RK are gasified. The gas constituents that are used for gasifying the carbonaceous residue RK are mainly water vapor and carbon dioxide.

(8) Under these conditions, a hot product gas PH that still contains an undesirably high proportion of tar, as well as activated carbon AK, are formed. The hot product gas PH and a certain amount of activated carbon MAK2 are subsequently conveyed to the cooling zone ZK in order to cool the product gas PH and the certain amount of activated carbon MAK1 together, so that the tar is transferred from the hot product gas PH to the certain amount of activated carbon MAK2 during the conjoined cooling. In this manner, a precipitation of the tar on the wall of the chamber that provides the cooling zone ZK is prevented, because the certain amount of activated carbon MAK2 adsorbs the tar. On the other hand, the activated carbon AK is utilized efficiently.

(9) The amount of activated carbon MAK2 that is cooled together with the product gas PH is determined based on the amount of supplied biomass MB that resulted in the activated carbon AK, as well as in the product gas PH. The supplied amount of biomass MB contains, as a rule, water and ash and contains a mass mBroh. This corresponds to a mass mBaf with a reference condition, free of water and free of ash (waf). The amount of activated carbon MAK2 that is supplied to the cooling zone contains a mass mAK2 that is a minimum of 2% up to a maximum of 10% of the mass mWAF of the supplied biomass B, with respect to a water-free and ash-free reference condition of the supplied biomass B.

(10) During a third process step 14 the hot product gas PH and the certain amount of activated carbon MAK2 and the ash forming in the gasifier are indirectly cooled with the aid of a cooling arrangement 17. In so doing, an adsorption process takes place in the cooling zone ZK, wherein the tar from the product gas PH bonds with the certain amount of activated carbon MAK2 during conjoined cooling. The amount of activated carbon MAK2 is enriched with tar from the product gas PH while cooling in a shared chamber.

(11) The hot product gas PH can be cooled within the cooling zone ZK, for example to a temperature of below 50°. The product gas PH and the certain amount of activated carbon MAK2 are preferably cooled together not below a lower temperature threshold in the third process step for the adsorption process, said temperature threshold being higher than the dew point temperature of the product gas PH. In this manner, it is possible to derive great use from the loading capacity of the activated carbon. By enriching the activated carbon MAK2 with the tar from the product gas PH, it is possible at the end of the cooling zone ZK for a cooled product gas PA to form, which product gas can also be referred to as pure gas PR. The pure gas PR is completely free of tar and only contains a negligible percentage of tar. The pure gas PR can be used for energy generation and, in particular, does not require any additional expensive post-treatment for tar removal. In particular, the pure gas PR can be used directly in cogeneration plants.

(12) Next to the certain amount of activated carbon MAK2 for conjoined cooling, there remains potentially an excess amount of activated carbon MAK1 from the gasification zone ZV. As indicated by arrow P in FIG. 1, this can be branched off or removed upstream of the cooling zone ZK. The excess partial amount MAK1 having a mass flow mAK1 can be supplied—for further fine cleaning of the pure gas PR—to a cleaning container arrangement to reduce the residual tar content of the pure gas PR after the conjoined cooling. Such a cleaning container arrangement for the cleaning of gas has been known per se, so that a detailed description thereof may be omitted.

(13) As shown in dashed lines in FIG. 1, the cooled product gas PA or the pure gas PR can be freed of dust in a suitable dust precipitation unit 18, for example with the use of filters, electrostatic arrangements, cyclones or the like.

(14) The amount of activated carbon MAK2 can be removed from the cooling zone ZK and ground or finely ground with the use of a grinding arrangement 19. The ground activated carbon, hereinafter referred to as coal dust SK, can be used as an energy carrier for combustion. For example, the carbon dust SK or at least a part thereof can be conveyed to the burner of the heating arrangement 15 for the indirect heating of the gasification zone ZV.

(15) Furthermore, FIG. 1 shows two options for using a exhaust gas G of the at least one burner 16 of the heating arrangement. The exhaust gas G can be used, on the one hand, in a drying arrangement 20 for drying the biomass B before it is conveyed into the oxidation zone ZO. Alternatively or additionally, the exhaust gas G can be used in a preheating arrangement 21 for preheating the air L or the oxygen-containing gas before being conveyed into the oxidation zone ZO.

(16) The process can be performed as a mixed form of an autothermal and allothermal gasification. For the optional indirect heating of the gasification zone ZV in the second process step 13, at most 10% of the energy content of the biomass are needed according to one example. The pure gas PR has a heating value between 1.5 and 2 kWh/cubic meter. Cold efficacy degrees of above 80% can be achieved. The removal of tar from the product gas Ph due to adsorption with the simultaneous cooling of the product gas PH and the certain amount of activated carbon MAK2 in the third process step 14 is extremely economical and requires neither high investment costs nor high maintenance costs.

(17) FIG. 2 shows another exemplary embodiment of the inventive process and the inventive apparatus, respectively. Hereinafter, the differences with respect to the exemplary embodiment in FIG. 1 will be described. Other than that, the description relating to the exemplary embodiment according to FIG. 1 applies.

(18) In FIG. 2, the first process step 12 in the exemplary embodiment is divided into a heating step 12i and an oxidation step 12ii. During the heating step 12i, the biomass B is supplied to a heating zone ZE. In the heating zone ZE, the biomass B is dried and heated in such a manner that the volatile constituents escape from the biomass B. In so doing, a gas is formed of the volatile constituents PY (pyrolysis gas) and a carbonaceous residue RK. As illustrated, the heating zone ZE can be heated with the exhaust gas G of the burner 16 of the heating arrangement 15. Alternatively or additionally, but not illustrated, the heating zone ZE may be heated with exhaust gas of a gas engine that is supplied with the pure gas PR from the process. The temperature TE in the heating zone is, for example, approximately 500° C. The pyrolysis gas PY is conveyed to the oxidation zone ZO. Furthermore, the oxidation zone ZO is supplied with an oxygen-containing gas, for example air L, in an amount that the pyrolysis gas PY oxidizes substoichiometrically in the oxidation zone ZO. The air L can be preheated in a preheating arrangement 21 that is supplied with heat of the exhaust gas of the burner 16.

(19) The carbonaceous residue RK can be supplied to the oxidation zone ZO together with the pyrolysis gas PY and/or, by bypassing the oxidation zone ZO, directly to the gasification zone ZV. A part of the carbonaceous residue RK is able to oxidize stoichiometrically in the oxidation zone ZO.

(20) The exhaust gas of the burner 16 of the heating arrangement 15 can optionally be used for heating the gasification zone ZV.

(21) Due to a spatial separation of heating for drying and pyrolysis, on the one hand, and oxidation, on the other had, the process is performed stepwise. The desired temperature TO in the oxidation zone ZO can thus be attained and adjusted largely independently of the piece size of the biomass B as well as of the humidity of the biomass.

(22) FIG. 3 shows schematically, partially in section, a side elevation of an exemplary embodiment of an apparatus 11 for gasifying biomass B. The apparatus 11 comprises an essentially vertically arranged, for example cylindrical, reaction container 22 that delimits a shared reaction chamber 23. In an upper section of the reaction chamber 23 or the reaction container 22, the oxidation zone ZO and the gasification zone ZV in an adjoining section are formed. Due to the vertical arrangement, a simplified transport within the reaction chamber 23 can be achieved, without expensive conveyor arrangements. As an alternative thereto, the at least one reaction chamber 23 can be oriented horizontally or inclined relative to the vertical and the horizontal.

(23) Alternatively, the oxidation zone ZO and the gasification zone ZV may also be formed in reaction chambers that are separate from one another (not shown in FIG. 3). The separated reaction chambers may be arranged in reaction chambers that are separated from each other.

(24) Carbonaceous residue RK, as well as pyrolysis gas PY, can be supplied at the vertically upper end of the reaction container 22 to the reaction chamber 23. The carbonaceous residue RK and the pyrolysis gas PY can be generated in a heating chamber 24 of the apparatus 11, separate from the reaction chamber 23, said heating chamber providing a heating zone ZE in the heating chamber 24 for drying and for the pyrolysis of the biomass B. The heating chamber is connected to the reaction chamber 23 via a line 25 for pyrolysis gas PY and carbonaceous residue RK.

(25) The heating chamber 24 is supplied with biomass B from a silo 26 or an intermediate container. To do so, the silo 26 or the intermediate container is connected to the inlet 27 of the heating chamber 24. Between the silo 26 and the heating chamber 24 for drying and pyrolysis, there is arranged a first lock 28. For example, with the use of this first lock 28, it is possible to adjust the mass flow mBroh of biomass B that is supplied to the heating chamber 24. In the heating chamber 24 that is oriented diagonally with respect to the vertical or horizontal, there is arranged a conveyor arrangement 29, for example a screw conveyor, to convey the biomass B from the inlet 27 of the heating chamber 24 through the heating chamber 24. On the outlet 30 of the heating chamber 24, said heating chamber is connected to the reaction chamber 24 via the line 25, said reaction chamber providing the oxidation zone ZO and the gasification zone ZV. The heating chamber ZE and the reaction chamber 23 are chambers that are separated from each other so that the temperatures in the reaction chamber 23 and the heating chamber 24 can be adjusted largely independently of each other. Furthermore, in the upper section of the reaction container 22, there is a gas supply arrangement 31 for supplying the oxygen-containing gas or the air L to the oxidation zone ZO. For example, the air is conveyed, by means of a line 32, of the gas supply arrangement 31, directly into the oxidation zone ZO. In the reaction chamber 23, there is provided a temperature sensor 33 for the detection of the temperature TO in the oxidation zone ZO. For temperature regulation, the detected temperature is transmitted to a not specifically illustrated process control arrangement. Likewise, not specifically illustrated temperature sensors may be arranged in the heating zone ZE, as well as in the gasification zone ZV, these being able to detect the temperature in the heating zone ZE and in the gasification zone ZV, respectively, and to deliver them to the process control arrangement.

(26) On the end 34 of the reaction chamber 23—viewed in conveying direction—there may be arranged a branch arrangement 35 indicated by the arrow in FIG. 3, said branch arrangement being disposed to branch off—upstream of the cooling zone ZK—excess activated carbon AK that is not to be used for the conjoined cooling of the activated carbon AK and the product gas PH in the cooling zone ZK. At the end 34 of the reaction chamber 23, said reaction chamber is connected to a cooling chamber 36 that is contained in a cooling chamber container 37. The cooling chamber 36 provides a cooling zone ZK. The cooling chamber 36 is also arranged diagonally with respect to the vertical and the horizontal. Alternatively, it may be oriented vertically or horizontally, for example. The cooling chamber 36 contains a conveyor arrangement 38, for example a screw conveyer, that is disposed to convey a certain amount, for example a certain mass flow of the activated carbon AK generated in the reaction chamber 23 through the cooling chamber 36. Furthermore, the conveyor arrangement 38 can contribute to conveying the hot product gas PH into the cooling chamber 36 or the cooling zone ZK. On the end 39 of the cooling chamber 36—viewed in conveyor direction of the activated carbon AK or the product gas PH—said cooling chamber is connected to a precipitation chamber 40 that comprises a filter 18, as well as an exhaust 41 for the pure gas PR. The filter 18 can be supplied, for example, with activated carbon AK that has been branched off upstream of the cooling zone ZK. Arranged on the exhaust 41, there is a temperature sensor 42 that detects the gas output temperature of the cleaned product gas PR and transmits it to the process control arrangement. Furthermore, the precipitation chamber 40 has on its lower end an exhaust 43 for the tar-loaded activated carbon AK. At the exhaust 43, the precipitation chamber 40 is connected to a reactor 44 for the combustion of the tar-loaded activated carbon AK. Between the precipitation chamber 40 and the reactor 44, there is a second lock 45 through which the tar-loaded activated carbon AK is conveyed into the reactor 44 for combustion of the tar-loaded activated carbon. Furthermore, in one exemplary embodiment, the reactor 44 can be supplied with excess activated carbon AK that has been branched off upstream of the cooling zone ZK, in which case an appropriate feed line is not shown in FIG. 3. The second lock 45, like the first lock 28 on the inlet 27 of the heating chamber 24, is set up in such a manner that the apparatus 11 in the heating chamber 24, the reaction chamber 23 of the reaction chamber 36, as well as the precipitation chamber 40 can be operated at a pressure that is elevated with respect to ambient pressure, for example at 5 Bar.

(27) The reactor 44 for the combustion of the tar-loaded activated carbon AK has an exhaust 46 for the ash, in which case the ash can be conveyed to the outlet, for example, by means of a turntable 47. At the exhaust 46, the reactor 44 comprises a third lock 48 that, like the other locks 28, 45, is set up in such a manner that the apparatus 11 can be operated at a pressure that is elevated with respect to ambient pressure.

(28) The heating chamber 24 that provides the heating zone ZE, is enclosed by an insulating jacket 49. A heating space 51 is formed between the insulating jacket 49 and the outside wall of the container 50 for the heating chamber 24. In the exemplary embodiment, the heating space 51 is connected to the reactor 44 for combustion of the tar-loaded activated carbon via a line 52, via which the heating space 51 can be supplied with exhaust gas G of the reactor 44. Alternatively or additionally, the heating space 51, as indicated by arrow 52, can be heated with the exhaust gases from a gas engine (not illustrated) for generating electricity, said gas engine being supplied with the cleaned product gas PA, PR that is used as fuel. The exhaust gas G can be discharged from the heating space 51 via an outlet 53 in the insulating jacket 49.

(29) The reaction chamber is also enclosed by an insulating jacket 54 that encloses the oxidation zone ZO, as well as the gasification zone ZV. Between the insulating jacket 54 and the reaction chamber 23, there may be arranged a heating space for the indirect heating of the gasification zone ZV and/or the oxidation zone ZO (not illustrated) that can also be supplied with the exhaust gas G of the reactor 44.

(30) The cooling chamber container 37 is enclosed by a jacket 56, in which case a cooling space 57 is formed between the jacket 56 and the cooling chamber container 37, wherein said cooling space can be supplied via an inlet 58 with a coolant C, said coolant being air in the exemplary embodiment. The cooling space 57 has an exhaust 59 for discharging the air C from the cooling space 57. The air C that has been heated by indirectly cooling the cooling chamber 36 can be supplied—via the line 60 arranged between the exhaust 59 and the reactor 44—to the reactor 44 for the combustion of activated carbon AK.

(31) The exhaust 41 for discharging the cleaning gas PR can be connected, for example, to a gas engine (not illustrated) that is to be operated with the pure gas PR. For example, for the generation of the pure gas PR, the apparatus 11 operates as follows:

(32) In stationary condition when the gas engine is to deliver constant mechanical power, the continuous generation of pure gas PR is demanded, as a rule, by the apparatus 11 and by the process 10, respectively. In order to generate the pure gas PR, as a rule, a constant mass flow of biomass mBroh (reference condition, crude) from the silo 26 for the biomass B is supplied with the aid of the first lock 28 and, for example, the force of gravity, as well as the conveyor device 29, to the heating chamber 24 for drying and pyrolysis of the biomass B. The biomass flow mBroh corresponds to a biomass flow mBwaf (condition, water-free and ash-free). In the heating chamber 24 and the heating zone ZE, respectively, the biomass B is dried and heated by indirect heating of the heating zone ZE with the exhaust gas G of the reactor 44 and/or the gas engine at, for example approximately 500° C., and heated in such a manner that the volatile constituents escape from the biomass B (pyrolysis). In so doing, carbonaceous residue RK, as well as the pyrolysis gas PY that may have a tar content of several grams per cubic meter, are formed.

(33) The carbonaceous residue RK, as well as the pyrolysis gas PY, are conveyed into the oxidation zone ZO with the aid of the conveyor arrangement 29. In said oxidation zone, the pyrolysis gas PY is substoichiometrically oxidized with the introduction of an oxygen-containing gas, for example air L, at a temperature of approximately 1000° C. to 1200° C., in which case a crude gas R is formed. The largest part of the tar constituents in the pyrolysis gas PY are cracked. The air of the oxygen-containing gas L is controlled for the adjustment of the temperature TO in the oxidation zone ZO. For example, 1 cubic meter of air is needed per kilogram of biomass (waf). Due to preheating, the amount of air can even be reduced and the heating value of the pure gas PR can be increased. In the oxidation zone ZO and the oxidation step 12ii, respectively, the proportion of tar in the crude gas R is clearly decreased below 500 mg per cubic meter.

(34) The gas transport of the crude gas R into the gasification zone ZV located below the oxidation zone ZO is achieved, for example, in that the oxygen-containing gas L is supplied on the vertically upper end 61 of the reaction chamber 23, and thus the gas L pushes the gases present in the reaction chamber 23 vertically downward. Alternatively or additionally, a not illustrated evacuation device for the product gas PH can be connected on the end 34 of the reaction chamber 23 of the apparatus 11 in order to initiate or promote the gas transport within the reaction chamber 23.

(35) In the gasification zone ZV that may also be referred to as the reduction zone, the predominant part of the carbonaceous residue RK is gasified endothermally, in which case the gas temperature decreases accordingly to 700° C., for example. In so doing, the proportion of carbonaceous residue RK can decrease from originally 20% after pyrolysis to, for example, 5% with respect to the supplied biomass mBwaf (reference condition, water-free and ash-free). Carbon AK having a highly porous structure (activated carbon) is formed.

(36) The process control arrangement of the apparatus 11 is disposed to convey—by control of the process parameters such as, for example the temperature and, optionally, also the pressure, and/or by means of the branch arrangement, and/or the conveyor arrangement 38 of the cooling chamber 36—a certain mass of activated carbon MAK2 out of a region from a minimum of 0.02 kilograms up to a maximum of 0.1 kilogram per kilogram of supplied biomass (with respect to the reference sate, water-free and ash-free), from which the activated carbon AK was generated, from the gasification zone ZV into the cooling zone ZK of the cooling chamber 36 and to indirectly cool said mass flow there, together with the tar-loaded product gas PH that has been produced during the gasification of the supplied biomass B, to near the temperature of the ambient temperature. During the conjoined cooling, the product gas PH is freed of the tar due to the adsorption process and subsequently conveyed as pure gas PR to the gas engine.

(37) If the demand for pure gas PR is changed or if the heating value of the currently provided biomass B is greatly changed, the mass flow mBroh of the supplied biomass B is changed accordingly. With a time delay, a changed mass flow of activated carbon mAK is generated in the gasification zone. The process control arrangement is disposed to take into account that the change of the mass flow mAK of generated activated carbon AK occurs with a delay relative to the change of the mass flow of supplied biomass material mBroh. Therefore, even if there is a changing demand for pure gas PR, the amount MAK2 or the mass flow mAK2 that is to be supplied to the cooling zone ZK from the mass flow mAK of activated carbon that is currently present in the gasification zone ZV, is determined in view of the amount or the supplied mass flow of biomass (amount and mass flow relative to the reference condition waf), from which the activated carbon mass flow mAK was generated in the gasification zone ZV.

(38) The tar constituents and other harmful substance from the product gas PH are adsorbed during the conjoined cooling of the activated carbon MAK2. The loading capacity (adsorption capacity) of the activated carbon AK is so high that—with a load of only 2 percent by weight per kilogram of biomass B (waf), for example 1 gram of tar constituents can be removed from the product gas PH. The product gas PH and the certain amount of activated carbon MAK2 are cooled during the conjoined cooling, preferably not below a lower temperature threshold above the dew point of the product gas PH, because the loading capacity of the activated carbon AK steeply decreases toward a relative humidity of the product gas PH of 100%. In the exemplary embodiment, indirect cooling in the cooling zone ZK is accomplished by air C, in which case the heated cooling air C is conveyed to the reactor for combustion of the tar-loaded activated carbon MAK2.

(39) In one exemplary embodiment, the product gas PA, PR is separated, downstream of the cooling zone ZK, with a dust filter 18 from the activated carbon MAK2 that is loaded with harmful substances. The activated carbon MAK2 that is loaded with harmful substances is conveyed to the reactor 22 via the second lock 45 and combusted with the spent cooling air C. The ash is precipitated, for example via the turntable 47 and the third lock 48.

(40) If the biomass B displays high humidity, it may be expedient to heat the heating zone ZE by indirect heating with the exhaust gases of the gas engine, as well as with exhaust gas of the reactor 44 for combustion of the tar-loaded activated carbon MAK2.

(41) The gasification at elevated pressure with appropriate locks 28, 45, 48 at the inlet and outlet of the gasifier 11 has the advantage that the cleaned product gas PR can be supplied to the pressurized gas engine without compressor. Furthermore, as a result of this, the loading capacity of activated carbon AK can be increased.

(42) With the inventive process 10 and the inventive apparatus 11 for fine cleaning, it is possible to generate an engine-compatible product gas PR, without requiring a subsequent cleaning (for example by wet scrubber, electrofilter or the like). The cold gas efficacy of the gasifier is above 80%, even in the event of a high-humidity biomass.

(43) The invention relates to a process 10 for gasification of biomass B and an apparatus adapted therefor 11. The process is effected in at least three process steps 12, 12i, 121ii, 13, 14. In a first process step 12 in one exemplary embodiment, biogenic residue—biomass—may be supplied to a heating zone ZE to dry the biomass B and allow the volatile constituents to escape in order to generate a pyrolysis gas PY therefrom. The pyrolysis gas PY is supplied to an oxidation zone ZO and substoichiometrically oxidized there to generate a crude gas R. The coke-like, carbonaceous residue RK generated in the heating zone ZE is—together with the crude gas R—partially gasified in a second process step 13 in a gasification zone ZV. The heating zone ZE may be heated indirectly. The gasification zone ZV may likewise be heated indirectly. The heating zone ZE and the oxidation zone ZO are preferably zones that are separate from one another in separate chambers 23, 24. The gasification forms activated carbon AK and a hot process gas PH. The process according to the invention 10 is disposed for, or the apparatus 11 is adapted for, cooling a certain amount of the activated carbon of not less than 0.02 kg to not more than 0.1 kg per kilogram of supplied biomass (water-free and ash-free, waf) from which the activated carbon is formed in the gasification zone ZV and also the hot product gas PH in a third process step 14 in a cooling zone, for example to not more than 50° C. It is preferable when the apparatus is adapted in such a manner or the process comprises conjoined cooling of the activated carbon AK and the hot process gas PH such that the temperature of the process gas PH in the cooling zone ZK during conjoined cooling with the activated carbon AK remains above a lower threshold temperature which is higher than the dew point temperature of the product gas PH. The adsorption process taking place during the conjoined cooling of the activated carbon AK and the product gas PH has the result that, during cooling, the tar from the hot process gas PH is absorbed on the activated carbon AK in the cooling zone. Consequently, after the third process step 14, a pure gas PR, PA which is substantially tar-free is obtained. The tar-enriched activated carbon AK may be at least partly burned for heating the heating zone ZE and/or the gasification zone ZV.

(44) TABLE-US-00001 List of Reference Signs 10 Process 11 Apparatus 12 First process step 12i Heating step 12ii Oxidation step 13 Second process step 14 Third process step 15 Heating arrangement 16 Burner 17 Cooling arrangement 18 Dust precipitation unit 19 Grinding arrangement 20 Drying arrangement 21 Preheating arrangement 22 Reaction container 23 Reaction chamber 24 Heating chamber 25 Line 26 Silo 27 Inlet 28 First lock 29 Conveyor arrangement 30 Outlet 31 Gas supply arrangement 32 Line 33 Temperature sensor 34 End 35 Branch arrangement 37 Cooling chamber container 38 Conveyor arrangement 39 End 40 Precipitation chamber 41 Exhaust 42 Temperature sensor 43 Exhaust 44 Reactor 45 Second lock 46 Exhaust 47 Turntable 48 Third lock 49 Insulating jacket 50 Container for the heating chamber 51 Heating space 52 Arrow 53 Exhaust 54 Insulating jacket 56 Jacket 57 Cooling space 58 Inlet 59 Exhaust 60 Line 61 Upper end B Biomass L Air R Crude gas RK Carbonaceous residue PH Product gas AK Activated carbon PA, PR Cooled product gas, pure gas SK Coal dust G Exhaust gas PY Pyrolysis gas MB Amount of supplied biomass MAK2 Certain amount of activated carbon MAK1 Excess amount of activated carbon mBroh Mass, mass flow of biomass (reference condition, crude) mBwaf Mass, mass flow of biomass (reference condition, water- free and ash-free mAK Mass, mass flow of activated carbon forming in the gasification zone mAK2 Mass, mass flow of activated carbon for conjoined cooling mAK1 Mass, mass flow of excess activated carbon ZO Oxidation zone TO Oxidation zone temperature ZV Gasification zone TV Gasification zone temperature ZK Cooling zone ZE Heating zone TE Heating zone temperature P Arrow