DE19720331A1 - Treatment of wet or dry, fine or lumpy bio-wastes - Google Patents

Abstract

New process treats biomass and waste; wet or dry, as lumps or fines. It removes gases from, and also gasifies or burns the feed, by means of added oxidant. In the novel method, the hot wall of a furnace (2) and influx of hot waste gas from it, removes gases from the raw bio-material feed (1), pyrolysing it to char, liberating pyrolysis gas. After passing through a comminuter (8), the char reaches the incandescent bed (20) of the gasifier (3). The pyrolysis gas is burned with limited air supply, in the combustion chamber (25) of the gasifier (3). The waste gas arising is passed through the incandescent bed (20). Carbon is oxidised to CO, with simultaneous reduction of CO2 and H2O to a combustible, weak (low calorific value) gas (CO, H2).

Description

The invention relates to a method and a Device for degassing and gasifying or burning biological raw materials.

The majority of gasification processes write a specific one te piece size of the fuel used. The techni cal stand for carburetors in which fuels largely regardless of the size of the piece is used in the Patents No. DE 41 30 416 C1 and EP 443596 A1 described. The disadvantage of this method is that it is suitable for smaller, decentralized plants due to the high expenditure on equipment is not suitable. The additionally required Oxygen generation system and the complex filter technology cause high investment costs and additional energy Energy consumption, so that the economy in small plants is not given.

In patent DE 44 14 579 a method is described that in small, decentralized systems can be used.

In low power gasification plants can only be small lump fuels are used. This is because that there is an inhomogeneous with large-sized fuels Embers bed that leads to increased pollutant emissions. In addition, automatic loading can only be done for small lumpy fuels are made. Disadvantageous for processes of Small plants is that for the crushing of the fuel a significant amount of energy is consumed.  

The main problem with gasification is that tar Products that are difficult to remove are created are. Elaborate filter systems increase the specific Ko and make small systems uneconomical. tries have shown that it is not enough to crack the gas just send it through a hot bed of embers. Inhomogeni the embers bed and the residence time too short This is caused by gases in the hot zone.

Other major disadvantages of the known Vergasungsver drive consist of that degassing zone, combustion zone and gasification zone are located directly next to each other and merge. As a result, the zone heights are indefinite and degassing, combustion and gasification can be local run incompletely. The bed of embers is wide and less high so that parts of the gas quickly pass this zone can. The dwell time of the smoldering gases in the high temperature range As a result, local temperatures may be too short, which leads to an outage collision with tar-containing products. The air or steam supply takes place locally and not evenly over the whole Reactor. A good mixing of the gases is therefore only limited possible. The composition of the by the reactor flowing gas is therefore inhomogeneous and the Verga Solution conditions vary from place to place.

All known gasification processes have the weight of To take fuel into account, because it leads to teamwork push the bed and thus to a lower gas permeability. That is why it is a continuous burning feed with the need for expensive automation necessary. This also applies to underfeed firing.

The object of the invention is to provide a gasification process develop that the described disadvantages of the known Fixed gasification processes in small plants.

This object is achieved by the features of the method claim 1 and the features of the device claim 8. Further design options result from subclaims 2 to 7 and 8-12.

The method is shown in Fig. 1. It is based on a clean separation of the individual gasification steps - degassing, combustion, gasification (reduction) - without significantly increasing the specific system costs. A combustion furnace ( 2 ) is installed in the degassing furnace ( 1 ). After filling the degassing furnace ( 1 ) and incinerator ( 2 ) with fuel ( 6 ), the doors ( 18 ) are closed and the fuel is ignited in the incinerator ( 2 ).

Through the hot wall ( 19 ) of the incinerator ( 2 ) through and through the exhaust gas ( 12 ), the energy required for degassing reaches the degassing furnace ( 1 ). To accelerate the degassing process, air can be metered into the degassing furnace ( 1 ) so that there is also a restrained combustion and the temperature required for the degassing of over 400 ° C is reached. The resulting coke (carbon, in the case of wood fuel: charcoal) reaches the shredder ( 8 ) and then falls onto the ember bed ( 20 ).

The advantage of producing coke (charcoal) is in that larger-sized fuels are also used can. The ener to be used to crush coke gie is much less than that for shredding Wood.  

The ash accumulating in the incinerator ( 2 ) under the grate ( 24 ) is conveyed by the ash removal device ( 13 ) into an ash container.

The carbonization gases and the exhaust gas enter the combustion chamber ( 25 ) of the gasification reactor ( 3 ), in which air ( 7 ) is supplied, so that the carbonization gases burn. The hot exhaust gas (CO ₂ , H ₂ O) flows through the embers ( 20 ). This is where the reduction to CO, H ₂ and O ₂ takes place. The carbon (coke) is oxidized to CO. Overall, air is only added sub-stoichiometrically, so that hardly any CO _{2 is} emitted. The resulting weak gas ( 16 ) is cooled in a heat exchanger ( 4 ). It is sucked off by a blower ( 17 ).

Despite the use of large-sized fuels, the ember bed ( 20 ) is homogeneous compared to conventional carburettors, since the coke gets into the gasification reactor in small pieces. The residues of the unburned carbonization gases are cracked in the ember bed ( 20 ). Since the gasification reactor ( 3 ) tapers, the glow bed ( 20 ) is high, so that the residence time of the gas in the glow bed ( 20 ) is extended and the glow bed ( 20 ) appears to be homogeneous for all of the gas.

With the method presented in the invention, pollutants can be filtered out using a simple filter technique (see FIG. 1). Due to the gasification, micropores form in the coke, which greatly enlarge the inner surface. Since the coke gets into the gasification reactor ( 3 ) in small pieces, activated carbon forms in the ember bed ( 20 ). With a screw ( 15 ), activated carbon is removed from the ember bed ( 20 ) and conveyed into the filter ( 5 ) via a cooled activated carbon channel ( 11 ). The lean gas ( 16 ) produced is passed through the filter ( 5 ). Pollutants remain in the activated carbon. The spent activated carbon is transported back into the gasification reactor ( 3 ) by means of a screw ( 15 ). Ultimately, the pollutants accumulate in the ash that forms at the exit of the gasification reactor ( 3 ). The ash is removed from the gasification reactor with an ash removal device ( 13 ).

The device for realizing the gasification process is shown in FIG. 2. In the degassing furnace (1) of the combustion furnace (2) is incorporated. The gasification reactor ( 3 ) consists of the combustion chamber ( 25 ) and the glow bed container ( 26 ). Degassing furnace ( 1 ) and gasification reactor ( 3 ) stand separately to reduce the height of the gasification plant.

The air ( 7 ) is fed to the incinerator ( 2 ) from above. So that the upper part of the degassing furnace ( 1 ) and incinerator ( 2 ) is cooled by the inflowing air and only in the lower part of the degassing furnace ( 1 ) and combustion furnace ( 2 ) degasses the fuel. The shredder ( 8 ) located in the degassing furnace ( 1 ) consists of two teethed rollers rotating in the opposite direction. The spacing of the rollers allows the piece size of the coke and thus the gas permeability and homogeneity of the ember bed ( 20 ) to be varied.

The coke is conveyed from the shredder ( 8 ) of the degassing furnace ( 1 ) by means of a piston ( 10 ) or screw through a coke channel ( 22 ) into the gasification reactor ( 3 ). Since the coke channel ( 22 ) is constantly filled with coke, the smoldering gases from the degassing furnace ( 1 ) together with the exhaust gas ( 12 ) from the combustion furnace ( 2 ) primarily through the gas pipe ( 21 ) into the combustion chamber ( 25 ) of the gasification reactor ( 3 ). The insertion opening is designed as a burner ( 23 ). As a result of the negative pressure that forms in the nozzle-shaped constriction, air is entrained. The gas-air mixture is ignited by an ignition spark. A flame guard monitors the flame to avoid the formation of explosive mixtures. The air supply is interrupted in the event of a flame failure. Deflection plates ( 14 ) ensure good mixing of the gases and avoid dead spaces. In the gasification reactor ( 3 ), the combustion of the carbonization gases creates a very high temperature.

In the known gasification processes there is the problem of good mixing of the carbonization gases with air. The air mostly only enters the gasification reactor through wall openings. This makes it difficult to evenly supply the entire volume with air and to achieve thorough mixing. In the device, on the other hand, which is provided in the invention, the carbonization gases flow concentratedly through a gas pipe ( 21 ). The smoldering gases are thoroughly mixed with air in the burner ( 23 ). Another advantage over conventional carburetors is that the residence time of the carbonization gases in the high temperature range is long, because it is mainly determined by the size of the gasification reactor ( 3 ). This can be designed accordingly large.

The energy required for the endothermic reduction reaction in the ember bed ( 20 ) is mainly introduced into the ember bed ( 20 ) by the exhaust gas from the burned smoldering gas. In order to be able to supply additional energy from the outside to the ember bed ( 20 ), the hot lean gas that forms is led past the ember bed container ( 26 ). If the outflowing weak gas is slightly mixed with air ( 7 ), it burns and the temperature of the wall of the material bed container ( 26 ) increases. The lean gas that forms can also be discharged through pipes that lead through the ember bed ( 20 ). A slight injection of air into these pipes leads to combustion of the weak gas and thus to an increase in the temperature of the ember bed. On the other hand, the temperature is reduced when water vapor is injected into the combustion chamber ( 25 ) of the gasification reactor ( 3 ). The temperature of the ember bed ( 20 ) can be regulated by the air or steam supply just described.

The method and the device for gasifying biological raw materials can also be used for combustion. For this purpose, only the air supply in the gasification reactor ( 3 ) is increased so that a complete combustion of the coke can take place.

The method and the device can also be used for the sole production of charcoal. In this case, only a small part of the charcoal for maintaining the ember bed ( 20 ), in which long-chain molecules are cracked, is branched off. This amount depends on the quality of the exhaust gas that remains after combustion of the Schwelga se in the upper part of the gasification reactor ( 3 ). If this combustion takes place completely, an ember bed ( 20 ) can be dispensed with.

The method and the device can also be used for the production of activated carbon. For this purpose, the Zer smaller ( 8 ) must be designed so that small-grain charcoal emerges from it. The gasification is carried out only partially, so that instead of ash, activated carbon is removed from the gasification reactor ( 3 ) with the discharge device ( 13 ). Partial gasification of the charcoal can be achieved by e.g. B. the dwell time of the charcoal in the ember bed ( 20 ) is reduced by faster activated carbon removal. This also reduces the ember bed height.

Reference list

1

Degassing furnace

2nd

Incinerator

3rd

Gasification reactor

4th

Heat exchanger

5

filter

6

fuel

7

air

8th

Shredder

9

coke

10th

piston

11

Activated carbon channel

12th

Exhaust gas

13

Ash removal device

14

Baffle plate

15

slug

16

Lean gas

17th

fan

18th

door

19th

Wall

20th

Ember bed

21

Gas pipe

22

Coke channel

23

burner

24th

rust

25th

Combustion chamber

26

Ember bed container

Claims (12)

1. Process for degassing and gasification or combustion of dry or moist, fine-grained or lumpy biomass and waste, characterized in that by the hot wall of an incinerator ( 2 ) and by the inflow of hot exhaust gas from the incinerator ( 2 ) into one Degassing furnace ( 1 ) degasses biological raw materials in this, whereby coke (carbon) and pyrolysis gas are formed, the coke after passing through the comminutor ( 8 ) reaches the ember bed ( 20 ) of the gasification reactor ( 3 ) while the pyrolysis gas in the combustion chamber ( 25 ) of the gasification reactor ( 3 ) burns with the supply of a limited amount of air and the resulting exhaust gas subsequently flows through the ember bed ( 20 ) of the gasification reactor ( 3 ) in which oxidation of the carbon to CO with simultaneous reduction of exhaust gas (CO ₂ ) and water vapor (H ₂ O) to a combustible lean gas (CO, H ₂ ) takes place. 2. A process for degassing and gasification or combustion according to claim 1, characterized in that via a För dereinrichtung from the ember bed ( 20 ) partially gasified coke (activated carbon) in the filter ( 5 ), through which the resulting lean gas flows, to renew the filter material rials is transported, while filter material enriched with pollutants (coke) is conveyed out of the filter ( 5 ) back into the ember bed ( 20 ). 3. Process for degassing and gasification or combustion according to one of claims 1 to 2, characterized in that the coke in the gasification reactor ( 3 ) is burned by supplying sufficient air. 4. Process for degassing and gasification or combustion according to one of claims 1 to 3, characterized in that fine-grained charcoal from the shredder ( 8 ) on the glow bed ( 20 ) of the gasification reactor ( 3 ), which after partial gasification as activated carbon the gasification reactor ( 3 ) is promoted. 5. Process for degassing and gasification or combustion according to one of claims 1 to 4, characterized in that charcoal is removed from the process after the shredder ( 8 ). 6. A method for degassing and gasification or combustion according to claim 1 to 5, characterized in that the ash from the combustion furnace ( 2 ) and the gasification reactor ( 3 ) is conveyed by means of an ash removal device ( 13 ) into an ash container. 7. A method for degassing and gasification or combustion according to one of claims 1 to 6, characterized in that the weak gas formed at the end of the gasification reactor ( 3 ) is suctioned off. 8. Device for performing the method according to one of claims 1 to 7, characterized in that the gasification reactor ( 3 ) separately from the combustion furnace ( 2 ) and Ent gasification furnace ( 1 ) is set up so that the coke after the shredder ( 8 ) passes via a Kokskanal (22) and the pyrolysis gas via a gas pipe (21) into the gasification reactor (3). 9. A device for performing the method according to claim 8, characterized in that the mixing of the pyroly segase with air in a burner ( 23 ). 10. Device for performing the method according to one of claims 8 to 9, characterized in that the lean gas flows past the ember bed container ( 26 ) of the gasification reactor ( 3 ), so that combustion starts by supplying air, which increases the temperature level in the ember bed ( 20 ) . 11. Device for performing the method according to one of claims 8 to 10, characterized in that the shredder ( 8 ) consists of two rollers rotating in the opposite direction, which are equipped with breaking teeth. 12. An apparatus for performing the method according to one of claims 8 to 11, characterized in that water is injected into the gasification reactor ( 3 ) to lower the temperature level of the ember bed ( 20 ).