DE19846805A1 - Process for gasifying or degasifying dry or moist finely ground or bulky biomass and waste comprises passing pyrolysis gas and coke to a gasifier after passing through a crusher joined to the lower end of the degasifier - Google Patents

Abstract

Process for gasifying or degasifying dry or moist finely ground or bulky biomass and waste comprises passing pyrolysis gas, produced in a degasifier (1), and coke to a gasifier (2) after passing through a crusher (5) joined to the lower end of the degasifier. The gasifier has a combustion chamber (3) in the upper part for combusting the coke and/or pyrolysis gas, and a glowing bed (7) onto which the coke falls. An Independent claim is also included for the apparatus for carrying out the gasifying or degasifying process.

Description

The invention relates to a method and a Device for the gasification of biological raw materials.

The state of the art for carburetors in which fuels largely used regardless of the piece size are in the patent numbers DE 41 30 416 C1 and EP 443596 A1 described. This method has the disadvantage that it for smaller, decentralized plants due to the high apparatus expenditure is not suitable. The additional required oxygen production system and the complex Filter technology cause high investment costs and additional energy consumption, so that in small systems Profitability is not given.

In the patents DE 44 14 579 and in the patent application 19720331 procedures are described that are in small, decentralized systems can be used.

In entrained flow gasifiers and fluidized bed gasifiers only small pieces of firing material can be used. This procedure can because of their complicated technology in small Performance range does not work economically. To a To get as homogeneous as possible ember bed is also in Fixed bed gasifiers used small-sized fuel. This is disadvantageous if for the crushing of the fuel a lot of energy needs to be consumed. Local differences in the dwell time of the smoldering gases in the ember bed and local Differences in temperature lead to increased damage fabric emission. In plants with low power therefore contains the gas produced tar and unpurified cannot one Gas engine are supplied. In known gasification plants is trying to get a homo by using stirrers to achieve genization of the fuel mixture. Means  The fuel is transported by screw conveyors. Thereby the technology becomes complicated and the economy is no longer available in the small power range. In the Support gas burners are used in most gasification processes. These burners have the disadvantage that they have the pressure ratio The carburetor changes when switched on and off become. This makes it difficult to control the air supply and it can lead to pollutant emissions. Become such Burner used continuously in the gasification process, so is gas or oil required, which affects the Profitability can impact.

The aim of the invention is to eliminate the disadvantages of the known gasification processes of small plants described above. This is to be solved according to the invention in that the individual gasification steps - degassing, combustion, gasification (reduction) - take place in separate rooms and can thus be individually optimized. The use of stirrers and screw conveyors is avoided by arranging these spaces one above the other so that the material to be fired moves from one space to another as a result of gravity. A shredder ( 5 ) ensures the metered supply of the fuel from the upper degassing furnace ( 1 ) to the lower combustion chamber ( 3 ) and gasification reactor ( 2 ). A burner ( 20 ) (e.g. gas, oil burner) can be used to ignite the smoldering gas that arises in the degassing furnace ( 1 ) and enters the combustion chamber ( 3 ) and to maintain the temperature required for the combustion of the smoldering gas. In the invention, a coke burner is described which is more suitable for the gasification process. Its advantage is that the pressure conditions in the carburettor are not affected and that no additional fuel (gas, oil) is required. The coke falls on the burner grate ( 4 ), which is attached in the combustion chamber ( 3 ) of the gasification reactor ( 2 ). Its combustion can result in a very high temperature when the air is supplied appropriately.

The advantage of the burner grate ( 4 ) is that the tar that forms in the degassing furnace ( 1 ) does not get into the ember bed, but drips onto the burner grate ( 4 ) and evaporates and burns there. Likewise, the coke pieces falling on the burner grate are further degassed, so that the volatile constituents still contained in the coke pieces escape and burn.

To avoid that not yet fully degassed charcoal falls on the bed of embers and causes ejection of tar-containing products, the burner grate ( 4 ) can be rotated through 180 ° each time the Zerklei nerers ( 5 ) is actuated. As a result, degassed charcoal as well as slag and metal parts fall from the burner grate ( 4 ) onto the ember bed ( 7 ). When the shredder ( 5 ) is then actuated, the charcoal falls onto the empty grate. For faster ignition, z. B. an oil burner can be switched on.

Another advantage of the method proposed in the invention is that coal dust is generated in the shredder ( 5 ), which trickles into the combustion chamber ( 3 ) and supports the combustion of the carbonization gases here. Very high temperatures can thus be achieved in the combustion chamber ( 3 ).

The device for the method is shown in FIG. 1. The gasification plant consists of the degassing furnace ( 1 ) and the gasification reactor ( 2 ) underneath. A combustion chamber ( 3 ) is arranged in the upper part of the gasification reactor ( 2 ). There is a burner grate in it ( 4 ). The kiln ( 9 ) passes through the lock ( 6 ) in the upper part of the Ent gasification furnace ( 1 ). In the degassing furnace ( 1 ) there is a restrained combustion by throttled air supply after the fired material has been ignited. Because of this slight combustion, the degassing furnace ( 1 ) has a sufficiently high temperature so that the volatile constituents escape from the fuel (pyrolysis gas). In order to prevent uncontrolled stoves from appearing after the fuel has been refilled several times, pilot burners ( 19 ) are installed in the air supply pipes. These are ignited after longer time intervals. At the lower end of the degassing furnace ( 1 ) there is a shredder ( 5 ). It causes the coke formed in the degassing furnace ( 1 ) to be comminuted and metered into the gasification reactor ( 2 ). The shredder ( 5 ) consists, for. B. from two ent in the opposite direction of rotation running with teeth rollers. When the rollers of the shredder ( 5 ) turn, coke falls on the burner grate ( 4 ) installed in the combustion chamber ( 3 ). After this is filled, the coke falls on the embers ( 7 ) of the gasification reactor ( 2 ). By adding air by means of lances, the coke burns on the burner grate ( 4 ) and the temperature required to maintain the combustion of the pyrolysis gas is created. The combustion temperature is regulated by the amount of air added. Coke not taken up by the burner grate falls on the ember bed ( 7 ).

The pyrolysis gas generated in the degassing furnace ( 1 ) passes through the shredder ( 5 ) into the combustion chamber ( 3 ) of the gasification reactor ( 2 ). Here it is ignited and burns with the addition of air. The exhaust gas (CO ₂ ) formed as a result of the combustion of the pyrolysis gas and the coke in the combustion chamber ( 3 ) flows through the ember bed ( 7 ) together with the steam of the water contained in the fuel. Here the reduction of CO ₂ to CO and the combustion of C to CO take place. Due to the high energy of the combustion gases emerging from the combustion chamber, the endothermic reduction process in the ember bed ( 7 ) can be maintained.

Air is only supplied substoichiometrically over the ember bed, so that no complete combustion takes place. The emission of CO ₂ is thus reduced to a minimum. The water is partially broken down into H ₂ and O ₂ . A weak gas consisting mainly of N ₂ CO and H ₂ leaves the gasifier. The resulting lean gas is cooled in a heat exchanger ( 10 ). It is sucked off by a fan ( 17 ). In addition to the suction fan, a pressure fan can be used to supply air ( 8 ).

To maintain the high temperature in the ember bed ( 7 ), energy can be added if necessary by slightly increasing the air supply above the ember bed. This means that combustion takes place in the upper ember layer, which leads to an increase in temperature. On the other hand, the temperature is lowered when water vapor is injected into the combustion chamber ( 3 ). The alternate additional supply of air and water vapor leads to an increase in the hydrogen content and thus the energy content of the gas produced. By adding z. B. generated in a pressure swing adsorption system, the temperature level is also increased. This means that moist firing material can also be used. The hydrogen content of the generated gas is increased and the nitrogen content is reduced. The energy content of the gas increases (power gas). This gas can serve as the starting gas for methanol synthesis.

The advantage of the gasification process shown in the invention is that both small and large pieces of fuel can be used. The coke is broken by the shredder. The energy required for this is low compared to the mechanical comminution of wood. The combustion chamber of the gasification reactor can be designed so large that the pyrolysis gases remain sufficiently long at very high temperatures so that cracking or combustion takes place reliably. Despite the use of large-sized fuels, the glow bed ( 7 ) is homogeneous compared to conventional fixed bed gasifiers, since pure coke gets into the gasification reactor in small pieces. In the ember bed ( 7 ), the remains of the unburned smoldering gases are cracked. The gas generated is therefore tar-free.

With the method presented in the invention, pollutants can be filtered out by a simple filter technique. Due to the gasification, micropores form in the coke, which greatly enlarge the inner surface. Since the coke gets into the gasification reactor ( 2 ) in small pieces, activated carbon forms in the ember bed. With a screw conveyor ( 15 ) activated carbon is removed from the edge of the ember bed ( 7 ) and conveyed into the filter ( 18 ) via a cooled channel. The lean gas ( 16 ) produced is passed through the filter ( 18 ). Pollutants remain in the activated carbon. The spent activated carbon is fed by means of the conveyor screw ( 15 ) to a location which is located away from the activated carbon extraction point, the ember bed ( 7 ). Ultimately, the pollutants accumulate in the ash that arises at the exit of the gasification reactor ( 2 ). The ash is removed from the gasification reactor with an ash removal device ( 13 ).

The gasification method presented in the invention can be used for pure combustion. An additional air supply takes place in the gas duct ( 11 ). The lean gas generated burns here. The high temperature thus arises in the gas channel and not in the ember bed. This largely prevents the formation of slag.

The gasification process presented in the invention can be used for charcoal production. Only a small part of the charcoal gets onto the burner grate ( 4 ). The formation of the embers bed ( 7 ) is avoided. The combustion of a small part of the charcoal on the burner grate ( 4 ) serves to support the pyrolysis gas combustion in the combustion chamber ( 3 ). The charcoal is removed immediately after the shredder ( 5 ) with a trough screw. There is a slot in the trough that enables the charcoal to be screened. Coal dust and small pieces of charcoal fall through the slot onto the burner grate ( 4 ).

An advantage of the gasification process shown in the invention is also that it can be used for the production of activated carbon. For this purpose, the shredder ( 5 ) has to work like a mill so that small-grain charcoal emerges from it. The gasification is only partially carried out so that, instead of ash, activated carbon is removed from the gasification reactor ( 2 ) with the discharge device.

Reference numerals

1

Degassing furnace

2nd

Gasification reactor

3rd

Combustion chamber

4th

Burner grate

5

Shredder

6

lock

7

Ember bed

8th

air

9

Brenngut

10th

Heat exchanger

11

Gas channel

13

Ash removal device

15

Auger

16

Lean gas

17th

fan

18th

filter

19th

Pilot burner

20th

burner

Claims (14)

1. Process for degassing and gasification or combustion of dry or moist, fine-grained or lumpy biomass and waste, characterized in that the pyrolysis gas and coke (carbon) forming in a degassing furnace ( 1 ) by throttled combustion of combustion material and after passing a shredder ( 5 ), which closes the Ent gasification furnace ( 1 ) at the lower end, into the gasification reactor ( 2 ), in which there is a combustion chamber ( 3 ) in the upper part for burning the coke and / or pyrolysis gas and in the lower one Part of an ember bed ( 7 ), on which the coke falls, for reduction and gasification. 2. Process for degassing and gasification or combustion according to claim 1, characterized in that burners ( 20 ) support the combustion of the Pyrolysega ses flowing in the combustion chamber ( 3 ) or ignite the pyrolysis gas-air mixture. 3. Process for degassing and gasification or combustion according to claim 1-2, characterized in that the resulting from the combustion of coke and / or pyrolysis gas in the combustion chamber ( 3 ) exhaust gas through the ember bed ( 7 ) of the gasification reactor ( 2 ), in an 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. 4. A method for degassing and gasification or combustion according to claims 1-3, characterized in that via a För dereinrichtung from the ember bed ( 7 ) partially gasified coke (activated carbon) in the filter ( 18 ) through which the resulting lean gas ( 16 ) flows , is transported to renew the filter material, while filter material (activated carbon) enriched with pollutants is conveyed out of the filter ( 18 ) back into the ember bed ( 7 ). 5. A method for degassing and gasification or combustion according to claims 1-4, characterized in that the lean gas formed in the end of the gasification reactor ( 2 ) angeord Neten gas channel ( 11 ) burns by local air supply. 6. A method for degassing and gasification or combustion according to claims 1-4, characterized in that the finely ground charcoal from the degassing furnace ( 1 ) on the ember bed ( 7 ) of the gasification reactor ( 2 ) is conveyed in a smaller size ( 5 ), whereby after a partial gasification activated carbon is produced which is removed from the gasification reactor ( 2 ). 7. Process for degassing and gasification or combustion according to claims 1-5, characterized in that charcoal is removed from the process after the shredder ( 5 ). 8. Process for degassing and gasification or combustion according to one of claims 1-7, characterized in that the gas is suctioned off at the end of the gasification reactor ( 2 ). 9. Device for performing the method according to one of claims 1-8, characterized in that the degassing furnace ( 1 ) is arranged above the gasification reactor ( 2 ). 10. Apparatus for performing the method according to claims 1-9, characterized in that in the combustion chamber ( 3 ) of the gasification reactor ( 2 ) a burner grate ( 4 ) is arranged, on which after actuation of the shredder ( 5 ) coke falls, which passes through here Air supply burns. 11. Apparatus for performing the method according to claim 9 and 10, characterized in that the symmetrically constructed burner grate ( 4 ) is rotated through 180 ° before actuating the shredder, so that coke and possibly metal parts or slag from the burner grate ( 4 ) the ember bed ( 7 ) fall. 12. An apparatus for performing the method according to claim 9 to 11, characterized in that after rotating the burner grate ( 4 ) and actuating the shredder ( 5 ) on the burner grate ( 4 ) falling coke is ignited by a burner. 13. An apparatus for performing the method according to claim 9 to 12, characterized in that the shredder rer ( 5 ) consists of two rollers rotating in the opposite direction, which are occupied by crushing teeth. 14. An apparatus for performing the method according to claim 9 to 13, characterized in that the fuel in the degassing furnace ( 1 ) by means of pilot burners ( 19 ), which are installed in the air supply pipes, is ignited.