DE10200180A1 - Wood chip gasification comprises drying wood shavings or chippings in heated hopper, then passing to oxidation chamber for partial burning prior to gasification - Google Patents

Abstract

In the conversion of wood to gas, wood shavings or chippings are first dried in a heated hopper (10) from which they are released to an oxidation chamber (12) in which they partially burn prior to gasification in a gasification unit (14). The gas generated in the hopper or gasification unit is passed through the gasification section before discharge as gas. Ambient air is admitted to and flows through the oxidation chamber (12), but limited to such a quantity as will maintain the temperature within the chamber at 800-1000 degrees C, facilitating sub-stoichiometric combustion. The gas is then allowed to expand (16) and cool to 100 degrees C. An Independent claim is also included for a wood gasification apparatus.

Description

The present invention relates to a wood gasifier with a Storage container for holding a defined amount of wood, with one attached to the Storage container adjoining the oxidation chamber, with one attached to the Oxidation chamber connecting carburetor and with a Product gas withdrawal, wherein the oxidation chamber has an air inlet, and a Process for the gasification of wood, the wood being a first Drying and / or a smoldering storage container passes through to then partially in an oxidation chamber burn before the partially burned wood continues in a carburetor is gassed.

Wood gasifiers are known from the prior art, which according to the principle of ascending gasification (counterflow gasifier), the barrier gasification (DC gasifier), crossflow gasification and Double gasification work. With the ascending gasification from fresh air sucked in below and led through the whole wood. This Fresh air is used to burn the wood and the resulting wood Product gas is removed from the top of the gasifier. Both other three types of gasification, the fresh air comes from the side inserted across the combustion chamber and used to burn the wood. The resulting product gas is mostly at the opposite one Taken from page. The is still under the combustion chamber red-hot charcoal, so that the resulting product gas rises can and by taking product gas from the wood gasifier is brought out.

In such processes, a gas yield of 65% to 75% reached, but the resulting product gas is strong. Impurities in the form of phenols and / or tea and / or others has undesirable components.

Proceeding from this, the present invention is based on the object a wood gasifier and a method for gasifying wood with a to create high quality product gas, the product gas of which is low Has contamination.

According to the invention, a method is used as a technical solution to this problem for gasifying wood with the features of claim 1 and a Wood gasifier proposed with the features of claim 6. Advantageous developments of the method and the wood gasifier are the the respective subclaims.

A procedure trained according to this technical teaching and an after This technical teaching of trained wood gasifiers have the advantage that by passing the product gas through the carburetor this for a longer period of the increased prevailing in the carburetor Exposed to temperature. During this time, the can Phenols, tars or other contaminants due to the high ambient temperature to harmless substances react, crack, split or the like, so that the The amount of contaminants present in the product gas is significantly reduced.

This effect is reinforced by the fact that the product gas between the Carburetor located charcoal must be passed through so that Product gas has to travel a long distance.

Another advantage is that the large surface area of the Charcoal in the carburetor contains parts of the phenols, tar or other contaminants on the charcoal, so that the Gas leaving gasifier has less impurities.

In a preferred embodiment is between carburetor and Product gas extraction a relaxation chamber (a relaxation zone) arranged in which the product gas leaving the carburetor first collects once. This also means that the product gas has started Reactions or splits to complete the degree of To further reduce impurities. In addition, the product gas in the Relaxation zone cooled to 250 ° C, or if in the Relaxation chamber a heat exchanger is provided, that is Product gas cooled down to 100 ° C. This has the advantage that cooled product gas without problems via the product gas extraction removed and fed to an internal combustion engine, for example can be.

In another preferred development, the carburetor is from Relax chamber surrounded so that the radiated from the carburetor Heat in the relaxation chamber to slowly cool the Product gas is used. This has the advantage that the product gas cools more slowly and thus breaks down further impurities.

In another very advantageous embodiment is in the Relaxation chamber at least partially surrounding the carburetor Heat exchanger provided, which is surrounded by the product gas. there it is preferably a water-carrying air / water Heat exchanger. The arrangement of such a heat exchanger has the The advantage of this is that the radiant heat emitted by the carburetor as well as the heat emitted by the product gas can be. Another advantage is that through the control of the medium flowing through the heat exchanger Cooling rate of the product gas can be influenced. On Another advantage is that the carburetor and / or the heat given off by the product gas is not released into the environment in an uncontrolled manner is delivered, but is caught by the cooler and one further use, for example for drying the wood, for Heating of buildings or the like can be used.

In a further preferred embodiment, external air of the type in the oxidation chamber let in that the air flows through it becomes. This has the advantage that the entire oxidation chamber of the Air flows through, so that a uniform combustion takes place can.

This effect is reinforced by the fact that the air inlet in the upper, outer edge of the oxidation chamber is provided and approximately is circumferentially formed. This makes the air ring-shaped on everyone Places introduced into the oxidation chamber, so that an even Combustion is achieved.

In a preferred development, the oxidation chamber is conical educated. Due to this narrowing of the cross-section, the air flows to the different locations of the oxidation chamber with a different Speed. By taking place in the oxidation chamber Combustion gradually becomes the oxygen in the air consumed so that the air flowing through the oxidation chamber with the Time has less and less oxygen. By increasing Flow rate is achieved, however, that the lower Layers within the oxidation chamber receive sufficient oxygen, to ensure even combustion of the inside of the oxidation chamber Sustain coal.

In another preferred embodiment, the external air is over a controllable blower is introduced into the oxidation chamber in a controlled manner. The combustion can be controlled by controlling the amount of air to be introduced be regulated so that there is always a burning in the oxidation chamber Embers can be held up. It has proven to be advantageous to control the amount of air to be introduced in such a way that in the Oxidation chamber always a temperature between 800 ° C and 1000 ° C is present. This has the advantage that there are no nitrogen oxides during combustion be formed, since these only arise from a temperature of 1000 ° C.

Another advantage of regulating the amount of air is that Wood can be burned substoichiometrically in the oxidation chamber. This creates no open flames in the oxidation chamber, but instead the wood is simply charred to charcoal, which is then gasified in the gasifier and generated most of the valuable product gas here.

In another preferred embodiment, an air duct carries the external air from a fan, for example Air intake point along the oxidation chamber to the air intake, whereby the external air is preheated. This has the advantage that the in the Air entering the oxidation chamber no longer needs to be warmed up and thus no energy is extracted from the actual oxidation zone with the Consequence that a more even combustion takes place.

In yet another preferred embodiment is the deepest A lock is provided at the point of the relaxation chamber. That lock is preferably designed as an impeller. At this lowest point and in The area trickling out of the sluice gathers out of the carburetor Ash. After a certain amount has accumulated, that becomes The impeller rotates and transports part of this ash to one worm wheel underneath. Through the lock and the Ashes lying on top of it are achieved that practically none at this point Product gas can escape undesirably, and that at this point none Were lost in an uncontrolled manner. Via the worm wheel the ashes are then finally removed.

Further advantages of the method according to the invention and the Wood gasifier according to the invention emerge from the accompanying drawing and the embodiments described below. Likewise, the the aforementioned and the features elaborated further according to the invention individually or in any combination can be used together. The mentioned embodiments are not to be understood as a final list, but rather to have exemplary character. Show it:

Figure 1 is a schematic side view of the interior of a wood gasifier according to the invention.

FIG. 2 shows a top view of the wood gasifier according to FIG. 1, cut along line II-II in FIG. 1.

The wood gasifier shown in a schematic representation in FIGS. 1 and 2 works according to the direct current principle, that is to say with descending gases. The actual wood gasifier includes a storage container 10 , an oxidation chamber 12 , a gasifier 14 and a relaxation chamber 16 , which are arranged one behind the other in such a way that the gas can flow through them in the same direction. A product gas withdrawal 18 is connected to the expansion chamber 16 and the product gas is sucked out of the wood gasifier by means of a pump 20 . At the lowest point of the expansion chamber 16 there is a lock 22 designed as an impeller, on which the ash 24 trickling out of the carburetor 14 collects. The lock 22 is rotatably mounted and is released if necessary. Part of the ash 24 is conveyed into an underlying worm wheel 26 , which then finally removes the ash 24 for disposal.

In the expansion chamber 16 , which is circular in cross section, the carburetor 14 , which is likewise circular in cross section, is arranged centrally. An annular heat exchanger 28 is provided within the expansion chamber 16 and around the carburetor 14 , through which water or another liquid medium flows. About this heat exchanger 28, the light emitted from the carburetor 14 and the heat given off from the product gas is collected and fed to a further use via the heat exchanger 28 located in the water.

A housing 30 is arranged around the oxidation chamber 12 and carries a positively driven fan 32 . In this case, an air duct 34 is formed between the housing 30 and the oxidation chamber 12 , via which ambient air sucked in by the blower 32 is directed into corresponding air inlets 36 provided at the upper edge of the oxidation chamber 12 . The oxidation chamber 12 is conical in such a way that its upper diameter is larger than the diameter of the storage container 10 lying above it, so that the protruding part of the oxidation chamber 12 forms the air inlets 36 .

In another embodiment, not shown here, the Air intakes also as slots, holes or other openings in the upper Edge area of the oxidation chamber can be formed.

Above the storage container 10 there is an intermediate chamber 38 , which is fed by a feed screw 40 with wood chips 42 . Between the storage container 10 and the intermediate chamber 38 and between the intermediate chamber 38 and the feed screw 40 , a slide 44 is attached, which controls a desired amount of wood chips 42 to the storage container 10 in each case controlled by a level meter 46 .

In the carburetor 14, a plurality of separating plates are inserted 48 several separating plates 48, so that in the carburetor 14, a plurality of gasification chambers 50 forms. The still glowing charcoal 52 formed in the oxidation chamber 12 falls into one of these gasification chambers 50 and there burns to ashes with the release of carbon monoxide, methane, hydrogen and other combustible gases.

The separating plates in the carburetor 14 achieve a relatively uniform temperature, which is generally below 1000 ° C., because on the one hand 50 individual glow centers are formed in the individual gasification chambers, which heat the gasification chamber 50 evenly. Without the separating plates 48 , a single but much hotter glow center would arise in the center of the carburetor, while a lower temperature would prevail at the edge of the carburetor due to the heat radiation. On the other hand, the preferably metallic separating plates 48 cause the heat within the carburetor 14 to be evenly distributed both in the horizontal and in the vertical and radial directions, so that approximately the same temperature prevails everywhere in the carburetor 14 . As a result, the product gas flowing through the gasifier 14 can be kept longer and more uniformly at a high temperature level, so that this ensures better processing of the impurities in the product gas.

The operation of the wood gasifier shown is described below as follows:
Via a feed screw 40 , wood chips are transported upwards from a supply store (not shown here) in such a way that they fall into the intermediate chamber 38 from above. The first slide 44 is open while the second slide 45 is closed. As soon as a sufficient quantity of wood chips 42 is present in the intermediate chamber 38 , the first fill level meter 46 detects this and stops the feed screw 40 and closes the first slide 44 . As soon as the second fill level sensor 47 determines that there are not enough wood chips 42 in the storage container 10 , the latter opens the slide 45 so that the wood chips 42 located in the intermediate chamber 38 slide into the storage chamber 10 . It should be ensured that the first slide 44 is closed during this time, so that flames do not accidentally penetrate from the wood gasifier onto the wood store. Then the second slide 45 is closed again, the first slide 44 is opened and new wood chips 42 are conveyed into the intermediate chamber 38 .

The storage container 10 , the oxidation chamber 12 and the carburetor 14 are connected to one another without any separation devices. A burning glow is formed in the oxidation chamber 12 with the supply of external air, which, among other things, persists from the conical configuration of the oxidation chamber 12 above the narrowest point of the oxidation chamber 12 . Further wood carvings 42 lie on this embers. The rising heat causes charring of the wood chips 42 lying above, outgassing of the wood chips 42 located above and drying of the uppermost layer of wood chips 42 . A drying zone and a smoldering zone are thus formed in the storage container 10 .

A substoichiometric combustion of the wood chips 42 takes place in the oxidation chamber 12 , so that charcoal is formed. At a given time, the latter falls out of the oxidation chamber 12 into one of the gasification chambers 50 of the gasifier 14 and continues to glow here until only one ash 24 which cannot be reused remains. The wood chips converted to charcoal lie in the carburetor 14 on a grate 52 which is permeable to gas and ash. Which are accumulated in the lowermost region of the expansion chamber 16 ash is discharged from time to time via the lock 22 and the worm wheel 26th

Exactly the required amount of air is sucked in from the environment via the controllable blower 32 and blown into the air duct 34 . In this air duct 34, the air is preheated by radiated from the oxidation chamber 12, heat and directed into the interior of the oxidation chamber 12 via a ring at the top of the oxidation chamber 12 recessed air inlets 36th Within the oxidation chamber 12 , the preheated air is conducted past the wood chips 42 to the embers in order to keep the combustion located there going with the freshly supplied oxygen. The air flows through the oxidation chamber 12 from top to bottom. Due to the conical design of the oxidation chamber 12 , the air inside the oxidation chamber 12 is accelerated, so that the air striking the upper area of the glow at this point flows more slowly than in the middle and especially in the lower part of the glow. As a result of this increased flow velocity, the lower oxygen content of the air in the middle and lower part of the embers is at least partially compensated, so that a uniform supply of oxygen to the embers is achieved. As a result, uniform combustion is achieved within the oxidation chamber 12 , so that slag formation is avoided. So much ambient air is always supplied to the oxidation chamber 12 that sub-stoichiometric combustion takes place.

Due to the air flowing through the oxidation chamber 12, a certain air negative pressure, through which the air in the Vorratsbehäslter 10 is entrained is formed in the reservoir 10 degrees. As a result, the moisture released in the drying zone and the volatile constituents of the wood released in the smoldering zone are entrained with the air and likewise transported through the oxidation zone 12 and passed together with the gases formed during the combustion into the gasifier 14 .

In the carburetor 14 , the wood chips 42 converted to charcoal glow until only ash remains, releasing, among other things, carbon monoxide (CO), methane (CH4) and hydrogen (H2). It is advantageous here to supply the oxidation chamber 12 with only enough fresh air that all the oxygen in the oxidation chamber 12 is used up. As a result, on the one hand, the water transported down from the drying zone can be split into hydrogen and oxygen in the gasifier, the latter combining with the carbon in the wood to form carbon monoxide and the hydrogen combining with the carbon to form methane.

All gases in the carburetor then pass into the expansion chamber 16 as so-called product gas and are calmed down here because of the increase in cross section. In parallel, the ash 24 accumulating in the carburetor 14 falls through the grate 52 onto the lock 22 and is discharged at the appropriate time. The lock serves as both a gas and temperature lock.

The carburetor 14 and on the other hand the heat exchanger 28 are arranged in the expansion chamber 16 , the ring-shaped heat exchanger 28 surrounding the carburetor 14 in order to absorb its radiant heat. Furthermore, the product gas located in the expansion chamber 16 is cooled, a large part of the heat also being absorbed by the heat exchanger. The heat exchanger 28 , preferably through which water flows, transports the heat absorbed in this way and leads it to further use. The heat can be used, for example, to dry the wood chips, grain, storage wood or other things, to heat buildings, swimming pools or the like. After the product gas has cooled to approximately 100 ° C., it is transported away by the pump 20 via the product withdrawal 18 and used for further use. This can be, for example, a low-gas engine for power generation or the like.

Uniform combustion of the embers in the oxidation chamber 12 ensures uniform combustion, so that a uniform temperature distribution is also achieved. The fact that the supplied air is initially preheated also contributes to this. This makes it possible to keep the temperature in the oxidation chamber 12 to 800 ° C. to 1000 ° C., so that the formation of nitrogen oxides, which arise from 1000 ° C., is prevented.

By forming the carburetor 14 with its gasification chambers 50 , a uniform temperature distribution is also achieved here, so that the carburetor 14 does not prevail at any point above 1000 ° C. As a result, no nitrogen oxides can form here either.

All gases produced during wood gasification are passed through the gasifier 14 and, moreover, the gases from the smoldering zone and the gases from the combustion are also passed through the oxidation chamber 12 . As a result, the gases are exposed to a temperature of 800 ° C. to 1000 ° C. for a comparatively long period of time, so that the impurities in the gas, such as phenols, tar or the like, react with other gases and / or split up, so that a clean product gas arises. Reference list 10 storage containers
12 oxidation chamber
14 carburetors
16 relaxation chamber
18 Product removal
20 pump
22 lock
24 ashes
26 worm wheel
28 heat exchangers
30 housing
32 blowers
34 air duct
36 air intake
38 intermediate chamber
40 feed screw
42 wood chips
44 slider
45 sliders
46 level meter
47 level meter
48 divider
50 gasification chamber
52 rust

Claims (17)

1. A process for gasifying wood, the wood first passing through a storage container ( 10 ) having a drying and / or a smoldering zone, in order to then partially burn in an oxidation chamber ( 12 ) before the partially burned wood in a gasifier ( 14 ) is further gasified, characterized in that the gas generated in the storage container ( 10 ) and / or in the oxidation chamber ( 12 ) and / or in the carburetor ( 14 ) is passed through the carburetor ( 14 ) before it is withdrawn via a product gas ( 18 ) is removed. 2. The method according to claim 1 , characterized in that external air is let into the oxidation chamber ( 12 ) such that the air flows through the oxidation chamber ( 12 ). 3. The method according to claim 2 , characterized in that only enough air is let into the oxidation chamber ( 12 ) that the combustion of the wood in the oxidation chamber ( 12 ) creates a temperature between 800 ° C and 1000 ° C. 4. The method according to any one of the preceding claims, characterized in that the wood burns substoichiometrically in the oxidation chamber ( 12 ). 5. The method according to any one of the preceding claims, characterized in that the carburetor is followed by a relaxation zone ( 16 ) in which the product gas is cooled down to 100 ° C. 6. Wood gasifier with a storage container ( 10 ) for holding a defined amount of wood, with an oxidation chamber ( 12 ) adjoining the storage container ( 10 ), with a gasifier ( 14 ) adjoining the oxidation chamber ( 12 ) and with a product gas extraction ( 18 ), the oxidation chamber ( 12 ) having an air inlet ( 36 ), characterized in that the product gas extraction ( 18 ) is arranged downstream of the carburetor ( 14 ). 7. Wood gasifier according to claim 6, characterized in that a relaxation chamber ( 16 ) is provided between the gasifier ( 14 ) and product gas extraction ( 18 ). 8. Wood gasifier according to claim 7, characterized in that the expansion chamber ( 16 ) surrounds the carburetor ( 14 ). 9. Wood gasifier according to one of claims 7 or 8, characterized in that a heat exchanger ( 28 ) at least partially surrounding the gasifier ( 14 ) is provided in the expansion chamber ( 16 ). 10. Wood gasifier according to at least one of claims 7 to 9, characterized in that a lock ( 22 ) is provided at the lowest point of the relaxation chamber ( 16 ). 11. Wood gasifier according to claim 10, characterized in that the lock ( 22 ) is designed as an impeller. 12. Wood gasifier according to at least one of claims 6 to 11, characterized in that the oxidation chamber ( 12 ) is conical. 13. Wood gasifier according to at least one of claims 6 to 12, characterized in that the air inlet ( 36 ) is provided in the upper, outer edge of the oxidation chamber ( 12 ). 14. Wood gasifier according to at least one of claims 6 to 13, characterized by a controllable fan ( 32 ) by means of which external air or another gas can be introduced in a controlled manner into the oxidation chamber ( 12 ) via the air inlets ( 36 ). 15. Wood gasifier according to at least one of claims 6 to 14, characterized in that an air channel ( 34 ) is formed around the oxidation chamber ( 12 ) which leads the air to the air inlet ( 36 ). 16. Wood gasifier according to at least one of claims 6 to 15, characterized in that a plurality of gasification chambers ( 50 ) are formed in the gasifier ( 14 ). 17. Wood gasifier according to claim 16, characterized in that the gasification chambers ( 50 ) are separated from one another by metallic separating plates ( 48 ).