JP4679390B2 - Gas generator for woody biomass - Google Patents

Description

The present invention relates to a gas generator that generates combustible gas using woody biomass as a raw material.
More specifically, the present invention generates a flammable gas using woody biomass such as wood from thinned wood or wood processing plant as a raw material, and uses the generated gas as power generation energy or fuel in the vicinity of the raw material production area. The present invention also relates to a gas generator suitable for reducing the size structurally or functionally.

Woody biomass such as thinned wood or miscellaneous trees has long been used as fuel for firewood or charcoal.
However, in Japan, gas fuels such as natural gas that can be easily used or liquid fuels such as kerosene and heavy oil are imported in large quantities and can be easily obtained. The use of has become extremely low in recent years.
Under such circumstances, gasification and utilization of woody biomass has advantages such as being able to be used as a fuel for internal combustion engines, and being able to use the energy of biomass with high efficiency, and further utilizing waste. Recently, attention has been focused on the use of the generated combustible gas as a fuel for power generation.

Published by Industrial Research Council “Chemical Equipment” 2004.03. "Biomass conversion technology" by Katsuo Joko T.B. Reed and A. Das Handbook of Biomass Downdraft Gasifier Engine Systems. p30 The gasification technology of woody biomass is to partially oxidize biomass to produce flammable gas, including fixed bed type such as downdraft type and updraft type, bubbling type, circulation type, etc. One using many types of gasification furnaces such as a fluidized bed type, a jet type such as a fine powder type, or a rotary kiln type such as an internal combustion type rotary kiln type or an external combustion type rotary kiln type is already known (see Non-Patent Document 1). ).

Among these types of gasification furnaces, there are advantages such as low capital investment, a small installation area, and a short time required for starting and stopping. A gasification furnace having a capacity, particularly a heat output of 1,000 KW / or less, is limited to a fixed bed type.
As described above, there are downdraft type and updraft type in the fixed bed type, but when using the generated combustible gas as energy for power generation, the tar content in the gas can be kept lower. A possible downdraft type is considered suitable.

A typical example of the downdraft gasifier is the Imbert gasifier that was produced in millions during World War II, and most of the gasifiers currently in operation are invert gas. Although the chemical reactor has been partially modified, the basic principle is the same as that before the modification.
The structure of the invert gasification furnace and the reaction region in the furnace are as shown in FIG.
The main structure of the invert type gasification furnace is that the cross section of the middle part of the vertical cylindrical furnace is narrowed, and the raw material solids are put into the upper part.

Air flows slightly above the constricted part of the gasification furnace, burns the raw material, flame pyrolysis occurs, and the solid matter that has become char after the pyrolysis is already exhausted Therefore, the reduction reaction is performed by the high temperature generated by the combustion so far.
As a result, hydrogen and carbon monoxide with a high calorific value are generated by the reduction reaction. On the other hand, heat is generated because carbon dioxide supplied with heat for the reduction reaction and remaining nitrogen depleted of oxygen in the air are included. The amount is low.

Further, in the gasification furnace, generally, an unburned char layer exists below the char in the reduction region, is supported by a grate, and the generated gas is discharged out of the furnace through the grate.
In that case, the volume of the raw material solid is reduced by flame pyrolysis, oxidation, and reduction reaction, and the solid moves by gravity downward from above so as to replenish it.
For this reason, a uniform flow of the raw material solids cannot be expected, and there are also disadvantages such as an increase in the tar content in the product gas.
In recent years, an open core type gasifier has been attempted to overcome the disadvantages of the invert type gasifier.

This method eliminates the restriction of the cross section of the middle part of the invert gasification furnace and allows the main air to flow from the open top of the furnace. The solid material flows down uniformly in the furnace tube with a uniform cross section. The reaction layer is constantly maintained at the same position in equilibrium with the upward transition of the reaction itself.
However, this improved system is similar to the inverted gasification furnace that the generated gas is discharged out of the furnace through a grate and that the movement of the raw material solids depends on gravity.
As described above, also in the invert type gasification furnace and the improved gasification furnace, the movement of the raw material solids in the furnace depends on gravity.

In the movement in the furnace due to gravity, the amount of solids decreases with the generation of gas, and it moves in such a way that solids make up for the disappeared space, but in that case the bridge phenomenon As a result, channeling from the location is likely to occur.
In addition, the grate at the bottom of the furnace is easily clogged by the unburned char or ash that has been subdivided, and it is necessary to move the grate to avoid this and restore the ventilation. The unburned char falls from the grate and easily disappears.
In addition, when the air volume is relatively high, unburned char is consumed and the grate is exposed to high temperatures, resulting in energy loss and maintenance disadvantages.

Therefore, the present inventor has eagerly sought to develop a gas generator that does not cause such a phenomenon, can be easily reduced in size, and can be easily installed in the vicinity of a biomass generation site as a raw material.
As a result, the present inventor has found that bridge and channeling (blow-through) do not occur by forcibly moving a solid biomass raw material from the lower part of the furnace while moving it upwards to generate a combustible gas.
Therefore, the present invention should solve the problem of providing a gas generator that does not generate a bridge phenomenon and channeling in the furnace, can be easily downsized, and can be easily installed in the vicinity of the biomass generation site of the raw material. Is.

  The present invention provides a gas generator for woody biomass for achieving the above-mentioned object, which comprises a woody biomass raw material supply port at the bottom and an open end for discharging generated gas and ash at the top. A gas and ash discharge outer cylinder that has a furnace inner cylinder and a gap through which ash generated around it can pass, and that has a supply port at the top that can prevent and discharge the generated gas. It is characterized by heat-treating while moving the woody biomass raw material which comprises and supplies the oxidizing gas supply port in the said inner cylinder from the downward direction upwards in a furnace.

Moreover, in the wood biomass gas generator, it is preferable to adopt the following.
(1) Oxidizing gas supply ports are an upper opening and a lower opening that are installed at two locations at intervals in the vertical direction in the furnace.
(2) An oxidizing gas supply port is provided in a concentric double pipe for supplying an oxidizing gas extending upward from the center of the bottom of the gas generating furnace inner cylinder, and an upper opening is provided at the top of the inner pipe. The opening is installed below the upper opening of the outer tube
(3) The inner tube moves in the vertical direction so that the interval between the upper opening and the lower opening can be adjusted.
(4) Connect a wood biomass material supply device with a drive means in the wood biomass material supply port.
(5) Install a level sensor near the top of the gas generating inner cylinder, detect the upper surface of the unburned char, and adjust the amount of wood biomass feed to prevent unburned char from being discharged from the inner cylinder. To control
(6) By installing multiple temperature sensors near the side surface of the gas generating furnace inner cylinder and adjusting the distribution ratio of the gas supply amount to the upper and lower openings for oxidizing gas supply, the temperature of the inner cylinder side surface is adjusted. To control the position where the maximum becomes 200 mm to 300 mm below the upper surface of the unburned char.

In the gas generator for woody biomass of the present invention, the biomass of the solid raw material is forcibly pushed up from the lower part of the furnace, so that the solid raw material may move downward by gravity as in the case of a conventional fixed bed type gas generator. There is no bridging and channeling.
Inheriting the advantages of the downdraft method, the flow of combustion air, which is an oxidizing gas, matches the movement direction of the raw material solids, and the generated combustible gas is also aligned in the same direction as the solids. It can flow smoothly through each layer of the flame pyrolysis layer and the reduction reaction layer.
During the passage, in the flame pyrolysis layer, the temperature rises due to the radiant heat from the combustion part, and in the initial stage, the raw material solids are pyrolyzed to form a combustible gas, and the formed combustible gas is It will be oxidized.

  In further regard to these points, in the conventional fixed bed type gas generator, as described above, the solid raw material moves in the furnace due to gravity, the amount decreases with the generation of gas, and disappears. In this case, the cross section of the furnace tube does not move evenly, and the reaction layer is disturbed and solids and gases remain incomplete. May pass downward.

In addition, in the conventional gas generator, the grate present at the bottom of the furnace is easily clogged by the subdivided unburned char or ash, and the grate can be moved in order to avoid this and restore the ventilation rate. In that case, unburned char falls from the grate and easily disappears.
In addition, when the air volume is relatively high, unburned char is consumed and the grate is exposed to high temperatures, resulting in energy loss and maintenance disadvantages.

In contrast, the gas generator of the present invention can avoid these problems.
That is, in the gas generator of the present invention, as described above, the solid raw material is forcibly pushed up from the lower part of the furnace so that it can move smoothly, and the cross-sectional area of the furnace and the cross-sectional area of the transfer cylinder of the raw material supply device are connected at the connecting portion. The material transfer rate distribution in the horizontal cross section of the furnace is made almost constant, that is, at each position such as the inner wall part of the furnace and the center of the furnace, the material transfer rate distribution is maintained regardless of the position. Can be close to constant.
Therefore, the solid matter can move in a uniform state while reducing the volume in the furnace from the lower side to the upper side with the gas generation reaction, and can contribute to the maintenance of the layered reaction layer.

Furthermore, in the gas generator of the present invention, the tar content can be adjusted, and the gas generated as a result can be kept low and suitable for use in power generation.
That is, in the present invention, since bridge and channeling do not occur, tar generated in the pyrolysis process always passes through the oxidation region in the flame pyrolysis layer and the high temperature portion of the reduction layer, and has a relatively low molecular weight component. Is broken down into

Further, in the present invention, the position at which the temperature of the inner cylinder side surface becomes the highest can be controlled to be 200 mm to 300 mm below the upper surface of the unburned char, so that at the final stage like the central portion of the raw material solids. Tar generated by thermal decomposition is also decomposed.
In addition, the distance between the upper opening 6 and the lower opening 7 can be adjusted, whereby the time from when the raw material starts flame pyrolysis until it reaches the high temperature char layer is controlled by the distance between both openings. Therefore, the generation of tar can be adjusted to a small extent according to the properties of the raw material such as the particle size distribution, without increasing the time unnecessarily, without causing a delay in the thermal decomposition rate and an increase in heat dissipation loss.

In the following, the best mode for carrying out the present invention will be described in detail with reference to FIG. 1, but the present invention is not limited in any way by this embodiment, and is specified by the claims. Needless to say, it is something.
FIG. 1 illustrates an overall image of a preferred wood biomass gas generator 1 according to the present invention. The gas generator 1 has a wood biomass feed port 4 at the bottom and gas and ash emissions at the top. A gas generating furnace inner cylinder 2 that has an open end 5 for generating flammable gas from woody biomass, a gas supply port 18 that surrounds the periphery thereof and guides the generated gas to the outside, An outer cylinder 3 having an ash passage 9 is provided between the cylinder and the cylinder.

A raw material supply device 8 is connected to the woody biomass raw material supply port 4 at the lower part of the gas generating furnace inner cylinder 2, and the supply device 8 is connected in series to a cylinder 22 having the same inner diameter as the lower part of the gas generating furnace inner cylinder 2. The structure is provided with an extrusion screw 20.
Further, the gas generating furnace inner cylinder 2 is provided with a concentric double pipe 11 for supplying an oxidizing gas such as air extending upward from the center of the bottom, and the inner pipe 12 extends to the upper part of the inner cylinder 2. An upper opening 6 for supplying oxidizing gas is provided at the top.
On the other hand, the outer tube 13 has a shorter entry distance into the inner tube 2 than the inner tube 12, and as a result, the lower opening 7 for supplying the oxidizing gas provided at the top is lower than the upper opening 6. It has become.

In the present invention, it is preferable that the oxidizing gas supply ports such as air are installed at two places separated in the vertical direction as described above, and thus the openings for supplying the oxidizing gas are installed at two places above and below. By doing so, combustible gas can be smoothly generated from the woody biomass supplied in the furnace.
That is, compared with the case where the oxidizing gas supply port is installed in one place in the furnace, it is possible to have an opportunity to decompose the tar content in the gas generated from the central portion of the solid matter, and as a result, the tar content is small. High quality combustible gas can be generated.
Regarding the installation position, specifically, the upper opening 6 is preferably located in the flame pyrolysis layer, and the lower opening 7 is located in the vicinity of the hydrant.

Further, in the present invention, the solid raw material biomass is forcibly pushed up from the lower part of the furnace as described above. Therefore, in the gas generating furnace inner cylinder 2, the woody biomass, the flame pyrolysis layer 15, the reduction layer 16, The combustion char layer 17 can move upward from below while maintaining the layer shape, and the movement by this forced push-up contributes to the homogenization and leveling of the solid material layer in the furnace tube 2.
In this case, in the flame pyrolysis layer, the temperature rises due to radiant heat from the combustion part, and at the initial stage, that is, in the lower part of the flame pyrolysis layer, the raw material solid is first pyrolyzed to form a combustible gas. As long as oxygen is present, the gas oxidizes and burns, and the heat promotes thermal decomposition of the raw material solids.

The double extrusion screw 9 provided in the raw material supply apparatus 8 is installed in the lower part of the raw material storage tank 21 which stores the woody biomass piece which cut | disconnected timbers, such as a thinning material, The wooden material stored in the storage tank 21 The biomass pieces can be continuously taken out from below and supplied to the gas generating furnace inner cylinder 2.
In the gas generator for woody biomass of the present invention, the cross-sectional area of the surface perpendicular to the direction in which the woody biomass piece of the cylinder 22 forming the raw material supply device 8 travels is the same as that of the gas generating furnace inner cylinder 2 as described above. It is desirable that the area and the cross-sectional area similar to the above in the connecting portion 27 between the cylinder 22 and the gas generating furnace inner cylinder 2 are the same.

In the present invention, the biomass pieces are smoothly introduced into the gas generating furnace inner cylinder 2 by the twin extrusion screw 20 in this way, and the gas generating furnace inner cylinder 2 is filled with air that is an oxidizing gas. It can move smoothly while maintaining a layered state while contacting and causing a gas generation reaction.
The cross-sectional areas are preferably as described above, but may be slightly different. In that case, the cross-sectional area at the lower end of the gas generating furnace inner cylinder 2 is about 0.8 to 1.2 times the cross-sectional area. It should be in range.

In FIG. 1, the diameter of the connecting portion 27 is illustrated so as to gradually become smaller in the direction of the double extrusion screw 20, but it is a plane orthogonal to the direction in which the woody biomass piece of the connecting portion 27 travels. It does not indicate that the cross-sectional area of is gradually reduced.
That is, the twin extrusion screw 20 has a biaxial structure, and therefore the cylinder 22 has an elliptical cross-sectional shape perpendicular to the direction in which the woody biomass piece travels.
As a result, there is a difference in the cross-sectional shape between the gas generating furnace inner cylinder having a circular cross-sectional shape and the cylinder 22 containing the double extrusion screw 9 having an elliptical cross-sectional shape. The structure up to the difference in cross-sectional shape has been shown until now.

The woody biomass piece supplied into the gas generating furnace inner cylinder 2 is ignited by the igniter plug 24 at the start of the gas generating apparatus of the present invention and thereafter by the radiant heat from the upper flame pyrolysis layer to start combustion. However, the amount of air supplied from the oxidizing gas supply port into the gas generating furnace inner cylinder 2 is much smaller than that for completely burning the woody biomass pieces.
That is, 20-30% of the theoretical air amount required for complete combustion is good, and ideally 25%.
Therefore, after the oxygen is exhausted, the inside of the furnace is in a reduced state, and a reaction for generating a combustible gas occurs by this reduction. The temperature at the reduction reaction start position is preferably 1100 ° C. to 1000 ° C.

In the present invention, wood biomass and air are introduced into the gas generating furnace inner cylinder 2 and ignited, so that the furnace has a flame pyrolysis layer, a reduction layer, and an unburned char layer in a layered form from below as described above. It is formed.
In the wood biomass gas generator 1 shown in FIG. 1, the level sensor 14 is installed so that the unburned char layer 17 rises and does not overflow into the ash passage 9 from the top of the gas generating furnace inner cylinder 2. ing.
This sensor 14 detects the upper surface of the unburned char layer, and controls the operation stop or rotational speed of the double extrusion screw 20 that forcibly moves the woody biomass so that it maintains a predetermined position.

The ash, which is the residue generated from the woody biomass after the combustible gas generation reaction in this furnace, is accompanied by the generated gas because the specific gravity is small and light, but the others are the top of the inner cylinder 2 Overflowing into the ash passage 9 formed in the gap between the outer cylinder and the inner cylinder from the open end for discharging, is taken out from the ash discharge port 19.
Furthermore, in the wood biomass gas generator 1 shown in FIG. 1, a control temperature sensor 23 is installed on the outer wall of the gas generating furnace inner cylinder 2, and a safety temperature sensor 26 is installed on the wall of the cylinder 22 of the raw material supply apparatus 8. In addition, the pipe 22 connected to the fire extinguishing water tank 25 is connected to the cylinder 22 of the raw material supply device 8 so that the wood biomass gas generator can be controlled and managed so that it can be operated safely. .

The wood biomass gas generator 1 of the present invention is suitable for downsizing structurally and functionally.
Therefore, it is suitable for use in the vicinity of the site where thinned wood or offcuts generated at a wood processing plant are generated, and to use the produced combustible gas as fuel or energy for power generation.
Specifically, the scale when reducing the size of the gas generator for woody biomass is preferably 500 mm to 300 mm in terms of the diameter in the furnace, but the gas generator for woody biomass of the present invention is like this. The present invention is not limited to such a small scale, and of course, it is an embodiment of the present invention as long as the requirements described in the claims are satisfied.

The transfer means in the raw material supply apparatus for introducing the wood biomass pieces into the furnace is not particularly limited, and various means can be adopted as long as the wood biomass pieces can be transported from the raw material storage tank to the gas generation furnace inner cylinder. However, a double-extrusion screw is preferable from the viewpoint of expanding the area of the connecting portion with the raw material reservoir.
The raw woody biomass is preferably cut into small pieces in order to smoothly generate and generate a combustible gas in the furnace. The longest part of the small pieces is preferably about 50 to 5 mm, preferably about 25 to 10 mm. Good thing.

In the present invention, the reduction reaction start position in the gas generating furnace inner cylinder is preferably controlled to be 200 mm to 300 mm below the upper surface of the unburned char, and the position is the capacity, length, etc. of the gas generating furnace inner cylinder. Regardless of the above, it is preferable to control within the above range.
Since the reduction reaction is completed at a relatively short distance in and out of 100 mm, as a result, the amount of unburned char can be kept almost constant at a layer thickness of 100 mm to 200 mm, corresponding to the amount of inflow air. Optimal gasification reaction can be ensured.

As for the concentric double pipe for introducing an oxidizing gas such as air into the furnace, the inner pipe is preferably installed so as to be movable in the vertical direction. By moving the inner pipe, the upper opening 6 and the lower opening 7 are moved. The interval between and can be changed.
Further, the upper opening 6 and the lower opening 7 can be formed as described above, and annular holes are formed in the upper and lower portions of the wall of the gas generating furnace inner cylinder 2, respectively. It can also be formed by installing an annular air supply pipe.

In addition, when gasifying thick biomass, the thermal decomposition inside the biomass may not be completed within the time for moving the high temperature portion at the initially set interval between both openings.
In that case, pyrolysis continues even after the biomass passes through the high temperature part where tar is expected to be decomposed, and the tar content of the product gas is increased.
In order to avoid this, increasing the distance between the two openings in advance regardless of the size of the raw material solids not only increases heat loss, but also reduces the amount of tar generated by delaying the thermal decomposition rate. Will increase.
However, in the present invention, the distance between the two openings can be adjusted to an optimum distance according to the shape of the raw material, so that the above disadvantages are not generated.

The whole image of the preferable gas generator 1 for woody biomass of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas generator for woody biomass 2 Gas generating furnace inner cylinder 3 Outer cylinder 4 Wood biomass raw material supply port 5 Open end part for gas and ash discharge 6 Upper opening 7 Lower opening 8 Raw material supply apparatus 9 Ash passage 11 Oxidizing gas Concentric double pipe for supply 12 Inner pipe 13 Outer pipe 14 Level sensor 15 Flame pyrolysis layer 16 Reduction layer 17 Unburned char layer 20 Double extrusion screw 21 Raw material storage tank

Claims (6)

A wood biomass feedstock supply port at the bottom, a gas generating furnace inner cylinder having an open end for discharging generated gas and ash at the top, and a gap through which the generated ash can pass and generated A wood biomass feedstock having a gas and ash discharge outer cylinder provided at the top with a supply port capable of preventing and discharging gas and having an oxidizing gas supply port in the inner cylinder A wood biomass gas generator characterized by heat treatment while moving from below to above. 2. The gas generator for woody biomass according to claim 1, wherein the supply ports for the oxidizing gas are an upper opening and a lower opening that are installed at two positions at intervals in the vertical direction in the furnace. An oxidizing gas supply port is provided in a concentric double pipe for supplying an oxidizing gas extending upward from the center of the bottom of the gas generating furnace inner cylinder, an upper opening is provided at the top of the inner tube, and a lower opening is provided outside. The gas generator for woody biomass according to claim 2 , installed below the upper opening of the pipe. The wood biomass gas generator according to claim 3 , wherein the inner pipe moves in the vertical direction so that the interval between the upper opening and the lower opening can be adjusted. The level sensor is placed near the top of the gas generating furnace tube, by detecting the upper surface of the unburned char, by adjusting the woody biomass material supply amount, unburned char is controlled so as not to be discharged from the inner tube The gas generator for woody biomass according to any one of claims 1 to 4. By installing multiple temperature sensors near the side surface of the gas generating furnace inner cylinder and adjusting the distribution ratio of the gas supply amount to the upper and lower openings for supplying oxidizing gas, the temperature on the inner cylinder side surface is the highest. The gas generator for woody biomass according to any one of claims 2 to 4 , wherein a position where the gas becomes becomes 200 mm to 300 mm below the upper surface of the unburned char.

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