JP2008081636A - Method for generating power from woody biomass and system for generating power from woody biomass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for generating a power from a woody biomass, such as a gasification power generation using the woody biomass, by which the production of clinkers can be prevented. <P>SOLUTION: The method for generating the power from the woody biomass comprises charging a raw material comprising the woody biomass into a fixed bed gasification oven 6 to gasify the raw material, and supplying the gas produced by the gasification into a gas engine 9 to generate the power, and is characterized by cooling the exhaust gas of the gas engine 9 in a cooling device 11 and then blowing the cooled gas into gasification oven 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for generating power using woody biomass, such as gasification power generation using woody biomass.

Conventionally, forest residue such as branches, leaves, treetops and roots obtained from forests, sawdust from lumber mills, residual materials such as bark, scraps and backboard, industrial waste such as construction and demolition materials, etc. Such woody biomass is gasified and used as fuel.
In this case, a fluidized bed type or a fixed bed type is widely used as a gasification furnace. In particular, since the fixed floor type can be designed as a relatively small-scale facility, it can be applied to small- and medium-scale facilities such as a mountain mill. In both types, the woody biomass to be gasified is generally fed after being crushed finely before the gasifier is charged. (For example, refer to Patent Document 2).
JP 59-38284 A JP 2002-38163 A

However, in a fixed bed gasification furnace, gasification proceeds with raw material accumulated, and thus, in the case of woody biomass having a low melting point such as bark (bark), clinker (burned ingot) is likely to be generated in the furnace. There was a problem.
Therefore, a main problem of the present invention is to suppress the generation of clinker.

The present invention that has solved the above problems is a method of generating power by supplying the gas generated by this gasification to a gas engine after gasifying the raw material consisting of woody biomass into a fixed bed gasification furnace,
The exhaust gas from the gas engine is cooled and then blown into the gasification furnace. In general, the temperature of the exhaust gas blown into the gasification furnace is preferably 50 to 150 ° C.
Since the exhaust gas has a low oxygen concentration, when it is blown into the furnace, the temperature rise is suppressed by the combustion suppressing action. However, since the exhaust gas itself has a high temperature, if it is blown into the furnace as it is, the temperature inside the furnace rises, and as a result, it becomes difficult to suppress the generation of clinker. Therefore, in the present invention, after the exhaust gas is cooled, it is blown into the furnace, thereby suppressing the rise in temperature by reducing the oxygen concentration while eliminating the influence of high heat of the exhaust gas, thereby preventing the generation of clinker. Is.
In the present invention, after the exhaust gas blown into the furnace passes through the combustion region and is heated, carbon dioxide (CO ₂ ) is converted into carbon monoxide (CO) and oxygen (O ₂ ) when passing through the char region. There is also a secondary advantage that the product gas generation amount is increased due to the decomposition reaction. Although this secondary advantage is described in Patent Document 2, the one described in Patent Document 2 does not assume the problem of clinker in a fixed bed type or cooling exhaust gas at all. Is completely different.
For example, the present invention can be used for gasification power generation using woody biomass that generates power by driving a generator by a gas engine.
The present invention includes a fixed bed gasification furnace to which woody biomass is supplied, a gas engine to which gas generated by the fixed bed gasification furnace is supplied, and a cooling device for cooling the exhaust gas of the gas engine. ,
A power generation system using woody biomass is also proposed in which the exhaust gas of the gas engine is cooled by the cooling device and then blown into the gasification furnace.

  As described above, according to the present invention, not only the generation of clinker can be suppressed, but also the amount of gas generation can be increased.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a flow sheet of an example of a gasification power generation facility. The woody biomass material B such as bark (bark) is stored in the material pit 1, and is sequentially taken out by the pit crane 2 and is introduced into the input hopper 3. Woody biomass raw materials include forest residue such as branches, leaves, treetops and roots obtained from forests, sawdust from lumber mills, bark (bark), scraps, backboard and other waste materials, building waste materials and demolition materials Industrial wastes such as can be used.

  The raw material thrown into the hopper 3 is transferred by the conveyor 4 and supplied to the fixed bed gasifier 6. In the illustrated embodiment, charging dampers 5A and 5B spaced apart from each other are provided on the inlet side of the gasification furnace 6, and both the lower damper 5B is closed and the upper damper 5A is opened. The raw material from the conveyor 4 is sequentially charged between the dampers 5A and 5B, and then the upper damper 5A is closed, and then the lower damper 5B is opened, so that the raw material held between the dampers 5A and 5B is gas. It is put into the upper part of the converter 6. Thereafter, the raw material is sequentially supplied into the gasification furnace 6 by this repetition. As long as it is a fixed bed, the gasification furnace 6 may be an upward flow type or a downward flow type (downdraft type). The downdraft type has the advantage of less tar and oil generation.

  A specific example of the downdraft type gasification furnace 6 is shown in FIG. That is, the gasification furnace 6 surrounds the upper cylindrical portion 61 serving as a hopper, the lower cylindrical portion 62 continuous from the bottom opening of the upper cylindrical portion 61, and the lower cylindrical portion 62 with a gap. And a cylindrical casing 63. These upper cylindrical portions 61, 62, 63 are arranged vertically and coaxially with each other. A grate 64 is provided at the bottom opening of the lower cylindrical portion 62. A partition plate 65 that partitions the inside of the furnace up and down is provided at an intermediate portion in the height direction of the lower cylindrical portion 62, and a passage hole 66 penetrating vertically is formed at the center in the width direction of the partition plate 65. ing. Further, an oxidant blowing port 67 projects from the inner peripheral wall above the partition plate 65 in the lower cylindrical portion 62 so as to face the center in the width direction in the furnace. The tip of the blowing port 67 is positioned outside the edge of the passage hole 66, that is, above the peripheral portion of the partition plate 65 that does not have the passage hole 66. It is preferable to provide a plurality of the blowing ports 67 at appropriate intervals (for example, at equal intervals) along the inner circumferential direction of the lower cylindrical portion 62. Further, the blowing port 67 can be formed in a slit shape that is continuous along the inner peripheral direction of the lower cylindrical portion 62.

  Although the supply path to the blowing port 67 can be appropriately formed, in the illustrated embodiment, the lower cylindrical portion 62 is formed in a double cylindrical shape including an inner cylindrical portion 62A and an outer cylindrical portion 62B, and the inner cylindrical portion 62A. The blower port 67 is communicated with the upper portion of the cylindrical space 62S between the outer cylinder part 62B and the supply pipe 70 penetrating the outer casing 63 is communicated with a portion below the blower port 67, thereby supplying the air. A road is constructed.

  An oxidant supply means such as an air supply pump (not shown) is connected to the supply pipe 70, and an oxidant such as air or oxygen for combustion is supplied through the supply pipe 70.

The raw material supplied into the gasification furnace 6 is gasified in the process of descending and passing through the upper cylindrical portion 61 and the lower cylindrical portion 62. That is, when the raw material sequentially supplied from the upper cylindrical portion 61 reaches the thermal decomposition zone slightly above the blowing port 67, thermal decomposition is started and gas (CO, H ₂ , CH ₄ , CO ₂ , H ₂ O), decomposed into char and hydrocarbon. The heat source of this pyrolysis step is heat generated by the combustion step described below.

Next, the gas, char, and hydrocarbons generated in this pyrolysis step reach the combustion / gasification zone from the inlet 67 to the partition plate 65 and are burned by the oxidant supplied from the inlet 67 and generated. The char is converted into CO and H ₂ at a temperature of about 700 to 1200 ° C. mainly by the Boudouard reaction and the aquatic gas reaction, and gasification is achieved. The generated gas passes through the grate 64, passes between the outer surface of the lower cylindrical portion 62 and the inner peripheral surface of the outer casing 63, and is taken out to the outside through the discharge port 71 provided in the outer casing 63. It is.

  While the ash in the gasification furnace 6 is discharged through the bottom outlet, the gas generated in the gasification furnace 6 is extracted from the side of the furnace and supplied to a dust collector 7 made of a cyclone or the like. The ash mixed in is removed and then cooled in the fuel gas cooling device 8 and then supplied to the gas engine 9 to be used as fuel. A generator 10 is connected to the gas engine 9 to generate power. The exhaust gas from the gas engine 9 is cooled by the exhaust gas cooling device 11 and released to the atmosphere. In the illustrated embodiment, each of the cooling devices 8 and 11 is configured by an indirect heat exchanger. After a coolant such as water is used for cooling the fuel gas by the fuel gas cooling device 8, the coolant is used as a coolant for the gas engine 9. After that, the exhaust gas cooling device 11 is used to cool the exhaust gas.

  In the present embodiment, a part (or all of the exhaust gas) of the gas engine 9 after being cooled is blown into the gasification furnace 6 according to the present invention. In the illustrated embodiment, the exhaust gas that has passed through the catalyst tower 12 is supplied to the gasification furnace 6, but it may be exhaust gas that has not passed through the catalyst tower 12 as long as it has been cooled. The degree of cooling by the exhaust gas cooling device 11 can be determined as appropriate, but the gas engine outlet temperature of the exhaust gas is usually 450 to 600 ° C., and this is cooled to 50 to 150 ° C. at the inlet temperature of the gasification furnace 6. It is preferable to do this. When the inlet temperature exceeds 150 ° C., the effect of the temperature rise in the furnace due to the temperature held by the exhaust gas becomes large due to the combustion suppression effect, and when it falls below 50 ° C., water droplets are generated due to condensation, which adversely affects gasification.

  Although the exhaust gas blowing position into the gasification furnace 6 can be determined as appropriate, it is in the vicinity of the blowing port 67 (particularly, the lower side of the blowing port 67 in the case of the downward flow type, and the blowing position in the case of the upward flow type. Since the clinker is likely to be generated at the upper side of the mouth, exhaust gas is blown together with the oxidant through the blow-in port 67, or the height position in the vicinity of the blow-in port 67 (in particular, in the case of the downward flow type, below the blow-in port 67 On the side, in the case of the upward flow type, it is preferable to provide a dedicated blowing port (above the blowing port) and blow the exhaust gas into the furnace 6 separately from the oxidant through this blowing port. In addition, in the present embodiment, both the oxidant and the exhaust gas are blown, but depending on the case, only the exhaust gas can be blown. It is desirable that the blowing ratio and the blowing amount of the oxidant and the exhaust gas are determined based on experiments so that the clinker is hardly generated.

  On the other hand, during gasification, a pyrolysis region, a combustion region, and a gasification region are formed in the furnace 6. If the bulk specific gravity of the solid in the gasification region is low, (1) the amount of components that can be gasified in the gasification region is small in the first place, and (2) the amount of oxygen that enters the gap increases and combustion proceeds. Due to the ease, the amount of gas generation is reduced. Therefore, it is also a preferable form that the bulk specific gravity of the solid substance at least in the gasification region is 0.5 or more, preferably 0.5 to 2.0. In order to set the bulk specific gravity to 0.5 or more, a compression device (not shown) such as a piston can be provided in the gasification furnace 6 to compress the solid matter in the furnace 6. It is easier and more preferable to perform compression processing so that the bulk specific gravity becomes 0.5 or more by forming, briquetting, extrusion molding, stirring molding, and the like, and putting this into the furnace 6 as a raw material. In this case, the size of the raw material is preferably 6 to 12 mm in diameter and 10 to 20 mm in length. If the size of the raw material is too small, there is a risk of increasing pressure loss and generating clinker (burned ingot). Conversely, if the raw material size is too large, a bridge may be generated in the furnace.

  Moreover, in order to prevent generation | occurrence | production of a clinker, gasification can also be aimed at in the state in which the substance which has the effect | action which raises melting | fusing point exists in the gasification furnace 6. FIG. For this reason, the melting point increasing substance can be supplied into the gasification furnace 6 together with the raw material by mixing the melting point increasing substance in the raw material in advance. The clinker is likely to be generated in the vicinity of the inlet 67 (particularly, the lower side of the inlet 67 in the case of the downward flow type and the upper side of the inlet in the case of the upward flow type). A melting point-raising substance is introduced into the furnace 6 together with air, or the height position near the inlet 67 (particularly the lower side of the inlet 67 in the case of the downward flow type, the inlet in the case of the upward flow type). It is a preferable mode that a dedicated inlet is provided on the upper side of the furnace 6 and a melting point-increasing substance is introduced into the furnace 6 separately from air through this inlet. The supply positions of these melting point raising substances can be used in appropriate combination. As the melting point raising substance, calcium carbonate, calcium hydroxide, calcium oxide, calcium phosphate, dolomite and the like can be used, and they can be used in the form of powder or particles. The addition amount of the melting point increasing substance can be appropriately determined, but is preferably 0.5 to 20% by weight with respect to the woody biomass raw material. As is apparent from this, the present invention can be applied in combination with other clinker generation prevention techniques.

  In order to confirm the effect of the exhaust gas injection of the present invention, an experiment was conducted on each example shown in Table 1 using a downdraft type fixed bed gasification furnace having a structure shown in FIG. In the conventional example, only air is blown without blowing exhaust gas. In Examples 1 to 4, exhaust gas was blown and the amount of air blown was reduced accordingly. Other conditions not shown in Table 1 are common to the examples. The results of the test are as shown in Table 1. It was found that by cooling the exhaust gas and blowing it into the gasification furnace together with air, the generation of clinker is suppressed and the amount of exhaust gas generated increases.

  As long as the woody biomass is gasified, the present invention is not limited to the use of the gas, and can be applied to a wide range of uses such as the use of fuel as well as the use of power as in the above example.

It is a flowchart of the example of gasification power generation equipment. It is a longitudinal cross-sectional view which shows a gasification furnace roughly.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Raw material pit, 2 ... Pit crane, 3 ... Hopper, 4 ... Conveyor, 5A, 5B ... Damper, 6 ... Fixed bed gasifier, 7 ... Dust collector, 8 ... Fuel gas cooling device, 9 ... Gas engine, 10 ... Generator, 11 ... Exhaust gas cooling device.

Claims (4)

In a method in which a raw material made of woody biomass is put into a fixed bed gasifier and gasified, and then gas generated by this gasification is supplied to a gas engine to generate power.
A method for generating power using woody biomass, wherein the exhaust gas from the gas engine is cooled and then blown into the gasification furnace.   The power generation method using woody biomass according to claim 1, wherein the temperature of exhaust gas blown into the gasification furnace is set to 50 to 150 ° C by the cooling.   The power generation method using woody biomass according to claim 1, wherein a power generator is driven by the gas engine to generate power. A fixed bed gasification furnace to which woody biomass is supplied, a gas engine to which gas generated by the fixed bed gasification furnace is supplied, and a cooling device for cooling the exhaust gas of the gas engine,
A power generation system using woody biomass, wherein exhaust gas from the gas engine is cooled by the cooling device and then blown into the gasification furnace.

Images