JP2010229207A - Apparatus and method for gasification of biomass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a process for gasification of a biomass preventing a tar from attaching to a heat exchanger for cooling a produced gas and preventing troublesome discharge of a tar-containing water. <P>SOLUTION: A gasification apparatus pyrolyzes a biomass supplied into a gasification furnace to obtain a produced gas, and includes at least one of a first water supplier 2A which supplies water to a biomass before being supplied to the gasification furnace 1 and a second water supplier 2B which supplies water to a biomass in a gasification furnace from the furnace top. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a biomass gasification apparatus and a gasification method for generating gas from biomass in a gasification furnace.

  Non-Patent Document 1 discloses a gasification furnace that gasifies woody biomass derived from forest resources such as wood scrap, bark, and wood scraps and supplies generated gas as fuel for a gas engine, for example. In this gasification furnace, biomass raw materials are supplied from the upper part of the gasification furnace, and a packed bed is formed in the furnace. This packed bed forms a wet layer, a dry region, a thermal decomposition region, a reduction region, and an oxidation region from the upper part, and the biomass descends from the upper part of the packed bed to the lower part as the gasification reaction proceeds. Steam and air are supplied as gasification agents from the lower part of the furnace, the gas flow in the furnace flows from the lower part of the furnace to the upper part of the furnace, and the generated gas is taken out from the discharge port in the upper part of the furnace.

The biomass supplied from the upper part of the gasification furnace contains about 30 to 55% of moisture in the case of wood mills, bark, wood chips, etc., so the wet layer formed at the top of the packed bed is moisture. High concentration. The biomass descending from the wet layer is dried by the heat of the generated gas to form a dry region. Biomass descending from the drying zone is pyrolyzed in the pyrolysis zone, producing flammable gases such as CH ₄ , CO, H ₂ , CO ₂ , H ₂ O, gaseous and mist-like tar, and fixed carbon. The combustible gas and the gas of CO ₂ , H ₂ O, gaseous and mist tars rise, and the fixed carbon falls. The fixed carbon descending from the pyrolysis region gasifies and reacts with water vapor in the reduction region to generate CO and H ₂ . In the oxidation area below the reduction area, the remaining fixed carbon, tar, and unpyrolyzed biomass are partially oxidized and burned, generating heat necessary for gasification, pyrolysis, and drying, and the combustion gas rises with heat. . Combustion ash is discharged from the bottom of the packed bed.

  The generated gas from the gasifier contains gaseous and mist tars. When the generated gas is used as a fuel in a gas engine or the like, the tar adheres to equipment and causes problems in operation. Tar may need to be removed. In Non-Patent Document 1, the product gas discharged from the gasification furnace is led to a heat exchanger (gas cooling device) that cools the product gas by heat exchange with the heat medium, and the gaseous tar and water vapor in the product gas are condensed to generate the tar. It is removed from the product gas by using water, and tar remaining with dust is removed by a wet electrostatic precipitator provided in the subsequent stage.

  Further, in the gasification furnace, the heavy tar among the generated tar is reformed to light tar.

  A wet layer having a high moisture concentration is formed on the top of the packed layer. Gaseous and mist tar generated in the pyrolysis zone formed below the wet layer in the packed bed rises with the generated gas together with the generated gas, and is trapped by moisture in the wet layer. The tar descends downward with the biomass and enters the pyrolysis region again. Among the tars, heavy tar is decomposed into light tar and light tar is decomposed into gas. By repeating the trapping of the tar in the wet layer and the decomposition in the thermal decomposition region, the tar content in the product gas increases in light tar, and the fluidity of the tar-containing water recovered by gas cooling in the heat exchanger is increased. High and smooth discharge is possible, and handling in the subsequent process becomes easy.

JFE Engineering Company Catalog (Cat. No. CA3047) “JFE-Felt-type woody biomass gasification power generation system” issued by JFE Engineering Corporation, 2004

  In the biomass gasification apparatus described in Non-Patent Document 1, when the moisture content of the woody biomass supplied to the gasification furnace is as high as about 30 to 55%, the uppermost part of the packed bed in the gasification furnace However, there are some construction waste materials, waste wood, and other woody biomass with a low moisture content of 20% or less. When such a low moisture content biomass having a moisture content of 20% or less is gasified in a gasification furnace, a sufficient wet layer is not formed, and it becomes difficult to capture tar by moisture. The tar content in the tar increased in the proportion of heavy tar and the viscosity of the tar obtained by condensation by gas cooling in the heat exchanger was high, and the tar adhered to the heat transfer surface of the heat exchanger or was recovered. The viscosity of tar-containing water is so high that it cannot be discharged smoothly and problems such as blockage arise.

  In addition, when such a low moisture content biomass having a moisture content of 20% or less is gasified, the amount of water condensed in the heat exchanger is less than the tar amount. If the amount of water is small relative to the amount of tar, the heat transfer surface (condensation part) of the heat exchanger will not be washed with condensed water, and tar will adhere to the heat transfer surface and heat exchange performance will be reduced. Further, the fluidity of the tar-containing water is low, and the gas flow path and the tar-containing water discharge section are clogged, so that heat exchange and discharge of the tar-containing water cannot be performed smoothly, and the tar in the gas cannot be removed.

  The present invention has been made in view of such circumstances, and even if low moisture content biomass having a moisture content of 20% or less is supplied to the gasifier, heavy tar among the tars contained in the generated gas A biomass gasification apparatus and a gasification method capable of preventing the occurrence of a problem that the ratio of the amount of gas is increased and adheres to the heat transfer surface of the heat exchanger that cools the generated gas or cannot be smoothly discharged. Let it be an issue.

  In the present invention, the above-described problems are solved by a biomass gasification apparatus and method having the following configuration.

<Biomass gasifier>
The present invention relates to a biomass gasification apparatus, a first water supply apparatus that supplies water to biomass before being supplied to the gasification furnace, and water is supplied to the biomass in the gasification furnace from the top of the gasification furnace. It is characterized by having at least one of the second water supply devices.

<Biomass gasification method>
Further, the present invention relates to a biomass gasification method, in which a biomass having a moisture content of 20% or less is pyrolyzed in a gasification furnace to obtain a product gas, the biomass before being supplied to the gasification furnace Having at least one of a first water supply step for supplying water to the gas and a second water supply step for supplying water to the biomass in the gasifier from the top of the gasifier, and the biomass in the gasifier It is characterized by increasing the moisture content of the wet layer formed at the top of the packed layer.

  According to the apparatus and method of the present invention having such a configuration, when gasifying biomass, particularly biomass having a low water content of 20% or less, the biomass is supplied from the first water supply device and the second water supply device. Receive water supply by at least one of them. The moisture content of the biomass can be estimated by the type of biomass. Or it can be measured even if estimation is difficult. Therefore, when biomass is supplied to the gasification furnace to form a wet layer at the top of the packed bed, the wet layer has a predetermined moisture content. Alternatively, it is possible to calculate how much water should be supplied when the wet layer is formed after the supply. This water supply is performed by one or both of the first water supply device and the second water supply device. Thus, the biomass having a predetermined moisture content is gasified, and most of the tar in the resulting product gas becomes light tar, and the tar-containing water taken out from the gasification furnace is taken out and then treated. It becomes easy.

  In the present invention, the first water supply device and the second water supply device have a total water supply amount of 30% or more of the moisture content of the biomass in the wet layer in the uppermost part of the biomass packed bed in the gasification furnace. It is preferable to set so as to.

  It is desirable to automatically set the moisture content of the biomass to a predetermined value. The amount of extracted tar-containing water can be measured, and if the type of biomass is specified, the amount of water can be calculated from its moisture content. It can be derived from the measured amount of tar-containing water whether it should be supplied.

  Therefore, when a heat exchanger is connected to the gasification furnace to condense the water vapor and tar in the generated gas to generate tar-containing water, the present invention device receives the generated gas from the gasifier and the heat medium. A heat exchanger that cools the product gas by heat exchange and condenses water vapor and tar contained in the product gas to produce tar-containing water, and an amount of water for measuring the amount of tar-containing water produced by the heat exchanger A water supply that controls the amount of water supplied by at least one of the first water supply device and the second water supply device so that the amount of tar-containing water measured by the measurement device and the water amount measurement device falls within a predetermined range. And a quantity control device.

  Therefore, as a method of the present invention, in the gasification method, the product gas is received from the gasification furnace to the heat exchanger, the product gas is cooled by heat exchange with the heat medium, and water vapor and tar contained in the product gas are condensed. A heat exchange step for generating tar-containing water, a water amount measuring step for measuring the amount of generated tar-containing water, a first water supply step so that the amount of tar-containing water measured is within a predetermined range, and At least one of the second water supply steps has a water amount control step for controlling the amount of water to be supplied.

  Thus, if the amount of generated tar-containing water is measured and water supply control is performed from at least one of the first water supply device and the second water supply device so that the amount of tar-containing water is within a predetermined range, As a result, the biomass has a moisture content within a predetermined range in the wet layer, and the ratio of light tar in the tar-containing water obtained by gasification increases.

  According to the present invention, the ratio of light tar among the tars contained in the product gas generated by supplying biomass with a low water content of 20% or less to the gasifier is increased, and heat exchange of the gas cooling device is performed. A biomass gasification apparatus and a biomass gasification method that can prevent tar from adhering to a heat transfer surface of a vessel or a problem that smooth discharge cannot be generated are obtained.

It is a schematic block diagram of the apparatus of one Embodiment of this invention. 1 is a schematic configuration diagram of a heat exchanger of the apparatus.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a gasification furnace for gasifying biomass, which is supplied with biomass from a supply port provided in the upper part of the furnace, and supplied with water vapor and air as a gasifying agent from the lower part. Biomass is roughly crushed to about 100 mm or less before supply, and is supplied from the supply port by a conveyor such as a conveyor or a screw feeder. In the gasification furnace 1, a packed bed of supplied biomass is formed, and the gasifying agent rises in the packed bed. The packed bed is formed with a wet layer, a dry region, a thermal decomposition region, a reduction region, and an oxidation region in this order from above. Biomass is pyrolyzed in a furnace to produce fixed carbon and product gas, and the fixed carbon gasifies with the gasifying agent while descending the packed bed to produce product gas and combustion ash. Combustion ash is discharged from the top and from the bottom of the furnace. The product gas contains flammable gas such as CH ₄ , CO, H ₂ , CO ₂ , H ₂ O, gaseous and mist tars.

  The gasification furnace 1 is connected to a first water supply device 2A and a second water supply device 2B for supplying water to the biomass. The first water supply device 2A supplies water to the biomass outside the gasification furnace 1, has a water tank, a water pump, and a spray nozzle (all not shown), and gasses the biomass. The biomass is sprayed (or sprinkled) before being supplied to the converter 1 or before the supply. Spraying is performed on the biomass on the conveyor and the biomass in the screw feeder. The amount of water spray (supply) is controlled by a supply water amount control device 6 described later. On the other hand, the second water supply device 2B sprays (sprinkles) the biomass at the top of the packed bed in the furnace from the top of the gasification furnace 1, and includes a water tank, a water pump, and a spray nozzle (all (Not shown). The water supply amount of the second water supply device 2B is the water supply described later so as to adjust the moisture content of the biomass at the uppermost part of the packed bed to a preferable range in combination with the first water supply device 2A. It is controlled by the control device 6.

  The gasification furnace 1 is connected to a heat exchanger 3 for cooling the produced gas.

  In the heat exchanger 3, a wet electric dust collector 7 and a gas engine 8 are sequentially connected. After the processing gas cooled by the heat exchanger 3 is removed by the wet electric dust collector 7, dust or the like is removed. It is sent to the gas engine 8 as combustible gas and used for driving the gas engine 8.

  As shown in FIG. 2, the heat exchanger 3 includes an introduction pipe 32 that introduces a generated gas into an upper portion of a container 31 that forms a sealed space, and a cooling process for the generated gas, and then uses the treated gas as a processing gas. And a lead-out pipe 33 to be taken out from the head. Further, a cooling pipe 34 that receives a heat medium (for example, cooling water) from the outside, penetrates the inside of the container 31, and discharges it outside the container 31 is disposed in the container 31. Further, a discharge pipe 35 for discharging discharged tar-containing water is provided at the lower portion of the container 31.

  In such a heat exchanger 3, the product gas introduced from the gasification furnace 1 is cooled to below the condensation temperature of tar and water (for example, 30 ° C. or less) by heat exchange with water or the like as a cooling heat medium. Both the gaseous tar and moisture in the product gas are condensed to form a mixture of tar and water (tar-containing water). Tar and water condensed on the heat transfer surface (outer surface) of the cooling pipe 34 through which the heat medium is circulated are stored in the lower portion of the container 31 as tar-containing water in a mixed state. Condensed water is dripped to wash the heat transfer surface (outer surface) of the cooling pipe 34, preventing condensed tar from adhering to the heat transfer surface, and maintaining the heat exchange performance of the cooling pipe 34.

  The discharge pipe 35 of the heat exchanger 3 is connected to the tar treatment device 5 via the tar-containing water amount measurement device 4.

  The tar-containing water amount measuring device 4 measures the amount of tar-containing water that is a mixture of tar and water condensed in the heat exchanger 3, and transmits the measured water amount measurement value data to the supply water amount control device 6. It is like that. The tar-containing water amount measuring device 4 can use a known flow rate measuring device, for example, a volumetric or electromagnetic flow meter.

  A tar treatment device 5 is connected to the tar-containing water amount measuring device 4, and a vaporizer (not shown) and a reservoir (not shown) are connected to the tar treatment device 5. The tar treatment device 5 is, for example, a specific gravity separator, and receives discharged tar-containing water after measurement by the tar-containing water amount measurement device 4, and the light tar containing water, heavy tar, To separate. Light tar containing water is separated into light tar and water by a vaporizer, and heavy tar is stored in a reservoir and used as fuel.

  The supply water amount control device 6 is (A) a wet bed at the uppermost part of the biomass packed bed in the gasifier with water supplied by at least one of the first water supply device 2A and the second water supply device 2B. In addition to controlling the amount of water supplied so that the moisture content of the water can be 30% or more, (B) the measured water amount measurement value data is received from the tar-containing water amount measuring device 4, and the tar-containing water amount is previously determined. In order to control the amount of water supplied by at least one of the first water supply device 2A and the second water supply device 2B so that the predetermined range is determined, the water pump output of these devices 2A, 2B, etc. Send the signal to be adjusted. When it is possible to control the amount of water supplied so that the moisture content of (A) the wet layer can be 30% or more by controlling (B), Control may be performed.

  Here, the predetermined range of the amount of water containing tar is to prevent the condensed tar from adhering to the heat transfer surface by washing the heat transfer surface (condensation surface) of the heat exchanger 3 with the condensed water. Is a range in which a preferable range of the amount of condensed water required is determined in advance, the amount of tar condensed is added thereto, and a preferable range of the amount of recovered tar-containing water is determined.

  Gasification of biomass having a high moisture content of 30 to 55% is gasified, and the amount of tar-containing water collected during the tar removal operation that does not cause a problem is measured. The measured value is determined in advance as the amount of tar-containing water. The predetermined range may be used.

  Measure the water concentration in the gas generated from the gasifier when it has been confirmed that tar can be removed smoothly in the heat exchanger, and the amount of recovered tar-containing water corresponding to the preferred range of the water concentration in this gas The range may be a predetermined range.

  Next, the procedure of gasification of biomass by the apparatus of this embodiment having such a configuration will be described.

(1) First, biomass is supplied to the gasifier 1. The feature of the apparatus of the present invention is particularly effective in the case of biomass having a low water content, and the case where the biomass supplied to the gasification furnace 1 has a low water content of 20% or less will be described. Biomass receives spray supply of water from at least one of the first water supply device 2A and the second water supply device 2B to form a packed bed in the gasification furnace 1, and from above the wet layer, the dry region, A pyrolysis region, a reduction region, and an oxidation region are formed. The gasification furnace 1 is supplied with water vapor and air as gasification agents from below, and the biomass in the packed bed finally becomes product gas and combustion ash by pyrolysis and gasification reaction. The generated gas contains a combustible gas such as CH ₄ , CO, and H ₂ , and CO ₂ , H ₂ O, gaseous and mist tars. Product gas is sent to the heat exchanger 3 from the upper part of the gasification furnace 1, and combustion ash is discharged | emitted from the furnace lower part.

  (2) The product gas from the gasification furnace 1 is introduced into the container 31 of the heat exchanger 3 from the introduction pipe 32. A cooling pipe 34 for circulating cooling water is disposed in the container 31, and the generated gas is cooled below the condensation temperature of tar using the outer surface of the cooling pipe 34 as a heat transfer surface. The condensation temperature of tar is lower than or equal to the condensation temperature of water, and the product gas is condensed into tar and water, and the mixture thereof becomes tar-containing water and drops inside the container 31 and is stored in the lower part of the container 31. When the condensed water is dropped, the outer surface of the cooling pipe 34 is washed to prevent tar from adhering. In the product gas thus cooled, tar-containing water is discharged from the discharge pipe 36 at the bottom of the container 31, and the gas body containing combustible gas and dust is led out from the outlet pipe 33 at the bottom of the container 31 as a processing gas. The

  (3) The discharged tar-containing water is sent to the tar treatment device 5 after its amount is measured by the tar-containing water amount measuring device 4. The water content measurement value data of the tar-containing water is sent to the spray water amount control device 6 and compared with whether or not the measured amount of tar-containing water is within a predetermined range. The water amount control device 6 sends a command signal to the first water supply device 2A and the second water supply device 2B so as to eliminate the difference, specifically, the shortage. The first water supply device 2A and the second water supply device 2B spray an amount of water that eliminates the shortage.

  In this embodiment, at least one of the first water supply device 2A and the second water supply device 2B is provided, and the moisture content of biomass that is supplied into the furnace and forms the packed bed uppermost portion is within a preferable range. By adjusting, a wet layer having a moderately high moisture content (for example, a moisture content of 30% or more) is formed. As a result, the tar generated in the pyrolysis zone is trapped by moisture in the wet layer, and the trapped tar falls to the bottom together with the biomass and enters the pyrolysis zone again. And light tar is broken down into gases. By repeating the trapping of the tar in the wet layer and the decomposition in the thermal decomposition region, the tar content in the product gas becomes relatively light tar and the fluidity of the tar-containing water recovered by the gas cooling device is high and smooth. Can be easily discharged, and handling in the subsequent process becomes easy.

  By using the biomass gasification apparatus and method according to the present invention configured as described above, even if biomass having a moisture content of 20% or less is supplied to the gasification furnace, light tar among the tars contained in the generated gas Therefore, it is possible to prevent the problem that it becomes difficult to adhere to the heat transfer surface of the heat exchanger of the gas cooling device or to prevent smooth discharge.

  The present invention can be used in the industrial field where fuel gas is generated from biomass.

DESCRIPTION OF SYMBOLS 1 Gasification furnace 2A 1st water supply apparatus 2B 2nd water supply apparatus 3 Heat exchanger 4 (tar containing) water quantity measuring device

Claims (5)

In a gasifier that pyrolyzes biomass supplied to a gasifier and obtains product gas,
At least one of a first water supply device that supplies water to the biomass before being supplied to the gasification furnace and a second water supply device that supplies water to the biomass in the gasification furnace from the top of the gasification furnace A biomass gasifier characterized by comprising:   The first water supply device and the second water supply device are set so that the total water supply amount is 30% or more of the moisture content of the wet layer in the uppermost part of the biomass packed bed in the gasification furnace. The biomass gasifier according to claim 1. The gasifier is
A heat exchanger that receives the generated gas from the gasification furnace, cools the generated gas by heat exchange with a heat medium, condenses water vapor and tar contained in the generated gas, and generates tar-containing water;
A water amount measuring device for measuring the amount of tar-containing water generated in the heat exchanger;
A water supply amount control device for controlling the amount of water supplied by at least one of the first water supply device and the second water supply device so that the amount of tar-containing water measured by the water amount measurement device falls within a predetermined range; The biomass gasification apparatus according to claim 1, further comprising: In a gasification method for pyrolyzing biomass having a moisture content of 20% or less in a gasification furnace to obtain a product gas,
At least one of a first water supply step for supplying water to the biomass before being supplied to the gasification furnace and a second water supply step for supplying water to the biomass in the gasification furnace from the top of the gasification furnace. Have
A biomass gasification method characterized by increasing the moisture content of a wet layer formed at the top of a biomass packed bed in a gasification furnace. Gasification method is
A heat exchange step of receiving the generated gas from the gasification furnace to the heat exchanger, cooling the generated gas by heat exchange with the heat medium, condensing water vapor and tar contained in the generated gas to generate tar-containing water;
A water amount measuring step for measuring the amount of tar-containing water produced;
A water amount control step of controlling the amount of water to be supplied by at least one of the first water supply step and the second water supply step so that the measured amount of tar-containing water falls within a predetermined range. The biomass gasification method according to claim 4, wherein the biomass gasification method is characterized.

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