JP2010229206A - Apparatus and process for removing tar from gas produced from biomass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a process for preventing degradation of heat exchange performance of a heat exchanger by an attached tar. <P>SOLUTION: A tar-removing apparatus from a produced gas removes a tar contained in the produced gas produced from a biomass in a gasification furnace 1. The apparatus includes a heat exchanger 3 which receives a gas from a gasification furnace 1 and cools the produced gas by heat exchange with a heat medium to generate a tar-containing water which comprises condensed water and condensed tar obtained by condensation of water vapor and a tar contained in the produced gas; a water spray device 4 which sprays water into a space containing the produced gas of the heat exchanger 3; a water amount measuring device 5 which measures the amount of a discharged tar-containing water discharged from the heat exchanger 3 as an admixture of the tar-containing water and the sprayed water; and a sprayed water controlling device 6 which controls the amount of the water sprayed from the water spraying device 4 so that the amount of the discharged tar-containing water measured by the water measuring device 5 falls within a predetermined range. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tar removal processing apparatus in a product gas for removing tar contained in a product gas generated from biomass in a gasification furnace and a method for removing a tar in the product gas.

  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 material is supplied into the furnace 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 top, and the biomass descends from the top to the bottom of the packed bed as the gasification reaction proceeds. Steam and air are supplied as gasifying agents from the lower part of the furnace, and the gas flow in the furnace rises in the packed bed from the lower part of the furnace to the upper part of the furnace, and the generated gas generated by gasification is taken out from the outlet at the upper part of the furnace. .

Since the biomass supplied from the upper part of the gasification furnace contains moisture, a wet layer having a high moisture concentration is first formed at the top of the packed bed. 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 generated gas containing the combustible gas and CO ₂ , H ₂ O, gaseous and mist tars rises, 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, and when the generated gas is used as a fuel for a gas engine or the like, there may be a problem in operation. 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 a heat medium, and gaseous and mist-like tar and water vapor in the product gas are removed. This is removed from the product gas by condensing and agglomerating to form tar-containing water, and the remaining tar is removed together with the dust in the product gas by a wet electrostatic precipitator provided in the subsequent stage.

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

  In the tar removal method in the product gas described in Non-Patent Document 1, the gaseous and mist-like tars and water vapor in the product gas are condensed and aggregated, and the mixture is discharged as tar-containing water from the heat exchanger. . When the moisture content of the woody biomass supplied to the gasification furnace is as high as about 30 to 50%, the condensed water is sufficiently produced by condensing the water vapor that is dried and evaporated by the heat exchanger. The heat transfer surface (condensation part) of the exchanger is washed with condensed water, preventing tar from adhering to the heat transfer surface and lowering the heat exchange performance. Also, the viscosity of the water containing tar is low and the fluidity is good. Therefore, it is discharged smoothly from the heat exchanger.

  On the other hand, some building waste materials, waste wood, and other woody biomass have a low moisture content of 20% or less. When such biomass having a moisture content of 20% or less is gasified, the amount of water condensed in the heat exchanger is reduced. If the amount of moisture is small, the heat transfer surface (condensation part) of the heat exchanger will not be sufficiently washed with condensed water, tar will adhere to the heat transfer surface and heat exchange performance will deteriorate, There is a problem that heat exchange and tar-containing water cannot be smoothly discharged because the water flowability is low and the gas flow path and the tar-containing water discharge section are clogged, and tar in the gas cannot be removed.

  The present invention has been made in view of such circumstances, and when removing tar contained in a product gas generated by supplying biomass having a moisture content of 20% or less to a gasifier, a heat exchanger is provided. It is an object of the present invention to provide a tar removal treatment device in a product gas and a tar removal treatment method in the product gas that can prevent problems such as deterioration in heat exchange performance and blockage.

  The present invention relates to an apparatus and method for removing tar contained in product gas, which removes tar contained in product gas generated from biomass in a gasification furnace. A heat exchanger that generates tar-containing water containing condensed water and condensed tar obtained by cooling the generated gas by heat exchange and condensing water vapor and tar contained in the generated gas, and a generated gas storage space of the heat exchanger Measured by a water spray device for spraying water inside, a water amount measuring device for measuring the amount of discharged tar-containing water discharged from the heat exchanger by mixing the tar-containing water and the spray water, and a water amount measuring device And a spray water amount control device that controls the amount of spray water sprayed by the water spray device so that the amount of discharged tar-containing water falls within a predetermined range.

  Further, the present invention relates to a tar removal treatment method in a product gas, wherein the tar contained in the product gas produced from biomass having a water content of 20% or less in a gasifier is removed. In the above, 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 the condensed water obtained by condensing water vapor and tar contained in the product gas is contained. A heat exchange process for generating tar-containing water, a water spraying process for spraying water into the generated gas storage space of the heat exchanger, and an exhaust tar discharged from the heat exchanger when spray water is mixed into the tar-containing water. It has the water quantity measurement process which measures the quantity of contained water, and the spray water quantity control process which controls the quantity of the water sprayed so that the quantity of the measured discharge | emission tar containing water may be made into a predetermined range, It is characterized by the above-mentioned.

  According to the present invention having such a configuration, for example, when biomass having a low water content of 20% or less is gasified in a gasification furnace, the produced gas generated by gasification is sent to the heat exchanger. The heat exchanger is cooled by heat exchange with a heat medium flowing in the heat transfer tube of the heat exchanger. When the product gas is cooled, the water vapor in the product gas and the gaseous and mist tars are condensed and aggregated to produce tar-containing water containing condensed water and condensed tars, which is dropped in the heat exchanger. . In the present invention, water is sprayed onto the product gas in the heat exchanger, and the sprayed water is mixed with the tar-containing water to form drained tar-containing water, which is discharged from the heat exchanger.

  In the heat exchanger, tar content may adhere to the outer surface of the heat transfer tube. However, since condensed water and spray water fall in the heat exchanger, the outer surface of the heat transfer tube is condensed during the lowering. Washing with water and spray water.

  The amount of discharged tar-containing water discharged from the heat exchanger is measured by a water amount measuring device. The spray water amount control device receives the measured water amount measurement value data, and controls the water spray device so that the discharged tar-containing water amount falls within a predetermined range.

The predetermined range described above is necessary for preventing the heat transfer surface (condensation surface) of the heat exchanger from being washed with spray water and condensed water and preventing the condensed tar from adhering to the heat transfer surface. A preferable range of the total water content of the spray water and the condensed water is obtained in advance, and the amount of tar to be condensed is added to the range, which is determined as a preferable range of the recovered exhaust tar-containing water amount.
Of the discharged tar-containing water, the amount of spray water is known in a water spray device, and when the amount of spray water is subtracted from the measured discharged tar-containing water, the spray water is a mixture of condensed water and condensed tar. Obtain the amount of tar-containing water before mixing.

  On the other hand, even if no spray water is required, a high moisture content that can obtain a sufficient amount of tar-containing water for washing the heat transfer tube, for example, gasification of woody biomass of 30 to 50% as described above, Since the amount of tar-containing water obtained when cooling is known, under the same biomass supply, biomass with a low water content of 20% or less is gasified in the gasifier and the heat exchanger The tar-containing water obtained by subtracting the spray water content from the discharged tar-containing water discharged and measured from the water is smaller than the amount of tar-containing water obtained from the biomass having a high water content.

  In the present invention, a predetermined range of the amount of discharged tar-containing water is set based on the amount of tar-containing water when gasifying high-moisture biomass, and the amount of tar-containing water is compared with the predetermined value range The difference may be detected, and an amount of spray water corresponding to the difference may be supplied and controlled. That is, when the product gas from biomass having a low water content is supplied to the apparatus of the present invention, the amount of discharged tar-containing water, which is the sum of spray water, condensed water, and condensed tar, is the content of tar in the case of biomass having a high water content. The amount of spray water may be controlled so as to be a value within a predetermined range set based on the amount of water.

  According to the present invention, when removing the tar contained in the gas generated by supplying biomass with a low moisture content of 20% or less to the gasifier, water is sprayed into the heat exchanger to The moisture content (condensed water and spray water) of the same level as in the case of biomass with moisture content can be obtained, and the heat transfer pipe outer surface of the heat medium in the heat exchanger can be sufficiently washed, and the heat exchange performance of the heat exchanger can be reduced. It is possible to provide a tar removal treatment apparatus in gas and a tar removal treatment method in gas that can prevent problems such as clogging.

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, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, the code | symbol 1 is a gasification furnace which gasifies biomass, receives supply of biomass from the upper part, and receives supply of water vapor | steam and air as a gasification agent from the lower part. In the gasification furnace 1, a packed bed of supplied biomass is formed, and the gasifying agent rises in the packed bed. 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 generated gas contains a combustible gas such as CH ₄ , CO, and H ₂ , CO ₂ , H ₂ O, and gaseous tar.

  The gasifier 1 is connected to the tar removal device 2 of the present embodiment on the downstream side. The tar removing device 2 includes a heat exchanger 3 that receives the generated gas from the gasification furnace 1, a water spray device 4 that sprays water into the generated gas receiving space in the heat exchanger 3, and an exhaust from the lower portion of the heat exchanger 3. A tar-containing water amount measuring device 5 that measures the amount of discharged tar-containing water to be discharged, and a spray water amount control device 6 that receives the detection signal from the tar-containing water amount measuring device 5 and controls the spray water amount of the water spraying device 4. is doing. The devices 3 to 6 of the tar removing device 2 will be described later again.

  The heat exchanger 3 of the tar removal device 2 is connected to a wet electric dust collector 7 and a gas engine 8 in order, and the processing gas cooled by the heat exchanger 3 is dust in the wet electric dust collector 7. After the removal, etc., it is sent to the gas engine 8 as combustible gas and used for driving the gas engine 8.

  A tar treatment device 9 is connected to the tar-containing water amount measurement device 5 of the tar removal device 2, and a vaporizer 10 and a reservoir 11 are connected to the tar treatment device 9. The tar treatment device 9 is, for example, a specific gravity separator, which receives discharged tar-containing water after measurement by the tar-containing water measuring device 5 and separates it into light tar and heavy tar containing water by specific gravity. To do. The light tar containing water is separated into light tar and water by the vaporizer 10, and the heavy tar is stored in the reservoir 11 and used as fuel.

<Heat exchanger>
As shown in FIG. 2, the heat exchanger 3 includes an introduction pipe 32 that introduces a generated gas into the upper part of a container 31 that forms a sealed space, and a cooling process for the generated gas, and then uses this as a processing gas to lower the container. 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 water sprayer 35 for spraying water downward into the container 31 is provided at the upper part of the container 31, and a discharge pipe 36 for discharging discharged tar-containing water is provided at the lower part 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.

  When a proper amount of water is sprayed by the water spraying device 35 into the generated gas storage space in the container 31 of the heat exchanger 3, the cooling pipe 34 is cleaned by the sprayed water and condensed water, and the condensation is condensed. It is possible to prevent the tar from adhering to the heat transfer surface, and to maintain the heat exchange performance of the cooling pipe 34. Further, since the viscosity of the discharged tar-containing water obtained by adding spray water to the tar-containing water which is a mixture of the condensed tar and the condensed water is small and has high fluidity, it is smoothly discharged from the discharge pipe 36.

<Water spray device>
The water spray device 35 includes a water tank provided outside the container 31 of the heat exchanger 3, a water supply pump (both not shown), and a spray nozzle provided above the container 31. The configuration of the water spraying device itself is not limited to this, and can be appropriately configured as long as water can be sprayed and the amount of sprayed water is controlled to a set amount upon receiving a command signal from the sprayed water amount control device 6. Can be taken.

<Tar water content measuring device>
The tar-containing water amount measuring device 5 measures the discharged tar-containing water amount in a state where spray water is added to the tar-containing water that is a mixture of tar and water condensed in the heat exchanger 3, and the measured water amount measurement value data Is transmitted to the spray water amount control device 6. The tar-containing water amount measuring device 6 can use a known flow rate measuring device, for example, a volumetric or electromagnetic flow meter.

<Spray water amount control device>
The spray water amount control device 6 receives the measured water amount measurement value data and outputs the water pump output of the water spray device 4, the opening degree of the spray nozzle, etc. so that the discharged tar-containing water amount falls within a predetermined range. The signal which adjusts is transmitted.

  The predetermined range described above is necessary for preventing the heat transfer surface (condensation surface) of the heat exchanger from being washed with spray water and condensed water and preventing the condensed tar from adhering to the heat transfer surface. A preferable range of the total water content of the spray water and the condensed water is obtained in advance, and the amount of tar to condense is added to the range, which is determined as a preferable range of the recovered exhaust tar-containing water amount.

  The biomass with high moisture content is gasified and the amount of tar-containing water recovered during the tar removal operation that does not cause problems is measured, and the measured value is preliminarily calculated for the amount of discharged tar-containing water, including the amount of spray water. A predetermined range may be set.

  Furthermore, the moisture concentration in the gas generated from the gasifier when it is confirmed that tar can be removed smoothly in the heat exchanger is measured, and the discharge corresponding to the preferable range of the moisture concentration in this gas is performed. The range of the tar-containing water content may be a predetermined range.

  Next, a procedure for tar removal 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 forms a packed bed in the gasification furnace 1, and forms a wet layer, a dry region, a thermal decomposition region, a reduction region, and an oxidation region from the top. 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. The product gas is sent from the upper part of the gasification furnace 1 to the heat exchanger 3 of the tar removal device 2, and the combustion ash is discharged from the lower part of the furnace.

  (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 and water using the outer surface of the cooling pipe 34 as a heat transfer surface. The tar and water inside are condensed and agglomerated, 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. On the other hand, spray water is sprayed from the upper water spray device 35 into the container 31. Therefore, when the amount of condensed water obtained by cooling the produced gas generated from biomass having a low moisture content is small, the outer surface of the cooling pipe 34 is washed with the condensed water and the spray water. The product gas thus cooled is discharged from the discharge pipe 36 at the lower part of the container 31 as tar-containing water together with the spray water, and the gas body containing combustible gas and dust is treated as a processing gas. 31 is led out from the outlet pipe 33 at the bottom.

  (3) The discharged tar-containing water is sent to the tar treatment device 9 after the amount thereof is measured by the tar-containing water amount measuring device 5. The measured amount data of the discharged tar-containing water is sent to the spray water amount control device 6 and compared with whether or not the measured amount of discharged tar-containing water is within a predetermined range. The spray water amount control device 6 sends a command signal to the water spray device 4 so as to eliminate the difference, specifically, the shortage. The water spraying device 4 sprays an amount of water that eliminates the shortage.

  (4) The processing gas led out from the lead-out pipe 33 of the heat exchanger 3 is sent to the wet electrostatic precipitator 7, where the dust is removed and supplied as a combustible gas to the gas engine 8 for driving the engine. Provided.

  (5) On the other hand, the discharged tar-containing water discharged from the heat exchanger 3 is sent to the tar treatment device 9 after being measured by the tar-containing water amount measuring device 5. The tar treatment device 9 is, for example, a specific gravity separator, and separates discharged tar-containing water into light tar and water (mixture) and heavy tar based on the specific gravity difference. The light tar and water mixture is separated into light tar and water by the vaporizer 10. Heavy tar is stored in the reservoir 11 and used as fuel.

  By using the tar removal processing apparatus and method of the present embodiment as described above, the inside of the heat exchanger can be washed to prevent the adhesion of tar, and problems such as deterioration of the heat exchange performance and blockage of the heat exchanger can be avoided. The tar can be removed smoothly.

    The present invention can be used in the industrial field of removing tar in gas.

DESCRIPTION OF SYMBOLS 1 Gasification furnace 2 Tar removal apparatus 3 Heat exchanger 4 Water spray apparatus 5 (tar containing) water measuring apparatus 6 Spray water quantity control apparatus

Claims (2)

In the tar removal processing apparatus in the generated gas, which removes tar contained in the generated gas generated from biomass in the gasifier,
Heat that receives gas from the gasification furnace and cools the product gas by heat exchange with the heat medium and condenses water vapor and tar contained in the product gas to produce tar-containing water containing condensed water and condensed tar An exchange,
A water spray device for spraying water into the product gas storage space of the heat exchanger;
A water amount measuring device for measuring the amount of discharged tar-containing water mixed with the tar-containing water and spray water and discharged from the heat exchanger;
A tar removal in generated gas, characterized by having a spray water amount control device for controlling the amount of spray water sprayed by a water spray device so that the amount of discharged tar-containing water measured by a water amount meter is within a predetermined range Processing equipment. In the tar removal treatment method in the product gas, which removes tar contained in the product gas generated from biomass having a moisture content of 20% or less in a gasification furnace,
Containing tar containing condensed water and condensed tar obtained by receiving the generated gas from the gasification furnace to the heat exchanger, cooling the generated gas by heat exchange with the heat medium, and condensing water vapor and tar contained in the generated gas A heat exchange process to produce water;
A water spraying step of spraying water into the product gas storage space of the heat exchanger;
A water amount measuring step for measuring the amount of discharged tar-containing water discharged from the heat exchanger when spray water is mixed into the tar-containing water,
And a spray water amount control step of controlling the amount of water sprayed so that the measured amount of discharged tar-containing water falls within a predetermined range.

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