JP2006124442A - Method for feeding water to heat recovery system and exhaust heat recovery boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for feeding water to a heat recovery system and an exhaust heat recovery boiler to effectively utilize the thermal energy removed at the inlet port of a combustion apparatus such as a gas engine. <P>SOLUTION: A tangible fuel is thermally cracked and reformed with steam to obtain a fuel for a combustion apparatus 12. In the above fuel gas system, the cooling water to be used for the cooling and refining of the gas in a gas scrubbing and cleaning apparatus 5 for removing residual water, residual tar and soot in the reformed thermally cracked gas is used as the feed water of an exhaust heat recovery boiler 14 placed at the downstream side of the combustion apparatus 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat recovery system for a pyrolysis gas fuel supply system using high-temperature pyrolysis gas as a fuel for a combustion apparatus, and more specifically, steam reforming tangible fuel such as biomass, plastic, etc. The present invention relates to a heat recovery system of a pyrolysis gas fuel supply system and a method of supplying water to an exhaust heat recovery boiler, characterized by utilizing exhaust heat of a fuel supply system as fuel.

  Patent Document 1 discloses heat that can generate pyrolysis gas in a fuel system of a combustion apparatus that uses high-temperature pyrolysis gas by thermal decomposition of tangible fuel such as waste plastic and biomass fuel (hereinafter referred to as tangible fuel). A cracking furnace, a heat exchanger that heats low-temperature steam and low-temperature air with sensible heat of high-temperature pyrolysis gas, burns part of the pyrolysis gas, and the low-temperature steam and low-temperature air by the combustion heat And a high-temperature steam and high-temperature air, and further introducing the high-temperature steam and high-temperature air into the reforming region of the pyrolysis gas, thereby suppressing the generation of soot associated with the gasification and melting reaction is described. Has been.

  In this prior art, in order to reform the hydrocarbons in the pyrolysis gas by the steam reforming action in the fuel reformer, high-temperature steam of 700 ° C. or higher and air are finally supplied to the reformer. This supplied thermal energy is originally the sensible heat and calorific value of the high-temperature pyrolysis gas, which circulates in the fuel system, but is used as fuel for combustion devices such as gas engines. Therefore, at the inlet, in addition to further cooling the reformed gas to a temperature that can be accepted as fuel for the combustion device, moisture, residual tar and soot remaining in the reformed pyrolysis gas are removed. A gas cleaning and purifying device for removal is provided. The fuel gas temperature at the inlet of the gas cleaning and purifying device described above varies depending on the type of tangible raw material that is the source of the pyrolysis gas, but the water content in the fuel gas before the fuel gas enters the gas cleaning and purifying device. In order to avoid dew condensation, the temperature is at least 150 ° C. or higher. On the other hand, the outlet fuel gas temperature of the gas cleaning and purifying apparatus needs to be a temperature at which moisture, remaining tar and soot in the fuel gas after reforming can be removed. This also differs depending on the type of tangible raw material that is the source of pyrolysis gas. For example, in the case of woody biomass gas, the fuel gas temperature needs to be lowered to 60 ° C. in order to fractionate wood tar. Furthermore, in order to condense and separate the water remaining in the fuel gas, it is necessary to cool the fuel gas to a temperature as close to room temperature as possible, so when supplying cooling water from the outside to the gas cleaning and purifying device and exchanging heat with the fuel gas When normal temperature water is used as the cooling water, the gas temperature at the outlet of the gas cleaning and purifying apparatus is about 40 ° C. That is, in the gas cleaning and purifying apparatus, the fuel gas is cooled from a high temperature of 150 ° C. or higher to a temperature close to room temperature of about 40 ° C.

JP 2001-158885 A

  In the prior art, the fuel gas is cooled from a high temperature of 150 ° C. or higher to a temperature close to room temperature of about 40 ° C. in the gas cleaning and purifying apparatus, but the heat is not utilized.

  An object of the present invention is to provide a heat recovery system and a method of supplying water to an exhaust heat recovery boiler that can effectively use heat energy removed at the entrance of a combustion apparatus such as a gas engine.

  The present invention includes a cracking furnace for thermally decomposing tangible fuel, a reformer for reforming generated pyrolysis gas, and gas cooling purification of moisture, residual tar and soot remaining in the reformed pyrolysis gas. In a heat recovery system comprising a gas cleaning and purifying device to be removed, a combustion device using a reformed gas from which moisture, residual tar and soot have been removed as fuel, and an exhaust heat recovery boiler for recovering thermal energy from combustion A heat recovery system provided with a pipe for supplying cooling water used for gas cooling purification in the gas cleaning and purifying apparatus as feed water for the exhaust heat recovery boiler is provided.

  The present invention also provides a cracking furnace for thermally decomposing tangible fuel, a reformer for reforming generated pyrolysis gas, and gas cooling of moisture, residual tar and soot remaining in the reformed pyrolysis gas. Heat recovery comprising a gas cleaning and purifying device to be removed by refining, a combustion device using a reformed gas from which moisture, residual tar and soot have been removed as fuel, and an exhaust heat recovery boiler for recovering thermal energy from combustion In the method of supplying water to the exhaust heat recovery boiler in the system, the cooling water used for gas cooling purification in the gas cleaning and purifying apparatus is supplied to the exhaust heat recovery boiler in the heat recovery system in which the cooling water is supplied as supply water for the exhaust heat recovery boiler. Provide water supply method.

  According to the present invention, the amount of boiler evaporation is obtained by using the cooling water used for gas cooling purification in the gas cleaning and purifying apparatus, which has not been used conventionally, as the feed water for the exhaust heat recovery boiler and preheating the boiler feed water. Therefore, it is possible to increase the total efficiency as a combined heat and power plant combining a combustion apparatus such as a gas engine and an exhaust heat recovery boiler. As a result, even if it is recovered alone, it can be recovered only as hot water (generally about 80 ° C. water), and it is possible to obtain a use destination as steam energy that is energy whose use is limited. .

  The boiler steam thus increased can also be used as a high-temperature steam source of 700 ° C. or higher necessary for steam reforming of pyrolysis gas, for example. The exhaust heat recovery boiler steam temperature of a combustion apparatus such as a gas engine is often about 180 ° C. (saturation temperature of 0.8 MPa), and when steam of this temperature is supplied to the steam generator upstream of the gas cleaning and purifying apparatus, Since less heat energy is required for steam heating, the fuel gas temperature at the gas cleaning and purifying device inlet rises, and the recovered heat energy for boiler feed water in the gas cleaning and purifying device can be increased accordingly. .

  A first embodiment for solving the above problems includes a cracking furnace for pyrolyzing tangible fuels such as woody biomass and plastic, a low-temperature steam generator and a high-temperature steam / air generator for reforming pyrolysis gas, Tar / moisture separator for further cooling the reformed gas to a temperature that can be accepted as fuel for the combustion device, together with removing moisture, residual tar and soot remaining in the pyrolysis gas after purification. A gas cleaning / purification device comprising a dust removal device, a combustion device using reformed gas as a fuel, and a fuel gas system equipped with an exhaust heat recovery boiler for recovering thermal energy of the combustion exhaust gas. A heat recovery system is provided in which piping for supplying cooling water used for cooling and purification as feed water for the exhaust heat recovery boiler is provided.

  Combustion devices such as gas engines are also used for power and power generation. In order to recover the thermal energy of the exhaust gas, an exhaust heat recovery boiler is installed in the exhaust gas system of the combustion device, and the exhaust heat recovery boiler It is common practice to supply steam and hot water generated in Japan to customers. According to the present invention, it is possible to increase the amount of boiler evaporation by using the cooling water of the gas cleaning and purifying device provided at the fuel inlet of the combustion device for supplying water to the exhaust heat recovery boiler and preheating the boiler supply water. To do.

  Further, in the second embodiment, the cooling water used for gas cooling purification in the gas cleaning and purifying apparatus by the heat recovery system is used as feed water for the exhaust heat recovery boiler, and at the same time, pyrolysis gas is used. A pipe for supplying cooling water for the gas cleaning and purifying apparatus as feed water for the exhaust heat recovery boiler and a pipe for supplying water for the low-temperature steam generator for use as feed water for a low-temperature steam generator for reforming; Further, in order to adjust the distribution of the cooling water of the gas cooling and purifying apparatus, a heat recovery system is provided in which a three-way valve is provided at a branch portion on the supply side of the exhaust heat recovery boiler and the supply side of the low-temperature steam generator. . As a result, the thermal energy fluctuation of the fuel system, which was conventionally discarded outside the system as the temperature fluctuation of the cooling water of the gas cleaning and purifying apparatus, is recovered as an increase / decrease in the evaporation amount of the exhaust heat recovery boiler, which is in high demand because the energy density is high. Make it possible to do.

  In the following, a first embodiment of the present invention will be described with reference to FIG.

  A heat recovery system 100 according to an embodiment of the present invention includes a cracking furnace 1 for thermally decomposing tangible fuel, a reformer (device) 2 for reforming generated pyrolysis gas, and the pyrolysis gas after reforming A gas cleaning and purifying device 5 that removes moisture, residual tar, and soot remaining in the gas by gas cooling purification, and a combustion device such as a gas engine 12 that uses the reformed gas from which moisture, residual tar, and soot are removed, as fuel, And an exhaust heat recovery boiler 14 that recovers thermal energy from combustion.

  A pipe between the reformer 2 and the gas cleaning and purifying device 5 is provided with a high-temperature steam generator 3 and a low-temperature steam generator 4 for generating high-temperature steam and air used in the reformer 2. Water is introduced into the low-temperature steam generator 4 from the pipe 30 to become steam, and is mixed with air introduced from the pipe 31. This mixed stream of steam and air is introduced into the high-temperature steam generator 3, converted into high-temperature steam / air, introduced into the reformer 2, and used as a reformed gas for the pyrolysis gas.

  The gas cleaning and purifying device 5 includes a tar / water separator 6 and a dust removing device 7 in this order.

  The pyrolysis furnace 1 is supplied with a tangible fuel material such as woody biomass or waste plastic. The high temperature pyrolysis gas leaving the pyrolysis furnace 1 is sent to the reformer 2. Since the pyrolysis gas contains a carbon compound, it is heated to 700 ° C. or more by passing through the low temperature steam generator 4 and the high temperature steam / air generator 3 in this reformer 2 in order to reform as a fuel gas for the combustion apparatus. Steam reforming is performed by the steam and air. Since the steam reforming here is an endothermic reaction, a part of the fuel gas pressurized by the gas charger 10 is sent to the reformer 2 through the pipe 11 from the inlet of the gas engine 12 used as a combustion device. The temperature is maintained by hot air and the combustion heat of combustion.

  The reformed fuel gas exiting the reformer 2 passes through the high-temperature steam / air generator 3 and the low-temperature steam generator 4 in order to reduce its temperature by exchanging heat with steam, air, and water, At the inlet of the gas cleaning and purifying apparatus 5, the temperature becomes relatively low (for example, about 150 ° C.). In this gas cleaning and purifying device 5, the remaining tar and soot that have not been removed by the reformer 2 and the excess of the high-temperature steam added to the reformer 2 are removed, so that an appropriate cleanliness as a fuel gas for the gas engine is obtained. Secure. Here, the gas cleaning and purifying device 5 is composed of the tar / water separator 6 and the dust removing device 7 as described above, and the remaining tar content and the surplus water vapor content in the fuel gas are the tar / water separator 6. By exchanging heat with normal-temperature cooling water at, it is condensed by being cooled to a low temperature (for example, about 40 ° C.) at once, and most of it is stored in the tar receiving tank 8. On the other hand, the soot is removed by a dust removing device 7 attached to the outlet of the tar / water separator 6 and stored in a soot receptacle 9. The fuel gas obtained by reforming the pyrolysis gas thus cleaned is supplied to the supply pressure of the gas engine 12 by the fuel gas charger 10, and most of the fuel gas is supplied to the gas engine 12. At this time, in order to reduce the supply amount of high-temperature air used for reforming the pyrolysis gas, a part of the fuel gas passes through the fuel gas recirculation line 11 and is sent to the reformer 2 first. As stated.

  Thus, the fuel gas sent to the gas engine 12 is combusted by the gas engine 12, and power is generated by the gas engine 12 turning the generator 13. When the calorific value of the reformed fuel gas is insufficient or when the calorific value fluctuation is large, a gas or liquid auxiliary fuel 20 is added as necessary. The combustion exhaust gas that has worked in the gas engine 12 recovers thermal energy in the exhaust heat recovery boiler 14 and is finally released from the chimney 15 to the atmosphere.

  Here, the outlet water of the tar / water separator 6 in the gas cleaning and purifying apparatus 5 is used for water supply to the exhaust heat recovery boiler 14. This water supply is supplied from the outlet of the tar / water separator 6 to the exhaust heat recovery boiler 14 via a pipe A21 connecting the tar / water separator 6 and the exhaust heat recovery boiler 14. When viewed from the exhaust heat recovery boiler 14 side, the tar / water separator 6 plays the role of a boiler feed water heater. The water quality required for boiler feed water is adjusted to the water quality required for boiler feed water by the feed water treatment device 17, stored in the feed water tank 18, pressurized by the feed water pump 19, and pumped to the tar / water separator 6. The tar / moisture separator 6 recovers the thermal energy of the fuel gas from the water supplied from the water supply tank 18 and heats it to below 100 ° C. (generally about 80 ° C.) before sending it to the exhaust heat recovery boiler 14. The supplied boiler feed water then exchanges heat with the exhaust gas of the gas engine 12 and sends steam to the customer through the exhaust heat recovery boiler steam pipe 16. At this time, since the feed water is preheated from room temperature to about 80 ° C., the amount of generated steam can be increased compared to the case where steam is generated only with the exhaust gas energy of the gas engine 12.

  The exhaust gas temperature at the outlet of the exhaust heat recovery boiler is generally maintained at 150 ° C. or higher in order to prevent the dew point temperature of the acidic component in the exhaust gas and the water vapor generated by combustion from condensing in the chimney. Therefore, before the heat exchange with the exhaust gas in the exhaust heat recovery boiler, even if the feed water is preheated to about 80 ° C., the heat recovery can be performed without any trouble in the exhaust heat recovery of the combustion device such as the gas engine in the exhaust heat recovery boiler.

  In this way, a cracking furnace 1 for pyrolyzing tangible fuel, a reformer 2 for reforming the generated pyrolysis gas, and water cooling of residual moisture, residual tar and soot in the reformed pyrolysis gas are gas-cooled. Gas cleaning and purifying device 5 to be removed by refining, a combustion device such as a gas engine 12 using the reformed gas from which moisture, residual tar and soot are removed as fuel, and an exhaust heat recovery boiler for recovering thermal energy by combustion 14, a heat recovery system provided with a pipe A <b> 21 that supplies cooling water used for gas cooling purification in the gas cleaning and purifying apparatus 5 as feed water for the exhaust heat recovery boiler 14 is configured. .

  A second embodiment of the present invention is shown in FIG. The same components as those in the first embodiment are denoted by the same reference numerals. Therefore, the description of the first embodiment is adopted for the description of the same configuration. In this embodiment, the outlet water of the tar / water separator 6 is changed to be supplied to the low-temperature steam generator 4 in addition to the exhaust heat recovery boiler 14 with respect to the first embodiment. At the same time as providing the piping A21 for supplying cooling water as the feed water for the exhaust heat recovery boiler 14 in the gas cleaning and purifying apparatus 5 of Embodiment 1, the tar / water separator 6 and the low-temperature steam generator 4 in the gas cleaning and purifying apparatus 5 are provided. Are connected by piping B22. Furthermore, a three-way valve 23 is provided at a branching portion of the tar / water separator 6 outlet water to the exhaust heat recovery boiler 14 side and the low-temperature steam generator 4 side, that is, a branching portion of the pipe A21 and the pipe B22. The controller 25 controls the distribution of hot water to the exhaust heat recovery boiler 14 side and the low-temperature steam generator 4 side in the three-way valve 23 so that the temperature of the thermometer 24 installed at the inlet of the generator 3 becomes a constant value. Shall. When the temperature of the thermometer 24 rises above the target value, the three-way valve 23 is controlled to open to the low temperature steam generator 4 side, and the temperature of the low temperature steam generator 4 outlet steam decreases, so the thermometer 24 is stable at the control target temperature. To do. When the temperature of the thermometer 24 is low, the operation is reversed and the control system is stabilized. If this is considered including the exhaust heat recovery boiler 14 side as well, fluctuations in the amount of heat in the fuel system can be absorbed on the exhaust heat recovery boiler 14 side. That is, surplus heat in the fuel system is released to the exhaust heat recovery boiler 14 side, and the amount of evaporation of the exhaust heat recovery boiler 14 increases accordingly.

  Alternatively, if desired, a valve that restricts the flow rate of the water supply is installed on either the exhaust heat recovery boiler 14 side or the low temperature steam generator 4 side instead of the three-way valve 23, and the exhaust heat recovery boiler 14 side and the low temperature steam generator 4 are installed. It is also possible to adjust the distribution of the cooling water in the gas cleaning and purifying device 5 to the side. Furthermore, instead of measuring the temperature of the mixture of steam and air at the inlet of the high-temperature steam / air generator 3, the thermometer 24 measures the temperature of the mixture of steam and air at the outlet of the high-temperature steam / air generator 3, for example. Alternatively, the fuel gas temperature is measured in the outlet steam temperature signal measured by a steam thermometer (not shown) provided on the outlet side of the low temperature steam generator 4 or in the pipe between the reformer 2 and the high temperature steam / air generator 3. The same effect can be obtained by controlling using a fuel gas temperature signal measured by a thermometer (not shown) installed.

  In this way, the control valve means for controlling the amount of water supplied to the exhaust heat recovery boiler 14 and the amount of water supplied to the low temperature steam generator 4 is provided, and the steam generated by the thermometer 24 provided in the pipe to the high temperature steam / air generator 3 is provided.・ Air temperature signal, outlet steam temperature signal from the steam thermometer provided on the outlet side of the low temperature steam generator 4, or thermometer provided in the pipe between the reformer 2 and the high temperature steam / air generator 3 A control device can be provided that inputs a fuel gas temperature signal and controls the amount of water supplied to the exhaust heat recovery boiler 14 and the amount of water supplied to the low-temperature steam generator 4.

  As a result, when steam having the same thermal energy as the outlet of the low-temperature steam generator 4 of Example 1 is generated, the low-temperature steam generator 4 has hot water of about 80 ° C. as a general temperature from the tar / water separator 6. Therefore, the heat transfer area of the low-temperature steam generator 4 can be designed to be small accordingly.

  In the heat recovery system 100, a high-temperature steam / air generator 3 and a low-temperature steam generator 4 are provided on the downstream side of the reformer 2, and a part of the cooling water is supplied as feed water for the low-temperature steam generator 4. A pipe B22 is provided.

  A part of the cooling water is branched by providing a three-way valve 23 at a branch portion of the pipe A21 that is supplied as feed water for the exhaust heat recovery boiler 14, and the exhaust heat recovery boiler 14 is controlled by controlling the three-way valve. And a control device for controlling the amount of water supplied to the low-temperature steam generator 4.

  Further, control valve means for controlling the amount of water supplied to the exhaust heat recovery boiler 14 and the amount of water supplied to the low-temperature steam generator 4 is provided, and the control device includes a thermometer 24 provided in a pipe to the high-temperature steam / air generator 3. Vapor / air temperature signal due to steam, outlet steam temperature signal due to steam thermometer provided on the outlet side of the low-temperature steam generator, or fuel due to thermometer provided on the pipe between the reformer 2 and the high-temperature steam / air generator It can be set as the control apparatus which inputs a gas temperature signal and controls the amount of water supply to the waste heat recovery boiler 14 and the amount of water supply to the low temperature steam generator 4.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications or changes can be made.

  For example, in order to suppress fluctuations in the evaporation amount of the exhaust heat recovery boiler 14, the flow rate at the outlet of the feed water pump 19 is controlled in addition to the control of the cooling water distribution of the gas cleaning and purifying device 5 according to the instruction of the thermometer 24 as described above. A control valve is provided to correct the flow rate adjustment amount to the exhaust heat recovery boiler 14 side in the three-way valve 23 so as not to change the feed water flow rate to the exhaust heat recovery boiler 14 side, or to suppress the time variation of the evaporation amount. It is also possible to provide a buffer tank in the pipe line between the three-way valve 23 and the exhaust heat recovery boiler 14 to equalize the flow rate.

It is a block diagram which shows embodiment of this invention. It is a block diagram which shows other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pyrolysis furnace, 2 ... Reformer, 3 ... High temperature steam / air generator, 4 ... Low temperature steam generator, 5 ... Gas cleaning and purification device, 6 ... Tar and moisture separator, 7 ... Dust removal device, 8 ... Tar receiving tank, 9 ... Proportion acceptor, 10 ... Fuel gas supplier, 11 ... Fuel gas recirculation system, 12 ... Gas engine, 13 ... Generator, 14 ... Waste heat recovery boiler, 15 ... Chimney, 16 ... Waste heat Recovery boiler steam pipe, 17 ... feed water treatment device, 18 ... feed water tank, 19 ... feed pump, 20 ... auxiliary fuel, 21 ... pipe A, 22 ... pipe B, 23 ... three-way valve, 24 ... thermometer, 25 ... control Apparatus, 100 ... heat recovery system.

Claims (6)

A cracking furnace that thermally decomposes tangible fuel, a reformer that reforms the generated pyrolysis gas, and gas cleaning that removes moisture, residual tar and soot remaining in the reformed pyrolysis gas by gas cooling purification In a heat recovery system comprising a purification device, a combustion device using the reformed gas from which moisture, residual tar and soot have been removed as fuel, and an exhaust heat recovery boiler for recovering thermal energy from combustion,
A heat recovery system comprising a pipe for supplying cooling water used for gas cooling purification in the gas cleaning and purifying apparatus as feed water for the exhaust heat recovery boiler.   2. The piping according to claim 1, wherein a high-temperature steam / air generator and a low-temperature steam generator are provided in a downstream side pipe of the reformer, and a part of the cooling water is supplied as water for the low-temperature steam generator. A heat recovery system characterized by being provided.   3. The exhaust heat recovery system according to claim 2, wherein a pipe is branched by providing a three-way valve at a branch portion of a pipe that supplies a part of the cooling water as feed water for the exhaust heat recovery boiler, and the exhaust heat recovery is performed by controlling the three-way valve. A heat recovery system comprising a control device for controlling the amount of water supplied to the boiler and the amount of water supplied to the low-temperature steam generator.   3. Steam according to claim 2, comprising control valve means for controlling the amount of water supplied to the exhaust heat recovery boiler and the amount of water supplied to the low-temperature steam generator, and a thermometer steam provided in a pipe to the high-temperature steam / air generator・ Air temperature signal, outlet steam temperature signal from a steam thermometer provided on the outlet side of the low temperature steam generator, or fuel from a thermometer provided in a pipe between the reformer and the high temperature steam / air generator A heat recovery system comprising a controller for inputting a gas temperature signal and controlling the amount of water supplied to the exhaust heat recovery boiler and the amount of water supplied to the low-temperature steam generator. A cracking furnace that thermally decomposes tangible fuel, a reformer that reforms the generated pyrolysis gas, and gas cleaning that removes moisture, residual tar and soot remaining in the reformed pyrolysis gas by gas cooling purification The exhaust heat recovery in a heat recovery system comprising a purification device, a combustion device using the reformed gas from which moisture, residual tar and soot are removed as fuel, and an exhaust heat recovery boiler for recovering thermal energy from the combustion In the method of water supply to the boiler,
A method of supplying water to an exhaust heat recovery boiler in a heat recovery system, wherein cooling water used for gas cooling purification in the gas cleaning and purifying apparatus is supplied as supply water for the exhaust heat recovery boiler. 2. A high-temperature steam / air generator and a low-temperature steam generator are provided in a downstream side pipe of the reformer, and a part of the cooling water is supplied as feed water for the low-temperature steam generator. A method of supplying water to an exhaust heat recovery boiler in a heat recovery system.

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