JP2010227742A - Apparatus and method for treating flue gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating a flue gas wherein the running cost of its absorption device is reduced by supplying heat recovered from emission to its boiler, upon recovering carbon dioxide from combustion emission by a chemical absorption treatment. <P>SOLUTION: Combustion air is preheated by emission discharged from a boiler 1 and is fed to the boiler 1. Heat is recovered from the emission cooled in the process of preheating the combustion air, by a heat recovery device 4 by virtue of a heating medium therein. Soot and smoke in the emission discharged from the heat recovery device 4 are collected by a dust collector 5. The emission removed of dust by the dust collector 5 is treated by a wet-type flue-gas desulfurization device 7. The CO<SB>2</SB>in the emission desulfurized by wet-type flue-gas desulfurization is absorbed/removed by a chemical absorption device 9 for CO<SB>2</SB>that absorbs/separates CO<SB>2</SB>using an absorption liquid comprised of an amine. Further, a heating medium circulation path 12 is disposed to connect the heat recovery device 4 and the chemical absorption device 9 for CO<SB>2</SB>, so that the heat recovered by the heat recovery device 4 is used as a heat source for the absorption liquid comprised of an amine in the chemical absorption device 9 for CO<SB>2</SB>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an exhaust gas treatment apparatus and method provided with a chemical absorption facility for carbon dioxide (CO ₂ ), and more particularly to an exhaust gas treatment device and method for utilizing heat for reducing the gas temperature of exhaust gas in the CO ₂ chemical absorption facility.

  In general, exhaust gas discharged from a coal-fired boiler, etc. contains nitrogen oxides, sulfur oxides, dust, and other heavy metals, so a smoke treatment device is installed downstream of the coal-fired boiler, After removing the harmful substances in the exhaust gas, it is released into the atmosphere as a clean gas. FIG. 5 shows an example of a conventional flue gas treatment system. The combustion exhaust gas discharged from the boiler 1 is subjected to heat exchange by the air preheater 3 after removing nitrogen oxides by the denitration device 2 and cooled to 120 to 170 ° C., for example.

  The exhaust gas that has passed through the air preheater 3 is deprived of heat by a heat medium in the heat recovery device 4, cooled to, for example, 75 ° C. to 110 ° C., dust is removed from the exhaust gas by the dust collector 5, and the attracting fan 6 Then, the sulfur oxide is removed by the wet flue gas desulfurization apparatus 7. The temperature of the exhaust gas that has passed through the wet flue gas desulfurization device 7 is usually lowered to about 40 to 60 ° C. and is in a water saturated state. When this exhaust gas is discharged as it is from the chimney 11 into the atmosphere, white smoke is generated. Therefore, the temperature is raised by the reheater 18 and is discharged from the chimney 11 via the desulfurization fan 10. The heat transfer pipes of the heat recovery device 4 and the reheater 18 are communicated by the heat medium circulation line 12, and the heat medium is circulated between the heat recovery device 4 and the reheater 18 by the heat medium circulation pump 13. ing.

The flue gas treatment system shown in FIG. 5 reduces the exhaust gas temperature by the heat recovery unit 4, adsorbs sulfur trioxide (SO ₃ ) and heavy metal to the ash, and removes SO ₃ and heavy metal together with the ash by the dust collector 5. The heat recovered by the heat recovery device 4 is used for reheating moisture saturated gas at the outlet of the wet desulfurization device 7 to prevent white smoke from the chimney 11 (see Patent Document 1). . In the future, CO ₂ recovery equipment is expected to be installed in the above flue gas treatment system.

As one of the CO ₂ recovery facilities, a CO ₂ chemical absorption facility (for example, Patent Document 2) that recovers CO ₂ using an aqueous solution of an amine compound as an absorbing solution has been proposed. FIG. 6 shows an example of chemical absorption equipment using an amine absorbing solution. The exhaust gas whose pressure has been increased by the blower 8 is introduced into the absorption tower 25, and the CO ₂ in the exhaust gas flows while flowing in the absorption tower 25 while coming into contact with the amine absorption liquid discharged from the nozzle 25n mainly through the absorption packed bed 25b. Is absorbed and removed by the amine absorbing solution. Further, there is a washing packed bed 25 a above the absorbing packed bed 25 _{b in the} absorption tower 25, and the exhaust gas washed with water in the washed packed bed 25 a is removed as CO ₂ gas 27 from the top of the absorbing tower 25. Discharged. Washing water is circulated and supplied to the water-filled packed bed 25a by a pump 40, and the water in the circulation is cooled by a heat exchanger 41 in order to prevent scattering of the amine absorbing liquid accompanying the exhaust gas as much as possible. Also, the amine absorbing solution that has absorbed CO ₂ stored in the lower portion of the absorption tower 25 is supplied to the regeneration tower 26 by a pump 28a. The amine absorption liquid before being supplied to the regeneration tower 26 is heated by exchanging heat in the heat exchanger 43, supplied to the upper part of the lower packed bed 26 b of the regeneration tower 26, and flows down the lower packed bed 26 b of the regeneration tower 26. Then, it flows naturally from the gas-liquid mixing plate 26 c and is supplied to the reboiler 30. In the reboiler 30, the absorption liquid naturally flowing from the regeneration tower 26 is indirectly heated by the heating steam 32, and the generated steam is supplied above the bottom liquid reservoir of the regeneration tower 26. By this steam, the amine absorbing solution that has absorbed CO ₂ in the lower packed bed 26b of the regeneration tower 26 is heated, and CO ₂ is degassed by the steam that becomes the carry gas. That is, the reboiler 30 has a function of supplying the regenerated tower 26 with steam generated by indirect heating of the absorption liquid supplied to the reboiler 30 after naturally degassing CO ₂ in the regenerating tower 26.

Further, the heating steam 32 is supplied to a reclaimer 31 used for regenerating an absorbing solution that has deteriorated by reacting with SOx or oxygen. The absorption liquid obtained by degassing CO ₂ stored at the bottom of the regeneration tower 26 is supplied to the upper part of the lower packed bed 25b of the absorption tower 25 by the pump 28b via the heat exchanger 43, and the gas liquid in the lower packed bed 25b. By contacting, CO ₂ in the exhaust gas is absorbed.

On the other hand, in the regeneration tower 26, CO ₂ released from the amine absorbing liquid is discharged to the outside from the top of the regeneration tower 26 via the lower packed bed 26b and the upper packed bed 26a, and cooled by cooling water in the heat exchanger 46. The CO ₂ separated by the separator 47 is recovered as a high purity CO ₂ gas 29. Further, the amine-containing absorbent component that separates CO ₂ and is scattered by the vapor and scattered is collected by the upper packed bed 26a. In the upper packed bed 26a, the gas is cooled by the cooling water supplied to the heat exchanger 46 in order to wash the collected absorbent component, and the drain water condensed with the vapor is separated by the separator 47, and the upper packed bed is filled. The layer 26a is fed by a pump 49.

The regeneration tower 26 is supplied with steam generated by indirectly heating the amine absorbing liquid with the reboiler 30 with the heating steam 32. Further, when sulfur oxide in the exhaust gas is absorbed in the amine absorption liquid by the absorption tower 25, an amine and a compound (amine-SOx salt) are formed. Therefore, an alkali salt such as sodium carbonate is added by the reclaimer 31 and heated steam. The amine is regenerated by indirect heating at 32. The CO ₂ chemical absorption method using an amine absorbing solution requires enormous heat such as heating steam, and the current operating cost can be very high.

Republished patent WO2004 / 023040 JP 2002-126439 A

In the CO ₂ chemical absorption facility using an amine absorbing solution disclosed in Patent Document 2 and the like, enormous heat energy is required for the regeneration of the amine absorbing solution, and there is a problem that the operating cost is remarkably increased.
An object of the present invention is to provide CO ₂ chemical absorption equipment that requires enormous heat energy when recovering carbon dioxide (CO ₂ ) from combustion exhaust gas by chemical absorption treatment, thereby supplying CO 2 ₍₂₎ To provide a smoke treatment method and apparatus that reduces the operating cost of chemical absorption equipment.

The above-mentioned problem of the present invention is achieved by recovering heat from the exhaust gas discharged from the boiler by using a heat recovery device in which a heat medium is circulated, and using the recovered heat as a heat source of a CO ₂ chemical absorption facility using an amine absorption liquid. Is done.

The invention according to claim 1 is an air preheater for heating combustion air with exhaust gas discharged from a combustion device including a boiler, and a heat recovery unit for recovering heat from the exhaust gas discharged from the air preheater with a heat medium. A dust collector that collects dust in the exhaust gas discharged from the heat recovery device, a wet flue gas desulfurization device that wet-treats the exhaust gas discharged from the dust collector, and the wet flue gas desulfurization device. A CO ₂ chemical absorption facility that absorbs and separates CO ₂ from the exhaust gas discharged by an amine absorbing liquid, and a smoke exhausting treatment device provided with a heat medium circuit between the heat recovery unit and the CO ₂ chemical absorption facility.

The invention according to claim 2 is provided with a reboiler for heating the amine absorbing solution and a reclaimer for regenerating the deteriorated amine absorbing solution in the CO ₂ chemical absorption facility, and the reboiler, the reclaimer and the heat recovery device The exhaust gas treatment apparatus according to claim 1, wherein a heating medium circulation path is provided between the reboiler and the reclaimer, and a heating steam introduction path is connected to the reboiler and the reclaimer in order to make up for the amount of heat that the reboiler and the reclaimer lack.

According to a third aspect of the present invention, the CO ₂ chemical absorption facility is provided with an amine absorption liquid regeneration tower that heats the amine absorption liquid used for CO ₂ absorption to separate and regenerate CO ₂ , and regenerates the amine absorption liquid. The smoke exhausting treatment apparatus according to claim 1, wherein the outer periphery of the tower is covered with a heat insulating material, a heat medium circulation path is provided between the heat insulating material and the heat recovery device, and the heat medium circulation path is connected.

  In the invention according to claim 4, a heat medium circulation path is provided between each of (a) the reboiler and the reclaimer, and (b) the heat insulating material on the outer periphery of the amine absorption liquid regeneration tower, and the heat recovery unit. The flue gas treatment apparatus according to claim 1, wherein the medium circulation path is provided with a switching valve capable of switching supply of the heat medium to any one of (a) the reboiler and the reclaimer and (b) the amine absorption liquid regeneration tower.

According to a fifth aspect of the present invention, combustion air is preheated with exhaust gas discharged from a combustion device including a boiler, supplied to the combustion device, and heat is recovered from the exhaust gas cooled by the preheating of the combustion air with a heat medium. A heat recovery device is provided to collect soot and dust in the exhaust gas discharged from the heat recovery device, the exhaust gas after dust collection is subjected to wet flue gas desulfurization treatment, and CO _{2 in} the exhaust gas subjected to wet exhaust gas desulfurization. at the CO ₂ chemical absorption equipment to absorb separated by amine absorbent is provided, the heat of CO ₂ recovery facility provided heat medium circulating passage is recovered in the heat recovery unit between the heat recovery unit and CO ₂ chemical absorption equipment It is a flue gas processing method used as a heat source of the amine absorption liquid.

The invention according to claim 6 uses the heat recovered from the heat recovery device as a heat source for heating the amine absorbing liquid in the reboiler and the reclaimer provided in the CO ₂ chemical absorption facility, and is insufficient for heating the amine absorbing liquid. The smoke exhausting method according to claim 5, wherein the amount of heat generated is supplemented with steam.

The invention described in claim 7 is the smoke processing method according to claim 5, wherein the heat recovered from the heat recovery unit is used as a heat source for heat retention in the regeneration tower provided in the CO ₂ chemical absorption facility.

The invention according to claim 8 uses the heat recovered from the heat recovery device as auxiliary heat at the start of the reboiler and reclaimer provided in the CO ₂ chemical absorption facility, and after the reboiler and reclaimer are started, It is a flue gas processing method of Claim 5 utilized as a heat source of heat retention.

(Function)
In the present invention, the heat of the exhaust gas is recovered by providing a heat recovery device upstream of the dust collector, the heat is transferred to the CO ₂ chemical absorption facility by the amine absorption liquid, and the heat source of the reboiler and the reclaimer and the heat retention of the regeneration tower By using a heat source or the like as a heat source necessary for regeneration of the amine absorbing liquid, it becomes possible to reduce the amount of heating steam necessary for the CO ₂ recovery facility, and to achieve a system with high thermal efficiency.

According to the first and fifth aspects of the present invention, it is possible to use the heat recovered from the exhaust gas in the CO ₂ recovery facility, so that the enormous heat energy required for CO ₂ recovery can be reduced. It is possible to effectively reduce operational costs.

According to the second and sixth aspects of the invention, in addition to the effects of the first and fifth aspects, the heat recovered from the exhaust gas by the heat recovery unit is used as a heat source for the reboiler and reclaimer of the CO ₂ chemical absorption facility. This enables the amount of heating steam required by the reboiler and reclaimer to be reduced.

According to the _{third and} seventh aspects of the invention, in addition to the effects of the first and fifth aspects, the heat recovered from the exhaust gas by the heat recovery unit is used as a heat source for the heat insulating material of the regeneration tower of the CO ₂ chemical absorption facility. Since it can be used, it is possible to reduce heat radiation from the regeneration tower and realize a CO ₂ recovery system with high thermal efficiency.

According to the inventions of claims 4 and 8, in addition to the effects of the inventions of claims 1 and 5, the heat recovered from the exhaust gas by the heat recovery device by switching to the circulation path of the heat medium is the reboiler and reclaimer's It is used for auxiliary heat at the start-up, and after the reboiler and reclaimer are started, the recovered heat can be used as a heat source for the heat insulating material of the regeneration tower, and the load due to the supply of heating steam at the start of the reboiler and reclaimer Since it is possible to reduce the heat radiation from the regeneration tower, it is possible to realize a CO ₂ recovery system with high thermal efficiency and capable of stable operation.

It is a block diagram of the flue gas processing system of the Example of this invention. It is a block diagram of a CO ₂ recovery facility in flue gas treating system of FIG. It is a block diagram of another embodiment of a CO ₂ recovery facility in flue gas treating system of FIG. It is a block diagram of another embodiment of a CO ₂ recovery facility in flue gas treating system of FIG. It is a block diagram of the conventional exhaust gas treatment system. It is a block diagram of a CO ₂ recovery facility according to the conventional amine absorption liquid (chemical absorption equipment).

  An embodiment of the flue gas treatment system of the present invention will be described below.

An embodiment of the smoke emission treatment system of the present invention is shown in FIG. The exhaust gas from the boiler 1 is introduced into the denitration device 2 and after removing nitrogen oxides, the combustion air used in the boiler 1 is heated by the exhaust gas in the air preheater 3. The exhaust gas discharged from the air preheater 3 is introduced into the heat recovery device 4, and heat is recovered by the heat medium circulating in the heat recovery device 4 and cooled. The dust in the exhaust gas discharged from the heat recovery unit 4 is collected by the dust collector 5, and the exhaust gas discharged from the dust collector 5 is pressurized by the induction fan 6 and introduced into the wet desulfurizer 7. In the wet desulfurization apparatus 7, the exhaust gas comes into contact with the sprayed calcium carbonate-containing slurry, so that sulfur oxides in the exhaust gas are removed from the exhaust gas. After that, the exhaust gas is pressurized by the blower 8 and the CO ₂ chemistry shown in FIG. After being sent to the absorption facility 9, CO ₂ in the exhaust gas is absorbed and removed by the amine absorbing solution, and the exhaust gas from which the CO ₂ has been removed is discharged into the atmosphere via the chimney 11 by the desulfurization fan 10.

In the above flue gas treatment system, the heat recovery unit 4 is provided with a heat medium circulation pipe 12 for circulating a heat medium between the CO ₂ chemical absorption equipment 9 and the heat medium is circulated by a heat medium circulation pump 13. configuration and has become, the heat recovered from the exhaust gas in the heat recovery unit 4 passes through the heat medium circulation line 12, is sent to the CO ₂ chemical absorption equipment 9, by utilizing as a heat source of CO ₂ chemical absorption equipment 9 in general, It becomes possible to reduce the amount of heating steam required in the CO ₂ chemical absorption equipment 9, and to reduce the operating cost. Further, the heat medium that has released heat in the CO ₂ chemical absorption equipment 9 is returned to the heat recovery unit 4 again.

FIG. 2 shows a CO ₂ chemical absorption facility 9 in the flue gas treatment system shown in FIG. The CO ₂ chemical absorption equipment 9 shown in FIG. 2 is provided with a heat medium circulation pipe 12 that circulates the heat medium recovered from the heat recovery device 4 shown in FIG. 1 in the CO ₂ chemical absorption equipment 9 shown in FIG. It is.
That is, the heat medium circulation pipe 12 is configured to supply the heat medium from the heat recovery device 4 to the reboiler 30 and the reclaimer 31 of the CO ₂ chemical absorption facility 9 and to circulate the heat medium to the heat recovery device 4 again. Yes.

Since the heat medium circulation line 12 is provided between the heat recovery device 4 and the reboiler 30 and the reclaimer 31 of the CO ₂ chemical absorption facility 9, the heat recovered from the exhaust gas by the heat recovery device 4 passes through the heat medium circulation line 12. Since it can be used as a heat source for the reboiler 30 and the reclaimer 31 of the CO ₂ chemical absorption facility 9 and a part of the amount of heat necessary for the reboiler 30 and the reclaimer 31 can be supplemented by the recovered heat of the exhaust gas, The amount of heating steam 32 required by the Kramer 31 can be reduced, and the operating cost of the CO ₂ chemical absorption facility 9 can be reduced.

FIG. 3 shows an embodiment in which the configuration of the CO ₂ chemical absorption equipment 9 in the smoke treatment system shown in FIG. 2 is modified. In the CO ₂ chemical absorption facility 9 of the present embodiment, the heat medium circulation pipe 12 for circulating the heat medium recovered from the heat recovery device 4 is used as the heat insulating material 33 that covers the outside of the regeneration tower 26 of the CO ₂ chemical absorption facility 9. Then, the heat medium is again circulated to the heat recovery unit 4.

Since the heat medium circulation line 12 is provided between the heat recovery unit 4 and the heat insulating material 33 of the regeneration tower 26 of the CO ₂ chemical absorption facility 9, the heat recovered from the exhaust gas by the heat recovery unit 4 is the heat medium circulation. Since it can be used as a heat source for the heat insulating material 33 of the regeneration tower 26 of the CO ₂ chemical absorption facility 9 through the line 12, heat radiation from the regeneration tower 26 is reduced, and a highly efficient CO ₂ recovery system is achieved. It can be realized.

FIG. 4 shows an embodiment in which the configuration of the CO ₂ chemical absorption facility 9 in the smoke treatment system shown in FIG. 2 is modified. 1 is passed through the reboiler 30 and the reclaimer 31 of the CO ₂ chemical absorption equipment 9 and the heat insulating material 33 of the regeneration tower 26, and the heat medium circulation pipe 12 for circulating the heat medium recovered from the heat recovery device 4 shown in FIG. A heat medium is circulated to the heat recovery unit 4. A switching valve 34 is installed in the heat medium circulation pipe 12 so that supply to the reboiler 30 and the reclaimer 31 or supply to the heat insulating material 33 covering the outside of the regeneration tower 26 can be performed.

A heat medium circulation line 12 is provided between the heat recovery device 4, the reboiler 30 and the reclaimer 31 of the CO ₂ chemical absorption equipment 9, and the heat insulating material 33 of the regeneration tower 26. Since the valve 34 is installed, the heat recovered from the exhaust gas by the heat recovery device 4 passes through the heat medium circulation line 12 and is used for assisting the startup of the reboiler 30 and the reclaimer 31 of the CO ₂ chemical absorption equipment 9. After the reboiler 30 and the reclaimer 31 are activated, the recovered heat is used as a heat source for the heat insulating material 33 of the regeneration tower 26 by operating the switching valve 34, so that the heating steam 32 when the reboiler 30 and the reclaimer 31 are activated is activated. to reduce the load by the supply, since it is possible to further reduce the heat radiation from the regenerator 26, heat efficiency is high and stable operation is possible CO ₂ recovery It is possible to realize a stem.

1 boiler 2 denitration apparatus 3 air preheater 4 heat recovery unit 5 dust collecting device 6 induction fan 7 wet desulfurization apparatus 8 blower 9 CO ₂ chemical absorption equipment 10 desulfurization fan 11 chimney 12 heat medium circulation line 13 heat medium circulation pump 18 reheated Equipment 25 Absorption tower 25n Nozzle 25b Absorption packed bed 25a Washing packed bed 26 Regeneration tower 26a Upper packed bed 26b Lower packed bed 26c Gas-liquid dispersion plate 27 De-CO ₂ gas 28, 40 Pump 29 CO ₂ gas 30 Reboiler 31 Reclaimer 32 Steam 33 Insulating material 34 Switching valve 40 Pump 41 Heat exchanger 43 Heat exchanger 44 Pump 46 Heat exchanger 47 Separator 49 Pump

Claims (8)

An air preheater that heats combustion air using exhaust gas discharged from a combustion device including a boiler;
A heat recovery device for recovering heat from the exhaust gas discharged from the air preheater with a heat medium;
A dust collector that collects dust in the exhaust gas discharged from the heat recovery device, a wet flue gas desulfurization device that wet-treats the exhaust gas discharged from the dust collector,
A CO ₂ chemical absorption facility that absorbs and separates CO ₂ from the exhaust gas discharged from the wet flue gas desulfurization apparatus with an amine absorbing solution;
A flue gas treatment apparatus, wherein a heat medium circulation path is provided between the heat recovery unit and the CO ₂ chemical absorption facility. The CO ₂ chemical absorption equipment is provided with a reboiler for heating the amine absorbing liquid and a reclaimer for regenerating the deteriorated amine absorbing liquid, and a heat medium circuit between the reboiler and the reclaimer and the heat recovery unit. The flue gas treatment apparatus according to claim 1, wherein a heating steam introduction path is connected to the reboiler and the reclaimer in order to compensate for a shortage of heat in the reboiler and the reclaimer. The CO ₂ chemical absorption facility is provided with an amine absorption liquid regeneration tower that heats the amine absorption liquid used for CO ₂ absorption to separate and regenerate CO ₂ , and the outer periphery of the amine absorption liquid regeneration tower is covered with a heat insulating material. 2. A smoke exhausting apparatus according to claim 1, wherein a heat medium circulation path is provided between the heat insulating material and the heat recovery unit, and the heat medium circulation path is connected.   (A) A reboiler and a reclaimer, and (b) a heat medium circulation path are provided between both of the heat retaining material on the outer periphery of the amine absorption liquid regeneration tower and the heat recovery unit, and the heat medium circulation path includes (a) The flue gas treatment apparatus according to claim 1, further comprising a switching valve capable of switching the supply of the heat medium to any of the reboiler and the reclaimer and (b) the amine absorbing liquid regeneration tower. A heat recovery device is provided that preheats combustion air with exhaust gas discharged from a combustion device including a boiler and supplies the combustion air to the combustion device, and recovers heat from the exhaust gas cooled by the preheating of the combustion air with a heat medium. Collecting soot and dust in exhaust gas discharged from the collector, subjecting the exhaust gas after dust collection to wet flue gas desulfurization, and absorbing and separating CO ₂ in the exhaust gas exhausted by wet exhaust gas using an amine absorbent A CO ₂ chemical absorption facility is provided, and a heat medium circulation path is provided between the heat recovery device and the CO ₂ chemical absorption facility, and the heat recovered by the heat recovery device is used as a heat source for the amine absorption liquid in the CO ₂ recovery facility. A method for treating flue gas. The heat recovered from the heat recovery unit is used as a heat source for heating the amine absorption liquid in the reboiler and reclaimer installed in the CO ₂ chemical absorption facility, and the amount of heat insufficient for heating the amine absorption liquid is supplemented with steam. 6. The method for treating smoke emission according to claim 5, wherein 6. The method according to claim 5, wherein the heat recovered from the heat recovery unit is used as a heat source for heat retention in the regeneration tower provided in the CO ₂ chemical absorption facility. Use the heat recovered from the heat recovery unit as auxiliary heat at the start-up of the reboiler and reclaimer installed in the CO ₂ chemical absorption facility, and use it as a heat source to keep the regeneration tower warm after the reboiler and reclaimer are started up. 6. The method for treating smoke emission according to claim 5, wherein

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