WO2011132660A1

WO2011132660A1 - Exhaust gas treatment system having carbon dioxide removal device

Info

Publication number: WO2011132660A1
Application number: PCT/JP2011/059599
Authority: WO
Inventors: 島村　潤; 祥悟盛; 斎藤　隆行; 尾田　直己; 一彦梶川
Original assignee: バブコック日立株式会社
Priority date: 2010-04-20
Filing date: 2011-04-19
Publication date: 2011-10-27
Also published as: JP2011240321A

Abstract

The disclosed exhaust gas treatment system having a CO₂ removal device maintains the steam balance of the entire generator system by adopting a new device and method for boiler steam cooling in the CO₂ removal device, and improves the efficiency of the CO₂ removal device, and thus of the entire generator system, by means of the efficient use of boiler heat. The disclosed exhaust gas treatment system is provided with a CO₂ absorption tower which brings an amine absorption solution into contact with the exhaust gas containing CO₂ emitted from a boiler; an absorption solution regeneration tower which heats the absorption solution which has absorbed said CO₂, and detaches the CO₂; an absorption solution circulation passage which removes the CO₂-detached absorption solution via a regeneration tower removal pipe, and, after cooling with a heat exchanger and a cooler, cycles said solution to the CO₂ absorption tower; and a reboiler which, after removing a portion of the aforementioned CO₂-detached absorption solution and raising the temperature, returns the same to the aforementioned regeneration tower. The disclosed system is further provided with a heat exchanger tube for cycling inside the condensate drum the amine absorption solution removed from the aforementioned CO₂ absorption tower as a coolant, and a flow control valve for the absorption solution flowing through said heat exchanger tube.

Description

Exhaust gas treatment system having carbon dioxide removal device

The present invention relates to an exhaust gas treatment system having a carbon dioxide removal device, and more particularly to an exhaust gas treatment system that removes carbon dioxide in combustion exhaust gas using an aqueous solution of amines as an absorbent of carbon dioxide.

In recent years, thermal power generation facilities and boiler facilities use a large amount of coal, heavy oil, etc. as fuel, and from the viewpoint of air pollution and global warming, a large amount of carbon dioxide (hereinafter referred to as CO ₂ ) has been released into the atmosphere. There is a problem, and CO ₂ emission control is being studied worldwide. As one of CO ₂ separation and recovery techniques, a chemical absorption method in which CO ₂ is absorbed and removed using an aqueous solution of an amine such as alkanolamine (hereinafter referred to as an amine absorbing solution) is widely known.
An example of conventional CO ₂ removal equipment is shown in FIG. The de-CO ₂ facility consists of a denitration device 2, an air heater 3, an electrostatic precipitator 4, a wet desulfurization device 5, a press clubber 10, a CO ₂ absorption tower 20, and a regeneration unit that are sequentially provided along the exhaust gas flow path from the boiler 1. It is composed of a tower 40 and a reboiler 60. The exhaust gas generated by burning coal, etc., in the boiler 1 is introduced into the denitration device 2, and after NOx (nitrogen oxide) contained in the gas is decomposed and removed, the temperature is adjusted to 200 to 160 ° C by the air heater 3. After that, dust is removed by the electrostatic precipitator 4, and after removing SO ₂ by the wet desulfurizer 5, high-efficiency desulfurization is performed by the press clubber 10 so that the remaining SO ₂ has a concentration of 1 ppm or less in the gas. . The press clubber is composed of an absorbent 11 to be supplied into the system, a circulation pump 14 for circulating the absorbent, a cooler 15 for cooling the circulating absorbent, and a spray section 16 for spraying the absorbent in countercurrent contact with the exhaust gas. It is configured. The SO ₂ contained in the exhaust gas from the wet desulfurizer outlet is contained in an amount of about 40 ppm to 80 ppm, but the press clubber removed SO ₂ that is a deterioration factor of the amine absorption liquid as much as possible (about 1 to several ppm at the press clubber outlet). Thereafter, it is introduced into the absorption tower 20 as the outlet gas 18. The absorption tower 20 has a packed bed 21 that absorbs CO ₂ in the exhaust gas into the amine absorption liquid, an absorbent spray portion 22 provided above it, and the temperature rises due to exothermic reaction by absorbing the CO ₂ in the exhaust gas. Rinsing unit 24 for cooling and washing the de-CO ₂ gas 23, washing spray unit 25, washing water reservoir 27 for storing the washed water, cooler 28 for cooling the circulating washing water, and circulating the washing water Mainly composed of a flush pump 29. In addition, a demister 26 is installed in the upper part of the washing unit, and the mist of the absorbing solution that has passed through the washing unit is removed. The process gas 37 discharged from the absorption tower outlet is introduced into a chimney inlet duct for discharge from a chimney (not shown).

The amine absorbing liquid that has absorbed CO ₂ is sent from the liquid reservoir at the bottom of the absorption tower 20 through the absorption tower extraction pump 33 through the regeneration tower liquid supply pipe 35 and sent to the regeneration tower 40 to be packed in the middle of the regeneration tower 41. When the absorbing liquid sprayed from the spray part 42 comes into gas-liquid contact with the vapor rising from the lower part in the upper part of the gas, CO ₂ contained in the amine absorbing liquid is degassed. Next, the degassed CO ₂ gas is entrained in the gas by the water washing section 43, and the mist that has passed through the water washing section is collected by the demister 45, and is discharged as CO ₂ gas 46 from the upper part of the regeneration tower. The CO ₂ gas is cooled by a cooler 47 and separated into gas and condensed water by a CO ₂ separator 48. The CO ₂ gas is introduced into a CO ₂ liquefaction facility (not shown), and the condensed water is drained. It is supplied to the washing spray section 44 by the pump 50. On the other hand, the amine liquid from which CO ₂ has been degassed is stored in the regeneration tower liquid reservoir 51 and then sent to the reboiler 60 through the reboiler liquid supply pipe 52. Inside the reboiler 60, heat transfer pipes and the like are installed. The amine solution is indirectly heated by the steam 62 supplied by the steam supply pipe 61, so that the steam generated inside the reboiler 60 passes through the steam supply pipe 65. Then, it is supplied to the regeneration tower 40. Further, the absorption liquid extracted from the liquid reservoir at the lower part of the regeneration tower passes through the regeneration tower liquid extraction pipe 66, is cooled by the heat exchanger 34 and the cooler 31, and is then introduced into the absorption tower 20. The steam 62 used in the reboiler 60 becomes steam drain in the heat transfer tube, is discharged to the condensed water drum 67, is mixed with the spray cooling water 68, and is sufficiently cooled to less than 100 ° C. The steam drain 71 that is free from the risk of flushing in the return pipe is returned to the boiler 1 by the condensed water pump 69.

In the above prior art, in order to cool the drain of the steam 62 described above in the condensate water drum 67, the spray cooling water 68 equivalent to the amount of steam is required. Specifically, the amount of spray cooling water 68 at about 30 ° C. required for cooling 1 t / h of steam 62 at about 140 ° C. to 85 to 90 ° C. is as follows.
(140 kcal / kg -85 kcal / kg) / (85 kcal / kg-30 kcal / kg) x 1 = 1 t / h
Therefore, in order to maintain the steam balance in the entire power generation system, a part of the cooled steam drain had to be discarded, and no consideration was given to the efficient use of boiler water and heat. Therefore, the wastewater treatment facility has to be enlarged and the boiler heat must be discarded together with the waste water.

An object of the present invention is to maintain a steam balance of the entire power generation system by adopting a new equipment and method for boiler steam cooling in a CO ₂ removal equipment, and to efficiently use boiler heat, thereby reducing CO _2. The purpose is to improve the efficiency of the removal equipment and thus the entire power generation system.

In order to achieve the above object, the present inventor uses the amine absorption liquid supplied to the regeneration tower 40 as a refrigerant without using the spray cooling water 68 to cool the drain of the condensed water drum 67, and generates power. We thought about maintaining the vapor balance of the entire system. Further, in the above system, in consideration of the temperature of the amine absorbing liquid at the outlet of the heat exchanger 34 rising, the condenser of the steam turbine equipment attached to the boiler 1 as the cooling water of the cooler 31 of the regeneration tower extraction pipe 66 By using the boiler water at the outlet, the problem of heat recovery of the heat exchanger 34 was also solved. That is, the invention claimed in the present application is as follows.
(1) heating the CO ₂ absorption tower for carbon dioxide (CO ₂₎ and the exhaust gas is contacted with the amine absorbing solution containing absorbed CO ₂ contained in exhaust gas discharged from the boiler, the absorption liquid which has absorbed the CO ₂ After the CO ₂ is released and the absorption liquid is regenerated, the absorption liquid after the CO ₂ separation is extracted through the regeneration tower extraction pipe, and cooled by a heat exchanger and a cooler provided in the middle. A recirculator that circulates to the CO ₂ absorption tower, and a reboiler that draws a part of the absorption liquid after the CO ₂ separation and raises the temperature and then returns to the regeneration tower. An exhaust gas treatment system having a heat transfer tube to which steam is supplied and a condensed water drum for condensing the steam discharged from the heat transfer tube and recovering it as a steam drain, the amine absorption extracted from the CO ₂ absorption tower A heat transfer tube for circulating a liquid as a refrigerant in the condensed water drum, An exhaust gas treatment system provided with a flow rate adjustment valve for absorbing liquid passing through a heat transfer tube.
(2) A bypass pipe connecting the upstream side and the downstream side of the heat exchanger provided in the middle of the regeneration tower extraction pipe is provided, and the flow rate of the amine absorbing liquid circulated to the absorption tower in the bypass pipe The system according to (1), wherein a flow control valve for adjusting the flow rate is provided.
(3) The boiler has steam turbine equipment and its condenser, and uses boiler water at the outlet of the condenser as a refrigerant for a cooler that cools the absorption liquid circulating in the CO ₂ absorption tower. The system according to (1) or (2), which is characterized.

According to the present invention, the steam balance of the power generation system including the CO ₂ removal facility can be maintained and can be stably operated, and the amine absorption discharged from the absorption tower to the refrigerant that cools the steam drain used in the reboiler. By using the liquid, the sensible heat of the amine absorption liquid in the regeneration tower can be increased, and the amount of steam supplied to the CO ₂ removal facility can be reduced. In addition to the configuration that uses the amine absorption liquid discharged from the absorption tower as a refrigerant for the vapor drain used in the reboiler of the de-CO ₂ facility, in the cooling water of the amine absorption liquid supplied from the regeneration tower to the absorption tower, By using the boiler water at the condenser outlet, the cooling water for cooling the amine absorption liquid becomes unnecessary, and at the same time the temperature of the feed water supplied to the boiler can be raised, so that the turbine output can be improved. Can be planned.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of an exhaust gas treatment system including a CO ₂ removal facility according to an embodiment of the present invention. Explanatory drawing of the waste gas processing system which shows the 2nd Example of this invention. Explanatory drawing of an exhaust gas treatment system including conventional CO ₂ removal equipment.

FIG. 1 is an explanatory diagram of an exhaust gas treatment system including a CO ₂ removal facility showing an embodiment of the present invention. This system consists of a denitration device 2, an air heater 3, an electrostatic precipitator 4, a wet desulfurization device 5, a press clubber 10, a CO ₂ absorption tower 20, and a CO ₂ absorption tower, which are sequentially installed along the exhaust gas flow path of the boiler 1. It mainly comprises a regeneration tower 40 that desorbs absorbed CO ₂ and regenerates the amine absorption liquid, and a reboiler 60 attached to the regeneration tower 40. Exhaust gas generated by burning coal or the like in the boiler 1 is introduced into the denitration device 2, and NOx (nitrogen oxide) contained in the gas is decomposed and removed. The temperature of the gas discharged from the denitration device 2 is adjusted to 200 to 160 ° C. by the air heater 3 and then the dust is removed by the electric dust collector 4. Dust gas is supplied to the wet desulfurization system 5 SO ₂ is removed, after removed as much as possible the remaining SO ₂ in the press scrubber 10, is introduced into the CO ₂ absorber 20.

The press clubber 10 is contained in the exhaust gas at the outlet of the wet desulfurization unit about 40ppm to 80ppm, and removes SO ₂ that causes deterioration of the amine absorption liquid as much as possible to about 1 to several ppm at the outlet of the press clubber. The absorption liquid 11 supplied to the refrigerant, the circulation pump 14 that circulates the absorption liquid, the cooler 15 that cools the absorption liquid that circulates, and the spray unit 16 that sprays the absorption liquid so as to make countercurrent contact with the exhaust gas. The
The inside of the absorption tower 20 generates heat when the CO ₂ in the exhaust gas is absorbed by the absorbing liquid, the packed bed 21 that absorbs the CO ₂ in the exhaust gas into the amine absorption liquid, the absorption liquid spray part 22 that sprays the absorption liquid, and the absorption liquid. The CO ₂ gas 23 whose temperature has risen due to the reaction is cooled and washed with water, and the water washing part 24 and the water washing spray part 25 for washing the amine absorbing liquid entrained in the exhaust gas, and the water washing water reservoir part 27 for collecting the water washed with water The cooler 28 cools the circulating flush water and the flush pump 29 circulates the flush water. Further, a demister 26 is installed on the upper part of the washing spray part, and the mist of the absorbing liquid that has passed through the washing part 24 is removed. The processing gas 37 discharged from the top of the absorption tower 20 is discharged out of the system from a chimney not shown in the figure.

The amine absorption liquid that has absorbed CO ₂ is extracted from the liquid reservoir at the bottom of the absorption tower 20 by the absorption tower extraction pump 33, and part of the condensed water is condensed by the branched heat transfer tube 70 before entering the heat exchanger 34. The heat is exchanged with the drain of the steam 62 through the heat transfer tube 70 after being sent to the drum 67 and then returned to the original pipe through the return heat transfer tube 70. The amine absorption liquid flow rate sent to the condensed water drum 67 is controlled by the flow rate adjusting valve 72 in order to control the temperature of the condensed water drum outlet drain 71. Next, the amine absorption liquid is joined from the heat transfer tube 70 to the regeneration tower liquid supply pipe 35, then passes through the heat exchanger 34, is introduced into the regeneration tower 40, and is sprayed from the spray section 42 above the packed bed 41, and the packed bed 41 CO ₂ contained in the amine absorbing liquid is degassed by coming into gas-liquid contact with the vapor rising from the lower part of the gas. Next, the degassed CO ₂ gas is entrained in the gas by the water washing section 43, and the mist containing amine that has passed through the water washing section is collected by the demister 45, and is discharged as CO ₂ gas 46 from the upper part of the regeneration tower. The CO ₂ gas is cooled by a cooler 47 and separated into gas and condensed water by a CO ₂ separator 48. The CO ₂ gas is introduced into a CO ₂ liquefaction facility (not shown), and the condensed water is drained. It is supplied to the washing spray section 44 by the pump 50. On the other hand, the amine absorption liquid from which CO ₂ has been degassed is stored in the regeneration tower liquid reservoir 51 and then sent to the reboiler 60 through the reboiler liquid supply pipe 52. In the reboiler 60, a steam supply pipe 61 is arranged as a heat transfer pipe. After the amine absorbing liquid is indirectly heated by the steam passing through the reboiler 60, it is returned from the reboiler 60 to the regeneration tower 40. Further, the absorption liquid extracted from the liquid reservoir at the lower part of the regeneration tower 40 passes through the regeneration tower liquid extraction pipe 66, is cooled by the heat exchanger 34 and the cooler 31, and is then introduced into the absorption tower 20.

The steam 62 of the heat transfer tube in the reboiler 60 becomes steam drain and is discharged to the condensed water drum 67. Therefore, the steam drain is sufficiently cooled to less than 100 ° C. by exchanging heat with the amine absorbing liquid passing through the heat transfer tube 70. After cooling, the outlet drain 71 of the condensed water drum, which is free from the risk of flushing, is returned to the boiler 1 by a condensed water pump 69 through a return pipe (not shown).
The flow rate of the absorption liquid in the heat transfer tube 70 can be adjusted by the amine flow rate adjustment valve A72 and the amine flow rate adjustment valve B73. For example, the temperature of the condensed water drum outlet drain 71 is detected by a thermometer (not shown), The flow

rate control valves

72 and 73 can be adjusted so as to reach a predetermined temperature. In this way, the inlet pipe of the heat exchanger 34 is branched into a heat transfer pipe 70, and the heat transfer pipe 70 is used as a heat exchange pipe with the drain water of the condensed water drum 67 of the regeneration tower 40, and then the original heat exchanger. By using the return pipe returning to the inlet of 34, the temperature of the amine absorbing liquid introduced into the regeneration tower 40 can be increased, and the amount of steam supplied to the regeneration tower can be reduced.

According to the above embodiment, the heat transfer pipe 70 is installed in the condensate water drum 67, and the amine absorption liquid is passed as a refrigerant in the condensate water drum 67, thereby cooling the drain of the steam 62 without the spray cooling water 68 (FIG. 3). Thus eliminating the need to dispose of steam drains. Further, the use of an absorption liquid of the amine discharged from the absorption tower 20 (absorption tower extraction pump 33) as a refrigerant can contribute to an increase in the temperature of the amine absorption solution in the regeneration tower 40. This also reduces the amount of heat supplied from the reboiler 60, leading to a reduction in the amount of heat in the entire CO ₂ absorption system. Specifically, the steam absorption of about 60 to 60 ° C. discharged from the absorption tower 20 (absorption tower extraction pump 33) is cooled to about 85 to 90 ° C. Thus, the spray cooling water 68 can be reduced to 0, and the recovered heat can be supplied to the regeneration tower 40.

In the present invention described above, stable operation is possible by maintaining the vapor balance of the entire power generation system. However, since the temperature of the amine absorbent at the outlet of the heat exchanger 34 rises, the heat exchanger and its cooling There was a problem that the amount of water increased. On the other hand, as an inevitable problem in the installation of such a de-CO ₂ equipment, there is reduction in plant efficiency due to bleeding of a large amount of steam, and an increase in the power required by the de-CO ₂ equipment, such as in the turbine equipment was attached to the boiler , therefore, after the introduction of the de CO ₂ facility, it is desirable to close as possible to plant efficiency installed in the previous levels.

FIG. 2 is an explanatory view of an exhaust gas treatment system showing a second embodiment of the present invention adapted to such a demand. 1 is different from the system of FIG. 1 in that a bypass pipe and a bypass valve 68 are provided to connect the upstream side and the downstream side of the heat exchanger 34 provided in the middle of the extraction pipe 66 of the regeneration tower 40. As the cooling water of the cooler 31 provided in the amine liquid return pipe 66 to the absorption tower 20, the flow rate of the regenerative amine liquid (lean amine liquid) flowing through is controlled to adjust the heat exchange amount. This is because the outlet boiler water 32 of the condenser 82 of the turbine equipment attached to the boiler 1 is used. This turbine equipment includes a steam turbine 81 and a generator 90 connected to the boiler 1, a condenser 82, a condensate pump 83, a low-pressure feed water heater 84, as shown in a broken-line frame in FIG. 2. And the outlet boiler water of the condenser 82 is indicated by reference numeral 32. Note that 85 is seawater, 86 and 87 are extracted steam, 88 is condensate, and 89 is water supply. As described above, by using the boiler water 32 at the outlet of the condenser 82 of the boiler 1 as the cooling water in the cooler 31, no new water for the cooler 31 is required. At the same time, since the amine liquid temperature at the inlet of the cooler 31 is high, the temperature of the boiler water can be raised, and the turbine output can be improved.

Specifically, by controlling the flow rate of the amine absorbent flowing into the heat exchanger 34 and adjusting the amount of exchange heat, the amine absorbent supplied to the regeneration tower 20 can flow down in a stable state. The temperature can be controlled to 100 ° C or lower. In addition, boiler water 32 having a temperature of about 35 ° C. at the outlet of the condenser 82 is used as cooling water for the cooler 31, and the boiler water 32 whose temperature has risen in the cooler 31 has a feed water temperature of 50 to 60 ° C. in the low-pressure feed water heater 84. It is returned to the place where it becomes and is supplied to the boiler. Specifically, the temperature rise of the cooling water in the cooler 31 of FIG. 1 was 5 ° C. (35 ° C. → 40 ° C.), but in this embodiment of FIG. Therefore, since this temperature rise can be used as the temperature rise of boiler feed water, an improvement in turbine output can be expected.

DESCRIPTION OF SYMBOLS 1 ... Boiler, 20 ... Absorption tower, 40 ... Regeneration tower, 60 ... Reboiler, 61 ... Steam supply piping, 62 ... Steam, 64 ... Reboiler liquid extraction piping, 65 ... Steam supply piping, 66 ... Regeneration tower liquid extraction piping, 67 ... Condensate water drum, 70 ... Heat transfer tube, 71 ... Condensate water drum drain, 72 ... Amine flow rate adjustment valve A, 73 ... Amine flow rate adjustment valve B

Claims

And the CO 2 absorber to carbon dioxide exhaust gas containing (CO 2) is contacted with an amine absorption liquid absorbs CO 2 in the exhaust gas discharged from the boiler to heat the absorbing liquid that has absorbed the CO 2 CO 2 And a regeneration tower for regenerating the absorption liquid, and the absorption liquid after the separation of CO 2 is extracted through a regeneration tower extraction pipe and cooled with a heat exchanger and a cooler provided in the middle, and then CO 2 An absorption liquid circulation path that circulates to the absorption tower, and a reboiler that draws a part of the absorption liquid after the CO 2 separation and raises the temperature, and then returns to the regeneration tower. The reboiler is supplied with heating steam. An exhaust gas treatment system having a heat transfer tube and a condensed water drum that condenses the steam discharged from the heat transfer tube and collects it as a steam drain, wherein the amine absorption liquid extracted from the CO 2 absorption tower is used as a refrigerant. A heat transfer tube to be circulated in the condensed water drum, and the heat transfer tube An exhaust gas treatment system, characterized in that a flow rate adjustment valve for absorbing liquid passing through is provided.
A bypass pipe connecting the upstream side and the downstream side of the heat exchanger provided in the middle of the regeneration tower extraction pipe is provided, and the flow rate of the amine absorbing liquid circulated to the absorption tower is adjusted in the bypass pipe. The system according to claim 1, further comprising a flow control valve.
The boiler has steam turbine equipment and its condenser, and uses boiler water at the outlet of the condenser as a refrigerant for a cooler that cools the absorption liquid circulating to the CO 2 absorption tower. The system according to claim 1 or 2.