JP2008023438A - Carbon dioxide recovery system and carbon dioxide recovery method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon dioxide recovery system capable of improving a system efficiency by regenerating an absorption liquid by utilizing steam led out from a steam turbine as a carrier gas for carbon dioxide radiated from the absorption liquid, and a carbon dioxide recovery method. <P>SOLUTION: The carbon dioxide recovery system comprises: the steam turbine 170; an absorption tower 100 making an exhaust gas 103 into gas/liquid contact with a lean absorption liquid 151; a regeneration tower 110 making a rich absorption liquid 152 absorbed with carbon dioxide into gas gas/liquid contact with steam 120 extracted from the steam turbine 170 to radiate carbon dioxide and regenerate the lean absorption liquid 151; a rich absorption liquid line 130 for leading the rich absorption liquid 152 to the regeneration tower 110 from the absorption tower 100; a lean absorption liquid line 131 for leading the lean absorption liquid 151 to the absorption tower 100 from the regeneration tower 110; and a steam supply line 171 for leading the steam 120 to the regeneration tower 110 from the steam turbine 170. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a carbon dioxide recovery system and a carbon dioxide recovery method for recovering carbon dioxide contained in combustion exhaust gas from a boiler in a thermal power plant.

  In recent years, the problem of global warming due to the greenhouse effect of carbon dioxide, which is a combustion product of fossil fuel, has been increasing. In the Kyoto Protocol of the United Nations Framework Convention on Climate Change, Japan's goal of reducing greenhouse gas emissions is to achieve the 1990 ratio of minus 6% between 2008 and 2012.

  Against this background, a system that recovers carbon dioxide by using, for example, an aqueous solution of potassium carbonate, which is a carbonate, as an absorbent, is proposed for carbon dioxide discharged from thermal power plants, municipal waste incinerators, etc. (See, for example, Non-Patent Document 1).

  Here, a conventional carbon dioxide recovery system 200 will be described with reference to FIG.

  FIG. 2 is a diagram showing an outline of a conventional carbon dioxide recovery system 200. This conventional carbon dioxide recovery system 200 is a system that recovers carbon dioxide using an aqueous potassium carbonate solution to which piperazine is added as an absorbent.

  As shown in FIG. 2, exhaust gas 201 discharged by burning fossil fuel is guided to an absorption tower 203 by a gas blower 202. A lean absorbing liquid 204 is supplied to the upper portion of the absorption tower 203, and the lean absorbing liquid 204 is in gas-liquid contact with the exhaust gas 201 introduced into the absorption tower 203 and absorbs carbon dioxide in the exhaust gas 201. On the other hand, the remaining exhaust gas 201 having carbon dioxide absorbed by the lean absorbent 204 is discharged from the upper part of the absorption tower 203 to the atmosphere. Here, the lean absorbent 204 is supplied to the absorption tower 203 at a temperature of 40 to 46 ° C., and the inside of the absorption tower 203 has an absolute pressure of about 100 kPa.

  The rich absorbent 205 that has absorbed carbon dioxide is extracted from the lower part of the absorption tower 203 and guided to the regeneration tower 207 by a pump 206. The rich absorbing liquid 205 guided to the regeneration tower 207 is heated to a temperature of 46 ° C. to 60 ° C. or more by the steam 209 of the heater 208 and is disturbed at an absolute pressure of 16 kPa. Then, carbon dioxide is dissipated from the rich absorbent 205 and regenerated to the lean absorbent 204 that can absorb carbon dioxide again. The regenerated lean absorbing liquid 204 is returned to the upper part of the absorption tower 203 via the cooler 211 by the circulation pump 210. On the other hand, the carbon dioxide diffused from the rich absorbing liquid 205 is guided to the vacuuming device 212 together with the steam 209 and further to the separator 213 to be separated from the steam 209 and collected. Here, the vacuuming device 212 includes a condenser for condensing and removing a part of the steam 209.

In the conventional carbon dioxide recovery system 200 configured as described above, in order to recover carbon dioxide, the rich absorbent 205 is heated in the regeneration tower 207 to a temperature of 46 ° C. to 60 ° C. Must be evacuated to an absolute pressure of 16 kPa.
J. Tim Cullinane and Gary T. Rochelle, “Carbon Dioxide Absorption with Aqueous Potassium Carbonate Promoted by Piperazine”, Greenhouse Gas Control Technologies II, J. Gale and Y. Kaya (Eds.), P1603-1606 (2003)

  In the above-described conventional carbon dioxide recovery system, the rich absorbing liquid is heated to a temperature of 46 ° C. to 60 ° C. or higher in the regeneration tower, so that a large amount of heat energy is consumed.

  Accordingly, the present invention has been made to solve the above-described problem, and the carrier gas of carbon dioxide diffused from the absorbing liquid is not used as a heating source for heating the absorbing liquid, instead of the water vapor derived from the steam turbine. It is an object of the present invention to provide a carbon dioxide recovery system and a carbon dioxide recovery method capable of significantly reducing the consumption of heat energy and improving the system efficiency by regenerating the absorbing liquid.

  In order to achieve the above object, a carbon dioxide recovery system according to the present invention is a carbon dioxide recovery system that includes a steam turbine and recovers carbon dioxide in exhaust gas, the exhaust gas inlet, the lean absorbent inlet, and the remaining Carbon dioxide in the exhaust gas, comprising a gas discharge port and a rich absorption liquid discharge port, and bringing the exhaust gas introduced from the gas introduction port into gas-liquid contact with the lean absorption liquid introduced from the lean absorption liquid introduction port And an absorbent device that absorbs the lean absorbent into the rich absorbent, a rich absorbent inlet, a lean absorbent outlet, an exhaust outlet, and a water vapor inlet, and introduced from the rich absorbent inlet. The rich absorbent is brought into gas-liquid contact with the steam derived from the steam turbine introduced from the steam inlet, so that the carbon dioxide is produced from the rich absorbent. A regenerator that diffuses into the water vapor, regenerates the rich absorbent to the lean absorbent, and discharges the water vapor mixed with the carbon dioxide from the exhaust outlet, and exhausts from the rich absorbent outlet of the absorber. A rich absorbing liquid line that guides the rich absorbing liquid to the rich absorbing liquid inlet of the regenerator and the lean absorbing liquid discharged from the lean absorbing liquid outlet of the regenerator to the lean absorbing liquid inlet of the absorber It is characterized by comprising a lean absorbing liquid line for guiding and a steam supply line for guiding the steam derived from the steam turbine to the steam inlet of the regenerator.

  According to this carbon dioxide recovery system, in the regenerator, the water vapor derived from the steam turbine is used as a carrier gas for carbon dioxide released from the absorption liquid rather than as a heating source for heating the absorption liquid. Can be played. Thereby, the consumption of heat energy can be significantly reduced, and the system efficiency can be improved.

  In the carbon dioxide recovery method of the present invention, the exhaust gas and the lean absorbing liquid are guided into an absorption device, and the exhaust gas and the lean absorbing liquid are brought into gas-liquid contact so that the lean absorbing liquid absorbs carbon dioxide in the exhaust gas. The rich absorption liquid that absorbs the carbon dioxide, and the water vapor derived from the steam turbine are led to the regenerator, and the rich absorbent liquid and the water vapor at substantially the same temperature are brought into gas-liquid contact. A regeneration step of releasing the carbon dioxide from the rich absorption liquid into the water vapor to regenerate the rich absorption liquid into the lean absorption liquid; and suctioning the water vapor mixed with the carbon dioxide from the regenerator; And a vacuum drawing step for evacuating the inside.

  According to this carbon dioxide recovery method, in the regeneration process, the water vapor derived from the steam turbine is used not as a heating source for heating the absorption liquid but as a carrier gas for carbon dioxide released from the absorption liquid. Can be played. Thereby, the consumption of heat energy can be significantly reduced, and the system efficiency can be improved.

  According to the carbon dioxide recovery system and the carbon dioxide recovery method of the present invention, water vapor derived from the steam turbine is used as a carrier gas for carbon dioxide released from the absorption liquid, not as a heating source for heating the absorption liquid. By regenerating the absorbent, the consumption of heat energy can be greatly reduced and the system efficiency can be improved.

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

(First embodiment)
FIG. 1 is a diagram showing an overview of a carbon dioxide recovery system 10 according to a first embodiment of this invention.

  The carbon dioxide recovery system 10 includes a steam turbine 170 from which low-temperature and low-pressure steam 120 is extracted, an absorption tower 100 that brings the introduced exhaust gas 103 and lean absorbent 151 into gas-liquid contact, and steam extracted from the steam turbine 170. 120, a regeneration tower 110 that regenerates the lean absorbent 151 by dissipating carbon dioxide from the rich absorbent 152 that has absorbed carbon dioxide, and a rich absorbent 152 that is discharged from the absorbent outlet 101 of the absorber 100. A rich absorbent line 130 that leads to the absorbent inlet 111 of the regeneration tower 110 and a lean absorbent that guides the lean absorbent 151 discharged from the absorbent outlet 112 of the regeneration tower 110 to the absorbent inlet 102 of the absorber 100. The steam 120 extracted from the line 131 and the steam turbine 170 is supplied to the steam inlet 121 of the regeneration tower 110. And Ku steam supply line 171, and is mainly a control unit 140 which controls the like each pump, each device. Further, the carbon dioxide recovery system 10 further cools the mixture of carbon dioxide and water vapor 120 by evacuating device 125 that sucks carbon dioxide and water vapor 120 from the regeneration tower 110 to depressurize the inside of the regeneration tower 110. And a separator 126 for separating them. The steam turbine 170 from which the low-temperature and low-pressure steam 120 is extracted is constituted by a low-pressure steam turbine.

  Here, the lean absorption liquid 151 is an absorption liquid before absorbing carbon dioxide in the absorption tower 100, and includes, for example, an absorption liquid regenerated by releasing carbon dioxide in the regeneration tower 110. The rich absorption liquid 152 is an absorption liquid in a state before absorbing carbon dioxide in the regeneration tower 110 after absorbing carbon dioxide or the like in the absorption tower 100.

  In FIG. 1, the control unit 140 is electrically connected to each pump, each component device, and the like, which will be described later, but the connection lines are not shown for clarity of the drawing.

  An exhaust gas inlet 104 for guiding the exhaust gas 103 containing carbon dioxide discharged from the boiler of the thermal power plant into the absorption tower 100 is provided at the lower part of the absorption tower 100. In addition, a gas blower 105 for sending the exhaust gas 103 into the absorption tower 100 is connected to the exhaust gas inlet 104.

  Further, an absorption liquid inlet 102 for introducing the lean absorption liquid 151 discharged from the absorption liquid discharge port 112 of the regeneration tower 110 is provided in the upper part of the absorption tower 100. The absorption liquid introduction port 102 is provided with an absorption liquid ejection part 106 for ejecting the lean absorption liquid 151. In addition, inside the absorption tower 100, a filler 107 is provided that mainly makes gas-liquid contact between the lean absorption liquid 151 ejected from the absorption liquid ejection section 106 and the exhaust gas 103 introduced into the absorption tower 100. Further, the upper end of the absorption tower 100 functions as a remaining gas discharge port, and passes through the filler 107 to exhaust the exhaust gas 103 after coming into gas-liquid contact with the lean absorbent 151 into the atmosphere. A mouth 108 is provided.

  Here, it is preferable that the lean absorbing liquid 151 ejected from the absorbing liquid ejecting section 106 is ejected uniformly. For example, the absorbing liquid ejecting section 106 has a spray nozzle or the like that can obtain a predetermined spray particle size and spray pattern. An air injection nozzle or the like may be used. In addition, if the lean absorbing liquid 151 can be dispersed almost uniformly in the absorption tower 100 by the configuration of the absorbing liquid inlet 102, the absorbing liquid ejection part 106 may not be provided. Further, the filler 107 may be formed of a material having a porous structure, a honeycomb structure, or the like, for example, as long as it has an action of disturbing the lean absorbent 151 that passes through the filler 107. Moreover, the filler 107 may be installed in multiple stages in the absorption tower 100. In the case where the fillers 107 are installed in multiple stages, for example, an absorbent liquid ejecting section 106 that ejects the lean absorbent 151 may be provided corresponding to each stage. In addition, in the absorption tower 100, when the gas-liquid contact of the exhaust gas 103 and the lean absorption liquid 151 can be performed efficiently, the absorption tower 100 can be configured without installing the filler 107.

  Furthermore, an absorption liquid discharge port 101 for discharging the rich absorption liquid 152 that has absorbed carbon dioxide is provided at the bottom of the absorption tower 100. The absorption liquid discharge port 101 is connected to one end of a rich absorption liquid line 130 with a liquid supply pump 160 interposed. The other end of the rich absorbent line 130 is connected to the absorbent inlet 111 of the regeneration tower 110.

  Here, the inside of the absorption tower 100 is set to 90 to 150 kPa in absolute pressure. The reason why the pressure in the absorption tower 100 is set in this range is that when the pressure is less than 90 kPa, the rate at which carbon dioxide in the exhaust gas 103 is absorbed by the lean absorbent 151 becomes insufficient, and the pressure exceeds 150 kPa. In this case, the power energy required for the gas blower 105 becomes excessive.

  An absorption liquid introduction port 111 for introducing the rich absorption liquid 152 is provided in the upper part of the regeneration tower 110, and an absorption liquid ejection part 118 for ejecting the rich absorption liquid 152 is provided in the absorption liquid introduction port 111. ing. The absorption liquid ejection part 118 has the same configuration as the absorption liquid ejection part 106 in the absorption tower 100 described above. Further, inside the regeneration tower 110, a filler 117 is provided for mainly bringing the rich absorbent liquid 152 ejected from the absorbent liquid ejection section 118 into contact with the water vapor 120 introduced into the regeneration tower 110 in a gas-liquid contact. . The filler 117 has the same configuration as the filler 107 in the absorption tower 100 described above. In addition, an exhaust port 119 is provided at the upper end of the regeneration tower 110 for exhausting the carbon dioxide released from the rich absorbent 152 into the water vapor 120 when the rich absorbent 152 passes through the filler 117. Yes.

  Further, an absorption liquid discharge port 112 for discharging the lean absorption liquid 151 regenerated by releasing carbon dioxide is provided at the bottom of the regeneration tower 110. The absorption liquid discharge port 112 is connected to one end of a lean absorption liquid line 131 with a liquid supply pump 161 interposed therebetween. The other end of the lean absorption liquid line 131 is connected to the absorption liquid inlet 102 of the absorption tower 100.

  Here, the inside of the regeneration tower 110 is set to 30 to 70 kPa in absolute pressure. The pressure in the regenerator 110 is set within this range because when the pressure is less than 30 kPa, the motive energy required for the vacuuming device 125 is excessive, and when the pressure exceeds 70 kPa, the rich absorbing liquid 152 This is because carbon dioxide is not easily dissipated.

  As described above, the rich absorption liquid 152 flows in the order of the absorption tower 100, the rich absorption liquid line 130, and the regeneration tower 110, and the lean absorption liquid 151 flows in the order of the regeneration tower 110, the lean absorption liquid line 131, and the absorption tower 100. , The reflux path of the absorbent is formed. The liquid feed pumps 160 and 161 operate based on a signal from the control unit 140, and control the flow rate of the rich absorbent 152 flowing in the rich absorbent line 130 and the flow rate of the lean absorbent 151 flowing in the lean absorbent line 131. It is adjusted.

  Here, the lean absorbent 151 and the rich absorbent 152 are aqueous solutions of potassium carbonate and potassium bicarbonate. The lean absorbent 151 at the initial stage of operation is adjusted to a weight concentration of potassium carbonate of 20 to 35% by dissolving 25 to 54 g of potassium carbonate per 100 g of water. The concentration of the aqueous potassium carbonate solution was set in this range because the amount of carbon dioxide absorbed becomes insufficient when the weight concentration is lower than 20%, and when the weight concentration is higher than 35%, This is because the rate of absorbing carbon dioxide is not sufficiently high. Further, the temperatures of the lean absorbent 151 and the rich absorbent 152 are set to 55 to 70 ° C. The reason why the temperature of the lean absorbent 151 is set within this range is that when the temperature is higher than 70 ° C., a sufficient amount of carbon dioxide is not absorbed in the absorption tower 100. The reason why the temperature of the rich absorbent 152 is set in this range is that carbon dioxide is not easily dissipated in the regeneration tower 110 when the temperature is lower than 55 ° C. In other words, the regeneration rate from the rich absorbent liquid 152 to the lean absorbent liquid 151 increases as the temperature of the rich absorbent liquid 152 increases, but when the temperature is higher than 70 ° C., the carbon dioxide to the lean absorbent liquid 151 is increased. This is because the absorptivity of the water decreases.

  In order to maintain the temperature of the lean absorbent 151 and the rich absorbent 152 in this temperature range, for example, a heater or the like is interposed in the reflux path of the absorbent such as the rich absorbent line 130 or the lean absorbent line 131. The temperature of the absorbing solution may be adjusted. Further, the lean absorbing liquid 151 and the rich absorbing liquid 152 are not added with organic substances such as diethanolamine and piperazine for promoting the absorption of carbon dioxide. Here, the reason why organic substances such as diethanolamine and piperazine are not added to the lean absorbent 151 and the rich absorbent 152 is that the oxygen in the exhaust gas 103 is dissolved in the lean absorbent 151 and the rich absorbent 152 in the absorption tower 100 and dissolved. This is because the oxidized oxygen oxidizes organic substances such as diethanolamine and piperazine, and the oxidized organic substances inhibit the absorption of carbon dioxide.

  Further, the temperature of the exhaust gas 103 introduced into the absorption tower 100 is set to 55 to 70 ° C., which is the same as the set temperature range of the above-described lean absorbent 151 and rich absorbent 152. Here, the temperature of the exhaust gas 103 introduced into the absorption tower 100 is set within this range when the temperature is lower than 55 ° C., the temperature of the rich absorption liquid 152 discharged from the lower part of the absorption tower 100 decreases. This is because if the temperature is higher than 70 ° C., the lean absorbing liquid 151 is heated in the absorption tower 100 to emit carbon dioxide.

  In addition, a steam inlet 121 for introducing steam 120 is provided in the lower part of the regeneration tower 110. The steam inlet 121 is connected to one end of a steam supply line 171, and the other end of the steam supply line 171 is connected to a steam extraction port 172 on the low pressure side of the steam turbine 170. Further, on the low pressure side of the steam turbine 170, a steam discharge port 176 for discharging low-pressure steam 175 that has performed expansion work in the steam turbine 170 is provided. The water vapor outlet 176 is connected to a condenser (not shown). On the other hand, a steam inlet 174 for introducing high-pressure steam 173 is provided on the high pressure side of the steam turbine 170. The steam inlet 174 is connected to, for example, a crossover pipe that guides exhaust from an intermediate pressure steam turbine. The steam turbine 170 is connected to a generator 180 that is driven to rotate by the expansion work of the steam turbine 170 to generate power.

  Here, the absolute pressure of the steam 120 extracted from the steam extraction port 172 of the steam turbine 170 is 50 to 150 kPa, and the temperature of the steam 120 is 40 to 80 ° C. The temperature of the water vapor 120 introduced into the regeneration tower 110 via the water vapor supply line 171 is 55 to 70 ° C.

  The reason why the absolute pressure of the steam 120 extracted from the steam extraction port 172 is set to 50 to 150 kPa is that when the absolute pressure is less than 50 kPa, the steam 120 is introduced into the regeneration tower 110 having an absolute pressure of 30 to 70 kPa. This is because the driving output of the steam turbine 170 is excessively reduced when the absolute pressure exceeds 150 kPa. The pressure of the steam 120 extracted is set higher than the pressure in the regeneration tower 110 in consideration of the pressure loss in the steam supply line 171. Further, the temperature of the steam 120 extracted from the steam extraction port 172 of the steam turbine 170 is set to 40 to 80 ° C. When the temperature is lower than 40 ° C., the absolute pressure at the steam extraction port 172 is changed to the regeneration tower 110. If the pressure is lower than the absolute pressure (30 to 70 kPa) inside, it is difficult to introduce the steam 120 into the regeneration tower 110, and if the temperature exceeds 80 ° C., the driving output of the steam turbine 170 is excessively reduced. is there.

  In addition, the temperature of the water vapor 120 introduced into the regeneration tower 110 is set to 55 to 70 ° C., which is the same as the set temperature range of the lean absorbent 151 and the rich absorbent 152 described above, when the temperature is lower than 55 ° C. This is because the rich absorption liquid 152 is cooled in the regeneration tower 110 and it is difficult to dissipate carbon dioxide. When the temperature is higher than 70 ° C., excess water vapor evaporates from the rich absorption liquid 152 or the lean absorption liquid 151. Because. Here, in the regeneration tower 110, it exists as water vapor even at a temperature of 55 to 70 ° C. because the pressure in the regeneration tower 110 is reduced. When the temperature of the steam 120 extracted from the steam extraction port 172 of the steam turbine 170 is low, a heater 122 is provided in the steam supply line 171 so that the temperature of the steam 120 introduced into the regeneration tower 110 is 55. It is preferable to heat to ˜70 ° C. As the heating medium of the heater 122, for example, industrial water heated by the exhaust gas 103 before being introduced into the absorption tower 100 or the exhaust gas 103 itself before being introduced into the absorption tower 100 may be used. Moreover, it is preferable that the pipe length of the water vapor supply line 171 is short in order to reduce the pressure loss in the pipe. That is, in order to reduce the pressure loss in the steam supply line 171, it is preferable to arrange the regeneration tower 110 and the steam turbine 170 close to each other.

  Here, an example in which the steam 120 having a temperature of 40 to 80 ° C. is extracted from the steam turbine 170 is shown. However, for example, the low-temperature low-pressure steam 175 that has performed expansion work in the steam turbine 170 is supplied to the steam supply line 171. Alternatively, the water vapor may be heated to 55 to 70 ° C. via the heater 122 and introduced into the regeneration tower 110. In this manner, by extracting the steam that has been completely expanded in the steam turbine 170, the steam can be extracted without reducing the thermal efficiency of the steam turbine 170.

  Further, steam 120 having a temperature of 40 to 80 ° C. is extracted from the steam turbine 170 and led to the regeneration tower 110, and part of the lean absorbing liquid 151 accumulated at the bottom of the regeneration tower 110 is guided to the heater 122, so that A part of the water in the absorption liquid 151 may be water vapor, and the water may be guided to the regeneration tower 110 together with the non-evaporated lean absorption liquid 151. Thus, by heating a part of the lean absorbent 151 to form steam, the amount of steam 120 extracted from the steam turbine 170 can be suppressed, and without reducing the thermal efficiency in the steam turbine 170, A predetermined amount of water vapor can be secured.

  Further, the steam 120, the high-pressure steam 173, and the low-pressure steam 175 are not added with an organic substance such as monoethanolamine for suppressing metal corrosion of the boiler or the steam turbine 170, and instead of the organic substance such as monoethanolamine. A small amount of ammonia (for example, the concentration of ammonia is about 1 mg / liter) is added as a metal corrosion inhibitor. Here, ammonia was added instead of organic substances such as monoethanolamine. When organic substances were added, the organic substances were oxidized to inhibit carbon dioxide absorption. However, when ammonia was added, ammonia was added. This is because carbon dioxide absorption is not hindered because it does not oxidize.

  Furthermore, the exhaust port 119 of the regeneration tower 110 is connected to a suction port 123 of a vacuum suction device 125 for sucking the water vapor 120 mixed with carbon dioxide through a pipe. The vacuuming device 125 includes a condenser for condensing and removing a part of the water vapor 120. In addition, a water vapor inlet 129 of a separator 126 that sufficiently condenses the water vapor 120 from the mixture of carbon dioxide and water vapor 120 and separates the carbon dioxide is connected to the exhaust port 124 of the vacuuming device 125. .

  A carbon dioxide recovery port 127 for recovering the separated carbon dioxide is provided at the upper end of the separator 126. Further, a water discharge port 128 for discharging water condensed with the water vapor 120 is provided at the bottom of the separator 126.

  Next, the operation of the carbon dioxide recovery system 10 will be described.

  The exhaust gas 103 discharged from the boiler of the thermal power plant is introduced into the absorption tower 100 by the gas blower 105 at a temperature of 55 to 70 ° C. When the exhaust gas 103 is introduced into the absorption tower 100, the lean absorption liquid 151 having a temperature of 55 to 70 ° C. is supplied to the absorption tower 100 by the liquid feed pump 161 and the lean absorption liquid line 131. It is ejected from the absorbing liquid ejection part 106. In the absorption tower 100, the lean absorbing liquid 151 having a temperature of 55 to 70 ° C. and the exhaust gas 103 are in gas-liquid contact, and the lean absorbing liquid 151 absorbs carbon dioxide contained in the exhaust gas 103 and becomes the rich absorbing liquid 152. . The rich absorbent liquid 152 rises in temperature by 1 to 5 ° C. as carbon dioxide is absorbed. The exhaust gas after the gas-liquid contact is released into the atmosphere from the exhaust port 108 of the absorption tower 100.

  Subsequently, the rich absorbing liquid 152 that has absorbed carbon dioxide or the like is supplied to the regeneration tower 110 by the liquid feed pump 160 and the rich absorbing liquid line 130, and is ejected from the absorbing liquid ejection section 118 at the upper part of the regeneration tower 110.

  On the other hand, the steam turbine 170 is rotated by the high-pressure steam 173 supplied from the steam inlet 174 to drive the generator 180. The high-pressure steam 173 is supplied from the steam inlet 174 into the steam turbine 170 at a temperature of 300 ° C. or higher, performs expansion work in the steam turbine 170, and has an absolute pressure of 50 to 150 kPa and a temperature of 40 to 80 ° C. Further, after the final stage of the steam turbine 170, the low-pressure steam 175 having a temperature of 40 ° C. or less is discharged from the steam outlet 176.

  When the rich absorbing liquid 152 is ejected into the regeneration tower 110, the steam 120 is extracted from the steam extraction port 172 of the steam turbine 170, and the steam 120 having a temperature of 55 to 70 ° C. is generated from the steam inlet 121 into the regeneration tower 110. Supplied. In the regeneration tower 110, the rich absorbent liquid 152 and the water vapor 120 come into gas-liquid contact, and the rich absorbent liquid 152 diffuses carbon dioxide into the water vapor 120 and is regenerated into the lean absorbent liquid 151. The lean absorbing liquid 151 drops by 1 to 5 ° C. as carbon dioxide is released. However, the temperature of the water vapor 120 is substantially the same as the temperature of the rich absorbent liquid 152, and the rich absorbent liquid 152 is not heated by the water vapor 120. In other words, the carbon dioxide emission from the rich absorbent liquid 152 is promoted by the effect of the reduced pressure in the regeneration tower 110, and the carbon dioxide diffused around the rich absorbent liquid 152 is caused to flow by the water vapor 120, so that the rich absorbent liquid 152 By lowering the partial pressure of carbon dioxide in the surroundings, the emission of carbon dioxide from the rich absorbent 152 is promoted. In other words, the water vapor 120 functions as a carrier gas for flowing the diffused carbon dioxide.

  Subsequently, the lean absorbent 151 regenerated in the regeneration tower 110 is supplied again to the absorption tower 100 by the liquid feed pump 161 and the lean absorbent liquid line 131. Here, in the regeneration tower 110, since the rich absorbent liquid 152 is not heated, the temperature of the regenerated lean absorbent 151 is substantially equal to the temperature of the rich absorbent 152 before being regenerated, and 55 Maintained at a temperature of ~ 70 ° C. In other words, the temperature of the lean absorbing liquid 151 and the rich absorbing liquid 152 changes from 1 to 5 ° C. as carbon dioxide is absorbed and released. Does not exist. Therefore, the lean absorbent 151 regenerated by the regeneration tower 110 can be directly supplied to the absorption tower 100 without providing the lean absorbent line 131 with a cooling device, for example.

  Further, the water vapor 120 in the regenerator 110 and the carbon dioxide diffused in the water vapor 120 are guided from the regenerator 110 into the separator 126 by the vacuuming device 125. In the separator 126, the water vapor 120 and carbon dioxide are cooled to 20 to 30 ° C., and the water vapor 120 is condensed into water and discharged from the water discharge port 128. On the other hand, the cooled carbon dioxide is recovered from the carbon dioxide recovery port 127 of the separator 126 as a gas component. In addition, since the emission of carbon dioxide in the regeneration tower 110 and the absorption of carbon dioxide in the absorption tower 100 are in an equilibrium state, the amount of carbon dioxide recovered from the carbon dioxide recovery port 127 is the carbon dioxide absorbed in the absorption tower 100. It becomes almost equal to the amount.

  Further, the vacuum pulling device 125 discharges the carbon dioxide and the water vapor 120 diffused in the water vapor 120 to the separator 126, whereby the absolute pressure in the regeneration tower 110 is maintained at 30 to 70 kPa. By maintaining the pressure in the regeneration tower 110 within this range, the carbon dioxide emission from the rich absorbent 152 is promoted in the regeneration tower 110.

  As described above, in the carbon dioxide recovery system 10 according to the first embodiment, the low-temperature and low-pressure steam 120 that has been used as power energy by performing expansion work in the steam turbine 170 is used as a heating source for heating the absorption liquid. Instead, the absorbing liquid can be regenerated by using it as a carrier gas for carbon dioxide released from the absorbing liquid. As a result, the consumption of heat energy can be greatly reduced, and the system efficiency can be improved.

(Other embodiments)
With reference to the carbon dioxide recovery system 10 of 1st Embodiment, the carbon dioxide recovery system of other embodiment is demonstrated.

  In the carbon dioxide recovery system 10 of the first embodiment described above, an example in which an aqueous solution of potassium carbonate and potassium hydrogen carbonate is used as the lean absorbent 151 and the rich absorbent 152 is shown, but the present invention is not limited thereto. Absent. As the lean absorbent 151 and the rich absorbent 152, an aqueous solution of sodium carbonate and sodium bicarbonate may be used.

  In this case, the weight concentration of sodium carbonate is adjusted to 9 to 23% by dissolving 10 to 30 g of sodium carbonate per 100 g of water as the lean absorbent 151 at the initial stage of operation. The concentration of the aqueous sodium carbonate solution was set within this range because the amount of carbon dioxide absorbed was insufficient when the weight concentration was lower than 9%, and when the weight concentration was higher than 23%, This is because the rate of absorbing carbon dioxide is not sufficiently high.

  Note that the temperatures of the lean absorbent 151 and the rich absorbent 152 are similar to the temperatures of the lean absorbent 151 and the rich absorbent 152 in the first embodiment for the same reason as described in the first embodiment. The same 55-70 ° C. is set. The setting conditions such as the pressure of the absorption tower 100 and the regeneration tower 110 are the same as those in the first embodiment.

  As described above, even if the lean absorbent 151 and the rich absorbent 152 are replaced with an aqueous solution of sodium carbonate and sodium hydrogen carbonate, the expansion work is performed in the steam turbine 170 in the same manner as the carbon dioxide recovery system 10 of the first embodiment. The low-temperature and low-pressure water vapor 120 after being used as motive energy is used not as a heating source for heating the absorption liquid but as a carrier gas of carbon dioxide released from the absorption liquid to regenerate the absorption liquid. be able to. As a result, the consumption of heat energy can be greatly reduced, and the system efficiency can be improved.

  Although the present invention has been specifically described above with reference to the embodiments, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention.

The figure which showed the outline | summary of the carbon dioxide collection system of the 1st Embodiment of this invention. The figure which showed the outline | summary of the conventional carbon dioxide collection system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Carbon dioxide recovery system, 100 ... Absorption tower, 103 ... Exhaust gas, 105 ... Gas blower, 107,117 ... Filler, 110 ... Regeneration tower, 120 ... Water vapor, 122 ... Heater, 125 ... Vacuum puller, 126 ... Separation 130 ... Rich absorption liquid line, 131 ... Lean absorption liquid line, 140 ... Control part, 151 ... Lean absorption liquid, 152 ... Rich absorption liquid, 160, 161 ... Feed pump, 170 ... Steam turbine, 171 ... Steam supply Line, 173 ... high pressure steam, 175 ... low pressure steam, 180 ... generator.

Claims (15)

A carbon dioxide recovery system for recovering carbon dioxide in exhaust gas, comprising a steam turbine,
An exhaust gas introduction port, a lean absorption liquid introduction port, a remaining gas discharge port, and a rich absorption liquid discharge port, the exhaust gas introduced from the gas introduction port and the lean absorption liquid introduced from the lean absorption liquid introduction port An absorbing device that makes gas-liquid contact and absorbs carbon dioxide in the exhaust gas into the lean absorbing liquid to form a rich absorbing liquid;
A rich absorption liquid introduction port, a lean absorption liquid discharge port, an exhaust port, and a water vapor introduction port, which are derived from the rich absorption liquid introduced from the rich absorption liquid introduction port and the steam turbine introduced from the water vapor introduction port The carbon dioxide is diffused into the water vapor from the rich absorption liquid by making gas-liquid contact with the generated water vapor, the rich absorption liquid is regenerated into the lean absorption liquid, and the water vapor mixed with the carbon dioxide is exhausted to the exhaust gas. A regeneration device for discharging from the mouth;
A rich absorbent liquid line that guides the rich absorbent discharged from the rich absorbent liquid outlet of the absorber to the rich absorbent inlet of the regenerator;
A lean absorbing liquid line that guides the lean absorbing liquid discharged from the lean absorbing liquid discharge port of the regenerating apparatus to the lean absorbing liquid inlet of the absorbing apparatus;
A carbon dioxide recovery system comprising: a steam supply line that guides steam derived from the steam turbine to a steam inlet of the regenerator.   The carbon dioxide recovery system according to claim 1, further comprising a vacuuming device that sucks water vapor mixed with carbon dioxide from an exhaust port of the regenerator and evacuates the regenerator.   The carbon dioxide recovery system according to claim 1 or 2, wherein the temperature of the lean absorbent and the rich absorbent is 55 to 70 ° C, and the absolute pressure in the regenerator is 30 to 70 kPa.   The carbon dioxide recovery system according to any one of claims 1 to 3, wherein a main solute of the lean absorbent is a carbonate.   The carbon dioxide recovery system according to any one of claims 1 to 4, wherein the temperature of water vapor introduced from the water vapor inlet of the regenerator is 55 to 70 ° C.   6. The steam according to claim 1, wherein steam having a temperature of 40 ° C. to 80 ° C. is led out from a portion of the steam turbine having an absolute pressure of 50 to 150 kPa, and led to the regenerator through the steam supply line. The carbon dioxide recovery system according to any one of claims.   The carbon dioxide recovery system according to any one of claims 1 to 6, wherein the water vapor does not contain an organic substance.   The carbon dioxide recovery system according to any one of claims 1 to 7, wherein the water vapor contains ammonia as a metal corrosion inhibitor.   The carbon dioxide recovery system according to any one of claims 1 to 8, wherein the exhaust gas is a combustion exhaust gas discharged from a thermal power plant.   The carbon dioxide recovery system according to any one of claims 1 to 9, further comprising a separation device that separates carbon dioxide from water vapor mixed with carbon dioxide sucked by the vacuuming device.   The carbon dioxide recovery system according to any one of claims 1 to 10, wherein the steam turbine is a low-pressure steam turbine. An absorption step of guiding the exhaust gas and the lean absorbing liquid into an absorption device, bringing the exhaust gas and the lean absorbing liquid into gas-liquid contact, and absorbing the carbon dioxide in the exhaust gas into the lean absorbing liquid to form a rich absorbing liquid;
The rich absorption liquid that has absorbed carbon dioxide and the water vapor derived from the steam turbine are guided to a regenerator, and the rich absorption liquid and the water vapor at substantially the same temperature are brought into gas-liquid contact to bring the carbon dioxide from the rich absorption liquid. A regeneration step for regenerating the rich absorbent into the lean absorbent by dissipating it into the water vapor;
And a vacuum drawing step of sucking the water vapor mixed with carbon dioxide from the regenerator and evacuating the regenerator.   The carbon dioxide recovery method according to claim 12, further comprising a separation step of separating carbon dioxide from water vapor mixed with carbon dioxide sucked in the vacuuming step.   The carbon dioxide recovery method according to claim 12 or 13, wherein the temperature of the lean absorbent and the rich absorbent is 55 to 70 ° C, and the absolute pressure in the regenerator is 30 to 70 kPa.   13. The steam having a temperature of 40 to 80 ° C. is derived from a portion of the steam turbine having an absolute pressure of 50 to 150 kPa, and the steam having a temperature of 55 to 70 ° C. is led to the regenerator. 14. The carbon dioxide recovery method according to any one of 14 above.

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