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EP-3546054-B1 - CO2 RECOVERY DEVICE AND METHOD FOR RECOVERING CO2

EP3546054B1EP 3546054 B1EP3546054 B1EP 3546054B1EP-3546054-B1

Inventors

  • TSUJIUCHI, TATSUYA
  • KAMIJO, TAKASHI
  • INUI, MASAYUKI
  • MIYAMOTO, OSAMU

Dates

Publication Date
20260506
Application Date
20170929

Claims (12)

  1. A CO2 recovery system (10A) comprising: a CO2 absorber (13) that brings a CO2-containing flue gas into contact with a CO2 absorbent to remove CO2 from the CO2-containing flue gas; an absorbent regenerator (16) that separates CO2 from a rich solution (14) which has absorbed CO2 to regenerate the CO2 absorbent as a lean solution (15); a rich solution supply line (L11) that supplies the rich solution (14) from a bottom (13b) of the CO2 absorber (13) to a rich solution supply portion (16c) on a top side of the absorbent regenerator (16); a lean solution supply line (L12) that supplies the lean solution (15) from a bottom (16b) of the absorbent regenerator (16) to a lean solution supply portion (13c) of the CO2 absorber (13), a rich/lean solution heat exchanger (21) that exchanges heat between the rich solution (14) and the lean solution(15); wherein all of the lean solution (15) from the bottom side (16b) a side of the absorbent regenerator (16) through the lean solution supply line (L12) is heat-exchanged with all of the rich solution coming from rich solution supply line (L11) in the rich/lean solution heat exchanger (21); a first rich solution dividing line (L13-1) that divides a part of the rich solution (14) as a first divided rich solution at a first dividing portion (A-1) in the rich solution supply line (L11) provided between the rich/lean solution heat exchanger (21), and the absorbent regenerator (16) and supplies the first divided rich solution at a first supply position (B-1) on a side wall closer to a bottom side (16b) than the top side of the absorbent regenerator; a first rich solution heat exchanger (22-1) that preheats the first divided rich solution, provided in the first rich solution dividing line (L13-1); and a first flow rate control device (23-1) that controls a flow rate of the first divided rich solution and that is configured to preheat the first divided rich solution to a predetermined temperature in the first rich solution heat exchanger (22-1), provided between the first dividing portion (A-1) in the first rich solution dividing line (L13-1) and the first rich solution heat exchanger (22-1).
  2. The CO2 recovery system according to claim 1, wherein a heat exchange medium in the first rich solution heat exchanger (22-1) is steam condensate derived from a reboiler (31) included in the absorbent regenerator.
  3. The CO2 recovery system according to claim 1, having a first stage regeneration unit (16-1) that regenerates the CO2 absorbent in the absorbent regenerator and a second stage regeneration unit (16-2) positioned below the first stage regeneration unit (16-1), comprising: a first semi-lean solution extraction line (L21-1) that extracts a first semi-lean solution in which a part of CO2 has been removed from the rich solution by the first stage regeneration unit (16-1) to an outside from a first liquid storage (18-1) for storing the semi-lean solution, connected to a supply position for supplying the first semi-lean solution to an upper portion of the second stage regeneration unit (16-2) on a lower stage side than an extraction position; and a mixing unit (24-1) of the second stage regeneration unit in the absorbent regenerator that mixes the first semi-lean solution and the first divided rich solution in the absorbent regenerator (16), in which the supply position in the first semi-lean solution extraction line in the absorbent regenerator has the same height as the supply position in the first rich solution dividing line.
  4. The CO2 recovery system according to claim 3 , wherein a first lean/semi-lean solution heat exchanger (25-1) that exchanges heat between the lean solution and the first semi-lean solution is provided at an intersection between the lean solution supply line (L12) and the first semi-lean solution extraction line (L21-1) between the bottom of the absorbent regenerator (16) in the lean solution supply line and the rich/lean solution heat exchanger.
  5. The CO2 recovery system according to claim 1, wherein the absorbent regenerator (16) includes a first stage regeneration unit (16-1) that regenerates the CO2 absorbent, a second stage regeneration unit (16-2) positioned below the first stage regeneration unit, and a third stage regeneration unit (16-3) positioned below the second stage regeneration unit (16-2), and the CO2 recovery system comprises: a first semi-lean solution extraction line (L21-1) that extracts all of a first semi-lean solution in which a part of CO2 has been removed from the rich solution by the first stage regeneration unit (16-1) to an outside from a first liquid storage (18-1) for storing the first semi-lean solution, connected to a supply position for supplying the first semi-lean solution to an upper portion of the second stage regeneration unit (16-2) on a lower stage side than the extraction position; a mixing unit (24-1) of the second stage regeneration unit in the absorbent regenerator that mixes the first semi-lean solution and the first divided rich solution in the absorbent regenerator, in which the supply position in the first semi-lean solution extraction line (L21-1) has the same height as the supply position in the first rich solution dividing line; and a second semi-lean solution extraction line (L21-2) that extracts a second semi-lean solution in which a part of CO2 has been further removed from the first semi-lean solution by the second stage (16-2) regeneration unit to an outside from a second liquid storage (18-3) for storing the second semi-lean solution, connected to a supply position for supplying the second semi-lean solution to an upper portion of the third stage regeneration unit (16-3) on a lower stage side than the extraction position.
  6. The CO2 recovery system according to claim 1, wherein the absorbent regenerator includes a first stage regeneration unit (16-1) that regenerates the CO2 absorbent, a second stage regeneration unit (16-2) positioned below the first stage regeneration unit (16-1), and a third stage regeneration unit (16-3) positioned below the second stage regeneration unit (16-2), and the CO2 recovery system comprises: a first semi-lean solution extraction line (L21-1) that extracts all of a first semi-lean solution in which a part of CO2 has been removed from the rich solution by the first stage regeneration unit (16-1) to an outside from a first liquid storage (18-1) for storing the semi-lean solution, connected to a supply position for supplying the first semi-lean solution to an upper portion of the second stage regeneration unit (16-2) on a lower stage side than the extraction position; a second semi-lean solution extraction line (L21-2) that extracts a second semi-lean solution in which a part of CO2 has been further removed from the first semi-lean solution by the second stage regeneration unit (16-2) to an outside from a second liquid storage (18-3) for storing the second semi-lean solution and supplies the second semi-lean solution at a supply position for supply in an upper portion of the third stage regeneration unit (16-3) on a lower stage side than the extraction position; and a mixing unit (24-2) of the third stage regeneration unit (16-3) in the absorbent regenerator that mixes the second semi-lean solution and the first divided rich solution in the absorbent regenerator, in which the supply position in the second semi-lean solution extraction line has the same height as the supply position in the first rich solution dividing line.
  7. The CO2 recovery system according to claim 1, wherein a second dividing portion (A-2) is further provided between the first dividing portion (A-1) and the absorbent regenerator (16), and the CO2 recovery system comprises: a second rich solution dividing line (L13-2) that further divides a part of the rich solution as a second divided rich solution at the second dividing portion (A-2) and supplies the second divided rich solution at a second supply position (B-2) on a side wall on a bottom side of the rich solution supply portion on the top side of the absorbent regenerator (16) and on a top side of the first rich solution dividing line (L13-1); a second rich solution heat exchanger (22-2) that preheats the second rich solution divided at the second dividing portion, provided in the second rich solution dividing line (L13-2); and a second flow rate control device (23-2) that controls a flow rate of the second rich solution divided at the second dividing portion (A-2), provided between the second dividing portion (A-2) in the second rich solution dividing line and the second rich solution heat exchanger (22-2).
  8. The CO2 recovery system according to claim 6, wherein a second dividing portion (A-2) is further provided between the first dividing portion (A-1) and the absorbent regenerator (16), and, the CO2 recovery system comprises: a second rich solution dividing line (L13-2) that further divides a part of the rich solution as a second divided rich solution at the second dividing portion (A-2) and supplies the second divided rich solution to any position on a side wall on a bottom side of the rich solution supply portion on the top side of the absorbent regenerator (16) and on a top side of the first rich solution dividing line (L13-2); a second rich solution heat exchanger (22-2) that preheats the second rich solution divided at the second dividing portion, provided in the second rich solution dividing line (L13-2); a second flow rate control device (23-2) that controls a flow rate of the second rich solution divided at the second dividing portion, provided between the second dividing portion (A-2) in the second rich solution dividing line(L13-2) and the second rich solution heat exchanger (22-2); and a mixing unit (24-1) of the second stage regeneration unit in the absorbent regenerator that mixes the first semi-lean solution and the second divided rich solution in the absorbent regenerator (16), in which the supply position in the first semi-lean solution extraction line (L21-1) has the same height as the supply position (B-2) in the second rich solution dividing line (L13-2).
  9. The CO2 recovery system according to claim 1, wherein the absorbent regenerator (16) includes a first stage regeneration unit (16-1) that regenerates the CO2 absorbent, a second stage regeneration unit (16-2) positioned below the first stage regeneration unit (16-1), and a third stage regeneration unit (16-3) positioned below the second stage regeneration unit (16-2), and the CO2 recovery system comprises: a first semi-lean solution extraction line (L21-1) that extracts all of a first semi-lean solution in which a part of CO2 has been removed from the rich solution by the first stage regeneration unit (16-1) to an outside from a first liquid storage for storing the semi-lean solution, connected to a supply position for supplying the first semi-lean solution to an upper portion of the second stage regeneration unit (16-2) on a lower stage side than the extraction position; a mixing unit (24-1) of the second stage regeneration unit in the absorbent regenerator that mixes the first semi-lean solution and the first divided rich solution in the absorbent regenerator (16), in which the supply position in the first semi-lean solution extraction line (L21-1) has the same height as the supply position in the first rich solution dividing line; a second semi-lean solution extraction line (L21-2) that extracts a second semi-lean solution in which a part of CO2 has been further removed from the first semi-lean solution by the second stage regeneration unit (16-2) to an outside from a second liquid storage (18-2) for storing the second semi-lean solution, connected to a supply position for supplying the second semi-lean solution to an upper portion of the third stage regeneration unit (16-3) on a lower stage side than the extraction position; a first lean/semi-lean solution heat exchanger (25-1) that exchanges heat between the lean solution and the first semi-lean solution, having a lean solution supply line for supplying the lean solution from a bottom of the absorbent regenerator to the CO2 absorber, and provided at an intersection between the lean solution supply line (L12) and the first semi-lean solution extraction line (L21-1) between the bottom of the absorbent regenerator (16) in the lean solution supply line and the rich/lean solution heat exchanger; and a second lean/semi-lean solution heat exchanger (25-2) that exchanges heat between the lean solution and the second semi-lean solution, provided at an intersection between the lean solution supply line (L12) and the second semi-lean solution extraction line (L21-2).
  10. The CO2 recovery system according to claim 1, wherein the absorbent regenerator includes a first stage regeneration unit (16-1) that regenerates the CO2 absorbent, a second stage regeneration unit (16-2) positioned below the first stage regeneration unit (16-1), and a third stage regeneration unit (16-3) positioned below the second stage regeneration unit (16-2), and the CO2 recovery system comprises: a first semi-lean solution extraction line (L21-1) that extracts all of a first semi-lean solution in which a part of CO2 has been removed from the rich solution by the first stage regeneration unit (16-1) to an outside from a first liquid storage for storing the semi-lean solution, connected to a supply position for supplying the first semi-lean solution to an upper portion of the second stage regeneration unit (16-2) on a lower stage side than the extraction position; a second semi-lean solution extraction line (L21-2) that extracts a second semi-lean solution in which a part of CO2 has been further removed from the first semi-lean solution by the second stage regeneration unit (16-2) to an outside from a second liquid storage for storing the semi-lean solution, and supplies the second semi-lean solution to an upper portion of the third stage regeneration unit (16-3) on a lower stage side than the extraction position; a mixing unit (24-2) of the third stage regeneration unit (16-3) in the absorbent regenerator that mixes the second semi-lean solution and the first divided rich solution in the absorbent regenerator, in which the supply position in the second semi-lean solution extraction line (L21-2) has the same height as the supply position in the first rich solution dividing line; a first lean/semi-lean solution heat exchanger (25-1) that exchanges heat between the lean solution and the first semi-lean solution, having a lean solution supply line for supplying the lean solution from a bottom of the absorbent regenerator to the CO2 absorber, and provided at an intersection between the lean solution supply line (L12) and the first semi-lean solution extraction line (L21-1) between the bottom of the absorbent regenerator in the lean solution supply line (L12) and the rich/lean solution heat exchanger; and a second lean/semi-lean solution heat exchanger (25-2) that exchanges heat between the lean solution and the second semi-lean solution, provided at an intersection between the lean solution supply line (L12) and the second semi-lean solution extraction line (L21-2).
  11. A method of recovering CO2 for circulating and reusing, using a CO2 absorber for bringing a CO2-containing flue gas into contact with a CO2 absorbent to remove CO2 from the CO2-containing flue gas and an absorbent regenerator for 20 separating CO2 from a rich solution which has absorbed CO2 to regenerate the CO2 absorbent as a lean solution, the CO2 absorbent from which CO2 has been removed by the absorbent regenerator in the CO2 absorber, the method comprising the steps of: heat-exchanging all of the lean solution (15) coming from a bottom side (16b) of the absorbent regenerator (16) with all of the rich solution fed coming from a bottom side (13b) of the CO2 absorber; dividing the rich solution which has been subjected to heat exchange in order to supply the rich solution to a rich solution supply portion (16c) on a top side (16a) of the absorbent regenerator (16) and a side wall positioned on a lower side of the rich solution supply portion; and preheating the divided rich solution supplied to a supply position on the side wall, wherein in the step of dividing the rich solution which has been subjected to heat exchange, an amount of the divided rich solution for heat exchange is adjusted such that a temperature of the rich solution which has been supplied from the rich solution supply portion on the top side of the absorbent regenerator (16) and from which a part of CO2 has been removed is the same as or higher than that of the divided rich solution supplied from the side wall of the absorbent regenerator (16).
  12. The method of recovering CO2 according to claim 11, wherein a heat medium to be supplied to the side wall for preheating the rich solution is steam condensate derived from the absorbent regenerator (16).

Description

Field The present invention relates to an energy-saving CO2 recovery system and a method of recovering CO2. Background In recent years, the greenhouse effect due to CO2 is pointed out as a factor of global warming, and thus the measure to cope with this has become an international urgent task in order to protect the global environment. The CO2 generation sources include a various fields of human activities that burn fossil fuels, and a demand for emission limitation of CO2 tends to be even stronger. In association with this, a method to remove and recover CO2 in the flue gas by bringing the flue gas from a boiler into contact with an amine-based CO2 absorbent for example and a method to store the recovered CO2 without releasing it to the atmosphere has been extensively investigated by taking the power generation facilities such as thermal power plants that use great amounts of fossil fuels as the target. As the method of removing and recovering CO2 from a flue gas using a CO2 absorbent, the following method has been employed. That is, a flue gas is brought into contact with a CO2 absorbent in an absorber, the absorbent which has absorbed CO2 is heated in a regenerator to release CO2 and regenerate the absorbent, and the regenerated absorbent is circulated again in the absorber to be reused (Japanese Patent Application Laid-open No. 2003-225537). In a method of absorbing, removing, and recovering CO2 from a CO2-containing gas such as a flue gas, it is necessary to add an absorber and a regenerator to a fuel facility for installation. Therefore, cost other than installation cost, for example, operation cost has to be reduced as much as possible. Particularly, when an absorbent is regenerated, a large amount of heat energy (water vapor) is consumed in order to release CO2 from a CO2 absorbent, and therefore a regeneration process needs to be an energy-saving process if possible. Therefore, the following carbon dioxide recovery system has been conventionally proposed (Japanese Patent Application Laid-open No. 2009-214089). That is, the carbon dioxide recovery system includes a dividing device for dividing a rich solution discharged from an absorber into a first heat exchanger for cooling a lean solution and a second heat exchanger for cooling carbon dioxide-containing vapor. The rich solutions introduced into the first heat exchanger and the second heat exchanger exchange heat with the lean solution and the carbon dioxide-containing vapor, respectively, and then are supplied to a regenerator for releasing CO2. Other known systems are provided in US 2015/174531 A1, CN204347000 A1 or EP3045218 A1. Citation List Summary Technical Problem However, the proposal in Japanese Patent Application Laid-open No. 2009-214089has the following problem. That is, the rich solution which has absorbed CO2 is divided on a former stage side of the lean/rich solution heat exchanger as the first heat exchanger, the divided rich solution is supplied to the regenerator while being heated by heat exchange with carbon dioxide-containing vapor discharged from a top of the regenerator, but the divided rich solution is supplied to an upper portion than the rich solution, therefore satisfactory regeneration cannot be performed when the divided rich solution is heated insufficiently, and stable energy-saving cannot be performed. In addition, the absorbent is circulated again, and therefore a cooling efficiency of the lean solution by the rich solution in the lean/rich solution heat exchanger is reduced disadvantageously when a part of the rich solution is divided and extracted on a former stage side of the lean/rich solution heat exchanger. As a result, it is necessary disadvantageously to increase cooling ability to cool the lean solution in a cooler provided before introduction to the absorber. In view of the foregoing problems, an object of the present invention is to provide a CO2 recovery system and a method of recovering CO2 which have an energy efficiency further improved with stable energy-saving. Solution to Problem The aforementioned problems is solved by a CO2 absorber and a method of recovering CO2 as claimed in the appended set of claims. Advantageous Effects of Invention According to the present invention, when a divided rich solution is preheated and then is supplied at a first supply position in an absorbent regenerator, an amount of the rich solution divided is adjusted by a flow rate adjuster, and the divided rich solution is preheated and introduced such that a temperature of the divided rich solution is approximately the same as or lower than that of a rich solution from which a part of CO2 has been removed in the absorbent regenerator. Therefore, variation in temperature of the joined solutions in the absorbent regenerator does not occur, CO2 is released efficiently, and a high energy-saving effect can be obtained. As a result, it is possible to reduce the amount of vapor necessary for a reboiler and the amount of cooling