Heat recovery system and heat recovery method of co2 recovery unit

Abstract

A heat recovery system of a CO 2 recovery unit ( 55 ) including an absorber that removes CO 2 in flue gas ( 101 ) discharged from a boiler ( 51 ) by absorbing CO 2 by an absorbent, and a regenerator that emits CO 2 from the absorbent having absorbed CO 2 for reusing the absorbent in the absorber. The heat recovery system further includes a Ljungström heat exchanger ( 57 ) that performs heat exchange between the flue gas ( 101 ) discharged from the boiler ( 51 ) and before reaching the CO 2 recovery unit ( 55 ) and unburned air ( 102 ) supplied to the boiler ( 51 ), and an air preheater ( 58 ) that preheats the unburned air ( 102 ) before reaching the Ljungström heat exchanger ( 57 ) by exhaust heat from the CO 2 recovery unit ( 55 ).

1 . A heat recovery system of a CO 2  recovery unit including an absorber that removes CO 2  in flue gas discharged from a boiler by absorbing CO 2  by an absorbent, and a regenerator that emits CO 2  from the absorbent having absorbed CO 2  for reusing the absorbent in the absorber, the heat recovery system comprising:
 a Ljungström heat exchanger that performs heat exchange between flue gas discharged from the boiler and before reaching the CO 2  recovery unit and unburned air supplied to the boiler; and   an air preheater that preheats the unburned air before reaching the Ljungström heat exchanger by exhaust heat from the CO 2  recovery unit.   
     
     
         2 . The heat recovery system of a CO 2  recovery unit according to  claim 1 , further comprising a heat recovery device that recovers heat of the flue gas before reaching the CO 2  recovery unit through the Ljungström heat exchanger and supplies recovered heat to the CO 2  recovery unit. 
     
     
         3 . The heat recovery system of a CO 2  recovery unit according to  claim 1 , wherein the heat recovery system is applied to a power generation plant that drives a steam turbine by superheated steam from the boiler to generate power. 
     
     
         4 . The heat recovery system of a CO 2  recovery unit according to  claim 1 , wherein the air preheater indirectly heats the unburned air by circulating a heat medium heated by heat transfer of exhaust heat from the CO 2  recovery unit. 
     
     
         5 . The heat recovery system of a CO 2  recovery unit according to  claim 1 , wherein the air preheater directly heats the unburned air by circulating a exhaust heat fluid from the CO 2  recovery unit. 
     
     
         6 . A heat recovery method of a CO 2  recovery unit including a CO 2  recovery step of removing CO 2  in flue gas discharged from a boiler by absorbing CO 2  by an absorbent, emitting CO 2  from the absorbent having absorbed CO 2 , and of reusing the absorbent for absorbing CO 2 , the heat recovery method comprising:
 a heat exchanging step of performing heat exchange between flue gas discharged from the boiler and before reaching the CO 2  recovery step and unburned air supplied to the boiler; and   an air preheating step of preheating the unburned air before reaching the heat exchanging step by exhaust heat from the CO 2  recovery step.   
     
     
         7 . The heat recovery method of a CO 2  recovery unit according to  claim 6 , further comprising a heat recovery step of recovering heat of the flue gas before reaching the CO 2  recovery step through the heat exchanging step and of supplying recovered heat to the CO 2  recovery step. 
     
     
         8 . The heat recovery method of a CO 2  recovery unit according to  claim 6 , further comprising a power generation step of driving a steam turbine by superheated steam from the boiler to generate power.