A CO 2 recovery system includes an absorption tower and a regeneration tower. CO 2 rich solution is produced in the absorption tower by absorbing CO 2 from CO 2 -containing gas. The CO 2 rich solution is conveyed to the regeneration tower where lean solution is produced from the rich solution by removing CO 2 . A regeneration heater heats lean solution that accumulates near a bottom portion of the regeneration tower with saturated steam thereby producing steam condensate from the saturated steam. A steam-condensate heat exchanger heats the rich solution conveyed from the absorption tower to the regeneration tower with the steam condensate.
1. A CO 2 recovery system including an absorption tower that receives CO 2 -containing gas and CO 2 -absorbing solution, and causes the CO 2 -containing gas to come in contact with the CO 2 -absorbing solution to produce CO 2 rich solution, and a regeneration tower, including an upper-portion regeneration tower, a middle-portion regeneration tower, and a lower-portion regeneration tower, that receives the rich solution and produces lean solution from the rich solution by removing CO 2 from the rich solution, the CO 2 recovery system comprising:
a bottom lean-solution extraction path that extracts lean solution that accumulates near a bottom portion of the regeneration tower from a first point of the regeneration tower and returns extracted lean solution to a second point of the regeneration tower that is downstream of the first point;
a regeneration heater arranged in the bottom lean-solution extraction path and heats the lean solution in the bottom lean-solution extraction path with saturated steam thereby producing steam condensate from the saturated steam;
a steam-condensate heat exchanger that heats, with the steam condensate, either one of
(a) the rich solution that is supplied from the absorption tower to the regeneration tower, and
(b) a semi-lean solution that is extracted outside from a middle portion of the regeneration tower and returned to the lower-portion of the regeneration tower;
an upper semi-lean-solution extraction path that extracts semi-lean solution from a fifteenth point of the upper-portion regeneration tower and returns extracted semi-lean solution to a sixteenth point of the middle-portion regeneration tower that is downstream of the fifteenth point;
a lean-solution supply member that extracts the lean solution from the regeneration tower and conveys extracted lean solution to an upper stage portion of the absorption tower;
a first lean-solution heat exchanger that is arranged in the upper semi-lean-solution extraction path and the lean-solution supply member and heats the semi-lean solution in the upper semi-lean-solution extraction path with the lean solution in the lean-solution supply member;
a semi-lean-solution extraction path that extracts semi-lean solution from a seventeenth point of the middle-portion regeneration tower and returns extracted semi-lean solution to an eighteenth point of the lower-portion regeneration tower that is downstream of the seventeenth point and also conveys the extracted semi-lean solution to a middle stage portion of the absorption tower;
a first steam-condensate heat exchanger that is arranged in the semi-lean-solution extraction path between the seventeenth point and the eighteenth point and heats the semi-lean solution in the semi-lean-solution extraction path with the steam condensate;
a rich-solution supply member that conveys the rich solution from the absorption tower to the regeneration tower;
a semi-lean-solution heat exchanger that is provided in the rich-solution supply member and the semi-lean-solution extraction path and heats the rich solution in the rich-solution supply member with the semi-lean solution in the semi-lean-solution extraction path; and
a second lean-solution heat exchanger that is provided downstream of the semi-lean-solution heat exchanger in the rich-solution supply member and downstream of the first lean-solution heat exchanger in lean-solution supply member, and heats the rich solution in the rich-solution supply member with the lean solution in the lean-solution supply member.
2. The CO 2 recovery system according to claim 1 , wherein
the absorption tower is divided into an upper stage and a lower stage, and
the semi-lean solution to be supplied to a portion between the upper stage and the lower stage of the absorption tower is jointed with a semi-lean solution extracted from the upper-stage absorption tower, to be supplied to the lower-stage absorption tower.