Acid gas removal apparatus and acid gas removal method

An acid gas removal apparatus comprising:

• an absorption tower bringing gas containing acid gas into contact with an acid gas absorbent composed of a solution containing a thermosensitive nitrogen-containing compound represented by the following formula (1) and having a lower critical solution temperature at a predetermined temperature to absorb the acid gas into the acid gas absorbent and to remove the acid gas from the gas;
• a first heater heating the acid gas absorbent that has absorbed the acid gas to the lower critical solution temperature of the solution or more;
• a phase separation tank phase-separating the heated acid gas absorbent into a rich absorbent phase and a lean absorbent phase, the lean absorbent phase containing more of the thermosensitive nitrogen-containing compound than the rich absorbent phase;
• a second heater heating the rich absorbent phase;
• a regeneration tower releasing the acid gas in the rich absorbent phase;
• and
• a third heater provided at the regeneration tower and heating the rich absorbent phase.
• (In the formula (1), R1 is a hydroxyalkyl group, R2 is a non-substituted cyclic alkyl group whose carbon number is 3 to 10, and R3 is a hydrogen atom or a non-substituted alkyl group.)