CO

1. A CO 2 recovery unit comprising:

a CO 2 absorber in which a gas containing CO 2 contacts a CO 2 -absorbing solution that absorbs the CO 2 in the gas;

a CO 2 -absorbing solution regenerator that heats the CO 2 -absorbing solution that has absorbed the CO 2 , releases the CO 2 from the CO 2 -absorbing solution, and regenerates the CO 2 -absorbing solution; and

at least one of:

a CO 2 recovery rate controller that controls a difference between an actual measured value and a target value of a recovery rate of the CO 2 to be within a predetermined range by changing, based on the actual measured value and the target value of the CO 2 recovery rate, a circulation amount of the CO 2 -absorbing solution to be supplied to the CO 2 absorber and a supply amount of saturated steam to be supplied to a regeneration heater of the CO 2 -absorbing solution regenerator; and

a CO 2 recovery amount controller that controls a difference between an actual measured value and a target value of a recovery amount of CO 2 to be within a predetermined range by changing, based on the actual measured value and the target value of the CO 2 recovery amount, the circulation amount of the CO 2 -absorbing solution to be supplied to the CO 2 absorber and the supply amount of the saturated steam to be supplied to the regeneration heater of the CO 2 -absorbing solution regenerator;

wherein the CO 2 recovery rate controller controls the CO 2 recovery rate through a proportional calculation and an integration calculation based on the difference between the actual measured value and the target value of the CO 2 recovery rate.

2. The CO 2 recovery unit according to claim 1 ,

wherein the CO 2 recovery amount controller controls the CO 2 recovery amount through a proportional calculation and an integration calculation based on the difference between the actual measured value and the target value of the CO 2 recovery amount.

3. The CO 2 recovery unit according to claim 1 ,

wherein the CO 2 recovery rate controller operates in one of:

a first control mode where the circulation amount and the supply amount of the saturated steam are calculated and controlled at any time, and

a second control mode where the circulation amount and the supply amount of the saturated steam are calculated and controlled for each predetermined period, and

wherein the CO 2 recovery amount controller operates in one of:

a first control mode where the circulation amount and the supply amount of the saturated steam are calculated and controlled at any time, and

a second control mode where the circulation amount and the supply amount of the saturated steam are calculated and controlled for each predetermined period.

4. The CO 2 recovery unit according to claim 3 ,

wherein one of the CO 2 recovery rate controller and the CO 2 recovery amount controller operates in the first control mode, and the other operates in the second control mode.

5. The CO 2 recovery unit according to claim 1 ,

wherein the CO 2 recovery rate controller operates in a first control mode where the circulation amount and the supply amount of the saturated steam are calculated and controlled at any time,

wherein the CO 2 recovery amount controller operates in a first control mode where the circulation amount and the supply amount of the saturated steam are calculated and controlled at any time, and

wherein one of the CO 2 recovery amount controller and the CO 2 recovery rate controller is provided with a dead band.