Carbon dioxide recovery method and recovery device

1. A carbon dioxide recovery apparatus, comprising:

a separator which separates carbon dioxide from a gas by utilizing adsorption and desorption of carbon dioxide to and from an adsorbent caused by pressure fluctuation and discharges a residual gas from which carbon dioxide has been removed;

a dryer which has a hygroscopic agent for drying the gas to be supplied to the separator;

a regeneration system which supplies the residual gas discharged from the separator to the dryer as a regeneration gas to be used for regeneration of the hygroscopic agent in the dryer; and

a supplement system which supplies a supplement gas from an outside to the residual gas depending on a flow rate of the residual gas discharged from the separator such that a flow rate of the regeneration gas is a predetermined rate,

wherein the supplement system includes:

a flowmeter which measures the flow rate of the regeneration gas to be supplied to the dryer, and

a flow regulating valve which is electrically connected to the flowmeter and which adjusts supply of the supplement gas.

2. The carbon dioxide recovery apparatus according to claim 1 , wherein the supplement system has a line which supplies a nitrogen gas discharged from an air separation unit as the supplement gas, and the adsorbent in the separator has a metal-organic framework.

3. The carbon dioxide recovery apparatus according to claim 1 , wherein

the separator includes a pressurizer which pressurizes the gas to be supplied to the separator to a pressure at which the adsorbent is capable of adsorbing carbon dioxide, and

the supplement system further includes a heat exchanger which exchanges heat between the gas pressurized by the pressurizer and the regeneration gas to be supplied to the dryer, and

by the heat exchange in the heat exchanger, the regeneration gas is heated and the pressurized gas is cooled and supplied to the dryer and the separator.

4. The carbon dioxide recovery apparatus according to claim 3 , wherein the regeneration gas subjected to the heat exchange by the heat exchanger is the residual gas to which the supplement gas has been supplied.

5. The carbon dioxide recovery apparatus according to claim 3 , wherein the separator includes paired columns which contain the adsorbent and a pressure reducer which reduces a pressure in each of the columns to a pressure at which desorption of carbon dioxide adsorbed on the adsorbent is possible.

6. The carbon dioxide recovery apparatus according to claim 5 , wherein

the pressurizer includes a compressor which compresses the gas, and

the pressure reducer includes an expander which is configured to cooperate with the compressor.

7. The carbon dioxide recovery apparatus according to claim 1 , further comprising a denitrator which removes a nitrogen oxide from the gas to be supplied to the separator.

8. The carbon dioxide recovery apparatus according to claim 7 , wherein

the denitrator includes a gas-liquid separator which separates condensate water condensed from the gas, thereby removing the nitrogen oxide contained in the condensate water.

9. A carbon dioxide recovery method, comprising:

separation processing of separating carbon dioxide from a gas by utilizing adsorption and desorption of carbon dioxide to and from an adsorbent caused by pressure fluctuation and of discharging a residual gas from which carbon dioxide has been removed;

drying treatment of drying the gas to be supplied to the separation processing by using a hygroscopic agent;

regeneration processing of supplying the residual gas discharged in the separation processing to the hygroscopic agent used in the drying treatment, as a regeneration gas to be used for regeneration of the hygroscopic agent; and

supplement processing of supplying a supplement gas from an outside depending on a flow rate of the residual gas discharged in the separation processing such that a flow rate of the regeneration gas is a predetermined rate,

wherein the supplement processing includes:

flow measurement of measuring the flow rate of the regeneration gas to be supplied to the dryer, and

flow regulation of adjusting supply of the supplement gas by using a flow regulating valve depending on the measured flow rate.