Carbon dioxide gas separation method and carbon dioxide gas separation apparatus

A carbon dioxide gas separation apparatus separating carbon dioxide gas contained in a gas to be treated, the carbon dioxide gas separation apparatus characterized by comprising:

• a separation membrane module including a separation membrane and allowing carbon dioxide gas to permeate from a primary side to a secondary side of the separation membrane to reduce the carbon dioxide gas in the gas to be treated;
• a gas-to-be-treated supply path connected to a space on the primary side in the separation membrane module and supplying the gas to be treated containing carbon dioxide gas;
• a carbon dioxide gas flow path connected to a space on the secondary side in the separation membrane module and allowing the carbon dioxide gas permeated through the separation membrane to flow out;
• a non-permeation gas flow path connected to the space on the primary side and allowing non-permeation gas obtained after the carbon dioxide gas is separated to flow out;
• and
• a preliminary boosted gas supply path supplying a preliminary boosted gas to the primary side of the separation membrane in the separation membrane module,
• wherein the preliminary boosted gas is supplied from the preliminary boosted gas supply path to boost the pressure in the space on the primary side to a preliminary pressure between a stand-by pressure and an operating pressure, before the gas to be treated is supplied at a supply pressure higher than the stand-by pressure to the separation membrane module in a state of the stand-by pressure lower than the operating pressure when the carbon dioxide gas is permeated through the separation membrane, in order to maintain a temperature of the gas to be treated in which a decrease in pressure occurs to a temperature higher than a condensation temperature of the carbon dioxide gas or a solidification temperature of the carbon dioxide gas.