Natural-gas purification apparatus

A natural-gas purification apparatus for purifying natural gas from ground by separating carbon dioxide from the natural gas, comprising:

• a first pressure adjuster that adjusts a pressure of the natural gas from the ground;
• a first high-boiling-point-hydrocarbon-component separator that liquefies and separates a high-boiling-point hydrocarbon component by cooling the natural gas after the pressure adjustment by the first pressure adjuster;
• a first heater that heats the natural gas after the separation of the high-boiling-point hydrocarbon component by the first high-boiling-point-hydrocarbon-component separator;
• a carbon-dioxide separator including a plurality of carbon-dioxide separation units that are arranged in series and separate carbon dioxide from the natural gas heated by the first heater through carbon-dioxide separation membranes;
• a bypass path that is provided in each of gas supply pipes connecting the plurality of carbon-dioxide separation units of the carbon-dioxide separator to each other in series, through a gas-flow switcher and supplies the natural gas after the carbon-dioxide separation by the carbon-dioxide separator;
• a second pressure adjuster that is provided on the bypass path and adjusts the pressure of the natural gas after the carbon-dioxide separation by the carbon-dioxide separators;
• a second high-boiling-point-hydrocarbon-component separator that liquefies and separates a high-boiling-point hydrocarbon component by cooling the natural gas after the pressure adjustment by the second pressure adjuster;
• and
• a second heater that heats the natural gas after the separation of the high-boiling-point hydrocarbon component by the second high-boiling-point-hydrocarbon-component separator,
• wherein the by-pass path includes:
• a first gas supply path that supplies the natural gas after the carbon dioxide separation by the carbon-dioxide separation unit that is arranged upstream of the gas-flow switcher in gas flow to the second pressure adjuster;
• and
• a second gas supply path that supplies the natural gas heated by the second heater to the carbon dioxide separation unit that is arranged downstream of the gas-flow switcher in the gas flow.