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 pressure adjuster that adjusts a pressure of the natural gas from the ground;
• a natural-gas-liquid separator that liquefies and separates a part of natural-gas liquid by cooling the natural gas after the pressure adjustment by the pressure adjuster;
• a heater that heats the natural gas after the separation of the part of the natural-gas liquid by the natural-gas-liquid separator;
• a carbon-dioxide separator that separates carbon dioxide from the natural gas heated by the heater through a carbon-dioxide separation membrane;
• a detection carbon-dioxide separator that further separates carbon dioxide from purified gas obtained as a result of the carbon-dioxide separation by the carbon-dioxide separator through a carbon-dioxide separation membrane;
• a carbon-dioxide-amount detector that detects an amount of carbon dioxide separated by the detection carbon-dioxide separator;
• and
• a controller that adjusts and controls at least one of:
• a pressure of the natural gas to be achieved by the pressure adjuster,
• a temperature to which the natural gas is to be cooled by the natural-gas-liquid separator, and
• a temperature to which the natural gas is to be heated by the heater based on information from the carbon-dioxide-amount detector such that the amount of carbon dioxide to be separated by the detection carbon-dioxide separator is higher than or equal to a prescribed amount.