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;
• 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 to a value which has been set in advance according to composition of the natural gas from the ground, such that the natural-gas-liquid separator liquefies and separates the part of the natural-gas liquid in the natural gas and the carbon-dioxide separator maintains a remaining part of the natural-gas liquid in the natural gas in gaseous form.