Methane separation method, methane separation apparatus, and methane utilization system

A methane separation apparatus where methane is separated from a biogas containing methane and carbon dioxide as components, the apparatus at least comprising:

• a mixer mixing the biogas and an absorbing liquid that absorbs carbon dioxide so as to form a mixed fluid of a gas-liquid mixed phase;
• a first gas/liquid separator in which the mixed fluid is introduced so as to separate the mixed fluid through gas/liquid separation into methane and a CO2-absorbed liquid formed due to an absorption of the carbon dioxide by the absorbing liquid;
• and
• a first separation unit having a membrane module comprised of a container and a plurality of hollow fiber permeable membranes built therein, in which the CO2-absorbed liquid is supplied through a supply port to inside of the permeable membranes so as to make the CO2-containing liquid permeate the permeable membranes, and a pressure outside the permeable membranes is lowered to a level lower than that inside the permeable membranes, thereby releasing the carbon dioxide contained in the CO2-absorbed liquid to outside of the permeable membranes so as to separate carbon dioxide, and recovering the absorbing liquid obtained by separating carbon dioxide from the CO2-absorbed liquid due to the membrane module.