Flammable gas concentration device and flammable gas concentration method

A flammable gas concentration device comprising:

• an adsorption tower filled by an adsorbent for adsorbing a flammable gas, wherein said adsorbent is a methane adsorbent for selectively adsorbing methane gas, wherein said adsorbent has a methane gas adsorption of 20 Ncc/g or higher at atmospheric pressure and 298 K, and wherein said adsorbent is at least one of active carbon, zeolite, silica gel and an organic metal complex;
• feeding means for feeding a raw gas containing air and a flammable gas to said adsorption tower at near atmospheric pressure via a feeding path and discharging an exhaust gas in said raw gas which has not been adsorbed to said adsorbent to an outside of said adsorption tower via a discharge path;
• collection means for reducing a pressure in said adsorption tower lower than an atmospheric pressure, and desorbing the flammable gas adsorbed by said adsorbent and collecting the flammable gas through a collection path;
• and
• control means for sequentially executing a flammable gas adsorption step of feeding said raw gas to said adsorption tower and discharging said exhaust gas from said adsorption tower by said feeding means, and a flammable gas desorption step of collecting said flammable gas desorbed by said collection means.