PROCESS FOR PURIFYING METHANE FERMENTATION GAS

PROBLEM TO BE SOLVED: To provide a purified methane gas useful as a fuel or the like by purifying a methane fermentation gas by using a relatively simple apparatus and method, and elevating a calorie per a unit volume of the gas. SOLUTION: The method comprises supplying the methane fermentation gas to the bottom of an absorption column pressurized at a pressure of≥1 atm., supplying an absorbing water to the top of the column, making an unnecessary gas such as carbon dioxide or the like contained in the methane fermentation gas absorbed into the absorbing water by bringing the methane fermentation gas into counter-current contact with the absorbing water and recovering the purified methane gas from the upper part of the column. The dissolved gas can be removed from the absorbing water by flushing or diffusing the absorbing water after the absorption treatment, and also the absorbing water after the diffusion treatment can be recycled/reused. Therefore, the calories per a unit volume of the purified methane gas is elevated. By the method, the amount of the absorbing water to be used in the absorption column can be reduced and the quality of the waste water is improved. From a standpoint of equipment, the diameter of the column can be reduced and the height of the column can be lowered. COPYRIGHT: (C)2004,JPO