NOVELTY - A mixed gas supply apparatus has an adsorption tower equipped with gas inlet portion, gas outlet portion and gas extraction portion which is provided in position more downstream than middle of gas inlet portion and gas outlet portion. The gas inlet portion and gas outlet portion are respectively linked to upstream and downstream piping of a supply line. The adsorption tower is filled with adsorbent through supply line path of mixed gas in which gas composition changes with time passage. Bypass piping and flow-ratio control unit are provided in the downstream of adsorption tower.    USE - Mixed gas supply apparatus is used for controlling composition fluctuation and adjusting emitted-heat amount of fuel gas e.g. town gas, byproduct gas, exhaust gas and biomass, using emitted-heat amount adjusting device (all claimed).    ADVANTAGE - The mixed gas supply apparatus enables emitted-heat amount stabilization of fuel gas, and restrains composition fluctuation to predetermined range.    DETAILED DESCRIPTION - A mixed gas supply apparatus has an adsorption tower equipped with gas inlet portion, gas outlet portion and gas extraction portion which is provided in position more downstream than middle of gas inlet portion and gas outlet portion. The gas inlet portion and gas outlet portion are respectively linked to upstream and downstream piping of a supply line. The adsorption tower is filled with adsorbent through supply line path of mixed gas in which gas composition changes with time passage. Bypass piping and flow-ratio control unit are provided in the downstream of adsorption tower. The bypass piping connects gas extraction portion and juncture of downstream piping. The flow-ratio control unit adjusts flow ratio of mixed gas passing through downstream piping and bypass piping in the path to the juncture of downstream piping, such that the composition fluctuation range of mixed gas is controlled after merging. INDEPENDENT CLAIMS are included for the following:    (1) method for controlling composition fluctuation, which involves adjusting flow ratio of mixed gas by flow-ratio control unit, such that the composition fluctuation of mixed gas is controlled to desired range;    (2) method for adjusting emission amount of heat, which involves adjusting flow ratio of gas composition containing fuel gas or town gas by flow-ratio control unit, such that the emitted-heat amount of town gas is adjusted to predetermined range; and    (3) emitted-heat amount adjusting device, which has mixed gas supply apparatus. The emitted heat-amount of fuel gas or town gas is adjusted to predetermined range, after passing through adsorption-tower passage.    DESCRIPTION OF DRAWING(S) - The drawing shows a typical view of mixed gas supply apparatus. (Drawing includes non-English language text)