To mix a low-calorie gas with a high-calorie gas by using a facility having simple constitution.
This fuel gas mixer for mixing a low-calorie gas such as bio-gas with a high-calorie gas such as city gas, etc., includes a low-calorie gas-supplying line 4 arranging a gas holder 12 for storing the low-calorie gas, a gas booster 44, and a gas flow rate-adjusting means 50 for adjusting the flow rate of the gas from an entrance one by one, a high-calorie gas-supplying line 62 and a mixing means 68 for receiving the gases supplied from both supplying lines and sending off as mixed gas. The above gas holder has a storage part 14 expanding and contracting by almost having a constant pressure under an atmospheric pressure within a fixed volume range, and an expanding amount-meter 34 expressing the inner volume of the storage part as a transferring amount of the portion of the storage part in expanding direction, and is constituted so that in the case that the expanding amount is at or more than a fixed amount, the gas booster is actuated and in the case that it is less than the fixed amount, the gas booster is stopped.
KAYANO HIDENORI
KAWAHITO NAOMI
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