To provide a gas mixing device, inexpensive and of high control accuracy and also a gas mixing control method thereof.
The flow rate control for a raw material gas is carried out by the control of the opening and closing time for shut-off valves, and the gas after mixing is accumulated in a buffer tank 2, and the opening time for the shut-off valves 8-1-8-3 for controlling the flow rate is adjusted based on the gas analysis result of the mixed gas. As the control method, a method for computing based on the computation of the buffer tank capacity, pressure and gas composition and filling the buffer tank with pressure by one control, a method for controlling repeatedly the similar computation for a given period and a method for carrying out the PID control based on the density difference of respective gas contents are adopted. The raw material gas can be a mixed gas. For the manufacture of synthetic air, the flow rate control for oxygen and nitrogen can be carried out while feeding a base gas. Although it is desirable to use a means for making constant the differential pressure in front and rear of the shut-off valves, alternatively the temperature and pressure of the raw material gas and the mixed gas can be sensed to correct the flow rate coefficient of the shut-off valves.
YOSHISAKA YOSHISUKE
NAKAMURA RYUICHI
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