Control system for combustible gas concentration

Purpose: To enable stabilized temperature control and flow rate control concerning combustible gas concentration control for keeping the hydrogen concentration to less than a specified level in a reactor container. Constitution: The gas concentration control system comprises control means for stabilizing the temperature in a recombiner by adjusting the recycling flow rate depending on the temperature change in the recombiner and means for stably controlling the flow rate by adjusting the flow rate at the inlet of the recombiner. In a case where the hydrogen concentration in the container is high and the temperature in the recombiner is increased, the reaction heat due to the recombination is suppressed by increasing the recycling flow rate to thereby dilute hydrogen. Since the recycling flow rate is controlled by the temperature in the recombiner, the changes in the flow rate due to the interactions with the inlet flow rate can be suppressed. (Horiuchi, T.)