Chemical reaction furnace system

A chemical reaction furnace apparatus employing a reaction furnace, a reaction gas main flowpath for conducting reaction gas away from the top of the reaction furnace, and a reaction gas scrubbing device (5) installed in said main flowpath and having a function of controlling the pressure of the reaction gas in the top of the reaction furnace, said apparatus comprising an expansion turbine provided in the gas main flowpath downstream from said scrubbing device and being operable to utilize energy in the reaction gas, a gas bypass flowpath branched from said main flowpath at a point thereof between said scrubbing device and said turbine and bypassing the turbine, a bypass valve installed in said bypass flowpath, a turbine inlet pressure detector for detecting inlet gas pressure of the turbine, turbine inlet pressure control means receiving a signal from said pressure detector to control said bypass valve thereby to maintain the inlet gas pressure of the turbine at the highest possible value at which the scrubbing performance of said scrubbing device can be maintained, a turbine speed regulating valve installed in said main flowpath between said pressure detector and said turbine, a speed detector for detecting the rotational speed of the turbine, and a turbine governor receiving signal from said speed detector to control said speed regulating valve.