Abstract: The present invention has been realized in order to treat noxious and combustible gases, which are exhausted during the start-up operation of a composite coal gasification-power plant and/or released from various safety valves arranged in such power plant and which have hitherto been discharged without treatment into the atmosphere, to make it innoxious and to attain an efficient energy utilization and concerns an improvement of such a composite coal gasification-power plant, which is characterized either in that an additional combustion unit is disposed parallel to the burner of the gas-turbine electric power generating unit and is arranged so as to supply the combustion exhaust gas of this additional combustion unit to as to supply the combustion exhaust gas of this additional combustion unit to the waste heat boiler, or in that an additional combustion unit, operative to effect to burn the noxious and combustible gases exhausted from the burner during start-up and/or those released from safety valves arran