Abstract: A washer having a controlled-gap scrubber is connected to the gas outlet of a pressure blast furnace and an expansion turbine for the recovery of energy is connected downstream of the controlled-gap washer unit while a bypass is connected across the turbine. The system has operating regions A and B on a diagram in which the gas pressure is plotted along the ordinate and the volume rate of flow of gas from said blast furnace is plotted along the abscissa, the region A being defined between the turbine-insertion and the turbine-operating characteristic curves plotted on the diagram, the region B being defined between the turbine-operating characteristic curve and the corrected blast-furnace characteristic curve. The pressure in the blast furnace where the operating point is in region A while the gas traverses the turbine is controlled by varying the gap width of said control-gap washer unit in response to the pressure.

Abstract: The gases emerging from a high-pressure gas furnace are subject to coarse particle separation and then to washing and scrubbing with water before driving an expansion turbine which has a gas bypass so that the turbine can be cut off. The scrubbing water recycled to the scrubber when the turbine is cut off, is permitted to traverse a cooler of the washing-water recovery unit but, when the turbine is operative, the scrubbing water bypasses the cooler. The water introduced into the scrubber can thus have a temperature of about 25.degree. C. when the turbine is bypassed and about 50.degree. C. when it is effective.