Abstract: The dry slaking of lime is carried out continuously in a vessel from which an exhaust gas is removed. Hot gas, preferably a flue gas to be desulfurized, is added to the exhaust gas to prevent it from contacting the inner surface of the exhaust gas duct and thereby reduce the tendency for deposits in lines traversed by the exhaust gas.

Abstract: A method of optimizing the collection efficiency of a dry-process electrostatic precipitator which is preceded by an evaporative cooler, wherein liquid is sprayed into the evaporative cooler at a rate which is controllable to maintain a desired temperature includes the steps of intermittently measuring the dew points of acid separately and setting the desired temperature T.sub.c in dependence on the measured dew point of acid and a preselected margin of safety .DELTA.T, in accordance with T.sub.c =T.sub.s +.DELTA.T, determining a desired input current I.sub.c for the electrostatic precipitator at T.sub.c and storing I.sub.c, and continuously calculating the deviations of the actual input current I of the precipitator from the desired input current I.sub.c and initiating the measurement of the dew point T.sub.s of acid in response to a predetermined deviation to update the desired temperature T.sub.c.