Process for purifying the off-gases from industrial furnaces, especially from waste incineration plants

摘要

A process for purifying the off-gases from industrial furnaces and especially from waste incineration plants is described in which process the off-gases which contain acid, neutral and/or basic pollutants in the gaseous or solid form or in the form of a mist, are treated in an evaporative cooler and then in a dry purifier, in which they are freed from at least a substantial portion of the solid pollutants, and finally in a scrubber by means of a wash liquid. The temperature of the off-gases in the evaporative cooler is kept above the dew point, and the wash liquid in the scrubber is cycled through a slurry separator, from which suspension or solution of pollutants is withdrawn from the sludge separator and fed into the evaporative cooler and mixed in a mixing space in the latter with the hot off-gases. Those walls of the evaporative cooler which come into contact with the mixture of off-gases and recycled suspension or solution of pollutants and which consist of a material that can be corroded by the said mixture at room temperature are heated from the outside to a temperature above the dew point.PP As a rule the pH value of the liquid phase in the sludge separator and in each of the gas wash stages of the scrubber directly upstream of the said separator is kept below 4.