Method of treating melodorous gases of a pulp mill

Abstract

A method is provided for reducing emissions of harmful nitrogen compounds from a pulp mill (e.g. kraft mill) having malodorous gases which include ammonia and reduced sulphur compounds therein. The method is practiced by (a) treating the pulp mill malodorous gases to lower the ammonia content thereof (e.g. by washing them with a bisulfite solution, such as one produced from washing flue gases with sodium sulphite), and then (b) burning the malodorous gases (e.g. in a dedicated incinerator, recovery boiler, power boiler, or lime kiln) under conditions which effect oxidation of reduced sulfur compounds therein (e.g. with an air excess of at least about 3% and a temperature of over 800 degrees C) so as to reduce odor emissions and emissions of harmful nitrogen compounds from the pulp mill. In the method (a) and (b) may be practiced using malodorous gas from a steam stripper as part of the malodorous gases treated, and the operating conditions, including the pH, of the stream stripper may be regulated in order to reduce the ammonia content of the clean condensate it produces.