Method for controlling chloride concentration in the flue gas of a recovery boiler

A method for reducing the chlorine concentration accumulating in a sulphate cellulose process, which comprises the steps of:

• a. feeding black liquor generated in the sulphate cellulose process to a soda recovery boiler for combustion and generation of flue gases;
• b. introducing sulphurous odor gases generated in the sulphate cellulose process into the soda recovery boiler for burning in the boiler to generate further flue gases including sulphur oxides;
• c. maintaining the feed rate of the sulphurous odor gases into the boiler in such an amount that the concentration of sulphur oxides in the recovery boiler is such that at least part of the sodium chloride content of the black liquor fed to the recovery boiler and vaporized in gaseous form from a bed in the lower portion of the recovery boiler is converted from sodium chloride by reaction with the sulphur oxides so as to produce hydrogen chloride present in the flue gases in the upper part of the recovery boiler;
• d. removing said flue gases from the upper part of the recovery boiler to a scrubber;
• e. removing hydrogen chloride by scrubbing said flue gases with a washing liquid in said scrubber;
• and
• f. separating at least a portion of said washing liquid.