METHOD AND DEVICE FOR TREATING WASTE GAS

PROBLEM TO BE SOLVED: To stably control the discharge concn. of an acidic component to a specific value or below by spraying the required minimum quantity of a neutralizing agent while utilizing the merit of semi-dry method. SOLUTION: This device consists of a stage where a residual component of the acidic component is removed with a dust collecting machine 4 by spraying the powdery neutralizing agent after removing a part of the acidic component in waste gas by introducing the waste gas into a semi-dry reaction column 3 and the spraying slurrfied neutralizing agent. At the time of spraying the later powdery neutralizing agent, the acidic component quantity of the whole subject to be treated is estimated by using one or more values among the waste gas flow rate after dust collecting treatment, the waste gas temp. at the upstream than a waste gas cooling means by water spraying, the steam generating quantity of a steam type heat recovering means, the air quantity for combustion to a waste incinerator, the secondary air quantity to the waste incinerator, the low level heat generation of the matter to be incinerated, the CO2 concn. in the waste gas after dust collecting treatment and the O2 concn. in the waste gas after dust collecting treatment without always detecting the acidic component concn. in untreated waste gas, and the spraying quantity of the powdery neutralizing agent corresponding to the residual acidic component after spraying the slurrfied neutralizing agent is controlled on the base of the acidic component quantity.