Patent ID: 8734747

Claim:
A method for treating exhaust gas, comprising the steps of: measuring SO 3 concentration in the exhaust gas which contains at least SO 2 and SO 3 by using an SO 3 gas analyzer; injecting fine particles into the exhaust gas after the step of measuring; cooling the exhaust gas after the step of injecting, by recovering heat from the exhaust gas; collecting fly ash from the cooled exhaust gas; and removing at least SO 2 from the exhaust gas after the step of collecting, by absorbing the SO 2 with an absorbing solution, wherein the step of injecting comprises controlling a injection amount of the fine particles so that a weight ratio of a sum of flying dust concentration A and fine particles concentration P to the SO 3 concentration S, as shown in an expression “{(A+P)/S)}”, becomes 2.0 or higher.