Wet type exhaust gas desulfurization method and apparatus utilizing solid desulfurizing agent

PCT No. PCT/JP95/00922 Sec. 371 Date Oct. 11, 1995 Sec. 102(e) Date Oct. 11, 1995 PCT Filed May 11, 1995 PCT Pub. No. WO96/26785 PCT Pub. Date Jun. 9, 1996Exhaust gas from combustion equipment such as a boiler is brought into contact with an absorbing liquid to absorb sulfur oxide from the exhaust gas into the absorbing liquid. Limestone particles having larger diameters are selectively retained in a zone wherein the absorbing liquid that has absorbed the sulfur oxide from the exhaust gas is neutralized. The absorbing liquid containing water and the gypsum thereby formed, as main constituents, are selectively drained from the neutralizing zone and recycled for renewed contact with the exhaust gas. Because of the possibility of a large decrease of desulfurizing performance due to a variation in the load on the boiler, etc., at least one of the following is monitored: pressure drop across the neutralizing zone, torque of a stirring device, solids concentration in the absorbing liquid, specific gravity of the absorbing liquid and viscosity of the absorbing liquid. Responsive to the monitored parameters outlet SO2 concentration is controlled within a predetermined range by regulation of at least one of the following: flow rate of the absorbing liquid circulated into contact with the exhaust gas, amount of the solid desulfurizing agent added to the absorbing liquid, particle diameter of the solid desulfurizing agent and speed of agitation of the solid desulfurizing agent in the neutralizing zone.