WET DESULFURIZATION PROCESS FOR ABSORPTIVE REMOVAL OF SULFUROUS ACID GAS IN EXHAUST GAS

摘要

PURPOSE:To bring the titled desulfurization system to a closed system not discharging a MgSO4 solution, by adding a chelate agent to the recirculation solution containing Mg(OH)2 as absorbent of an absorbing tower and keeping the pH thereof low while depositing, separating and recovering MgSO4 from a waste absorbing solution. CONSTITUTION:Exhaust gas is guided to an absorbing tower 1 and brought into contact with a recirculation solution, of which the pH is adjusted to 4.0-6.5 by an Mg(OH)2 slurry and to which a chelate agent such as EDTA is added from a pipe 9, to absorb and remove SO2. A part of the recirculation solution is guided to a neutralization/crystallization tank 2 while Mg(OH)2 is added thereto from a pipe 14 to convert Mg(HSO3)2 in the solution to Mg(SO3)2. The deposited MgSO3 crystal is guided to a solid-liquid separator 3 and separated and recovered. The filtrate is refluxed into the absorbing tower 1 through a filtrate tank 16 and a pipe 18.