Patent ID: 7998446

Claim:
A flue gas desulfurization process which comprises (i) contacting a SO 2 -containing flue gas stream with a recirculating stream of an aqueous medium containing concentrated sulfuric acid of at least 40 wt % H 2 SO 4 and hydrogen peroxide, under conditions such that SO 2 is absorbed from the flue gas into the aqueous medium to yield a desulfurized flue gas stream and such that the absorbed SO 2 reacts with the hydrogen peroxide to produce additional sulfuric acid in the recirculating stream; (ii) diverting a portion of the recirculating aqueous sulfuric acid stream for recovery of the additional sulfuric acid as gypsum in a neutralization step, in which sufficient neutralizing agent selected from limestone, lime and calcium hydroxide is introduced into the diverted aqueous sulfuric acid stream portion to neutralize the sulfuric acid present and produce a gypsum product; (iii) refortifying the recirculating aqueous sulfuric acid stream with concentrated hydrogen peroxide to maintain a steady state H 2 O 2 concentration in the recirculating aqueous sulfuric acid stream introduced in step (i) into contact with the SO 2 -containing flue gas stream; and (iv) evaporating free water from the diverted and neutralized portion of the recirculating aqueous sulfuric acid stream, using the heat of reaction generated during the neutralization step, to yield a gypsum product that is substantially dry.