Patent ID: 7419643

Claim:
An apparatus for recovering gypsum product and magnesium hydroxide product from flue gas containing sulfur dioxide, the apparatus comprising: a scrubber for removing sulfur dioxide from the flue gas and producing magnesium sulfite and magnesium bisulfite, wherein said apparatus is structured for oxidizing the magnesium sulfite and magnesium bisulfite by reaction with air to produce magnesium sulfate blowdown; a gypsum crystallization unit for reacting the magnesium sulfate blowdown with calcium chloride to produce gypsum slurry; a gypsum fines separation unit for removing gypsum fines from the gypsum slurry; a dewatering filter belt for washing the gypsum slurry after the gypsum fines are removed to produce gypsum product, a magnesium chloride filtrate, and a residual stream; a magnesium hydroxide production vessel for reacting the magnesium chloride filtrate with calcium hydroxide to produce magnesium hydroxide slurry; a grit removal unit for removing grit and unreacted calcium hydroxide from the magnesium hydroxide slurry to produce a treated magnesium hydroxide slurry; and a magnesium hydroxide purification unit for purifying the treated magnesium hydroxide slurry to produce a magnesium hydroxide product and a calcium chloride solution.