Recovery of sulfur dioxide from waste gas streams

Claim 2

The process of claim 1, in which said solid crystals are processed by adding a solid particulate carbonaceous material to said solid crystals, heating the resulting solids mixture under reducing conditions, whereby an off-gas stream containing elemental sulfur vapor is evolved, and cooling the off-gas stream to condense product elemental sulfur.

Claim 3

The process of claim 1, in which said solid crystals are processed by calcining said solid crystals at a temperature in the range of 400* C. to 1200* C., whereby an off-gas stream containing sulfur dioxide is evolved, and cooling said off-gas stream to condense product liquid sulfur dioxide.

Claim 4

The process of claim 1, in which said solid crystals are processed by calcining said solid crystals at a temperature in the range of 400* C. to 1200* C., whereby an off-gas stream containing sulfur dioxide is evolved, and passing said off-gas stream to a sulfuric acid production facility, whereby the sulfur dioxide content of said off-gas stream is converted to sulfuric acid.

Claim 5

The process of claim 1, in which said waste gas stream contains sulfur trioxide, said sulfur trioxide is absorbed into said aqueous absorbent solution whereby sodium sulfate is formed in solution, the sodium sulfate content of said second solution portion is converted to a solid sulfate selected from the group consisting of magnesium sulfate and calcium sulfate and dissolved sodium carbonate by the addition of said mineral carbonate particles, whereby said solid crystals contain a solid sulfate, and the solid sulfate content of said solid crystals is also converted to a sulfur-containing product and an oxide selected from the group consisting of magnesium oxide and calcium oxide by the processing of said solid crystals at elevated temperature.

Claim 6

A process for the recovery of sulfur dioxide from a waste gas stream containing sulfur dioxide which comprises scrubbing said waste gas stream with an aqueous absorbent solution containing dissolved sodium sulfite, whereby sulfur dioxide is absorbed into said aqueous absorbent solution and reacts with a portion of the dissolved sodium sulfite to form sodium bisulfite, dividing the resulting solution into a first portion and a second portion, adding a reactant stream comprising sodium carbonate to said first solution portion, whereby sodium bisulfite in said first solution portion is converted to sodium sulfite, recycling the resulting first solution portion for further waste gas scrubbing, forming aqueous sodium carbonate solution by adding dolomite particles to said second solution portion, whereby said dolomite reacts with dissolved sodium sulfite and sodium bisulfite in said second solution portion to form dissolved sodium carbonate and insoluble solid crystals containing magnesium sulfite and calcium sulfite, said solid crystals being precipitated from residual aqueous solution containing sodium carbonate, recycling sodium carbonate contained in said residual aqueous solution as said reactant stream comprising sodium carbonate, calcining said solid crystals at a temperature in the range of 400* C. to 1200* C., whereby an off-gas stream containing sulfur dioxide is evolved and a mixture of solid magnesium oxide and calcium oxide is produced, and processing said off-gas stream to produce a sulfur containing product.

Claim 7

The process of claim 7, in which said waste gas stream contains entrained solid particles, said solid particles are scrubbed from said waste gas stream by said aqueous absorbent solution, and said second solution portion is processed to remove the solid particles component prior to addition of said dolomite particles.

Claim 8

The process of claim 7, in which said off-gas stream is processed to produce a sulfur-containing product by cooling said off-gas stream to selectively condense product liquid sulfur dioxide.

Claim 9

The process of claim 7, in which said off-gas stream is processed to produce a sulfur-containing product by passing said off-gas stream to a sulfuric acid production facility, whereby the sulfur dioxide content of said off-gas stream is converted to sulfuric acid.

Claim 10

The process of claim 7, in which said waste gas stream contains sulfur trioxide, said sulfur trioxide is absorbed into said aqueous absorbent solution whereby sodium sulfate is formed in solution, the sodium sulfate content of said seconD solution portion is converted to solid calcium sulfate and dissolved sodium carbonate by the addition of said dolomite particles, whereby said solid crystals contain calcium sulfate, and the calcium sulfate content of said solid crystals is also converted to gaseous sulfur dioxide and calcium oxide by the calcining of said solid crystals.