Patent ID: 7927576

Claim:
A process for continuous production of a concentrated solution of ammonium thiosulfate (ATS) comprising the steps of: (a) contacting an SO 2 containing feed gas stream with a re-circulating liquid stream of ATS solution to absorb and react with the SO 2 , to produce a sulfite rich ATS solution; (b) contacting an H 2 S containing feed gas stream with a re-circulating liquid stream of ATS solution to absorb and react with the H 2 S, to produce an ATS solution having a low sulfite content; (c) recycling the sulfite rich ATS solution produced in Step (a) to contact the H 2 S containing feed gas stream of Step (b), and recycling the ATS solution having a low sulfite content produced in Step (b) to contact the SO 2 containing feed gas stream of Step (a), to produce additional ATS having a high sulfite content; (d) stopping the recycling in Step (c) to cause the re-circulating liquid stream of ATS solution in Step (a) to convert to an ABS solution, and contacting the SO 2 containing feed gas stream with a re-circulating liquid stream of the ABS solution to absorb and react with the SO 2 , to produce a sulfite rich ABS solution; (e) contacting the sulfite rich ABS solution produced in Step (d) with the re-circulating liquid stream of ATS solution in Step (b); and (f) removing the ATS solution produced in Steps (a), (b) and/or (c) to obtain a concentrated solution of ATS having optimum sulfite concentration and pH.