GB1346838A - Removal of sulphur dioxide from gas streams - Google Patents

Abstract

1346838 Removal of sulphur dioxide from gas streams CHEMICAL CONSTRUCTION CORP 27 Oct 1971 49935/71 Heading C1A Sulphur dioxide is removed from a gas stream by scrubbing with an aqueous solution of magnesium sulphite and magnesium bisulphite, the gas passing downwards through a Venturi passage provided with a central conical baffle, part of the solution being sprayed centrally down on to the apex of the baffle and the remainder flowing down on the inner converging walls of the Venturi, the liquid to gas flow ratio being maintained below 5 kg. liquid per kg. gas, separating the resultant scrubbing solution after separation of the gas into two streams, the first (1%-30% by volume) being processed to produce a sulphur-containing product, magnesium oxide being added to the second to convert at least a portion of the dissolved magnesium bisulphate into magnesium sulphite and recycling to the scrubbing stage. As shown, an aqueous solution of magnesium sulphite and magnesium bisulphite containing 50 to 90% magnesium bisulphite is passed via stream 2 and divided into streams 3 and 4 to the reaction vessel. Stream 4 is sprayed on to the conical baffle 7 while stream 3 is allowed to trickle down the inner faces 12 and 13 of the Venturi. Waste gas containing, e.g. 0-01 to 8À0% sulphur dioxide is fed through pipe 9 into the Venturi at an initial temperature of 40‹ to 350‹ C. Any entrained particles of solid material such as fly ash are carried by the liquid droplets into the collecting chamber 23, purified gas passing upwards through the ring shaped separator 20 to remove any liquid droplets and out to the atmosphere via pipe 22. The liquid stream 24 from 23 is filtered or centrifuged at 25 to remove solids, and the separated solids in stream 26 washed to remove any magnesium sulphite and then sent to waste. Wash water and the clear stream from 26 are combined and divided into two streams, one 28 passed to magnesium sulphite recovery and the other 29 recycled. Any magnesium bisulphite in stream 28 is converted to sulphite by addition of MgO. The so-formed MgSO 3 may be recovered or processed into MgO and SO 2 which in its turn may be processed into sulphur or sulphuric acid. To stream 29 makeup magnesium oxide slurry is added and the resulting stream recycled via line 2. Reference has been directed by the Comptroller to Specification 1,275,266.