GB1162610A - Sulfur Dioxide Recovery Process - Google Patents

Abstract

1,162,610. Extracting SO 2 from waste gas. TREADWELL CORP. 24 Oct., 1967 [25 Oct., 1966], No. 48211/67. Heading C1A. Sulphur dioxide is recovered from hot waste combustion gas by (i) cooling gas, (ii) contacting gas at atmospheric pressure in an absorber with sufficient water to dissolve a major proportion of the sulphur dioxide, (iii) flashing the solution in a gas recovery zone at reduced pressure to obtain gas and water vapour which is condensed, and (iv) recycling water to the absorber. Cooling may take place using recycled water and the flashing apparatus may incorporate a stripper operating at very low pressure for final recovery of gas. Waste gas supplied, e.g. at 150-500‹ F., may contain less than 7% SO 2 : product gas may contain at least 25% SO 2 . As shown, in cooler 11 gas from 10 flows counter current to cooling water 12. Cooled gas passes to absorber 18, there contacting water spray 18. Waste gas is expelled at 20 and a solution comprising, e.g., 75% of the SO 2 present passes to a gas recovery zone comprising flashing tanks 22, 34, 41, 48 (operating at successively reduced pressure) and stripper 55. Product gas is discharged to line 27 via lines 23, 35, 42, 49, 64, water vapour being removed in condensers 26, 38, 45, 51, 59, 63 with discharge of water via lines 29, 32. Water from stripper 55 is recycled to absorber 17, minus bleed-off at 81 (to maintain constant acidity), plus make-up at 82. Lowpressure steam for stripper 55 is provided via lines 72, 77 after passing water from cooler 11 through flash steam generators 71, 74 operating at substantially stripper pressure: residual water is recycled to cooler 11.