GB785153A - Improvements in or relating to separation of acid gases from coal carbonisation gases - Google Patents

Abstract

<PICT:0785153/III/1> In recovering acidic gases, for example hydrogen cyanide, hydrogen sulphide and carbon dioxide, from the actifier vapours of a hot-vacuum-actification process for fuel gas purification wherein the gases are passed through condensing equipment, at least one steam jet evacuator is provided in series with the condensing equipment to prevent the formation of hard polymer. Coke-oven gas is treated in a scrubber 4 with a countercurrent of aqueous sodium carbonatebicarbonate solution circulating in a closed circuit between scrubber 4 and actifier 12, the latter being under a vacuum of four inches mercury and being heated by a coil 16. The recovered acid gases with ammonia, any high-melting compounds and an excess of water vapour pass from actifier 12 to condenser 21 at the same pressure as the actifier. A petroleum distillate boiling at 100 DEG to 300 DEG C. is led from tank 47 by pipe 50 to steam-jacketed vaporizer 52 and thence into the gases through pipe 53 before they enter condenser 21. The gases are then passed into a jet evacuator 66 into which steam is passed through a line 67. The exhausted, mixed, steam and gases, leaving the evacuator 66 at about 75 DEG to 80 DEG C., are passed through a scrubber 25 counter-current to water from spray 26 to remove ammonia. The gases then flow to condenser 30 after a further injection of oil from pipe 53, and thence through liquid trap 23 to vacuum pump 33. The acid gases at 5-10 lb. pressure pass to final condenser 35, after treatment with excess fresh oil vapour through steam-jacketed vaporizer 42 and pipe 43, and are withdrawn at 36 for refining and separation. The oil-water condensate from condensers 21, 30 and trap 23, is transferred by pipe 22 to separator 54, the water is separated and passed to tank 56 and may be re-cycled to make up the alkaline solution from actifier 12 through line 58 and pump 59 while the oil is separated and passed to tank 60 and may be drawn off through line 62 for use as fuel. The oil-water condensate from condenser 35 is separated in separator 40 and the water is discarded while the oil passes to tank 47. Live steam may be used to help vaporize the oil. In a modification the steam jet evacuator may be placed before the condenser 21 or after the ammonia scrubber 25. Also the scrubber 25 may be omitted if desired. In a further form three vaporizers for oil are used instead of two. In another modification in which hydrogen cyanide is not recovered two jet evacuators are used instead of a jet evacuator and a pump. Specifcations 190,115, [Class I (ii)], 612,122, and 675,348 are referred to.