GB664733A - Coke oven gas purification process - Google Patents

Abstract

664,733. Revivifying gas-purifier liquor. KOPPERS CO., Inc. July 21; 1949 [Nov. 23, 1948], No. 19231/49. Class 55 (ii).. Coke oven gas is scrubbed with alkaline aqueous absorbent which is then regenerated under sub-atmospheric pressure, evolved vapours being scrubbed with a different absorbent, thus reducing the volume of gas to be handled by a vacuum pump which maintains the sub-atmospheric conditions in the actifier or regenerator. Gases from oven 10 are sprayed with liquor in a collecting main 12, traversing thence a primary cooler 18, tar extractor 21 and absorber 26 supplied with a solution, e.g. sodium carbonate, from the bottom of an actifier 30 through a cooler 32, all the hydrogen sulphide, hydrogen cyanide, and ammonia content of the gas being absorbed. The solution collecting at the bottom of the absorber ascends round baffles 33 in counterflow with tar pumped from a tank 16 below a downcomer 15 at the outlet of the main, naphthalene being thereby removed from the solution which is pumped to sprayers 40 at an intermediate point in the actifier. At the base the fouled solution is indirectly heated by a reboiler 41 through which rela: tively hot flushing liquor is circulated by a pump 25. By means of a vacuum pump 72 the pressure within the actifier may be as low as 4 ins. mercury; ammonia, hydrogen sulphide and hydrogen cyanide emitted pass through a deflegmator 43, which condenses steam returned as water to sprays 46, to a wash oil spray chamber 54 to remove naphthalene traces before treatment in an absorber 60 with ammoniacal liquor circulated by a pump 61 through a cooler 62 to sprays 64. Liquor pumped through reboiler 41 is subjected to the reduced pressure of the actifier in a flash tank 50, water vapour therefrom passing to the actifier to make up for moisture not returned by deflegmator 43. The liquid is returned by a pump 57 to sprays 14 in the main, a portion being diverted into the circuit of the secondary absorber 60. Compounds formed in the absorber by reaction of ammonia with the sulphide and cyanide remain in the solution passing to an ammonia still 70. Residual gases flow from the absorber through a water separator 67 to an acid washer 71 for removal of traces of ammonia before passage through the vacuum pump. Gases from still 70 are delivered to an ammonia saturator 75. Specification 209,379, [Class 55 (ii)], is referred to.