Patent GB-261755-A (GB)
Title: Improvements in or relating to gas purification process and apparatus
IPC: C10K1/12
Filed: 1926-11-17
Abstract: 261,755. Koppers Co., (Assignees of Sperr, F. W.). Nov. 18, 1925, [Convention date]. Purifying processes; purifier waste, revivifying.-Sulphuretted hydrogen is removed from gases by absorption in a wash liquor containing ammonia and an iron or other metal compound. The ammonia is distilled or otherwise removed from the sulphided liquor and is recovered or fixed. The liquor is then aerated to regenerate the wash liquor. The ammonia required for the latter may be absorbed from the gas being purified, as in the arrangement of plant shown in plan in Fig. 2 in which coke oven gases are treated according to the direct ammonia recovery process. The gases from a battery of coke ovens pass up stand pipes 2 into collecting main 3 and then through mains 10, 11, 14, 15 and manifold 16 to the primary coolers 17. Leaving the latter the gases pass through manifold 19, tar extractor 21, exhauster 24 to manifold 26 and then to either or both ammonia washers 27. Tar and ammonia liquor collect in a hot drain tank 5 and pass to separating tank 51, the tar entering tank 52 and ammonia liquor collecting in tank 53. Instead of washing out the uncondensed ammonia in the scrubbers 27 with water, an aqueous suspension of hydrated ferric oxide prepared as described in Specification 255,140 is employed. The ammonia and sulphuretted hydrogen are absorbed and the. sulphided liquor passes through pipe 31 to an ordinary steam still 32, the ammonia being condensed in condenser 34 and collected in tank 37. The sulphided suspension leaves the still through pipe 38 and is regenerated in a thionizer 40 constructed and operated as described in Specification 255,139. It is advantageous to provide baffles 80 and to subdivide the thionizer into compartments to facilitate cleaning. Air is supplied to the sulphided liquor in finely divided condition through fabric tubes. Sulphur collects as a foam and enters trough 41, from which it may be led to a centrifuge. Flotation agents e.g. kerosene may be used. The hot regenerated liquor is pumped to coils 45 cooled with water and thence through pipe 47 to scrubbers 27. Instead of iron hydrate other metal compounds, for example of manganese, cobalt and nickel may be used but preferably in the form of oxide, hydroxide, carbonate or sulphide in order to avoid forming fixed ammonium salts. Soluble metal salts such as the chloride or sulphate may however be added merely to replenish losses. The ammonia liquor from tank 53 is pumped to the usual free ammonia still 58 with liming section and to the fixed ammonia still 60, the ammonia passing to the condenser 34. As ammonium thiosulphate and thiocyanate are formed in the washing liquor circulating between the scrubber and the regenerator, portions of it may be withdrawn by pipe 62 to still 58. In a modification, the invention is applied to a direct process of ammonia recovery from fuel gases. Plant similar to that shown in Fig. 2 may be employed but the temperature of the gas or liquor in the scrubbers 27 which may be constructed as described in Specification 238,172 is regulated so that only sufficient ammonia is absorbed to facilitate the removal of sulphuretted hydrogen. The gas freed from sulphuretted hydrogen is partially reheated and then enters a saturator for the production of ammonium sulphate and finally passes to an acid trap and cooler. The washing liquor is regenerated as before and the ammonia 'both from still 32 and still 58 is passed to the saturator. In the arrangement of plant shown in Fig. 5, the invention is applied to the treatment of a gas containing sulphuretted hydrogen and no ammonia. The gas is first washed in an absorber 100 preferably constructed as described in Specification 255,142, and having two sections. Into the upper section a suspension of an iron compound is sprayed and into the lower an ammonia liquor is introduced through sprays 103. Sulphuretted hydrogen is absorbed in the lower section and the liquor after being cooled in a recuperator 108 passes to a still 109 and is regenerated as in the previous processes in a thionizer 117. Concentrated ammonia from the still 109 heats the recuperator 108, is condensed in coil 111 and collects in a tank 112 whence it is circulated in the lower section of the absorber 100. The regenerated iron liquor after cooling in coils 45 is returned to the upper half of the absorber to catch any ammonia leaving the lower section. Additional ammonia is introduced as required, and fixed ammonia from the thionizer is regenerated. Instead of distilling off the ammonia before aeration, the ammonia may be fixed or removed by other means e.g. by acidifying or blowing in heated gas. Soluble substances may be present such as a little sodium carbonate or other alkaline material to assist the ammonia. Inert substances may also be present.