GB727028A - Process for removing constituents of coke-oven gas - Google Patents

Abstract

727,028. Purifying gases. ENGEL, E., and HARPENER BERGBAU AKT.-GES. Jan. 9, 1953 [Jan. 10, 1952], No. 746/52. Class 55 (2). Constituents are removed from coke-oven gas, from which ammonia has already been removed, by compressing the gas to a pressure suitable for long distance distribution, indirectly cooling the compressed gas to a temperature below about 25‹ C. so that a liquid solution of part of the hydrocarbons and naphthalene contained in the gas separates out, and subsequently indirectly cooling the still unexpanded gas to a temperature in the range -20‹ C, to -50‹ C. whereby the residual benzol and naphthalene are separated out in solid form. As shown, gas from a coke-oven battery 1 passes through coolers 3, 4 for removal of most of the water vapour, tar and naphthalene, to a scrubber 5 for removal of ammonia. The gas is then compressed at 6 where the temperature rises to 100‹-140‹ C., the gas being then cooled at 7 to 50‹-60‹ C. and at 8 to 20‹-25‹ C. Benzol and further naphthalene is thus condensed out of the gas, the naphthalene dissolving in the benzol and collecting therewith in a receiver 9. The gas is desulphurized by a dry process in the apparatus 10, but is conditioned for this treatment in apparatus 11 wherein it is heated and moistened by injection of water-vapour condensate. The gas is at about 35‹ C. during the desulphurization, but is cooled to about 20‹ C. in two re-coolers 12, 13 before passing to the coolers 14, 15 in which the temperature falls to about - 15‹ C. to -25‹C., thereby effecting a further separation of benzol and naphthalene. The coolers 14, 15 operate reversibly in series and are cooled indirectly, in counterflow, by very cold purified gas from the final coolers 18, 19 which are used in alternation and are cooled by an ammonia refrigerating plant having a compressor 25. The gas from the coolers 12, 13 passes through a first cooler, say 14, in which the temperature falls to about 3‹ C. causing liquid condensate to collect in a trap 16. The temperature falls to about -25‹ C. in the second cooler 15 which causes solid condensate to contract the gas-flow passages. The solid condensate is thawed by passing the gas firstly through the cooler 15 and reversing also the direction of coolant gas flow, which latter may be heated by steam at 17. The gas passes through one or other of the final coolers 18, 19, where the temperature is lowered to about - 50‹ C. and the final separation of benzol and naphthalene occurs, through benzol traps 20, 21 to the main 29, part of the gas being tapped off by an expansion device 30 for heating the battery 1. When one of the coolers is obstucted with solid naphthalene, it is shut off, the gas passing through the other cooler whilst the obstructed cooler is thawed out by means of the refrigerant which has condensed, the melted deposits flowing to the receiver 9. In the refrigerating plant, ammonia vapour is drawn from the trap 24 into the low-pressure stage of the compressor 25, and passes from thence via an intermediate pressure cylinder 26 to the high pressure stage of the compressor. The compressed vapours are condensed in a water-cooled liquifier 27, pass through the cylinder 26 to the trap 24 and from thence to one or other cooler 18, 19. The return flow is through the trap 24.