GB750399A - Process of removing constituents from gases - Google Patents

Abstract

750,399. Purifying gases. GES. FUR LINDE'S EISMASCHINEN AKT.-GES., and LURGI GES. FUR WARMETECHNIK. Sept. 11, 1952 [Aug. 11, 1952] No. 22863/52. Class 55(2). In a process for removing water, benzene and homologues, resin-forming substances, hydrocyanic acid, nitrogen oxides, inorganic and organic sulphur compounds, and carbon di-oxide from coke-oven gases, the compressed gas is subjected to the following treatments : washing with cold water to remove hydro, cyanic acid ; cooling to + 5‹ to -35‹C. for separating out the naphthalene, the benzene hydrocarbons and the water; low temperature cooling to about -70‹C. as a preparation for a first washing stage in which hydrogen sulphide and organic sulphur compounds are removed and a second washing stage in which carbon di-oxide is removed, both washings being by a low-cooled solvent and the cold losses being made up by a cooling machine. In the Figure coke-oven gas under 16 atmospheres pressure enters at 103 a scrubber 104 where hydrocyanic acid is removed by washing with water at + 20‹C. Hydrocyanic acid is recovered by expansion and heating of the aqueous solution in a tower 105. Water from the tower 105 is cooled in a scrubber 106 to +20‹C. by contacting it with a dry methane fraction and is recirculated to scrubber 104. The gas/from scrubber 104 is then cooled to between + 5‹ and -25‹C. in coolers 108, 109 and 110, the latter being cooled with liquid ammonia. Benzene and homologues are recovered from the condensate from these coolers, acetone being sprayed into the coolers to prevent deposition of solids. The gas is then cooled to -70‹C. in cooler 111 by a cold methane fraction obtained in a subsequent fractional separation of the purified coke-oven gas, this methane fraction subsequently passes as coolant through scrubbers 108 and 109. In scrubber 112 the gas cooled to -70‹C., is washed to remove H 2 S with acetone at -70‹C., a cooling coil 113 supplied with liquid ethane being provided in the scrubber. The gas is then washed with acetone at -92‹C. in a scrubber 121 to remove last traces of H 2 S and the CO 2 , purified gas leaves at 127b for fractional separation. Used acetone from scrubber 121 passes in part through an expansion valve 123 to a regenerator 124 and in part through a cooler 126b for use in scrubber 112. In regenerator 124 the acetone is stripped of dissolved substances by passing methane therethrough at -95‹C., the methane and liberated gases leave the regenerator to pass through active carbon absorbers 128a and 128b to recover acetone and may be used in coolers 111, 109 and 108. Regenerated acetone is returned to the scrubber 121, being cooled in cooler 126a cooled by liquid ethane. Washing liquid from scrubber 112 passes through an expansion valve 114 and heat exchangers 116 and 117 and undergoes rectification at 118. The gas obtained during the rectification may be worked up into sulphur or sulphuric acid. Rectified acetone is pumped by 119 through heat exchanger 117, cooler 120 which is cooled by liquid ammonia, heat exchanger 116 and cooler 126a to the top of scrubber 121. Other solvents may be employed as washing liquids, e.g. methylethyl ketone at temperatures between -60‹ and -86‹C., methanol at temperatures between -70‹ and -97‹C., methanol containing between 10 and 20 per cent by weight of water at temperatures below -90‹C. and commercial dimethyl-formamide at temperatures between -55‹ and -77‹C. In these cases ethylene and ethane may be dissolved in the scrubber 121 and may be recovered from the gases liberated from the regenerator 124 by washing with a solvent, e.g. acetone or caustic potash, in which they are sparingly soluble. Reference has been directed by the Comptroller to Specification 692,804.