GB304345A - Improvements in the treatment of coal distillation gases - Google Patents

Abstract

304,345. Imperial Chemical Industries, Ltd., Gordon, K., and Hughes, J. Oct. 17, 1927. Materials for purifying ; washing processes.- Coal distillation gases are washed with water and scrubbed with oil to remove tar, ammonia and benzene and the clean gas compressed preferably to 250 atmospheres. Carbon dioxide, hydrogen sulphide and sulphur compounds are removed by ammonia liquor and the gas is then treated in a tower with, an ammoniacal cuprous salt e.g. formate, acetate or carbonate, practically all the carbon monoxide and unsaturated hydrocarbons (principally ethylene) being absorbed. The gas is now washed with a high-boiling solvent e.g. kerosene to remove most of the methane as described in Specification 293,138, [Class 1 (i), Chemical processes &c.], and after the addition of gases to adjust the ratio of hydrogen to nitrogen to 3 :1 the mixture is employed for the synthesis of ammonia. The liquor resulting from the first treatment may be utilized in making ammonium sulphate from gypsum and ammonium carbonate. The gases driven off from the second washing solution by heat may be treated under pressure with silver nitrate solution which absorbs ethylene, as described in Specification 291,186, [Class 1 (i), Chemical processes &c.]. The remaining gas, mainly carbon monoxide, may be utilized in the manufacture of formates, formamide, hydrogen or carbon. The ethylene may be recovered by heating or reducing the pressure and utilized in making ethylene glycol, ethyl alcohol or ethylene dichloride. A gas consisting of about 80 per cent of methane is recovered from the third washing liquid and may be passed through an electric arc to form acetylene which is removable by a solution of mercurous sulphate in sulphuric acid and the residual gas may be recirculated through the arc or burnt to supply heat to the coke ovens. In modifications the gas may be subjected to increasing pressures for the successive washings, or the first two steps may be effected at 50 atmospheres, the final stage requiring, however, about 250 atmospheres. The sulphur compounds may be removed by the dry iron oxide process before the washing treatment.