GB190203A - Improvements in the recovery of valuable products from coal gases - Google Patents

Abstract

Coal or coke-oven gas, previously freed from tar, cyanogen compounds and part of the ammonia content, is passed at ordinary or slightly raised temperature through a number of towers containing active charcoal, such as is obtained by charring wood with zinc chloride. In the first towers, all the benzene hydrocarbons are absorbed; in the next towers, the hydrogen sulphide is removed in the state of free sulphur, after a sufficient amount of oxygen-containing gas with or without ammonia has been added; finally, if desired, the ethylene hydrocarbons are absorbed in the last towers. By employing an arrangement of interchangeable towers, the process may be conducted in a continuous manner. Instead of absorbing ethylene as such in the last towers, it may be converted into ethylene compounds by interaction with halogens &c. in the presence of the active charcoal, and these compounds are then retained. The absorbed substances are removed at intervals, for instance, by extraction with a solvent or by expulsion with steam; and by diminishing the pressure in steps during the operation, a fractional removal of the absorbed substances may be effected. Specifications 153,297, 170,152, [both in Class 55 (ii), Gas manufacture &c.], and 177,362, [Class 2 (iii), Dyes &c.] are referred to.ALSO:Coal or coke-oven gas, previously freed from tar, cyanogen compounds and part of the ammonia content, is passed at ordinary or slightly raised temperature through a number of towers containing active charcoal, such as is obtained by charring wood with zinc chloride. Ethylene hydrocarbons are either absorbed as such in the last towers or are converted into compounds by interaction with halogens, &c., in the presence of the active charcoal, and these compounds then retained. Specification 177,362 is referred to.ALSO:Coal or coke-oven gas, previously freed from tar, cyanogen compounds and part of the ammonia content, is passed at ordinary or slightly raised temperature through a number of towers containing active charcoal, such as is obtained by charring wood with zinc chloride. IN the first towers, all the benzene hydrocarbons are absorbed, whilst any hydrocyanic acid present becomes converted by the ammonia and sulphur compounds into ammonium thiocyanate and is also deposited in the first towers. Before entering the last towers for the absorption of ethylene, the gas may be freed from ammonia by washing with aqueous sulphuric acid or other acid, or the ethylene may be scrubbed after liberation from the charcoal.