GB670028A - Improvements in and relating to the removal of nitric oxide-hydrogen cyanide and sulphide from coal distillation gases - Google Patents

Abstract

670,028. Purifying coal gas. HAMBURGER GASWERKE GES. March 29, 1949 [Nov. 8, 1948], No. 8472/49. Class 55 (ii). Hydrogen cyanide, gum - forming nitric oxide and hydrogen sulphide are removed from coal gas which has been freed from tar but which still contains ammonia, by first removing the HCN and NO in a preliminary purifier in which is a mass containing iron oxide which has been sulphided by the H 2 S and rendered alkaline by the ammonia in the gas, and then removing the H 2 S in one or more subsequent iron oxide purifiers. The apparatus shown consists of three purifiers I, II and III, each having an insulated vertical, cylindrical shell containing superimposed, removable containers 8, 9 and 10 through which passes an axial gas inlet pipe 7. Gas flows through the three purifiers in series, entering the first through a pipe 1 to flow upwardly past a heating or cooling coil 5, up through the pipe 7 and downwardly through the purifying mass in each container, discharging through a pipe 13 into a vessel 15 where it is heated to between 30‹ and 40‹ C. and saturated by steam admitted through a pipe 15a, before entering purifier II. Air for the revivification in situ of the material in purifier II is also admitted through pipe 15a. Initially, all the purifiers are charged with iron oxide. The mass in purifier I is rapidly sulphided and rendered alkaline and in this condition absorbs the HCN and NO from the gas with evolution of H 2 S which, with the H 2 S present in the gas, is removed in purifiers II and III by the normal reaction. Two distinct spent masses result from the process, first, a normal spent oxide from II and III and second, a mass containing ferrocyanide from purifier I. To overcome the decrease in gas permeability which would otherwise occur, the fresh oxide is briquetted before loading it into the containers. For the HCN and NO removal, a particularly suitable mass is produced by melting crystalline ferrous sulphate solidifying, and exposing it to the gas, when it is converted into a lumpy mass containing ferrous oxide. U.S.A. Specification 1,976,704 is referred to.