GB137071A - Improvements in the production of concentrated nitrous gases and nitric acid - Google Patents

Abstract

137,071. Norsk Hydro - Elektrisk Kvµlstofaktieselskab. Oct. 21, 1916, [Convention date]. Nitrogen oxides. - Dilutegases containing nitrogen oxides are treated with a solid absorbent consisting of a mixture of a base such as an alkali or alkaline earth hydrate with one or more metal oxides, which form easily decomposable compounds with alkalies and alkaline earths, such as iron, zinc, and aluminium oxides, the saturated absorbent being then heated to expel the nitrogen oxides in a concentrated condition. The absorption may be effected under pressure and at a raised temperature, for instance 400-500‹ C., and the decomposition may be assisted by steam or vacuum. In the example described, two retorts (or batteries of retorts) C, H are arranged to be used as absorbers and decomposers alternately. Hot gas containing nitrogen oxides is supplied by a valve B from a main A to the jacket of the retort C, which contains saturated absorbent to be decomposed, and a portion of the hot gas is admitted to the retort C by a valve D or by perforations in the retort wall, valves b, g, i being closed. Concentrated nitrogen oxides escape from the retort C by valve E and pipe F. The main part of the gases from the jacket of the retort C pass by valves G to the jacket of the retort H and thence through a valve D<1> into the retort H, where the nitrogen oxides are absorbed and the waste gases escape by valves J and pipe L. When the decomposition in C and the absorption in H are complete, the valves B, G, J are closed and the corresponding valves b, g, i are opened so that H becomes the decomposer and C the absorber.