GB443314A - Process for the recovery of sulphur dioxide from gases containing same - Google Patents

Abstract

In the recovery of sulphur dioxide from gases by washing them with a mixture of organic bases and water, and thereafter heating the reaction product, there is added to the circulating absorption liquor, either before, during or after the absorption step, compounds of alkaline-earth metals, which precipitate in the form of sparingly soluble alkaline-earth sulphates, the sulphuric acid formed by secondary reactions (e.g. the oxidation produced by the oxygen present and the autoxidation of the sulphur dioxide). The troublesome formation of sulphates of organic bases is thereby avoided and the separation of the aqueous liquid from the organic liquid is facilitated. In addition, the effluent gas from the absorption treatment and/or the sulphur dioxide recovered in the heating step may be treated with the above compounds in the presence of water, the organic base content of these gases being thereby recovered; the liquors thus obtained may be used in the main process. The oxides, hydroxides, carbonates, neutral and acid sulphites and other weak acid salts of the alkaline-earth metals, (e.g. calcium) may be employed in the process. Suitable organic bases include aniline and its homologues, toluidines, xylidines, compounds of the above kind alkylated in the amine group, pyridine, pyridine bases, quinoline, triethanolamine, hydroxylamines and hydrazines. As regards details, the process may be conducted in the manner described in the parent Specification. The presence of elementary sulphur or substances furnishing it under the conditions of working, e.g. sulphides of alkaline-earth metals or barium hydroxide obtained by reducing barium sulphate and containing sulphide, should be avoided since sulphur catalytically accelerates the autoxidation of sulphur dioxide.