Modern Gasworks Practice

542 MODERN GASWORKS PRACTICE The war, unfortunately, ratter interfered with tlie progress of processes of this kind; and, although the Burkheiser process is said to be in constant operation at the Tegel gasworks, it is to be noted that wlicn tried at a gasworks in this country it proved a failure and was discontinuecL Parrish 1 has suggested that the original failure of the process was due mainly to two defects :— (1) So far as the sulphur cycle is concerned, it was found that the introduction of heated air to the purifiers containing FeS, together with free sulphur along with iron oxide, led to the formation of soluble iron salts, such as FeSO4. This fixation of the SO 2 was disastrous from two points of view. It represented the loss of acid gases and the inability to regenerate completely oxide of iron, except by special means which had. not apparently been originally contemplated. (2) The presence of H2S in the gases from which ammonia was to be removed by the sulphurouß acid solution resulted in the reduction of the H2S and the precipita-tion of sulphur in the bath—thus impairing the quality of the ammonium salts produced. Careful reflection on the various reactions involved in the Burkheiser process certainly leads to the conviction that, by suitable modification, the process could be operated successfully. One of the directions in which modification will need to proceed is in the removal of the H2S from the crude gas before absorption in the acid bath is effected. Certain portions of the Burkheiser process can be applied to ordinary gasworks practice. It is conceivable that if ammoniacal liquor were first desulphurized—the sulphur-freed ammoniacal liquor being next distilled to release the ammonia—the latter gas could be absorbed in an acid solution prepared by the absorption of SO2 in water, such SO2 being produced. by the combustion of spent oxide. In this way tliere would be no necessity for the expensive Glover and Gay Lussac towers and acid chamberc of the sulphuric acid plant. By pursuing this method, saleable ammonium salts could conceivably be produced. The Feld Process The Feld plant extracts ammonia and sulphuretted hydrogen simultaneously, at the same time oxidizing an amount of sulphuretted hydrogen equivalent to the ammonia in the gas. Sulphate of ammonia is yielded, whilst the surplus sulphur is obtained in the solid form. Within the last year or so, the plant has undergone some modification.; the original process is, however, of considerable interest, and is de-scribed in outline below. For the sake of simplicity, the various stages in the working are sub-divided under different headings, so that there should be no difficulty in following out the scheine with. the aid. of the accompanying diagram (Fig. 342). Process 1.—Gas containing NH3 and H2S is washed with a weak solution of ferrous sulphate. Sulphate of ammonia is formed, and sulphide of iron precipitated— (a) FeSO4 + 2NH4,OH = (NH4)2SO4 + Fe(0H)2. (&) Fe(OH2) + H2S = FeS + 2 H2O. 1 Proc. Southern Assocn. Gas Eng., Nov., 1913.