Patent GB-190903061-A (GB)
Title: Improvements in or connected with the Obtainment and Utilisation of Sulphur from Sulphuretted Hydrogen and Sulphur Dioxide.
Inventor: FELD WALTHER
IPC: C10K1/10
Filed: 1909-02-08
Granted: 1910-02-08
Abstract: 3061. Feld, W. Feb. 8. Sulphur is obtained from hydrogen sulphide and sulphur dioxide, pure or contained in other gases, such as coal-gas, and gases from sulphur ovens, boiler furnaces, coal, ore, or other ovens, gas-producers, retorts, &c., respectively, by treatment, simultaneously or consecutively, with a liquid containing in solution, or suspension, or both, compounds of certain metals. The sulphides of these metals are insoluble in basic, neutral, or, in some cases in weak acid, solutions, but are decomposable by sulphur dioxide, alone or in the presence of air, or other ozidizing-agent, or sulphur, or basic or acid substances, or a mixture thereof. Examples are the oxides, hydroxides, carbonates, sulphites, thionates, and basic, neutral, or weak-acid salts of zinc, manganese, iron, and other suitable metals. In an example, conducted hot or cold, zinc oxide is suspended in water, salt solution, oil, &c., and coal-gas, hot or cold, treated therewith, zinc sulphide being formed. When the resulting suspension of zinc sulphide, with or without undecomposed oxide, is treated with hot or cold sulphur dioxide, the sulphide forms free sulphur and a soluble thiosulphate, or polythionates, or both. The alternate gaseous treatment is repeated continuously, the ' thionates,' (general term for the last-mentioned salts), decomposing into zinc sulphide and free sulphur. If the treatment commences with sulphur dioxide, zinc sulphite is first formed. The gases may be treated simultaneously, or mixed prior to treatment. In these cases the result of deficiency of one gas can be remedied by subsequent treatment of the liquor with such gas. The accumulated sulphur can be separated, if dissolved, by crystallation, if not, by filtration, decantation, or melting out, most conveniently after the treatment with sulphur dioxide, when the zinc compounds are dissolved. Excess of free gas present may be expelled by blowing air through the liquor. In the presence of air and heat zinc sulphate is formed and must be decomposed, as by adding to the liquor a basic compound or weak-acid salt such as a sulphite, thionate, acetate, or sulphide, or by treating the liquor with gases containing ammonia, such as illuminating or coke-oven gas. Ammonium sulphate and zinc sulphide are formed, the latter being separable by decantation or filtration. If an excess of ammonia is employed, ammonium thionates are formed which can be transformed into the sulphate. When the hydrogen sulphide contains ammonia, more zinc sulphate is formed by heating the treating liquor, the heating and air-supply being regulated according to the amount of ammonia present. Ammonium sulphate may also be formed by using other sources of ammonia, weak-acid salts of ammonia, virgin liquor, &c., and heating them with the zinc liquor and air, during or after the ordinary gas treatment. The treatment may be carried out with the compounds of zinc or other suitable metals in a solid or humid state, instead of in a liquor, the finally obtained sulphur, thionates, and sulphate being separated by extraction, precipitation, and filtration. When compounds of iron or manganese, in particular, are used, the liquor must be well mixed with the sulphurdioxide gases, the escaping gases containing any trace of hydrogen sulphide being treated according to the present process, or having the sulphide extracted in any known way, as by burning, the resultant sulphur dioxide being used in the main process. Liberation of hydrogen sulphide is avoided, however, by running the liquor containing the metal sulphide into excess of a solution of sulphur dioxide. In practice the process may be carried out, in connexion with extracting hydrogen sulphide from coal-gas, as follews:-The gas passes up through a washer A against a counter current of a liquor containing, say, zinc thionates, which is pumped up from a tank F and passes out of the washer A, now containing zinc sulphide, sulphur, and thionates, to the top of an absorption tower B. Here the liquor meets a counter current of air and sulphur dioxide from a sulphur oven J fed with compressed air by a compressor I, and flows out at the bottom to a tank C provided with a stirrer c to complete the regeneration of the thionates. The suspended free sulphur thus formed is removed in a filter-press E, to which the liquor is next pumped. The liquor runs out of the press E, and into a receptacle e<2>, whence it flows into the original tank F for re-use. The sulphur from the press E may be dried and burnt in the oven J.