Improvements relating to the extraction by organic solvents of sulphur from material containing free sulphur and inorganic compounds

摘要

PICT:0608143/III/1 A process for the recovery of sulphur from an aqueous paste of sulphur-containing material, especially mixtures of sulphur and iron compounds, such as the settled, filtered or otherwise partially de-watered crude sulphur obtained in gas purification by washing with aqueous iron oxide suspensions consisting of sulphur containing up to 50 per cent by weight of water, comprises treating the paste with a solvent consisting mainly or entirely of aromatic hydrocarbons boiling between 100 DEG C. and 140 DEG C., such as toluene or xylene or a mixture of these, or the aromatic hydrocarbons obtained in admixture with paraffins and olefins from coal gas, preferably the fraction with a boiling range approximating closely to that of toluene or xylene, and removing the water from the sulphur paste as a low boiling mixture with the solvent, the mixture of water and solvent vapour being condensed and separated, and the solvent returned to the system. In one embodiment the aqueous sulphur paste is fed from a hopper to the steam jacketted kettle 13 provided with perforated shelves 16 affording maximum exposure to hot solvent entering through 17, 18 which boils freely in contact with paste giving a mixture of steam and solvent vapour which passes to condensers 27, 28, thence to a distillate separator 31 whence the water is continuously discharged, the sulphur forming a solution which, with the suspension of inorganic compounds, falls to the cone-shaped bottom 15 of the kettle 13. The sulphur solution passes to the steam jacketted separator 19 which is in hydraulic balance with the kettle 13, wherein the inorganic compounds settle in the conical base 21 whence they may be discharged to receiver 22, while clear sulphur solution passes continuously to the evaporator 23 having steam chest 24 and vertical boiling tubes 25 wherein sulphur separates as crystals or liquid depending on the boiling point of the solution, which may be fixed by choice of suitable solvent, or may be kept above the melting point of sulphur by admitting live steam at 26 to promote boiling at a reduced temperature. Mixed vapours from the evaporator 23 pass to the condensers 27, 28 and distillate separator 31 as before, whence the solvent is returned to kettle 13. The sulphur is collected in receiver 31a and this and the solid matter in receiver 22 are deprived of their solvent content before discharge by blowing live steam through the masses. In this arrangement provision is made for the removal of a portion of the circulating solvent from time to time for redistillation in a regenerator to remove tar fouling the solvent; solvent vapour from the regenerator is returned to the condensing system described. In an alternative arrangement, the kettle and separator are combined in a single steam jacketted vessel which is more economical thermally.