Improvements in and relating to the treatment of sulphur

摘要

Impure sulphur is rapidly heated through the plastic range, preferably 160 DEG -370 DEG C., by mixing with a relatively large body of liquid sulphur at a temperature above the plastic range and subjecting the mixture to fractional distillation. The process may be applied to the purification by distillation of sulphur in sulphur-selenium anode sludge produced in the electrolytic refining of nickel sulphide. As shown, impure sulphur is delivered tangentially to one or more bubble tray units 25 (Figs. 2 and 3, not shown) in a distillation column 10 having a reboiler 34 from one or more steam-jacketed inlet pipes 14-16 at a temperature of 120-162 DEG C., preferably 120-154 DEG C., and is mixed with, for example, 5-20 times its volume of reflux so as to raise the temperature rapidly above 260 DEG C. Sulphur containing concentrated impurities is periodically removed through steam-heated bottoms cooling tank 62 while sulphur vapour is passed through condenser 17. Condensed sulphur, e.g. at 370 DEG C., is passed through reflux tank 18 and is then partly recycled as reflux via line 19 and partly passed to sulphur quenching and surge tank 21 (Figs. 4 and 5, not shown) via line 20, while uncondensed sulphur vapour is passed through vent condenser 60, wherein the vapour is cooled to below 150 DEG C., and vented wash tower 61, residual gas being passed to the atmosphere. The condensed sulphur is rapidly cooled in tank 21 to below 160 DEG C., e.g. to 120 DEG C., by 10-20 times its volume of sulphur which is recycled between tank 21 and a waste-heat boiler comprising a heat exchanger 48 and a liquid-vapour separator 52. Tank 21 is provided with a steam coil to melt sulphur when starting up. Cooled liquid sulphur is passed through one or more of lines 55 to water-cooled trays in solidifier 24. The heat exchange medium for reboiler 34 and condenser 17 may be a fused mixture of sodium nitrate and nitrite. The process may be carried out in the presence of nitrogen.