The technology of desulfurization of the sludge fraction descending from consumed battery recast and utilization of the after-leaching solutions

摘要

The processing of wastes or secondary rawmaterials, considering economic and ecological problems,makes still new demands, which oblige to search andelaboration of new technological solutions. Among thosematerials are the sludges deriving from the recast of consumedbatteries. They contain about 6 percent of sulphate sulphur.The processing technology of these materials includes smeltingwith coke, soda and scrap-iron. It is accompanied by largeemission of SO_2 to the atmosphere and the obtained slagscontain about 4 percent Pb. Such slags don't meet ecologicalconditions. The principle of the worked out method is based onleaching of PbSO_4 in Na_2CO_3 solution. The result is: adeposit containing lead carbonate and a solution of sodiumsulphate. In known technologies this solution is used for theproduction of sodium sulphate by thickening andcrystallization. Actually presented technology includes anotherutilization manner for sodium sulphate solution. It is based ondifferent solubility of sodium and potassium compounds. KOHis added to the solution after leaching, which reacts withNa_2SO_4, forming K_2SO_4. It is precipitated from thesolution after having exceeded the solubility limit.Subsequently the solution is carbonized by gaseous CO_2 andreverted to leaching, after filtration of waterless K_2SO_4.