Improvement in the process for the treatment of trap containing sulphate from the process of recovery of SO2 and improvement in the process for recovering SO2

摘要

Metal, e.g. sodium sulfate, is separated from metal, e.g. sodium sulfite, in a solution, for instance a solution used in a system involving contact of sulfur dioxide-containing gases with the sodium sulfite solution as an absorbing solution to recover sulfur dioxide wherein the absorbing solution is regenerated after contact with the gas and recycled for further use. A portion of the absorbing solution is purged to avoid the unduly large build-up of sodium sulfate in it. The purge stream is contacted with sulfur dioxide to reduce the amount of sodium sulfite therein to relatively soluble sodium bisulfite, and the relatively insoluble sodium sulfate is recovered therefrom as undissolved solids. The liquid separated from the sodium sulfate, which is rich in sodium bisulfite, is returned to the absorbing solution. In a preferred aspect, the purge stream is withdrawn from the absorbing solution subsequent to contact with the sulfur dioxide-containing gases and before regeneration.