Verfahren zur Aufarbeitung von Sulfitablaugen

摘要

In an operation in which spent soda-base liquor from the digestion of wood is evaporated and burned under reducing conditions to form a smelt of sodium carbonate and sodium sulphide, the smelt is cooled and solidified by pouring it on to a cooled metal surface and is ground with a solution of sodium carbonate and sodium sulphide, the ground smelt then being contacted with a concentrated sodium carbonate solution to dissolve sodium sulphide. The ground smelt is preferably such a size as will pass through a screen of 10 mesh per lineal inch. The particles are passed countercurrent to the sodium carbonate solution and the resulting solution of sodium carbonate and sodium sulphide is passed to a carbonation stage to produce hydrogen sulphide and sodium carbonate. A slurry of sodium carbonate crystals is obtained from the extraction column. The slurry is separated and part of the sodium carbonate solution is recycled to the extraction stage, some is used to slurry the crystals and some is incorporated in the spent soda-base liquor. The solution of sodium carbonate obtained from the carbonation stage may be divided into three parts, one to slurry the solid smelt to the grinder, one part is sent to the extraction column and one is used to sluice the sodium carbonate crystals from a separator at the base of the extraction column.