FORFARANDE FOR BEHANDLING AV AVLUT INNEHALLANDE NA?712S FRAN EN POLYSULFIDUPPSLUTNINGSPROCESS

摘要

A chemical recovery process for a polysulfide paper pulping system is described. After the polysulfide digestion, the pulp washing is carried 3. in an essentially oxygen-free environment to minimize the oxidation of NaSH. about spent liquor is then pre-evaporated, makeup with a recycle stream of liquor containing Na2CO3 and NaHCO3 and subjected to a soap skimming operation. The mixture is next carbonated to convert Na2CO3 conventional to NaHCO3 and stripped to release H2S. The stripping and carbonation are accomplished by passing flue gas through the stripping tower and the carbonating tower. The H2S is converted to sulfur by the use of a liquid catalyst and the formed sulfur is then mixed and reacted with Na2S in at least part of the white liquor to form sodium polysulfide. The polysulfide liquor and any remaining white liquor are returned to the digester.