| 摘要 |
During the production of cellulose pulp, the concentration and temperature of the green liquor in the chemical recovery system, are controlled so as to produce pure monohydrate or pure decahydrate sodium carbonate crystals. The crystals are removed from the green liquor by a centrifuging or screening operation to produce a first stream of green liquor having high sulfidity. The sodium carbonate crystals can be causticized to produce a treatment liquor containing essentially sulfur-free sodium hydroxide. The green liquor may be causticized, and may be further treated with sulfur compounds obtained by the heat treatment of black liquor, so as to increase its sulfidity to over 50%. The sodium hydroxide can either be used in later stages of pulping, in the bleach plant, or for scrubbing the sulfur containing gases from heat treatment of black liquor so as to produce sodium hydrosulfide. In general, a feasible way of producing liquor streams having vastly different sulfidity in a cellulose pulping process and chemical recovery system is provided. |
