In Korea, 450,000 TDS(ton dry solid) of black liquor is generating at pulp process every year. Black liquor is a byproduct of the Kraft pulp production process when digesting wood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers with sodium-based alkali compounds such as sodium hydroxide and sodium sulfide.fl] Dry base black liquor contains ca. 35% of alkali compounds and 65% of lignin-based organics. Most pulp mills have used black liquor as an energy source by burning in recovery boilers and alkali compounds is recovered from ash. Because this recovery process is not so economic but it is performed instead of waste treatment, value improvement of black liquor is still needed.
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