In developing countries more than 50 percent of the pulp is manufactured from nonwood raw materials, mainly agricultural residues (bagasse, wheat and rice straw) and various grasses. Most of the mills are of small- and medium-size (30-200 BDMTD) and are using alkaline pulping process (soda, soda-AQ kraft). While all wood based pulp mills are recovering the chemicals from spent liquor (black liquor) generated in allcaline pulping, most of the small agro-based mills are draining the black liquor (BL), in water bodies causing heavy water pollution. In 1995-1996 a study was carried out by UNIDO for evaluation of equipment and technologies available and commercially used, especially in China and India, on recovery of chemicals from nonwood black liquor in small-and medium-size mills (50-200 BDMTD). Existing recovery systems, including pulp washing and black liquor desilicaiton were reviewed. A pre-feasibility study for a black liquor desilication and chemical recovery was carried out taking into consideration various pulp production capacities.
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