Process Control for Dissolving Pulp by Super Batch Cooking

Dissolving pulp is a raw material consisting of regenerated cellulose and other cellulose derivatives and is widely used in products including viscose rayon, cellulose, and cellulose ester. The raw material used to produce dissolving pulp is wood and cotton linter. Since 2007, because of the shortage of cotton linter, viscose mills have used dissolved wood pulp as the raw material instead of dissolved cotton pulp. Domestic pulp mills have built and rebuilt several dissolving pulp lines. In 2014, the global dissolving pulp capacity was 6.4~6.8 million tons; the device utilization was roughly 80%. Because the price of dissolving pulp remains low and the dissolving pulp capacity continues to increase, the amount of dissolving pulp released is expected to exceed 2.6 million tons in the next five years. Because of the development of the viscose industry, the price of viscose has fallen sharply, and competition has increased in intensity. However, the quality of domestically produced dissolving pulp is not good, and thus, it can only be used to produce viscose; the demand of dissolving pulp in other areas, such as the production of cellulose ether and acetate fiber, must be satisfied by imports. Therefore, improving the quality of the dissolving pulp is urgently needed. A good dissolving pulp should have a high a -cellulose content, low contents of ash, iron, and hemicellulose or other impurities (non-cellulosic components), and high brightness. The degree of polymerization should be uniform, and the distribution should be as narrow as possible. The chemical reactivity of the dissolving pulp should be high, and good contact between cellulose and chemicals should be achieved. JinPing He, technical manager; research interests: chemical pulping process; E-mail:jinping.he@valmet.com Abstract: The process of producing dissolving pulp with SuperBatch cooking was introduced. The factors that affected the quality of the dissolving pulp and the corresponding operations were investigated. JinPing He, SuJin Xie