Study On Potassium Sulfite Process And Mechanism Of Rice Straw

In China, non-wood raw material is one of main raw material for pulping. But alkali from spent liquor is difficult to be recycled, which caused resource waste and environment pollution. To enrich the application of raw material and offset the fertilizer lacking element of K in our country, seawater extracting potassium sulfite cooking rice straw was adopted. Seawater extracting potassium sulfite cooking rice straw so not make use of sea water resources, reduce the cooking of production costs, and also be able to make use of spent liquor in potassium sulfite pulping of rice straw which have potassium elements and organic matter. The spent liquid produces agricultural liquid fertilizer to irrigate field or valid compound fertilizer. Seawater extraction of potassium sulfite pulping realized thepurpose in circulative economy such as process of agriculture produces──rice straw using──pulping──fertilizer──agriculture.In this paper, using the method of single factor experiment study potassium sulfite pulping of rice straw technical parameters and then through four single factor optimize experiment, at last get optimal technical parameters for potassium sulfite pulping of rice straw: potassium sulfite chargel4%, potassium hydrate charg3%, maximum temperature 170℃, time at maximum temperature is 120min, liquor ratio 1:6. Further potassium sulfite dosage on wheat straw cooking were optimized on the basis of the discussed optimal technical parameters of potassium sulfite pulping of rice straw. The optimal technical parameters of potassium sulfite pulping of wheat straw were as following: potassium sulfite charge 15%, potassium hydrate charg3%, maximum temperature170℃, time at maximum temperature is 180min, liquor ratio1:6.Effects of the novel cooking additive potassium phosphate and routine cooking additives (AQ, CT-1) on potassium sulfite cooking of rice and wheat straw were studied in this paper. Effects of ammonium sulfate on potassium sulfite cooking of rice straw were studied. The results show that potassium phosphate can decrease the kappa number of the pulps in varying degrees. AQ has positive effect on potassium sulfite pulping of wheat straw while AQ and CT-1 can not obviously effect on potassium sulfite pulping of rice straw. Ammonium sulfate is against potassium sulfite pulping of rice straw. Adding ammonium sulfate on the pulping process can increase the pulp kappa number of the pulps and lower the pulp yield.Delignification mechanism of potassium sulfite pulping of rice straw were studied by pulping experiment carried out under stable and well-defined conditions. Results show that two distinct delignification stages occur during pulping process, namely, the fast speed delignification stage from 50℃to 170℃, the slow speed delignification stage at beginning of time at maximum temperature to the cooking end. It is found that about 73.06% of the lignin is dissolved in the fast speed delignification stage.Seawater extracting potassium sulfite cooking rice straw was studied. The results show seawater extracting potassium sulfite cooking rice straw and chemically pure potassium sulfite cooking rice straw have similar results.