Cotton Koh - Nh < Sub > 4 < / Sub > Oh Clean Pulping Process Research

Cotton stalk is a good raw material of pulping.However, due to difficulties of the black liquor treatment in the alkaline pulping process, hindering the development of cotton stalk pulping industry to some degrees.In the thesis, the pulping methods of cotton stalk and treatment of pulping black liquor were reviewed in detail.And a new clean pulping method with KOH-NH4OH was put forward, the pulping liquor not only contained two nutritional elements of K and N, but also dissolved lignin and other organic matters can be further processed into organic slow release fertilizer,it can solve the the pulping pollution problem from the source.Various factors on the effects of cooking condition were studied,using response surface methodology to optimize the cooking conditions, and the optimum pulping process conditions was obtained:KOH dosage was30%,NH4OH dosage was12.6%, liquid ratio was1:7, maximum cooking temperature was170℃, time to maximum temperature was120min, time at maximum temperature was60min. Concluded from the research that pulping yield was45.63%, Kappa number was29.2, pH of the black liquor was12.08and residual alkali concentration was19.04g/L.Delignification reaction course and kinetics of cotton stalk by KOH-NH4OH method were also studied.The result indicated that the delignification course could be divided into3stages:the initial deligninfication stage from the beginning temperature raised to150℃, and the delignification rate was34.84%;the bulk deligninfication stage from the temperature of150℃to170℃for preserving60minutes, and the delignification rate was reached87.41%;the residual delignification stage from170℃preserving for60minutes to the end, and the lignin was further removed.Kinetics studies showed at the initial delignification stage, the reaction order to pulp lignin and OH-concentraction was1and0.7respectively, the activation energy was58.49kJ/mol; at the bulk deligninfication stage,the reaction order to pulp lignin and OH-concentraction were both l,the activation energy was50.63kJ/mol.Black liquor could be made into fertilizer after acid neutralization and mixed, the ammonia volatilization and soil column leaching tests were carried out compared with clean liquid fertilizer with same nutrients to verify the effectiveness of N, P, K. The results showed that ammonia volatilization of black liquid fertilizer was significantly lower than clear liquid fertilizer, also it can reduce the leaching rate of N, K and soil P fixed,and it had a good slow-release effect.