Technological Study Of Cooking And Bleaching In The Process Of Refined Cotton Production

Refined cotton,commonly known as"industrial monosodium glutamate",is a high-purity cellulose product made from cotton linter as raw material refined by alkali cooking,widely used in the manufacture of cellulose esters,nitrocellulose（nitrocellulose）and cellulose acetate,etc.It is estimated that domestic refined cotton.The output will reach400,000 tons,with a good market prospect.However,there are still some problems in the production process of the refined cotton,such as,the circulating water used in the washing and bleaching process has an effect on the viscosity of the product;chlorine dioxide is easily decomposed in aqueous solution;and repeated utilization ratio of cooking lye is low.And all of these problems seriously restrict the development of refined cotton industry.Many scholars have devoted themselves to the study of new cooking methods,but their practical application is limited.The top priority in solving the problems of the refined cotton industry is to optimize the water quality at the process stage.During the production process,the refined cotton is soaked with bleaching water,bleaching liquor,cooking cycle alkali,etc.This paper has studied the process of cooking-chlorine dioxide bleaching,optimized the process parameters,compared the changes of the whiteness of cotton pulp before and after the addition of stabilizer;explored the treatment effect of different kinds of activated carbon on the COD in the cooking waste alkali.Conclusions are as follows:（1）The results showed that four factors influenced the viscosity in different degrees,that is,residual chlorine>Ca²⁺>washing time>pH.When the residual chlorine concentration was 0.035g/L,the Ca²⁺concentration 90 mg/L,the residence time 1h and the pH 7,the optimum washing parameters could be achieved.When residual chlorine concentration was changed,it was found that viscosity decent rate intended to increase after decreasing with the increase of residual chlorine,and the minimum rate was 11%.When Ca²⁺concentration was altered,it was discovered that the minimum rate could be realized with Ca²⁺concentration being 110mg/L.When NaCl was added,the rate could be2.2%.When bleaching liquid purity was changed in bleaching process,the rate could be only 2.1%.（2）The results showed that purity stability was best measured by the malonic acid method.The best single-component stabilizer is sodium borate,and the purity drop of chlorine dioxide is only 5%;the best multi-component stabilizer is sodium borate+EDTA.Although the drop rate of chlorine dioxide purity was 10.67%,but the initial purity was0.76 times higher than that of sodium borate.The add of sodium dodecyl benzene sulfonate as auxiliaries to sodium borate+EDTA system can achieve the best results.Its initial purity is 1.73 times higher than that of the original system.With orthogonal method being used to optimize parameters,it was found that when the stabilizer component was sodium borate+EDTA+sodium dodecyl benzene sulfonate,the optimal stabilizer parameters were as follows:the concentration was 2g/L,and the ratio was 5:3:2,absorption temperature was 60°C;With optimum parameters,the bleaching effects of the bleaching solution before and after the addtion of stabilizer were compared by the contrast method,and it was found that the whiteness of the cotton pulp remains basically stable after adding the stabilizer.（3）The results showed that the effect of coal granular DC-101 activated carbon was better,and it took 3 hours for the activated carbon to reach equilibrium at 25℃.The removal rate of COD in cooking waste alkali was 43.25%;in a certain period of time,the lower the temperature was,the better the adsorption temperature was.The removal rate of COD in cooking waste alkali at 20℃was 45.37%.