Research On The Process And Mechanism Of Wheat Straw Alkaline Pulping With Microwave Irradiation

Microwave radiation pulping has more merits than the traditional method. Forexample, it can pulp at atmospheric pressure, shorten the time, lower the energyconsumption, reduce the dosage of the drug and pulping equipment was simple. Whatis more, it could resolve long-troubling environmental pollution which is namelydecomposition of pulp black liquor. This paper mainly studied the process andmechanism of wheat straw alkaline pulping with microwave irradiation and thetreatment of pulping black liquor. At the same time, the main conclusions are listed:（1） Raw material composition of wheatgrass is respectively the water6.57%, coldwater content10.36%, hot water drawn out things18.20%,1%sodium hydroxide takethings46.13%, benzene-alcohol content1.99%, cellulose71.37%, to take the contentof cellulose38.76%and lignin15.90%.（2） This paper eventually got the best technological conditions according to thesingle factor experiment, orthogonal experiment and level experiments.Under atmospheric conditions, when was the conditions of power450W, liquidairratio1:6, NaOH: Na₂S=6:1, time45min got pulp yield52.53%, the fiber content77.27%, kappa number22.23.Under pressure conditions, when was the conditions of power450W, liquidairratio1:7, NaOH: Na2S=8:1, time40min got pulp yield49.79%, the fiber content76.21%, kappa number15.16.Through Comparative, the process of atmospheric conditions can get high yield andhigh pulp fiber content, but a bit low delignification.（3） Delignification was indicated by the lignin content in pulping black liquor.Delignification was divided into two stages, which were principal phases ofdelignification and residual stage of delignification, through analyzing lignin contentand [OH-] in the pulping black liquor changing with time. At the same time, the twostages of delignification all followed pseudo-first-order reaction dynamics.Preliminary stage in the reaction, lignin removal needed to consume large amountsof alkali, alkali consumption of principal phases less than the one of residualdelignification stage, in general. Atmospheric cooking, reaction order of OH-inprincipal phases and residual phases was0.7and4.4, respectively. It was separately1.1and6.5under pressure cooking.It was cocluded that residual phases need muchalkali amount.On the basis of Arrhenius formula, the calculated Arrhenius activation energy Ep（principal phases） and Er （residual phases） was29.3016KJ·mol^-1and91.3051KJ·mol^-1under atmospheric cooking, respectively. It was separately86.3614KJ·mol^-1and673.5279KJ·mol^-1under pressure cooking. So, residual phases need enoughenergy to insure lignin desulphurization rate.（4） For futher, this paper studied the results of treating papermaking black liquidusing the technology of microwave radiation. The granular activated carbon was usedas a catalyst. By using this method, the effect of effective factors such as activecarbon dosage，microwave power，irradiation time on treating this black liquid were studied．The results showed that the effect order of treatment was microwave power>active carbon dosage> irradiation time. The most optimum treating conditions wereradiation power700W, active carbon10g, reaction time10min. Special mention wasgiven here to the effect of treating black liquid was acceptable, that is, its removalratio was94%.