Research Of Waste Recycling And Washing Method Of Poplar Auto-catalytic Ethanol Pulping

Ethanol pulping is a revolutionary reform of existing chemical pulping method, sincecatalytic ethanol pulping is an important branch of ethanol pulping, for today’s increasinglystringent environmental protection, the catalytic ethanol pulping has advantages that otherpulping methods unmatched. Compared with other solvent pulping, the catalytic ethanol ischaracterized by cooking in the process of delignification paragraph do not need to add anyadditives or catalyst. The disadvantage is that the pulp of ethanol pulping can not be washedby the traditional method, the pulp of organic solvent pulping washed by water could makelignin re-dissolved in the fibers. Ethanol lignin is hydrophobic, it need to use hot ethanolwater washing.The pulp of the experimental conditions used for cooking are: liquid ratio1:10, ethanolconcentration60%（volume fraction）,cooking temperature205℃, holding time150min.Under the conditions of the experiment in the laboratory, we discussed the washing conditionsand investigated the preliminary research of waste recycling.Use of a certain concentration of ethanol solution allowed within the temperature rangeof hand-washing to discuss the pulp washing conditions. To ensure the washing time andwashing intensity parameters be consistency as much as possible in washing process. Usingthe method of orthogonal test the concentration of ethanol, washing temperature, washingliquid ratio and washing stages on the ethanol pulp Kappa number, washing yield andwhiteness, then evaluate the effect of pulp washing. The results show that the better methodfor pulp washing is ethanol concentration60%, pulp washing temperature60℃, liquid ratio1:20, washing stages:3. Then test in the other conditions remain unchanged and apply aconcentration of60%,50%and40%aqueous solution of ethanol respectively for threesections of washing. Optimize the use of the above-mentioned conditions of washing, thewashing yield is87.38%, Kappa number is22.91, the brightness is25.8%ISO.The study on the effects of repeated experiments on the recovery of waste water reuse isachieved through multiple boiling. Each time the cooking liquid concluded waste recyclingethanol solution and washing recycling ethanol solution from the last time. Each cycle of waste water received an average of205ml, and back with the volume of170ml. Back after theexperimental results with five: waste pH value decreased from4.02to3.43; recycling wastewater pH value decreased from4.54to4.18; pulp yield decreased from49.23%to43.87%;pulp Kappa number decreased from27.71to19.15; acetic acid content in recycling wasteincreased from0.23%to1.12%. The results show that the ethanol pulping system pHdecreasing, but the acetic acid content in recycling waste water increasing with the conduct ofcooking. Therefore, waste recycling had a positive effect on the pulp in the poplar catalyticethanol pulping which is beneficial to the further removal of lignin. But with theaccumulation of acetic acid content the Kappa number will always be lower, therefore wehave to control the number of reuse. In this paper, when the back is used the fourth time thepulp yield is45.33%and the Kappa number is22.37, the acetic acid content in recyclingwaste is0.97%; while when the back is used the fifth time the pulp yield is43.87%and theKappa number decreased to19.15. Taking into account the requirements of paper strength, thearticle suggests that when the waste water back use to the fourth time we’d better to separatethe acetic and ethanol in recycling waste, and the separated ethanol will continue to be used.Separation experiment of ethanol and acetic had been carried out with205ml recyclingwaste, which consumed272.9ml NaOH solution of concentration0.1mol/L, after distillationof the separated ethanol, the concentration is76%. At last, after the ethanol distillation for thenext round of cooking, cooking experimental data measured as follows: pulp yield48.54%,pulp Kappa number26.73, waste pH value3.98, recycling waste water pH value4.53,acetic acid content in recycling waste0.25%. As can be seen through the experiment, theacetic acid and ethanol in recycling waste had a better separation effect. Therefore, reuse ofthe poplar catalytic ethanol pulping waste liquor can be achieved.