Enzyme And Chemical Combined Control Of DCS In Papermaking With Chemi-Mechanical Pulp

During the pulping and bleaching process in chemi-mechanical pulp, a wide variety of chemical species are released to be dissolved and colloidal substances (DCS). Under many circumstances, the DCS can be deposited, deteriorating paper machine runnabilty and paper product quality.Therefore, there is significant economical incentive to develop practical strategies to control DCS in chemi-mechanical pulp. Chemical control agents can fix DCS onto fibers and take them out of papermaking system through sheet forming,but the improper application of chemical control agents could increase the burden of the environment.Previous study have showed that the poly-galacturonic acids in DCS have more contribution to the cationic demand (CD).As CD is one of the main parameters of DCS, and pectinase treatment can degrade the dissolved polygalacturonic acids into monomeric galacturonic acid, eliminating the cationic demand caused by DCS.Therefore, the pectinase combined with chemical control agent to treat DCS is an effective way.In this paper, simulated white-water was prepared by softwood BCTMP, physicochemical characteristics of DCS in the softwood BCTMP were analyzed by parameters determination and apparatus analysis method, and the primary components of DCS and its accumulating rule were analyzed.Then the simulated white-water from softwood BCTMP was treated by different kinds of pectinase.The results showed that Pectinase BE-Colour could significantly decrease the CD of simulated white-water at the conditions:Pectinase BE-Coulour dosage5U/100mL,treating time2.5hr,pH7,50℃.The CD of simulated white-water from softwood BCTMP decreased by32.27%, and the particle size and turbidity also decreased,but the conductivity increased a little. The DCS was analyzed by GC-MS and the results showed that Pectinase BE-Colour can degrade the dissolved polygalacturonic acids into monomeric galacturonic acid, eliminating the cationic demand caused by DCS.The simulated white-water from softwood BCTMP was also treated by chemical control agents. The results showed that the DCS control effect were the best for the triple system composed of PA/HCS/CPAM, the cationic polymers had very good synergism effect in the triple system.The CD of simulated white-water from softwood BCTMP decreased by59.63%at the conditions:PA:0.005g/100mL, HCS:0.005g/100mL, CPAM:0.0005g/100mL. The DCS was analyzed by GC-MS and the results showed that the triple system (PA/HCS/CPAM) could fix the fatty acid and resin acid such as abietic acid on the fines and then remove them away effectively.Based on the advantages of both pectinase and chemical control agents, the simulated white-water was treated by the combination of pectinase with triple chemical control system.The results showed that the combination of pectinase and chemical control agens could significantly reduce the dosage of pectinase.The CD of simulated white-water from softwood BCTMP decreased by77.43%at the conditions:PA:0.005g/100mL, HCS:0.005g/100mL, CPAM:0.0005g/100mL,Pectinase BE-Colour:0.5U/100mL.Finally, the furnishes from aspen APMP and aspen BCTMP were treated by the combined of pectinase and triple chemical control system.The experimental results showed that the combination of pectinase with triple chemical control system could effectively control the DCS from aspen chemi-mechical pulp.The CD of aspen APMP and aspen BCTMP simulated white-water decreased by51.81%and48.32%respectively when the dosage of PA0.16%, HCS0.33%, CPAM0.03%, Pectinase-SDU1U/g. The DCS was analyzed by GC-MS chromatography and the results showed that the pectinase and triple system (PA/HCS/CPAM) can degrade the dissolved polygalacturonic acids and reduce the fatty acid and resin acid,and then eliminating the cationic demand caused by DCS.