Effects Of Auto-hydralysis On Subsequent Kraft Pulping Of Acacia Wood

At present,the global raised a hot trend of biomass refining,all countries in biomass refining have kept a continued strong focus.At the same time,the combination of pulp and paper industry and biomass refining has become a research hotspot,for the transformation of pulp and paper enterprises change provides good opportunities for development,making the biomass refining in the pulp and paper industry has an important research significance.Acacia wood has a low usage of alkaline cooking and cooking liquid is relatively easy to permeate.So it is a kind of suitable pulp and papermaking raw material.Based on combining biomass refining and pulp and paper-making,so the study was focus on hot water pre-hydrolysis of acacia wood on subsequent Kraft pulping.First of all,the chemical composition of acacia wood used in the experiment was analyzed,and the analysis results shows that the acacia wood has a higher of the pentose content than some biomass materials,so we can obtain higher sugar conversion rate by hot water pre-hydrolysis,and then those sugars could converted to other high value-added products.And remaining wood chip of pre-hydrolysis were used to carry out Kraft pulping,so we can have the difference between the pulp or hand sheet properties from hot water pre-hydrolysis of acacia wood.Secondly,based on the results of orthogonal experiment of Kraft cooking of acacia wood as well as beating and paper-making experiments.Then comprehensive coordinate method was applied for optimal cooking conditions of acacia wood.The results shows that at the conditions of alkali charge?Na₂O?15%,sulfidity 30%,liquor to wood ratio of 4:1,temperature raising time1h,at the max temperature 165?for 2h.According to the above process conditions,acacia wood Kraft pulp with yield 52.25%,Kappa number 17.9,viscosity 987.3mL·g^-1,break length9.32km,tensile index 93.63 N·m·g^-1,tearing index 10.03 mN·m2·g^-1 and bursting index 5.34kPa·m2·g^-1.Thirdly,the pre-hydrolysis of acacia wood with hot water was carried out,and then the Kraft cooking was proceeded.The influence of three typical pre-hydrolysis conditions on the properties of pulp,black liquid?BL?and hand sheet were investigated.The results indicated that pre-hydrolysis can obviously improve the effect of delignification in subsequent Kraft cooking,thus reduce the alkali charge.The yield of pulp decreases significantly and the kappa number drops remarkably with the increase of intensity of pre-hydrolysis.The viscosity of pulp increases slightly when the intensity of pre-hydrolysis is relatively low and then the viscosity of pulp decreases acutely.To some extent,pre-hydrolysis contributes to the utilization of BL in alkali recovery plant because of the higher solid content.However,pre-hydrolysis will increase the difficulty of beating,having a negative effect on the physical properties except for the brightness and opacity.And tensile index,tear index and burst index such as physics performance degradation is relatively obvious,they dropped of 74.50%,74.50%and 61.80%,respectively.Finally,the P-factor of acacia wood on subsequent Kraft pulping was studied.The influence of the experimental results show that as the P-factor increases gradually,the pulp yield of pre-hydrolyzed acacia wood decreased gradually,and it is falling slowly in the first.When the P-factor was reach or exceed 886,the decline trend becomes faster than before;Kappa number and the pulp viscosity also gradually reduce with the increase of the P-factor,they decline reached by 39.05%,42.81%,respectively.Pre-hydrolysis have great influence on the physical strength properties of hand sheet,which,with the increase of P-factor,tensile index,tear index and burst index declined significantly.Under the condition of each P-factor,all acacia wood chips have the same structure of cellulose?.It is shows that hot water pre-hydrolysis did not change the crystal structure of cellulose in the acacia wood.Besides,the technology of dissolving pulp of Acacia wood by pre-hydrolysis Kraft process has a basic research.It shows that the bleached pulp although have a high?-cellulose and viscosity,the whiteness and content of ash are not meet the demands of dissolving pulp.Compared with the standard indicators of dissolving pulp,the technology of dissolving pulp of acacia wood need to be optimized in terms of pulping and bleaching process.Pre-hydrolysis has removed the part of hemicellulose and a small amount of lignin,crystallization index of cellulose were increased.After hydrolysis of Acacia wood,Kappa number is decreased,but the yield of pulp,the physical strength properties and viscosity of hand sheet show varying degrees of decline.The condition of Kraft pulping of pre-hydrolyzed acacia wood should be optimized if we want to combining the idea of biomass refining and pulp and paper-making industry.