Study On Several Issues Related To The Agricultural Straw High Yield Pulping By Hydrothermal Method

With the gradual implementation of the national system of banning the import of foreign wastes,making full use of the huge amount of agricultural straw resources is one of the effective measures to solve the shortage of packaging paper and paperboard raw materials.The hydrothermal high yield pulping technology for agricultural straw is attracted much attention because of its green environmental protection characteristics.In order to further optimize the hydrothermal pulping technology and promote its rapid industrial application as soon as possible,several key issues in the hydrothermal high yield pulping process of corn stover was studied,including the impact of pH value of hydrothermal treatment,refining conditions after hydrothermal treatment and hydrothermal treatment method and hydrolysate recycling,etc.The results showed that the pH value of hydrothermal treatment had a great influence on the properties of high yield corn stover pulp and the composition of hydrolysate.The pH value of hydrothermal treatment can be adjusted by adding a small amount of acetic acid or sodium hydroxide.When the pH value of the hydrolysate is equal to 5.81,the pulp yield is the highest.When the pH value of the hydrolysate is less than 5.81,the degradation sugars of cellulose and hemicellulose in the hydrolysate increase with the decrease of pH value,but when the pH value is as low as 4.7,the generated sugars begin to be further dehydrated and degraded.At this time,the tensile index,ring crush index and bursting index of the pulp have no obvious change.When the pH value of the hydrolysate is greater than 5.81,with the increase of pH value,the lignin dissolution rate increases,and the tensile index,ring crush index and bursting index of the pulp increase rapidly.The refining conditions after hydrothermal treatment also have a great impact on the performance of high yield corn stover pulp.The mechanical properties and dewartering performance of the pulp can be taken into account by using medium consistency pulping and controlling the refining clearance.The room temperature for refining is more favorable for the performance of the pulp.The results also show that the pulps obtained by the vertical digester have low yield,good mechanical strength and low steam consumption compared with the rotary digester,.The physical properties and the main components of the hydrolysate were affected by the reuse of the dilute hydrolysate.Compared with the utilization of 100%tap water,all of the tensile index,bursting index and ring crush index of the pulp were decreased a little.The dissolution of xylose,xylooligosaccharide and acetic acid in the hydrolysate increased with the increase of the reuse times of dilute hydrolysate.The above research laid a foundation for the industrial production of the novel hydrothermal high yield pulping technology for agricultural straw.