Study On Seawater Pulping And Performance Of Its Black Liquor

With the improvement of China's industrial level,industrial water has increased significantly,and industrial wastewater has become an urgent problem for many industries.So,the effective use of water and wastewater treatment have become the focus of China's sustainable industrial development.However,China's freshwater resources are not abundant,and seawater utilization has become an effective solution.Pulp and paper,electric power,petrochemical,etc.all belong to large water-consuming industries,and seawater has been used in some areas,but most of them are cooling water,and seawater utilization is not high.In addition,the widely used seawater desalination technology will generate a large amount of high-salt wastewater,which is difficult to treat and use,and pulp and paper will also produce high-salt wastewater.Therefore,in this paper,seawater and other high-concentration brines are used as cooking media to study the alkaline pulping process of wheat straw and the resource utilization of seawater pulping black liquor.First,in this paper,the seawater pulping process of wheat straw is optimized.The best process conditions are as follows:alkali charge 15%,liquid ratio 1:5,maximum reaction temperature of 155~oC,heating and holding time are 90 min and 30min.Next,the mechanism of salt on the straw pulping of wheat straw was explored,and the conclusions were as follows:salt is not conducive to delignification,and if the salt content is too high,the delignification reaction will stop early,in addition,the pulp composition and fiber distribution will also be affected by it.Then,the performance of seawater pulping black liquor of wheat straw and poplar was studied in this paper.The conclusions are as follows:due to the large amount of salt in seawater,the pulping of seawater will increase the black liquor ash content and the solid content will increase.Compared with fresh water pulping,the black liquor ash content of wheat straw and poplar will increase by 1.88%and 2.82%,and the solid content increased by 1.79%and 2.11%respectively;at the same time,seawater will reduce the response of black liquor viscosity to temperature changes,and the higher the solid content,the greater the impact,and when the black liquor temperature is lower(grass pulp<55~oC,wood pulp<90~oC),the viscosity of black liquor of seawater pulping is always lower than that of fresh water,and the higher the solid content and the lower the temperature,the greater the viscosity difference between the two media black liquors.Finally,this article explores the resource utilization of black liquor.The conclusions are as follows:Removal of silicon by Ca(OH)2 precipitation method and removal of chlorine by Friedel's salt method both have good removal effect(removal rate is above 70%),but due to the addition of a large amount of Ca(OH)2,nearly one third of the alkali lignin was removed;In addition,using the surface activity of alkali lignin in black liquor,a water-based liquid dust-proof coating with good performance was successfully prepared for dust and sand fixation.The composition is as follows:Mass ratio(microcrystalline cellulose:black liquor:AKD emulsion:CMC:PAE:H2O)=1.2:7.2:14.5:1:6:70.In addition,the coating added with seawater slurry black liquor has better effect than ordinary black liquor,and can stabilize the sand for more than two weeks.