Study On The New Type Of High Consistence Cleaner System With Injection Of Dissolved Air Water Into Waster Pulp

At present,waste paper accounts for over 65% of China's papermaking industry raw materials.Using waste paper as raw material of papermaking can save a lot of forest fiber resources,which is conducive to save energy and reduce emission,at the same time,lower production and investment costs.In the use and recovery process of waste paper,a large amount of impurities such as metal and gravel must be mixed,which have to be effectively removed through the purification equipment.The separation efficiency and energy consumption of the purification equipment are directly related to the purification principles and methods of the equipment.Therefore,it is of great significance to study a new type of energy-efficient purification separation principle and method and corresponding equipment.Based on an in-depth analysis of the existing principles and methods of various types of waste pulp purification technology,this research proposes the principle of the existing waste pulp purification equipment from the perspective of separation power for the first time,which is divided into two methods: gravity settlement and centrifugal purification.and then propose an innovative high-concentration waste paper purification principle and technology: that is based on the injection of dissolved air water into pulp suspension,the new type high concentration cleaner system purification principle.This research selects representative ONP and OCC waste papers as experimental materials,and further studies the working state and purification efficiency of the new high-consistence cleaner system under the conventional working conditions of the traditional high-consistence cleaner.This provides theoretical guidance for the development of a new generation of high-consistency cleaner for waste pulp.The main achievements of this paper are as follows:(1)The principle and method of an innovative high-consistence cleaner for impurities removal based on dissolved-air water are proposed.By injecting the slightly dissolved air in the pulp suspension,the difference in specific gravity between the slightly dissolved air suspension and the relatively large mass of impurities is increased,thereby,increasing the centrifugal force difference in the separation field and improving the purification efficiency.(2)Under the working conditions of traditional high consistence cleaner,ie,the feed concentration is 1%~4%,the feed pressure is 0.20~0.50 MPa,the pressure drop is 0.10~0.35 MPa,and the dissolved air water is injected into the puree water 60%.In air and water,the purification efficiency of the new waste pulp purification technology is 18.4-27.2 percentage point higher than that of the traditional purification technology.(3)With the increase of dissolved air water pressure,the density of suspension with air water decreases.Under the conventional working conditions of the conventional high-concentration cleaner,the pulp suspension concentration is 3%,the feed pressure is 0.30 MPa,the pressure difference is 0.25 MPa,and 60% injections are made,the density of the slightly dissolved air suspension of ONP and OCC respectively decreased by 14.4% and 14.5%,and the purification efficiency increased by 21.9 and 27.2 percentage point respectively.(4)Under the same purification pressure and pulp consistency,after injecting 60% supersaturated dissolved air water,the density of OCC slightly dissolved air suspension was 13.4% lower than that of the slightly air suspension of ONP,and the purification efficiency was 4.2 percentage point higher than that of the slightly dissolved air slurry of ONP.So,the OCC slightly air suspension purification effect is better.(5)In the actual engineering application design,the new type high consistence cleaner system is set to a 0.25~0.40 MPa feed pressure,a pressure difference of 0.15~0.35 MPa,the pump delivery concentration of 2.5%~8.0%,and a desulfurizer inlet concentration of 1.0%~ 4.0%,the density of the slightly air pulp entering the new high-concentration cleaner was reduced by 12.9% to 18.2%,and the purification efficiency was increased by 18.4 to 27.2 percentage point.(6)The energy produced by the dissolved air system can be used as a part of the input power when releasing the dissolved air under decompression.The increased energy of the new type high-concentration cleaner system is far less than the added equipment to achieve the same purifying effect.The air introduced in the pulp can be removed in the subsequent sections without adversely affecting the production or paper quality of the machine.(7)The traditional high consistency waste pulp purification and separation technology is divided into natural gravity sedimentation method and centrifugal separation method according to the principle of separation power.Based on the new high consistency pulp purification systems principles and methods for injecting dissolved air water proposed in this study,the traditional classification can be changed to two major categories,namely the purification separation technology based on the difference in the natural proportion of pulp miscellaneous and the difference in the proportion of pulp miscellaneous expansion.The former is subdivided into two subcategories: natural gravity settlement and natural gravity difference centrifugal separation,and the latter is the “centrifugal separation method that increases the proportion of natural miscellaneous impurities”.