| Waste paper papermaking is a way of recycling,but waste paper papermaking enterprises produce large amout of sludge in papermaking process including pulp residue and sludge from waste water treatment process.The treatment and disposal of papermaking sludge is the main bottleneck of the development of waste paper papermaking enterprises.The national and local governments attach great importance to the treatment and disposal of paper sludge.Facing the urgent requirements of the development policy of paper industry,the process of paper sludge treatment and disposal should follow the principle of resource utilization and reductionand combined with the characteristics of sludge to actively explore the utilization technology of paper sludge.This has important practical significance for realizing the healthy and sustainable development of the paper industry.In this paper,a typical waste papermaking enterprise was selected.Through the research on the production of paper sludge and the determination of its properties,the technical model of waste papermaking sludge resource utilization was constructed.For the sludge with high cellulose content and long width,the feasibility of its use as a raw material for papermaking was investigated.The influence of the amount of reinforcing agent,dry strength agent and starch on the sludge papermaking was investigated.In addition,the optimal ratio of pulp to sludge in accordance with national standards was studied and it was used in the actual project.For sludge with low cellulose content and short width,due to its high water content,it was not conducive to subsequent resource utilization.Hence it was chemically conditioned with cetyltrimethylammonium bromide(CTMAB)and fly ash combined conditioning technology,reducing the moisture content of sludge.The mechanism of combined conditioning was discussed in four aspects: particle size distribution,zeta potential,extracellular polymeric substance and bound water content.The optimal process conditions were also explored.The main conclusions were as follows:11.Research on the properties of waste paper sludge.The production of pulp residue,inclined net sludge,primary sludge and biochemical sludgefor every ton of paper produced was 1.574 t(water content 97.44%),0.585 t(water content 97.35%),0.491 t(water content 98.05%)and 0.491 t(water content 98.80%)respectively.The pH of the sludge was 6.89~7.96 and the metal element content did not exceed the limit of the shale selectivity control index in?Sludge mud of urban sewage treatment plant?(GB/T 24188-2009).The content of cellulose in the inclined net sludge and pulp resude was 37.76% and 36.69% respectively.They were mainly composed of staggered fibers,the fiber length was about 3-4 mm and the width was 30~60 ?m.The fiber was of high quality and its rich fiber can be used as a raw material for papermaking for comprehensive utilization.The content of cellulose in primary sludge and biochemical sludge was 28.15% and 20.48%,the fiber length was only0.15~0.40 mm and the width was 4~10?m.2.Research on technology of recycling and utilization of inclined net sludge and pulp residue.When the ratio of pulp to pulp residue in papermaking raw materials was 9:1 and the ratio of pulp to inclined net sludge was 7:3,handsheets can reach the standard of qualified products,but handsheets made from primary sludge can not meet the standard of qualified products.With no additives added,when the ratio of pulp to mixed sludge(pulp residue:inclined net sludge=2.7:1)was 9:1,the handsheets can reach superior products,7:3 can reach qualified products.When a 1000 g mixed paper pulp(concentration 4%)was used to make a handsheet of 140 g·m-2,the optimum amount of dry strength and reinforcing agent was 3 g and 2 g respectively,and starch did not improve the paper properties.After adding additives,when the ratio of pulp to mixed sludge was 7:3,the handsheets can reach superior product,6:4 can reach A product,and the qualified product can be achieved at 4:6.The sludge papermaking technology was applied to the actual project.The results showed that the indexes of the bobbin paper made in the production test all reached the standard of qualified products.In the large-scale application,57158 t waste paper(solid content85%),2045407 t pulp residue(water content 97.44%)and 76000 t(water content97.56%)inclined net sludge were used to produce 108644 t bobbin paper.The reduction of pulp residue and inclined net sludge reached 1984988 tons/year and760000 tons/year,and the reduction of waste paper consumption was 82926 tons/year.The disposal cost of pulp residue and inclined net sludge could be reduced by 14.50 million yuan/year,and the cost of waste paper was reduced by 182 million yuan /year.3.Research on conditioning technology of primary sludge and biochemical sludge.Compared with suction filtration,centrifugation and sedimentation performance,fly ash and CTMAB had the best combined conditioning effect,and the specific resistance of sludge was reduced by 87.28%.The results of conditioning mechanism showed that the bound water content in the sludge was reduced by 1.26%,the particle size of the sludge hardly changed,the zeta potential changed from negative to near zero potential,and the protein content in EPS increased by 156.02%.In addition,the three conditioning factors including the order of addition,dosage and agitation of the joint conditioning were investigated.The optimal process conditions were determined: for firstly add 0.10 g fly ash to 150 mL paper sludge,stir for two minutes with a fast agitation strength of 200 r·min-1 and five minutes with a slow agitation strength of 90 r·min-1,and then add 0.35 g CTMAB,stir for two minutes with a fast agitation strength of 200 r·min-1 and fifteen minutes with a slow agitation strength of 90 r·min-1.Under optimal process conditions,the sludge specific resistance decreased to 9.837×1013 m·kg-1,and the moisture content of the filter cake decreased to 55.31%. |
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