Study On The Causes And Modifications Of UHMWPE Pipe Scaling In The Production Process Of Wet-process Phosphoric Acid

Phosphate rock is an important raw material for the production of wet-process phosphoric acid,which contains P,Na,K,Ca,Fe,Al and other elements.At present,domestic phosphate mines,especially Hubei phosphate mines,are mostly low-grade ores with high impurity content.The scaling problem in wet-process phosphoric acid production has become one of the common problems that plague the chemical industry.The fouling material is hard and difficult to clean,which leads to blockage of the pipeline,which seriously affects the safe operation and normal progress of production.Because of the influence of multiple factors such as solution medium,pipeline material characteristics and process conditions,many researchers at home and abroad have done exploration and research,and proposed Some improvement measures have been adopted,and some results have been achieved,but mainly focus on equipment and technology,and there is less research on scale prevention of production and transmission pipelines.Therefore,this paper takes the medium-purity ultra-high molecular weight polyethylene pipeline in the production of wet phosphoric acid as the research object.By analyzing the chemical reaction process of its production process,the formation process of various scales and the main factors affecting pipeline scaling are determined.Combined with the analysis of scale samples,it is determined that the main components of pipeline scale are sodium fluorosilicate,potassium fluorosilicate and calcium sulfate dihydrate;Further combined with the theories of thermodynamics,crystallization kinetics and fluid dynamics,on the basis of various influencing factors,the fouling mechanism of UHMWPE pipelines was analyzed to provide theoretical basis for its anti-fouling.In view of this,this paper explores to further improve the anti-fouling performance of UHMWPE pipeline materials.Nano-PTFE/UHMWPE composites with different mass fractions（1wt%-7wt%）were prepared by filling and modifying ultra-high molecular weight polyethylene with nano-polytetrafluoroethylene as filler.Through routine performance experiments,the hardness,friction and wear,Vicat softening temperature of the composites were tested and characterized,and the application test of anti-scaling coupons was carried out.Then different nano-PTFE/UHMWPE composites were compared,and the influence of nano-PTFE filled with different mass fractions on various properties of UHMWPE matrix was analyzed,and the mechanism of various performance indicators was analyzed.The experimental results have shown that the hardness,friction and wear properties,and heat resistance of pure UHMWPE can be improved by filling an appropriate amount of nano-PTFE particles,and the amount of scaling on the surface of the composite can be effectively reduced.When the nano-PTFE filling amount was 5wt%,the hardness of the UHMWPE composite reaches the maximum value of 67HRR;the friction coefficient reaches the minimum value of 0.155,and the wear rate reaches the minimum value of0.8×10^-6 mm³/（N·m）;the Vicat softening temperature reaches the maximum value107.9℃;the surface fouling amount was the least at this time,and the surface fouling amount on the surface of pure UHMWPE was reduced by 26%.It provides relevant data support for the further development of composite materials with excellent anti-fouling properties under wet-process phosphoric acid production conditions.