Study On Grinding And Grading Of Heavy Calcium Carbonate For Breathable Membrane

Fine heavy calcium carbonate belongs to the"New Materials-New Inorganic Non metallic Materials for Energy Conservation and Environmental Protection"category in the"National Key Supported High tech Fields".It is a low-carbon and environmentally friendly functional filler widely used in industries such as papermaking,plastics,coatings,artificial stones,silicone adhesives,etc.In recent years,research has emerged as a pore forming agent in breathable membranes.However,in the process of preparing fine heavy calcium carbonate powder,it is faced with problems such as unreasonable fineness and particle size distribution span of finished powder,less spheroidization,high energy consumption,and large fluctuation of product quality.The root cause lies in the difficulty of grinding/grading equipment to produce enough fine powder,poor grading accuracy,lack of coordination in grinding and grading process parameters,and insufficient intelligent control technology for system equipment and its processes.Therefore,in response to the above difficulties,combined with the production practice and technical research of heavy calcium carbonate grinding and grading,the research content and technical route of this project are determined,as follows:Firstly,based on the basic production process of determining raw materials and equipment,this study proposes a new scheme for improving the fine structure of grinding and grading equipment,combined with automatic control optimization.Experimental design studies were conducted on three aspects,namely,ultra-fine grinding,fine classification,and optimal control.In terms of ultra-fine grinding,the working principle of the grinding device is analyzed,and a structural design scheme for the coordination of tire type grinding rollers and grinding discs is proposed to improve the grinding efficiency;In terms of fine classification,the movement trajectory of particle flow field is analyzed,and a combined device of rotor and rotor is used to refine the classification effect;In terms of control optimization,a control system based on secondary classification is proposed and equipped with temperature and pressure control devices inside the mill.Finally,a monitoring system is designed to make the production line intelligent.Secondly,based on the process optimization scheme in this article,a simulation model was established using Solid Works software according to the HRM1700X vertical mill structure,and the flow simulation was used to analyze the environmental factors of the model flow field.Based on the calculation of boundary conditions in the early stage,by comparing the velocity field,pressure field,and temperature field in different regions,the movement rules of the flow field in the mill are obtained,and under environmental conditions such as lower than the pressure difference and maximum temperature value of the mill,the actual production requirements are basically met.Finally,after completing the above theoretical work,I actually participated in the construction and design of the heavy calcium production line in the enterprise’s factory building.HRM1700X vertical mill was selected as the grinding and grading equipment,and the above optimized design scheme was applied and put into experimental production.In order to maximize the efficiency of production,based on the impact of grinding classification process parameters,the optimal grinding process parameters for this production line were obtained through research:the rotational speed of the grinding disc was 42 rpm,the standard size of the incoming particles was≤8 mm,the material layer thickness was 6 cm,and the grinding roller rolling pressure was 60 kpa.The optimal classification process parameters obtained are:the optimal wind pressure is 11.6 kpa,and the optimal air volume is 27×10~3m~3/h,with a classifier rotating speed of 1400 r/min.Through the above research,combined with actual production,verify the results from both real-time monitoring and particle size detection.The operating parameters in real-time monitoring are normal,indicating stable operation.The particle size distribution measured by particle size testing with 600 mesh,800 mesh,and 1000mesh is more concentrated.The single unit output of 600 mesh heavy calcium is 6.32t/h,and the product energy consumption is 54.98 kwh/t,with a distribution span of1.904,and the content of 10 is as high as 70.59%.However,the single unit output of800 mesh heavy calcium is 4.17 t/h,and the product energy consumption is 72.14kwh/t,with a distribution span of 1.972,and the content of 10 is 80.91%.This basically meets the target requirements set for the project,and has achieved significant improvement over the original production line.