| Lithium hydroxide powder,as an important lithium salt product,is widely used in pharmaceutical,grease and battery industry.But in recent years,with the vigorous development of the new energy industry,the global market demand for lithium hydroxide powder is increasing.Improving the production efficiency of lithium hydroxide powder has become a top priority.However,the screw conveyor used in the production line of lithium hydroxide powder is often prone to problems such as arching,bridging and blockage during the transfer and conveying process.And it is difficult to achieve the actual production requirements of lithium hydroxide powder conveying volume and conveying stability,which seriously affects the stable operation of the production line.Therefore,this paper takes lithium hydroxide powder screw conveyor as the research object.According to the actual production line requirements and the flow characteristics of lithium hydroxide powder,the overall structure design of the lithium hydroxide powder screw conveyor was carried out.By establishing the simulation model of lithium hydroxide powder screw conveyor,and optimizing its parameters and screw structure based on discrete element method.ANSYS Workbench software was used to conduct static and modal analysis of the conveying screw.Finally,the prototype performance test proved the reasonableness of the optimized design of lithium hydroxide powder screw conveyor.The main research work and achievements are as follows:（1）Taking lithium hydroxide powder as the research object,the morphology of lithium hydroxide powder under different particle size distribution was analyzed.The flow characteristics of lithium hydroxide powder were also analyzed by rest angle method,HR method and Carr fl ow index method.The test results show that the fluidity of lithium hydroxide powder gradually deteriorates as the particle size becomes smaller.The selected test lithium hydroxide powder samples show good fluidity performance.It has a rest angle of 35.2 0°,HR value of 1.08,Carr mobility index of 86,bulk density of 0.907 g.cm-3 and an average particle size of358.503μm.（2）According to the actual production demand,three kinds of screw conveyors with different structure types are compared,and the horizontal screw conveyors as lithium hydroxide powder screw conveyors are determined.At the same time,according to the physical properties of lithium hydroxide powder and the demand of the actual production line,the key parts of the lithium hydroxide p owder screw conveyor were selected and designed,and the relevant structure and operating parameters were determined.（3）The lithium hydroxide powder was scaled up by particle scaling theory,and a simulation model of lithium hydroxide powder screw convey or was established according to the flow characteristics of lithium hydroxide powder.Spiral shaft diameter,pitch and rotational speed are the optimization parameters,and the average mass flow rate and coefficient of variation of transport stability are the evaluation indexes.Box-Behnke orthogonal test was designed based on the discrete unit method,and parameter and screw structure optimization was performed.The simulation shows that when the screw shaft diameter is 26 mm,the pitch is 75 mm and the speed is 108 r/min,and the screw at the discharge position is designed without a screw blade.The coefficient of variation of transport stability is 8.96%,which achieves the transport stability target of less than 10%coefficient of variation of transport stability.（4）The finite element model of the conveying screw was established by ANSYS Workbench software.The static and modal analysis of the conveying screw was carried out,and the equivalent force cloud,total deformation cloud and vibration cloud of the conveying screw were obtained.The results show that under full load conveying conditions,the maximum stress of the conveying screw occurs in the root area of the screw blade,with a maximum equivalent force of 122.65 MPa.The maximum deformation o ccurs at the outer edge of the spiral blade,with a maximum deformation of 0.34732 mm.With the increasing order of the vibration pattern,the inherent frequency increases,and the maximum deformation area of the conveying screw moves from the middle to th e two ends,where the inherent frequency of the first order vibration pattern is 75.900 HZ.It shows that the lithium hydroxide powder screw conveyor can carry out conveying work safely and reliably.（5）According to the design of lithium hydroxide powder screw conveyor prototype machining,based on Lab VIEW development platform and MCU design of a flow monitoring system.Finally,the prototype is tested after installation and debugging.The test result s show that the designed control system can monitor the flow rate of lithium hydroxide powder in real time and adjust the conveying capacity of lithium hydroxide powder screw conveyor by changing the rotating speed.When the rotational speed is108rpm/min,the throughput is 1170 kg/h,and the error with the target throughput of 1200 kg/h is 2.50%.The variation coefficient of transport stability is 2.03%,which is further improved compared with the variation coefficient of transport stability under simulati on test.The rationality of the optimized design of the screw conveyor for lithium hydroxide powder was verified,and the actual engineering problems in the process of transferring and conveying lithium hydroxide powder were solved. |
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