Drying Equipment And Process For Lithium Iron Phosphate With Trace Moisture

Lithium iron phosphate cathode material is the mainstream power battery material on the market,and its different moisture content is closely related to battery cycle performance and rate performance.When the moisture content is between 400⁵00 ppm?0.04%⁰.05%,parts per million?,the cycle performance is optimal.When the moisture content exceeds 600 ppm,the electrochemical performance is seriously attenuated.Therefore,during the processing of lithium iron phosphate Trace moisture control is particularly important.In the conventional process,drying in a double-cone rotary vacuum drying method for 12 hours can reduce the water content to about 1000 ppm,and has reached the drying limit,and it is difficult to further reduce the moisture content.In this paper,for the drying demand of trace moisture of lithium iron phosphate powder,the new method and process of supersonic airflow pulverization and drying were studied for the first time,and the temperature control and dehumidification equipment of gas source and gas source post-treatment process were matched and selected.optimization.Finally,combined with the experimental parameters of industrial experiments,the CFD numerical simulation of the airflow pulverizing equipment was carried out to study the flow field and the accelerated motion characteristics of the pulverizing chamber,and the drying characteristics of the granules during the airflow pulverization process were further analyzed.In the industrial experiment,the lithium iron phosphate powder was ultra-finely pulverized and simultaneously dried using a LNJST-120HT closed nitrogen gas flow pulverization drying system.The results show that the control screw feeder and classifier rotate at 62 and1072 r/min respectively,the gas source pressure and temperature are 0.5 MPa and 120°C,respectively,and the average dew point temperature of the packaging room is-34.5°C.Both are below 600 ppm,the finished product particle size d₅₀ is stable at 1¹.2?m,d₁₀₀ is stable at 6.7⁷.1?m,and the yield is controlled at 210²30 kg/h.All the indexes meet the production requirements of lithium iron phosphate.According to the existing industrial experimental data and operating parameters,combined with CFD numerical simulation software,the flow field and particle acceleration motion characteristics of the supersonic airflow pulverizing chamber were studied,and the drying advantages in the airflow pulverization process were further analyzed.The simulation results show that the supersonic nozzle with Mach number of 1.78 is designed to generate shock waves in the nozzle jet region under the conditions of high pressure?0.5 Mpa?and low back pressure?-2 kpa?.Among them,the maximum air velocity can reach 621 m/s,and a partial negative pressure of-32 kpa will be formed at the nozzle outlet,and the low pressure condition is favorable for the evaporation of water from the particles to the gas phase.At the same time,during the accelerated motion,the relative velocity between gas and solid shows a tendency of pulsation to decrease.This process is similar to straight tube pulse drying.There is always a large speed difference between gas and solid,which enhances heat and mass transfer.rate.Moreover,the particles are dried in the pulverizing chamber accompanied by ultrafine pulverization,and the moisture inside the granules is instantaneously exposed to the surface gas in the gas phase main body during the pulverization process,further accelerating the drying process of the particles.