摘要
【目的】制备锂离子电池正极导电浆料中水分含量(质量分数,下同)极低(<10-3)的碳纳米管,研究对碳纳米管物料水分含量的影响因素。【方法】利用LNJ-12A型气流磨对碳纳米管湿物料进行超细粉碎干燥;通过改变气流磨的分级机转速、引风机转速、喷嘴喉部直径、粉碎腔体积,分析不同参数对碳纳米管物料水分含量的影响。【结果】在综合考虑能耗和实际工况下,当单因素变量为分级机转速4800 r/min、引风机转速2400 r/min、直喷嘴喉部直径4.5 mm、粉碎腔体积从1.14×10^(-2) m^(3)增加至23.56×10^(-2) m^(3)时,碳纳米管干燥后的水分含量分别为8.45×10^(-4)、6.68×10^(-4)、6.88×10^(-4)、5.89×10^(-4)。【结论】适当增大分级机转速,减小引风机转速,使用直径合适的直喷嘴,增大气流磨粉碎腔体积,对碳纳米管的水分干燥效果会产生有益影响,相同干燥次数下碳纳米管物料水分含量更低,且达到水分要求时的干燥次数更少。
Objective In the production of lithium-ion batteries positive electrode conductive paste,it′s imperative to incorporate carbon nanotubes with extremely low moisture content(moisture content<103).Currently,the Chemical Vapor Deposition(CVD)method is widely employed in industry to prepare carbon nanotubes,which requires the use of a double cone rotary vacuum dryer.However,this process has disadvantages such as a low filling rate and high energy consumption.This study proposes the use of jet mill in the moisture drying process of carbon nanotubes and analyzes the influence of various process parameters on moisture content.It aims to provide insights into the industrial-scale moisture drying of carbon nanotubes.Methods In this study,the LNJ-12A jet mill was utilized to ultrafine crush and dry wet carbon nanotubes materials.A series of single-factor experiments were conducted to investigate the effects of various parameters,including the speed of the classifier,the speed of the induced draft fan,the diameter of the nozzle throat,and the volume of the grinding chamber on the water content of carbon nanotubes.Finally,the optimal parameter combination for moisture drying of carbon nanotubes was obtained.Results and Discussion Increasing the speed of the classifier enhanced the drying effect of carbon nanotube moisture.As the classifier speed increased,the coarse particles experienced heightened forces from the blades,resulting in increased centrifugal force that propelled them outwards from the classification wheel.Subsequently,these particles descended into the crushing area for further refinement and drying.Moreover,an elevated classifier speed amplified the blowing effect of the classifier blades,extending the residence time of carbon nanotube materials within the crushing chamber.However,excessive classifier speed could also lead to increased energy consumption,therefore a reasonable increase in speed was required.It was observed that reducing the speed of the induced draft fan enhanced the drying effect of carbon nanotubes.An escalation in the speed of the induced draft fan induced a corresponding increase in the axial velocity of the airflow within the classification area.This,in turn,diminished the descent rate of coarse particles impeded by the impeller,extending their residence time in the classification area and leading to an augmented concentration.This heightened concentration facilitated the particles’facile descent into the dust collector through the classification machine.Additionally,the reduced drying extent of moisture in the coarse particles contributed to a higher proportion of coarse particles in the carbon nanotube material collected in the dust collector,resulting in an elevated moisture content of the overall carbon nanotube material.However,if the speed of the induced draft fan was too low,the insufficient negative pressure it provided could lead to difficulty in feeding.Therefore,the speed of the induced draft fan should not be too low.The diameter of the nozzle throat affected the jet velocity of the material in the crushing chamber.When the gas source pressure was constant,a smaller nozzle throat diameter and higher jet velocity facilitated the entry of carbon nanotubes into the classification zone.This,in turn,reduced the residence time in the crushing chamber,resulting in incomplete internal water release and elevated water content in the final carbon nanotube product.Conversely,a larger nozzle throat diameter lowered the jet velocity at the nozzle,diminishing the kinetic energy applied to carbon nanotubes by the airflow and leading to a decrease in the collision,shear,and fragmentation of carbon nanotubes within the crushing chamber.The inadequate release of internal moisture in turn resulted in higher moisture content in the finished product.When the volume of the crushing chamber increaseed,the migration path of the material from the crushing zone to the classification zone was extended,increasing the retention time of the material in the crushing chamber and improving the moisture drying effect of the carbon nanotubes.Considering energy consumption and actual operating conditions,optimal drying effects for carbon nanotubes were achieved with a classifier speed of 4800 r/min(the single-factor variables),induced draft fan speed of 2400 r/min,straight nozzle throat diameter of 4.5 mm,and a crushing chamber volume of 23.56×10^(-2) m^(3),resulting in moisture content of 845×10^(-6),668×10^(-6),688×10^(-6),and 589×10^(-6),respectively.Conclusion In this paper,optimizing the process by appropriately increasing the speed of the classifier,reducing the speed of the induced draft fan,using a suitable diameter straight nozzle,and increasing the volume of the airflow grinding chamber is found to have a beneficial effect on the moisture drying effect of carbon nanotubes.With consistent drying times,this approach results in lower moisture content in carbon nanotubes materials,thereby efficiently meeting moisture requirements.
作者
颜翠平
李杨
李世龙
严绍文
张明星
李红
YAN Cuiping;LI Yang;LI Shilong;YAN Shaowen;ZHANG Mingxing;LI Hong(School of Environment and Resources,Key Laboratory of Solid Waste Treatment and Resource Recycle,Ministry of Education,Southwest University of Science and Technology,Mianyang 621000,China)
出处
《中国粉体技术》
CAS
CSCD
2024年第3期150-157,共8页
China Powder Science and Technology
基金
国家自然科学基金项目,编号:52204286。
关键词
碳纳米管
超细粉碎
气流粉碎
carbon nanotube
ultrafine powdering
jet milling