Research on Processing Technology of Calcined Kaolin Powder Using A Fluidized Bed Jet Mill at Different Temperatures

TLDR: In this paper, the authors used a fluidized bed jet mill with three nozzles to extract calcined coal kaolin clay from a 2-3 mm size distribution of the material.

Abstract: The calcined kaolin powder was obtained using a fluidized bed jet mill at the temperatures 17°C and 280°C.The theoretical arithmetic, numerical simulation and experiment were used to compare and discuss the results at the two temperatures. The particle size D50=2.401μm 与 D50=2.003μm of kaolin powder was obtained. The theoretical arithmetic shows that the outlet velocity of the nozzle at the temperature 280°C is higher (38%) than that at the temperature 17°C. The grinding kinetic energy of the jet mill at the temperature 280°Cis twice as that at the temperature 17°C. The numerical simulation of grinding cavity at the temperatures 17°Cand 280°Cshows that nozzle axial velocity is 513m/s at the temperature 17°Cand nozzle axial velocity is 712m/s at the temperature 280°C. Therefore, the grinding particle size at the temperature 280°Cis smaller than that at the temperature 17°C. The yields of calcined kaolin powder and energy consumption of jet mill are obtained through the experiment. The yield of calcined kaolin powder at the temperature 280°Cis higher (14%) than that at the temperature 17°C. The energy consumption of air jet mill at the temperature 280°Cis higher (30%) than that at the temperature 17°C. The results show that the calcined kaolin powder at the temperature 280°Cis beneficial to grinding materials with the smaller particle size and higher yield than that at the temperature 17°C. Otherwise, the energy consumption of jet mill increase from the temperature 17°Cto 280°C. Introduction The kaolin powder has been widely used in the fields of papermaking, ceramics, plastics, coating, etc. [1-7]. In industry applications, the different grades of kaolin powder were classified based on fineness and whiteness. The fineness of kaolin used for the senior painting was lower than 2μm [8]. Recently, the ultrafine kaolin has gradually used in the new materials of refractory castable, 4A zeolite and carbon-white, etc. [9-10]. The prepared kaolin was obtained from mechanical method. The prepared kaolin has the characteristics of fine size and high specific area [11-12]. The Chinese processing technic for grinding kaolin has a distance to the national level [13]. However, the grinding method has obtained a notable progress in China. Ding et al. experiment showed that the 90% particle size of calcined coal kaolin clay was lower than 2 μm using a wet grinding process [14]. Zhang et al. obtained that the mean particle size of calcined kaolin was lower than 4 μm using a mechanical kinetic energy mill [15]. However, the purity of kaolin has a great influence on its application. The Fluidized bed jet mill is suitable for grinding the kaolin. The jet mill has no pollution on the kaolin in the grinding process. The qualified size distribution of the kaolin can be obtained using jet mill [16]. The fluidized bed jet mill uses the compressed air as the grinding energy. The compressed air goes through the supersonic nozzle and into grinding chamber. Then, the compressed air induces the kaolin particles to grind. The gas with the high temperature has a higher dynamic energy than the gas with normal temperature [17]. When the compressed air is heated, the grinding process of kaolin particles are carried at the high temperature. The kaolin particles should have fine particle size using the same classifier and the yield production of kaolin powder increases. International Conference on Material Science and Application (ICMSA 2015) © 2015. The authors Published by Atlantis Press 475 The 2-3 mm size distribution of kaolin was chosen as the raw material in this experiment. The fluidized bed jet mill with three nozzles was used to grind the kaolin at the temperature 17°C and 280°C. The three aspects of theoretical arithmetic, numeric simulation and experiment were used to compare and discuss the kaolin particle size, yields, energy consumption and grinding kinetic energy. This can provide an environment-friendly way that prepares the high quality and high-yield kaolin powder. Experimental Apparatus and Parameters Raw Materials The calcined kaolin was used in this experiment. The kaolin was obtained from the Guizhou. The Moh's hardness was 7-8. The particle size was 2-3 mm. The main chemical components were as follows using the XRF: ω(SiO2)=59.29%, ω(Al2O3)=19.44%, ω(Fe2O3)=14.14%, ω(CeO2)=2.15%, ω(TiO2)=1.98%, ω(K2O)=1.27%. Experimental Apparatus The flow sheet is shown in Fig.1. The main apparatus and parameters: LNJH-60A type fluidized bed jet mill (Designed by Mianyang, Liuneng, Powder Equipment, Co., Ltd.), LNJ-36A type classifier (Power of motor is 4 Kw, Transmission ratio is 1.5:1), Y4-73 type induced fan (Power of motor is 15Kw, The maximum airflow is 1400 m 3 /h), OG-150W type air compressor (Power is 37 Kw). The 27 bags are installed in a filter. The dimensions of bag are φ120×1500mm and the filtration area is 15 m 2 . The filter medium with the surface treatment can resistance to 300°C. Three nozzles are installed in the fluidized bed jet mill. The nozzle diameter is 5.8 mm and the Mach number is 1.98. The particle size of kaolin is measured using a laser particle size analyzer (Beckman Kurt LS13-320 type). Fig.1 Flow sheet Experimental Process The fluidized bed jet mill is used to prepare the kaolin powder in this experiment. The compressed pressure (0.76 MPa) can be obtained using an air compressor. The compressed air goes through the supersonic nozzles and is used to induce the kaolin particles to grind. In order to investigate the grinding process under the different temperatures, the compressed air is heated using a heater. The temperatures of the compressed air are controlled at the 17°C and 280°C. The 2~3 mm raw materials of kaolin go into grinding chamber using a screw feeding machine. The kaolin particles are grinded in the grinding chamber. The total system has a negative condition using an induced fan. The grinded particles go into classification section with the high-speed airflow. The qualified kaolin particles go into the turbo classifier and then are collected in a filter. The coarse kaolin particles are separated from turbo classifier and go into grinding chamber. The coarse kaolin