The Optimization Design And Simulation Of Carbon Nanotubes CVD Furnace

Because of its unique structure, carbon nanotubes have excellent mechanical, electrical and thermal properties. Carbon nanotubes(CNTs) have good potential application in different fileds, including composite materials, catalyst carrier, lithium ion battery, field emission materials and stealth materials. Currently, the chemical vapor deposition method is the main method used to produce carbon nanotubes which have many defects, such as low graphite-level, large curvature, intertwined, uneasy to disperse. So based on the chemical vapor deposition method, developing new technology and equipment to prepare CNTs with high-quality is a hot spot. Insight into the temperature and flow field distribution of the furnace is very important to guide the study on the synthesis of carbon nanotubes. To analysis the flow field distribution and separation efficiency of the cyclone separator which has important practical significance on device structure designing and improving.Firstly, designing the structure of the furnace. According to geometric dimensions of the CVD furnace, the 2D and 3D calculation model of the furance are established. Based on FLUENT software,the process of synthesizing CNTs are simulated. The temperature field contour and the velocity field contour of the CVD furnace are obtained,and compared the simulation results with experimental result. The 3D calculation model of cyclone separator is established. The separation process of cyclone separator is simulated, and the flow field distribution in the separator and the trajectories of carbon nanotubes are obtained.The simulation results show that the 2D and 3D results of the furnace are basically the same. Airflow mainly affects the furnace in central area of zone 1 and zone 2, but it has little influence on zone 3 and zone 4. The temperature field in the furnace is not uniform. Along the axial direction, the higher the position, the higher the temperature(except the central area). While along the radial direction, the temperature in zone 1 changs greatly, and in other zones the temperature maintain a relatively stable temperature. The maximum error between the simulation temperature and experimental temperature of the heater is within the margin of error, which means that the caculation modle is reliable and the simulation results have a certain reference value. The flow of gas phase in separator is mainly double vortex. One rotates down and the other rotates up, and both spin in the same direction. The particle size and the entrance position have a great influence on the particle trajectory in the cyclone. The structure and fluid parameters of cyclone separator influence the separation efficiency.