| High-purity gallium is mainly used in wireless communication and photoelectric semiconductor field in the form of GaAs, GaP and GaN. With the rapid development of the market on 3G smartphone and LED, the demand for High-purity Gallium increases steadily, so it is essential to enhance the research and production of high-purity gallium. At present, electrolysis is usual method for preparing high-purity gallium, owing to separation effect of Pb, Cu and other impurity elements is not ideal in the electrolytic tail period, and using a crystallization method to deal with it. This thesis is to research crystallization equipment and technology process as well as the purification effect of the gallium by crystallization.This thesis designed and made two different crystallizers based on the principle of crystallization method. This paper meshed calculation area by using hybrid grid, defined the boundary conditions and set the material properties, assumed part of the boundary conditions, established the physical model of the cooling water fluxion and heat transfer in crystallizer. The temperature distribution of cooling water during the crystallization process for two different crystallizers was made a comparative analysis. This paper measured the solidification time under different polytetrafluoroethylene (PTFE) coating thickness; measured the crystallization (solidification) time of liquid gallium at the cooling water temperature 5,10,15 and 20 ℃ respectively; experiment measured solidification time and cooling curve of liquid gallium under different cooling water flow when the cooling water temperature is 15 ℃; carried out comparison experiment between extraction time ratio and solidification percentage; explored solidification time and the cooling curve of different quality of gallium when the cooling water temperature is 10℃ and cooling water flow is 10 L·h-1; studied the refining effect of 99.99% gallium by 7 times recrystallization purification under 80% solidification percentage.The following results has been obtained through experimental research:1. The paper has developed two different schemes of gallium purification crystallizers, comparative analysis of cooling water temperature distribution in crystallizers shows that 2# crystallizer can provide a stable temperature field;2. Experimental studies find that 1# crystallizer has yet to form a stable cooling water of 15℃ temperature field when cooling water flow as high as 150 L·h-1; however 2# crystallizer can provide a stable and uniform temperature field as cooling water flow reach as 75 L·h-1, it confirms that 1# crystallizer is more reasonable than 2# crystallizer.3. The PTFE coating inside crystallizer is thicker, the crystallization time is longer, so liquid gallium crystallization rate can be controlled by changing the PTFE coating thickness.4.While the cooling water total flow reach as 75 L·h-1 in 2# crystallizer, the fitting relation formula between solidification time t and the the cooling water temperature T is t=2.3eT/6.27+31.2, it explains that solidification time is exponential changing with temperature.5. The fitting relation formula between solidification time t and the the cooling water flow Q in 2# crystallizer is it found that the solidification time of liquid gallium significantly decreased with the increase of water flow, and the effective flow of 15℃ cooling water is 75 L·h-1.6. Experiment found that the error between extraction time ratio and solidification percentage is 2.4%, so it can control the solidification percentage of liquid gallium by extracting time ratio.7. Under certain cooling water temperature and flow conditions, the cooling rate for different quantity of liquid gallium is close, to temperature on vertical direction, it distribute uniformly in 2# crystallizer, and cooling intensity has a liitle difference8. The main impurities removing percentage of 99.99% rude gallium was 91.6% on average by 7 times recrystallization purification under solidification percentage of 80%, removing impurity effect is obvious. |
PDF Full Text Request