Purification Of High-purity Gallium By Directional Crystallization Method

With the rapid development of microelectronics and optical component industry such as wireless communication, smart phones and LED technology, the demands of high-purity gallium are increasing rapidly with the purity of gallium. The preparation of high-purity gallium has become a hot spot of research on a world scale. Crystallization method has simple operation, short production cycle, and low production process energy consumption that can be used as an efficient method of preparing high-purity gallium. The thesis based on the independent design of crystallizer, Studied the technologic conditions of preparing high-gallium by directional crystallization, and successfully prepared6N and7N high-gallium products accordance with the relevant national standard.This thesis designed and constructed a crystallizer based on the principle of crystallization method, and the crystallizer conform to the requirements of the experiments; By comparing and analyzing the dissolubility of chemical constituents on several kinds of material, Select the stable chemistry character and almost zero dissolubility components Polytetrafluoroethylene Plastics as the crystallizer wall material; According to the experimental requirements, designed and installed the crystallization device to determine and optimize the experimental process. The effects of cooling water flow, temperature and the number of grafting crystal seed on solidification time and crystal growth were examined in detail and the process parameters were determined. The experimental results show that:(1) The crystallization time decreases constantly with the cooling water temperature increasing, at the cooling water flow rate after reaching60L·h-1, crystallization time is no longer change with the flow, the functional relation with flow is t=108.8+8.2/(1+(e(Q-48.3/4.4)), the cooling water flow control in50to75L·h-1makes uniform crystal growth;(2) The crystallization time increases constantly with the cooling water temperature increasing, the cooling water temperature control in20 to22℃makes uniform crystal growth and crystal grain size is consistent, the functional relation of crystallization time with temperature is t=131.2-18.7T+0.87T2;(3) The experiment also indicates that grafting crystal seed can induce nucleation and shorten crystallization time. The results above show that the best technological parameters are cooling water flow of60L·h-1, Cooling water temperature of20to22℃and grafting four symmetrical distribution crystal seed at the beginning of the crystallization.HR-GDMS testing results show that under the condition of22℃cooling water temperature of,60L·h-1cooling water flow rate and90%solidification rate, after7times recrystallization the product purity can reach the national standard of6N high-purity gallium, and the product yield is45.92%. Finally, the paper according to the variation of contents of each impurity elements in the process of crystallization, calculated the part of the impurity elements segregation coefficient at22℃cooling water temperature:KCu=0.003、KPb=0.01、KT1=0.026、KBi=0.013。Thesis research results show that crystallization can be used as an efficient method of preparing high-purity gallium, the independent designed crystallization device can meet the production requirements of purifying gallium by crystallization, Under selected Crystallization parameters the thesis successfully refining6N and7N high-purity gallium that can meets national standards.