Study On Design And Technology Of Dry Synthesis Of Aluminum Fluoride Reactor

In the domestic, many phosphate compound fertilizer enterprises made use of by-product fluosilicic acid to product ammonium fluoride solution or solid ammonium fluoride products. Due to the ammonium fluoride products is not high purity, impurity content is more, it is difficult for applying to the higher purity industry; Combined with ammonium fluoride has smaller market capacity, and market competitiveness is not strong. Therefore, how to effectively develop and product high value-added fine fluoride salt using ammonium fluoride, is one of the problems to be solved in Yunnan Yuntianhua International Chemical Co.,Ltd. and the whole phosphate compound fertilizer enterprises. At present, YTHIC has the patented technology of continuous ammonification to make ammonium fluoride, but there has been no patented technology for production of ammonium fluoride to product aluminum fluoride products. Aluminum fluoride is a high value-added fluoride salt, industrial use is very broad, this experimental subject proposes that by the use of solid ammonium fluoride and aluminum hydroxide, to dry compose aluminum fluoride, and conduct experimental study and discussion, trying to inspiration for technological development in the industry of the company.At first, making the study of the theoretical analysis, main the thermodynamic analysis and reaction mechanism analysis. Decomposition of solid ammonium fluoride thermal process is complex, the pyrolysis process has more side effects, by using the chemical thermodynamic calculation software HSC on raw material ammonium fluoride heat are analyzed in detail, mainly studied the temperature dependency of the equilibrium constant and conversion rate of reactions; At the same time, used the TG/DTA to carried out a detailed analysis of the thermal decomposition for ammonium fluoride. To another experiment main raw materials of aluminum hydroxide, we got a preliminary understanding of the law of removal of water of crystallization of aluminum hydroxide at high temperatures and crystal transformation. Through the main reaction feasibility analysis of T-△G、T-△H、T-△S, obtained the experimental temperature range is about 400℃-600℃.Secondly, making the study of thermal decomposition of solid ammonium fluoride in a muffle furnace, using the different cross-sectional area crucible to experiment, to study the impact of different sizes, different feeding methods of ammonium fluoride, the size on the thermal decomposition of ammonium fluoride is almost no effect, influence of different feeding methods more on the decomposition of ammonium fluoride. By using small crucible maximum surface decomposition rate of ammonium fluoride and technical requirements, calculated the size of the thermal decomposition device and parameter estimation. Selected the pyrolysis device body anticorrosion material and setted gas, pipeline layout of equipment, and then made the device.Then, according to the requirements of the experimental technical conditions and materials property data, maked the calculations of umf、ut、uo、Dand H for subsequent experimental device manufacturing.Finally, with the designed device and fluidized-bed reactor, makes the gas-solid dry synthesis of aluminum fluoride experimental research and discussion. Constant temperature of pyrolysis device was measured, respectively, the effects of pyrolysis temperature、pyrolysis time、gas operating speed、fluidized bed temperature、fluidized bed reaction time and other factors on the synthesis process were studied. Through the identification of the interaction between factorsre、sponse surface analysis、 orthogonal regression experiment analysis、orthogonal experimental analysis and repeated experiment, obtained the optimum process conditions for the preparation of aluminum fluoride:(1) The thermal decomposition temperature of ammonium fluoride is 265℃;(2) The thermal decomposition time of ammonium fluoride is 83min;(3) n(NH4F):n(Al(OH)3)=18:1;(4) The gas operating speed is 1.0 m3/h;(5) The bed temperature of the fluidized bed is 554℃;(6) The reaction time of the fluidized bed is 68min;In the experiments, industry aluminum fluoride of w=90.26%was obtained, its technical specifications can reach or exceed the requirement of Chinese standard GB/T 4292-2007. The feasibility for preparation of industry aluminum fluoride from ammonium fluoride is verified. In addition, the research provides a new approach to comprehensive utilization of ammonium fluoride.