Comprehensive Utilization Technology Of Potash Feldspar

This thesis focused on two aspects of work. Firstly, based on the laboratory experiments, the pilot-plant test were conducted to extract Potassium from Potash feldspar-phosphate-sulfuric acid system with mechanical and chemical method. Also, the performance of self-made equipment was evaluated. Secondly, the optimum process, that potassium sulphate and aluminium oxide were prepared by thermal decomposition method from potassium alum, were investigated. The decomposition behavior and the kinetics of decomposition of potassium alum were studied through TG-DSC thermal analysis.When the pilot-plant test of a cycle of continuous operation run 3.25 h,150 kg products were obtained. The amount of available NPK in products accounted for about 10%. The decomposition rate of potassium feldspar and phosphate reached 39.84% and 58.10% respectively. Potassium feldspar and phosphate rock, which is not completely broken down in products, would continue to release the potassium and phosphorus slowly in the soil environment. And the long-term sustained release effect was formed. Appropriate ammonium bicarbonate can not only control the pH of the product to precipitate the aluminum ion completely, but also keep the product being dry powder. The pilot-plant test achieved the desired goal, the product has good effect, and the reliability and stability of the process was verified. It can provide some reference data for the further expansion of production design.Potassium alum, which was prepared by potash feldspar, was used as raw material. Aluminum oxide and potassium sulfate were prepared from alum with thermal decomposition method. After being purified, potassium alum was decomposed to generate the aluminum oxide and potassium sulfate by roasting-water leaching process. Experiment results showed that the optimum conditions were:roasting temperature was 850℃, roasting time was 20 min, leaching temperature was 100℃, the ratio of solid to liquid was 1/5 g/mL, and the leaching time was 20 min. Aluminum oxide was obtained after drying out the filter cake, while potassium sulfate was obtained after evaporating and crystallizing the filtrate. The yield coefficient of aluminum oxide and potassium sulfate were 86.52% and 85.02% respectively. The purity of aluminum oxide is 98.52%, which conforms to the standards of GB/T 24487-2009. The content of potassium oxide in potassium sulfate is 47.85%, which conforms to the standards of agricultural potassium sulfate in GB 20406-2006. The decomposition process of potassium alum was analyzed by TG-DSC thermal analysis, and the product was detected using XRD. Results showed that the thermal decomposition process of potassium alum is first order reaction. Thermal process can be divided into three steps, including two steps to break out the crystal water, and one step to decompose the aluminum sulfate. Finally, the product of alumina is presented in the form of alpha alumina.