| Tungsten and molybdenum are two very important rare metal elements and molybdenum can provide nutrition to crops. It would produce large amounts of acid processing wastewater in the dressing process in China Molybdenum Co.,Ltd. The acid processing wastewater couldn't be discharged into water bodies. If the company did, it would be polluted mining environment and ruin the environment.In this paper, the group's processing wastewater was the research object. The purpose of the research was utilization of the mineral water. After analysis to know that it contains phosphorus, fluorine, calcium and chlorine etc. in the mineral processing wastewater of tungsten and molybdenum. I decided to use the following method after access to a large number of domestic and foreign literature and combining the actual situation of waste paper. First, we could obtain calcium hydrogen phosphate products by adding quicklime to mineral processing waste water. Second, we could obtain calcium chloride by cooling crystallization from filtrate in the previous step. Finally, mineral processing waste water that was treated through the above two steps could be cycled to the upstream process. Specific implementation and conclusions are as follows.(1) Sink phosphorus:About calcium hydrogen phosphate products the paper studied the following two conditions which were added quicklime for one-time and two sections.In the first case, it was added in quicklime in the reaction conditions of 700r/min, 35℃,2h and WCaO/H2O=1:5. Phosphorus in waste water could be reduced to below 0.4g/L and fertilizer-grade calcium hydrogen phosphate of 25% available phosphorus content could also be obtained when mineral processing waste was in 6～7 of pH.In the second case,first, it was added in quicklime in the reaction conditions of 200r/min,45℃and 3h.The fluorine of wastewater would be removed and a small part of the sediment phosphorus conformed HG-T 3275-1999 would be obtained by filtration. More than 90% of waste phosphorus was remained in the filtrate as the raw material of the next step. Second, at 50℃, 1h and 600r/min reaction conditions, the other solid product would be obtained from filtrate added in quicklime (WCaO/H2O= 1:4). Almost all the phosphorus would be precipitated out this time and feed-grade calcium hydrogen phosphate conformed GB-T 22549-2008 I could be obtained. XRD showed that the first solid products were calcium fluoride,calcium fluophosphate,calcium hydrogen phosphate and the second solid product was dihydrate calcium hydrogen phosphate.(2) Remove calcium:Solubility experiment of calcium chloride in different concentrations of hydrochloric acid showed the solubility of calcium chloride increases with increasing temperature and reduces with increasing concentration of hydrochloric acid. The results of the model associated showed solubility of calcium chloride in different concentrations of hydrochloric acid came to heel polynomial equations better.(3) Crystallization:The cooling crystallization kinetics of calcium chloride in the filtrate above was experimentally measured by the batch dynamic method. The effects of the cooling rate, the stirring rate on the crystal growth rate and the nucleation rate were investigated. A size-independent model and the moment transform method of the intermittent dynamic method were chosen to deal with the experimental data, and the model equations of the crystal growth rate and the nucleation rate in the crystallization process of calcium chloride were finally obtained through the least square multivariate linear regression. |
PDF Full Text Request