| Rare earth is one of indispensable fundamental matters for the development of high-tech. In the hydrometallurgy processes of bastnasite to produce rare earth, there are two conceptual defections: the unilateral resource idea, which don't treat fluorinate as resource, and the lower material utilization rate, which results in heavy pollution during the rare earth producing. This dissertation studies on the environmental benign hydrometallurgy of bastnasite of Sichuan province and puts forward three innovative theories as following:1. The traditional idea, that only rare earth is resource but fluorine not, should be changed. Fluorine in bastnasite should be regarded as resource. Only when the transformation of fluorine to resource is internalized into the smelting process of rare earth, and become a indispensable step, can the pollution problem in rare earth producing be resolved radically.2. The traditional idea, which excluding the rare earth producing system outside the substance system of natural environment, is changed also. Only when the substance producing system of resource transformation is contacted closely with the substance system of natural environment, can the environmental benign process be realized in the course of rare earth producing.3. Three greenization principles of the course of resource transformation, which are listed below,1) The sufficient condition of resource transformation in green chemistry is that all atoms of materials should be transformed into products, and then zero discharge is reached. If the condition does not meet, the atoms of materials should be circulated and reused, or minimize the consumption of materials, near to zero discharge.2) Circulation and regeneration principle of resource transformation. In the system of resource transformation, the transformation system of each unitprocess should be created as closed circulation system.3) The principle ofth". minimum of the environmental load. In the course of resource transformation raw materials and energy should be saved as more as possible, the quantities and toxicity of byproducts should be reduced greatly, so that the impact of producing system on environment can be minimized.Such principles can be applied widely not only in rare earth smelting process, but also in other hydrometallurgies.In light of the actuality of bastnasite hydrometallurgy to produce rare earth, three novel environmental benign processes are created, which are listed as following,In environmental benign process I, guided by the greenization principles of resource transformation, primarily aiming at the problems of high consumption, high cost and heavy pollution, three unit processes with heaviest pollution are altered, which are separation, Fe and Th elimination, base conversion. One green reducer LY is selected out, which can reuse most H2SO4 and Na2SO4, and then the consumption of raw materials and the discharge of waste can be reduced. A new process of Fe and Th eliminating by complexing is Created, which is united with the purging process of precipitation of composite salt of Ce2(804)3. Therefore, two former steps of hydrochloric acid prior resolving and ammonic carbonic depositing are saved, and then the great use of hydrochloric acid and ammonic carbonic are avoided, and the yield ratio of CeO2 are improved. Based on the chemical dynamic analyse of base conversion, the process parameters of base conversion are modified. With the newly proposed parameters, the amount of NaOH can be reduced by 50%, and the conversion time form 4h to Ih. For a factory producing 500t CeOaper year, process /can economize the cost of the raw materials by 3,438 thousand Yuan, reduce 58% pollution, and cut down refined mineral 8%. It's no need to reform today's rare earthfactory and buy new equipments for the application of environmental benign process I, therefore it has great application prospect in rare earth industry.In environmental benign process II, aiming at utilizing fluorine resource, the process principles and...
|
PDF Full Text Request