The reaction process and mechanism were studied of scheelite synthesis by calcination of wolf- ramite and calcium carbonate. The experimental results show that scheelite begins to form during wolframite calcination at 550 ℃. Wolframite and calcium carbonate can be completely synthesized into scheelite at 800 ℃, and the main products are CaWO4, Fe2O3 and Mn2 O3. Scheelite synthesis reaction in air takes place by two steps. The first step is generation of CaWO4, FeO and MnO, and the second step is oxidization of FeO and MnO into Fe2O3 and Mn2O3.

For development and utilization of a tungsten molybdenum ore, flotation experiments of molybde nite recovery were carried out. According to the nature of the ore,the process is employed of Mo-S mixed flotation-regrinding and separation of mixed concentrate,obtaining molybdenum concentrate with Mo grade of 46.14% and Mo recovery of 80.38%. Compared with the process of preferential molybdenum flotation, Mo recovery rate of the above process is higher.

Experiments were carried out on two kinds of ultrafine WO3 preparation processes, easy to industrialize. The first process is calcining H2 WO4 to prepare ultrafine WO3. The second process is APT thermal dissociation-leaching-spray drying-calcining AMT to prepare ultrafine WO3. The morphology and particle size of ultrafine WO3 from the two processes were analyzed respectively by SEM and nitrogen adsorption. The results show that the second process is characterized by better WO3 morphology and particle size, more convenient production organization, less difficulty in the process control and better working environment. L9 （34） orthogonal experiments of thermal dissociation step in the second process were carried out. The results show that the factors affecting leaching rate of dissociated material have the following descending order：thermal dissociation temperature, feed rate and thermal dissociation time. Calcination experiment was carried out with the same batch of spray drying material,to research the influence of AMT calcination temperature on Fisher particle size and specific surface of WO3 powders. As a result, ultrafine WO3 powders are obtained with BET size of 75 nm. The results show that calcination temperature slightly influences Fisher particle size of WO3 powders, but strongly influences their specific surface. Lower calcination temperature is helpful for ultrafine WO3 preparation.

A new metallurgical process of roasting-counter current leaching-acidification-releaching is developed to treat the low grade beryllium concentrate with BeO content of 1.13%. Firstly,the beryllium conc entrate is roasted at 1 050 ℃ for 120 min and the resultant calcine,ground to the particle size less than 0.1 mm,is processed by counter current leaching at 30 ℃ for 60 min with the liquid-solid ratio （i. e. the mass ratio of the returned releaching solution to calcine ） of 4 ： 1 . Then , the counter current leaching residue is acidized at 100 ℃ for 30 min by adding sulfuric acid with the acid ore ratio of 1 ~ 1. Finally, the acidifica- tion residue is releached at 30 ℃ for 60 min by adding water with the liquid-solid ratio of 4 ： 1. Through the above process,the BeO content of the leaching residue decreases to 0.14%,the leaching rate of beryll- ium reaches 88.88% ,and the leaching solution can be used for subsequent beryllium oxide extraction.

The characterization parameters are summarized for performance evaluation of molten salt system in TICl4 molten salt chlorinator, and a preliminary analysis of its influencing factors is carried out. The causes of molten salt system deterioration during TICl4 molten salt chlorination are analyzed based on pro duction practice. According to the causes of molten salt system deterioration and the related factors,control measures for molten salt system stability are presented.

In view of the off-standard contents of the copper,iron and some other impurities in high-purity niobium oxide produced in a company,the causes of the quality accident are analyzed. The results indicate that the nitric acid mixed in hydrofluoric acid can rapidly oxidize 2-octanol into organic acid in extraction process. The resultant organic acid interferes with the acid pickling process of the niobium oxide,resulting in the off-standard impurity （i. e. copper and iron） contents in the product.

Concentration distribution of Nd2O3 in electrolysis cell were studied with self-made multipoint sampling device for high temperature molten salt,and the reason for the regular distribution pattern was analyzed. The results show that concentration of Nd2O3 is always less than 4 % and its vertical distribution is decreasing from top to bottom, in accordance with Nd2O3 consumption near anode in the actual production,while its horizontal distribution is increasing from cathode to anode.

To solve the problems of stockpiling of waste rare earth fluorescent resources, and for the environmental concern and recycling of secondary valuable resources,recovery methods of the waste rare earth fluorescent resources and Hg and RE are emphatically summarized. A new concept of environmental friendly and efficient recovery is proposed,and its prospect is also pointed out.

The latest development is reviewed of radioactive pollution in rare earth production. A detailed description is made of the common radioactive detectors in rare earth production. The future development trend is proposed mainly towards the low-energy ray detection and weak radioactive sample determination in rare earth production.

Various sintering methods are reviewed,including solid phase sintering, spark plasma sintering, microwave sintering, two-step sintering, low-temperature activated sintering, selective laser sintering, stacking sintering and so on. Besides, the problems of these methods are summarized.