# Technological Aspects of Sintering Low-Quality Wolframite Concentrate with Potassium Carbonate
###### Abstract  
The loss of quality of wolframite concentrates determines the need to improve their processing method that ensures maximum conversion of tungsten into water-soluble wolframate and a reduction in water-soluble impurities. The results of thermodynamic modeling of the sintering of wolframite concentrate with sodium and potassium carbonates indicate a greater efficiency of K\({}_{2}\)CO\({}_{3}\): The reagent consumption required for complete conversion of tungsten into solution decreases from 170% from stoichiometric sintering with Na\({}_{2}\)CO\({}_{3}\) to 110% for K\({}_{2}\)CO\({}_{3}\), as well as the proportion of soluble silicates up to 0.1%. In addition, sintering with K\({}_{2}\)CO\({}_{3}\) is accompanied by the formation of compounds with a higher melting point, preventing melting and coating formation during the process. Mathematical sintering models were obtained by the method of probabilistically deterministic planning of this experiment. Optimal parameters have been determined: The extraction of tungsten into a solution of more than 95% is achieved by sintering with K\({}_{2}\)CO\({}_{3}\) in an amount of 105-110% according to the stoichiometric requirements for the formation of K\({}_{2}\)WO\({}_{4}\), K\({}_{2}\)MoO\({}_{4}\), and K\({}_{2}\)SO\({}_{4}\) at temperatures of 1073-1123 K for 100-120 min. Pilot tests have confirmed the effectiveness of the process. The possibility of sintering a cinder of wolframite concentrate with K\({}_{2}\)CO\({}_{3}\) without the introduction of recycled materials has been established. Sintering under optimal conditions ensures the transition of tungsten to water-soluble tungstate by 97.5%.  
wolframite concentrate; potassium carbonate; sintering; pilot tests +
Footnote †: journal: Applied Sciences  
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products to 20-22% and the formation of poorly filtered sodium silicates. Consequently, there has been a reduction in the efficiency of the tungsten extraction technology.  
In relation to low-quality raw materials [5; 13; 14; 15; 16], containing 28.2-42% WO\({}_{3}\) and 20% SiO\({}_{2}\), the processing of concentrates is promising, including oxidative roasting with the transfer of sulfur to the gas phase and the sintering of the resulting product with potassium carbonate (instead of Na\({}_{2}\)CO\({}_{3}\)), which allows for the elimination of these disadvantages of classical technology (with sintering with Na\({}_{2}\)CO\({}_{3}\)) and a reduction in reagent consumption and an increase in the unit efficiency. Sintering with K\({}_{2}\)CO\({}_{3}\) ensures the formation of the target compound K\({}_{2}\)WO\({}_{4}\), which has a higher melting point (1196 K [17]), and prevents premature melting of the interaction products. The literature contains a lot of information on the sintering process of tungsten-containing raw materials with sodium carbonate, but the data on the interaction with K\({}_{2}\)CO\({}_{3}\) during heating are very limited.  
The theoretical and experimental studies carried out made it possible to determine the sintering parameters and justify the process modes for processing low-quality raw materials under enlarged conditions. Experimental data [18] showed that the mechanism and kinetics of interaction of wolframite concentrates with sodium and potassium carbonates are close to each other. The peculiarities of their use manifest themselves with a quality decrease in the initial concentration.  
The purpose of this work is to determine the optimal parameters of the sintering process of low-quality wolframite concentrate with sodium and potassium carbonates, ensuring maximum conversion of tungsten into water-soluble tungstate, and to assess the prospects of using potassium carbonate based on the results of pilot tests.