# Technological Aspects of Sintering Low-Quality Wolframite Concentrate with Potassium Carbonate
## 2 Materials and Methods  
The object of this study is a low-quality wolframite concentrate from the ore of the Kalgutinsky deposit (Russia, Altai Republic, the headwaters of the Kalguty River). According to X-ray phase analysis (XRF), quartz--\(\alpha\)-SiO\({}_{2}\), chalcopyrite--CuFeS\({}_{2}\), pyrite--FeS\({}_{2}\), molybdenum--MoS\({}_{2}\), iron oxide--\(\epsilon\)-Fe\({}_{2}\)O\({}_{3}\) were detected in the concentrate. The mineral composition of the concentrate sample indicates that the behavior of sulfur during thermal interaction with sodium or potassium carbonates will affect its results and thereby the subsequent stages of processing. In this connection, the initial concentrate was subjected to oxidative roasting in a chamber furnace (1073 K, air, 1 h). The outcomes of atomic emission spectroscopy of both the initial and post-treatment concentrates are presented in Table 1. According to X-ray phase analysis, the cinder has the following rational composition, % by weight: 40.7 Fe\({}_{0.5}\)Mn\({}_{0.5}\)WO\({}_{4}\) (20.3 MnWO\({}_{4}\) and 20.4 FeWO\({}_{4}\)), 28.8 SiO\({}_{2}\), 6.5 CuFeO\({}_{2}\), 5.1 CuMoO\({}_{4}\), 5.0 FeMoO\({}_{4}\), 7.2 Fe\({}_{2}\)O\({}_{3}\), 2.7 Al\({}_{2}\)SiO\({}_{5}\), 2.5 Cu\({}_{2}\)S, 1,4 FeS. The following reagents were used in the experiments: sodium and potassium carbonates, reagent grade contained at least 99.2% and 99.0% of the basic substance, respectively. The chemical analyses of the initial concentrate, intermediate, and final products were carried out on an inductively coupled plasma Spectroflame Modula S spectrometer (SPECTRO, Kleve, Germany). The phase composition of the concentrate and processed products was determined using a Shimadzu XRD-7000 diffractometer, Shimadzu, Tokyo, Japan (Cu-K\(\alpha\) radiation, graphite monochromator, Bragg-Brentano focusing), shooting pitch 0.02\({}^{\circ}\), shutter speed 2 s. The decoding of diffractograms was carried out using the ICDD PDF-2 database. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Concentrate**} & \multicolumn{8}{c}{**Content, Mass. \%**} \\ \cline{2-9}  & **W** & **Si** & **S** & **Mo** & **Mn** & **Fe** & **Cu** & **Al** \\ \hline Initial & 22.9 & 11.6 & 10.7 & 4.3 & 3.6 & 12.2 & 6.2 & 1.4 \\ Post-Treatment & 24.7 & 13.5 & 1.01 & 4.41 & 3.69 & 13.4 & 6.35 & 1.44 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Composition of initial and post-treatment concentrates. Thermodynamic modeling (TDM) of phase formation during sintering of wolframite concentrate with sodium and potassium carbonates was carried out in order to pre-select processing modes, as well as to evaluate the equilibrium compositions and quantities of the products formed. The simulation was carried out on the Chemistry HSC 6.12 software package (Outokumpu, Helsinki, Finland) based on the minimization of Gibbs energy. The data of the phase composition of the cinder were taken as the fundamental components of the working fluid for thermodynamic modeling. Calculations were performed for 100 kg of the mass of the working fluid made up of wolframite raw materials and sodium (potassium) carbonate. The number of carbonates and oxygen (air) introduced into the working fluid were taken according to stoichiometric requirements for the formation of tungstates and molybdates of sodium and potassium (Na\({}_{2}\)WO\({}_{4}\), K\({}_{2}\)WO\({}_{4}\) and Na\({}_{2}\)MoO\({}_{4}\), K\({}_{2}\)MoO\({}_{4}\)), as well as the conversion of sulfur into sulfate, and iron and manganese oxides to higher degrees of oxidation.