DTA/TG study of tungsten oxide and ammonium tungstate reduction by (Mg + C) combined reducers at non-isothermal conditions

Abstract In this work the reaction mechanism in the WO 3 –Mg/C systems and ammonium paratungstate (APT)–Mg/C systems are studied. As reducer magnesium, carbon or combinations of both are explored. It is shown that in the WO 3 –Mg system the reduction undergoes by solid–solid mechanism before melting Mg, where metallic tungsten and MgO are formed. Unlike this system, in the WO 3 –C system mainly WO x ( 2 (> 960 °C) and small amount W is formed. In the WO 3 –Mg–C ternary system reduction temperature shifts to higher temperature range and depends on amount of carbon. Similar to WO 3 –Mg system, APT–Mg reaction starts and completes in the solid state. Thus, firstly the APT decomposes, then reduction of formed WO 3 takes place at ~ 600 °C yielding W and MgO. Likewise to WO 3 –Mg system adding carbon into APT–Mg mixture shifts reduction temperature to even higher temperature zone which can exceed melting point of Mg and further reduction undergoes with molten magnesium. It is shown that the reduction products are MgO and W.