Thermodynamic investigation of lime-enhanced molybdenite reduction using methane-containing gases

Lime-enhanced molybdenite reduction (LEMR) with methane-containing gases has been thermodynamically studied. The reaction proceeds through the direct oxidation of MoS2 by CaO to form intermediate molybdenum oxidized species, MoO2 and CaMoO4. The thermodynamics of Mo–O–C–H and Mo–Ca–O–C–H systems has been investigated instead of Mo–Ca–S–O–C–H system, as the sulfur is captured by calcium and forms a neutral compound (i.e. calcium sulfide). The role of reducing agent is the reduction of these oxidized species. Reduction of oxidized species by methane will yield Mo, Mo2C or MoC. The thermodynamic investigation resulted in construction of stability diagrams of molybdenum compounds. These diagrams were constructed for CH4–H2, CH4–H2–Ar and CH4–CO2–H2O gas mixtures. In addition to stability regions of Mo, Mo2C and MoC, the carbon deposition area was also identified. The results showed that by using appropriate gas composition and temperature, different molybdenum-containing phases would be stable thermodynamically while soot formation can be avoided.