Abstract: The article is about thermodynamic calculations of waste honeycomb SCR catalysts in sodium roasting process un- der different conditions.Temperature and sodium carbonate addition were variable during the process，and the corresponding phase diagrams were made by thermodynamic software HSC Chemistry while their effect on leaching rate of tungsten and vanadium was analyzed.The leaching rates of tungsten and vanadium under different roasting conditions were studied.The opti- mum conditions were obtained：the addition amount of sodium carbonate was 30%，the roasting temperature was 800 ℃，the grain size was at 75～100 μm，and the roasting time was at 2～2.5 h.The phase and morphology of raw catalysts and roasted samples were analyzed by XRD and SEM.The mechanism of recovery of tungsten and vanadium from waste SCR catalysts in soda roasting process was studied from the point of theory analysis and experiment.

Key words: waste SCR catalysts, recovery of tungsten and vanadium, soda roasting, mechanism study