▎ 摘　　要

NOVELTY - Preparing low-valent vanadium tail gas from ammonium metavanadate comprises e.g. (1) heating and dissolving crude ammonium metavanadate in water, adjusting pH to 8-9 with sodium hydroxide solution after dissolving, and filtering to obtain sodium metavanadate solution, adding sodium hydroxide, generating ammonia gas, and collecting, (2) adding aqueous ammonia to sodium metavanadate solution to obtain ammonium metavanadate precipitation, dehydrating and washing ammonium metavanadate precipitate with aqueous solution of dilute ammonium chloride, and dehydrating and calcining to obtain vanadium pentoxide, generating ammonia gas, ammonium chloride gas, hydrogen chloride gas, and collecting gas, (3) mixing vanadium pentoxide with carbon powder and graphene at a molar ratio of 2:1:0.005-0.01 to obtain a mixture, (4) heating mixture at 500-650 degrees C for 1-5 hours under protection of inert gas to obtain vanadium trioxide, and producing mixed gas of carbon dioxide and inert gas. USE - The method is useful for preparing low-valent vanadium tail gas from ammonium metavanadate. ADVANTAGE - The method: has short calcining time, high reaction activity, purity of vanadium trioxide is less than or equal to 99.8%, and no ammonia gas is detected in exhaust gas. DETAILED DESCRIPTION - Preparing low-valent vanadium tail gas from ammonium metavanadate comprises (1) heating and dissolving crude ammonium metavanadate in water, adjusting pH to 8-9 with sodium hydroxide solution after dissolving, and filtering to obtain sodium metavanadate solution, adding sodium hydroxide, generating ammonia gas, and collecting, (2) adding aqueous ammonia to sodium metavanadate solution to obtain ammonium metavanadate precipitation, dehydrating and washing ammonium metavanadate precipitate with aqueous solution of dilute ammonium chloride, and dehydrating and calcining to obtain vanadium pentoxide, during operation and reaction, generating ammonia gas, ammonium chloride gas, hydrogen chloride gas, and collecting gas, (3) mixing vanadium pentoxide with carbon powder and graphene at a molar ratio of 2:1:0.005-0.01 to obtain a mixture, (4) heating mixture at 500-650 degrees C for 1-5 hours under protection of inert gas to obtain vanadium trioxide, and producing mixed gas of carbon dioxide and inert gas, and (5) collecting gas generated to obtain a mixed gas, passing mixed gas into spray tank, and spraying solution with ferrous sulfate aqueous solution, cooling gas to 5 degrees C and liquefying, cooling and discharging.