System and method for producing 3.5-valent highly pure vanadium electrolyte

A system and method for producing a 3.5-valent highly pure vanadium electrolyte: use a fluidized bed (2) to hydrolyze highly pure vanadium oxytrichloride to vanadium pentoxide by means of gas-phase hydrolysis, accurately control the reduction of vanadium pentoxide in a reducing fluidized bed (5) to a low-valent vanadium oxide with an average vanadium valence state at 3.5, and under an externally applied microwave field, add water and a sulfuric acid solution to dissolve at a low temperature to obtain a 3.5-valent highly pure vanadium electrolyte, which can be directly used in new piles of vanadium redox flow batteries. The preparation of vanadium pentoxide by means of gas-phase hydrolysis by using the fluidized bed (2) has a short flow and high efficiency. By providing an internal member within the reducing fluidized bed (5), the accurate regulation of the valence state of reduction products may be achieved. The special chemical effect of the microwave field promotes dissolution of vanadium oxides and activates vanadium ions. The dissolution and preparation of an electrolyte in a low temperature range greatly improves the activity of the electrolyte. The method has advantages of short flow, high efficiency, environmental friendliness, and steady product quality, which is applicable to large-scale industrial productions, while offering excellent economic and social benefits.