Method for controlling out-of-kettle particle size of small-particle-size tricobalt tetraoxide

The invention discloses a method for controlling the out-of-kettle particle size of small-particle-size tricobalt tetraoxide. The method comprises the following steps: preparing a cobalt salt solutionwith the cobalt ion concentration of 108-112 g/L, preparing a sodium hydroxide solution, and preparing an inhibitor solution with the mass percentage content of 8-10%; adding an ammonia water solution with the concentration of 180-200g/L into the sodium hydroxide solution to obtain a mixed solution; adding the mixed solution into a synthesis kettle added with a base solution to enable the pH value in the synthesis kettle to be 10-10.2, then adding a cobalt salt solution into the synthesis kettle, finally adding the inhibitor solution into the synthesis kettle, and carrying out a synthesis reaction to obtain slurry; and sequentially carrying out centrifugal washing, drying and calcining on the slurry to obtain a small-granularity tricobalt tetraoxide product. According to the method, the out-of-kettle particle siz