Preparation method and device of ferrous sulfate monohydrate

The invention provides a preparation method and device of ferrous sulfate monohydrate, and the preparation method comprises the following steps: (1) dissolving a ferrous sulfate heptahydrate solid by adopting one or more of secondary steam, high-temperature condensed water and crystal mush generated in the evaporation and concentration process of ferrous sulfate monohydrate filtrate to obtain a ferrous sulfate solution; (2) heating the ferrous sulfate solution for crystal transformation, and carrying out solid-liquid separation to obtain ferrous sulfate monohydrate solid and ferrous sulfate monohydrate filtrate; (3) evaporating and concentrating the ferrous sulfate monohydrate filtrate by adopting live steam to obtain secondary steam, high-temperature condensed water and crystal mush, and enabling the secondary steam and the high-temperature condensed water to enter the next cycle; (4) carrying out solid-liquid separation on the crystal mush to obtain ferrous sulfate monohydrate solid and crystal mush filtrat