Flue gas desulfurization wastewater salt separation zero discharge system and process

The invention provides a flue gas desulfurization wastewater salt separation zero discharge system and process. The system comprises a pretreatment system, a first-stage nanofiltration system, a second-stage nanofiltration system, a high-pressure reverse osmosis system, a sodium chloride evaporative crystallization system, a sodium chloride drying system, a mother liquor tank and a carnallite drying system. Desulfurization wastewater is connected with the pretreatment system, and the pretreatment system, the primary nanofiltration system, the secondary nanofiltration system, the high-pressure reverse osmosis system, the sodium chloride evaporative crystallization system and the sodium chloride drying system are sequentially connected through pipelines. The sodium chloride evaporative crystallization is connected with the mother liquor tank through a pipeline; the mother liquor tank is connected with the carnallite drying system through a pipeline; the outlet of the sodium chloride drying system outputs sodium