Pilot-scale study on seeded precipitation assisted nanofiltration for flue-gas desulfurization wastewater softening

Pilot-scale study on seeded precipitation assisted nanofiltration for flue-gas desulfurization wastewater softening

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In order to reduce the cost of chemical softening, the seeded precipitation assisted nanofiltration Rug (NF) process was introduced into zero liquid discharge (ZLD) of flue-gas desulfurization (FGD) wastewater treatment.A pilot-scale system was developed and run for 168 h in a coal-fired power plant.The system mainly consists of lime softening, ambient temperature crystallizer (ATC) and NF, in which the raw water treatment capacity was 1 m3/h.The results indicated that the system operated stably, the softening cost was 13.30 RMB/m3, and the electricity cost was 3.

39 RMB/m3 for the FGD wastewater in this pilot system.High quality gypsum was got from the ATC unit, of which the purity was 95.8%.Through this system, the hardness Wipes removal rate was higher than 98.9% and the water recovery rate reached 96%.

In addition, the pressure and permeate flux kept stable in the ultrafiltration (UF) unit and NF unit, indicating no scaling occurred in the two units during 168 h test.Thus, a feasible and cost-effective process was provided by using the seeded precipitation assisted NF to deal with the FGD wastewater.HIGHLIGHTS Seeded precipitation assisted NF is introduced into ZLD process of FGD wastewater.; The softening cost is 13.30 RMB/m3 and much less than softening by Na2CO3.

; The hardness removal rate of this pilot system is higher than 98.9%.; High quality gypsum was got from the ATC unit, of which the purity was 95.8%.;.