Experimental Study On Degradation Of Desulphurization Wastewater From Coal-fired Power Plant Based On Nanofiltration Technology

The desulfurization wastewater produced in the flue gas desulfurization process of the coal-fired power plant mainly adopts the triple-box treatment process.The effluent contains a large amount of calcium and magnesium ions,and the salt content is as high as 2%-4%,which is harmful to the environment.In this paper,the chemical softening-nanofiltration technology of deep treatment of coal-fired power plant desulfurization wastewater test study,and the daily processing capacity of 10 tons of desulfurization wastewater treatment plant pilot test study.In this paper,several chemical softening processes are studied.The results show that the chemical softening process of calcium hydroxide-sodium sulfate-flocculation-sodium carbonate-flocculation is efficient and economical,and the chemical softening process of calcium carbonate-Can reduce the calcium ions in the wastewater to ? 100 mg / L,and the magnesium ion drops to ? 30 mg / L.Pharmacy dosing costs of10.7 yuan / ton.In the chemical softening process added flocculation,to improve the process of chemical softening reaction sedimentation sedimentation,speed up the sedimentation rate,reduce the size of the sedimentation tank design,effective savings in equipment pre-investment costs.The NF-270,NF90 and ESNA3 nanofiltration membranes were investigated.Three kinds of membrane properties were investigated from the aspects of flux,salt effect and desalination effect.The results show that the fluxes of NF270,NF90 and ESNA3 are stable at 17.06,12.46 and 8.85 L /? h,and the purity of sodium chloride can reach93.53%,90.21% and 97.09% under the operating pressure of 0.5 Mpa.In the case of salt effect,the ESNA3 nanofiltration membrane was selected as the membrane for desulfurization wastewater treatment.The effects of waste water hardness,nanofiltration operating parameters and sulfate content on the nanofiltration treatment were analyzed by a small test.The results show that the membrane flux can be stabilized at 25 L/?·h and the conductivity of the water is stable at 25 ms / cm after 10 h of the test run,indicating that the chemical softening Treatment meets nanofiltration requirements.The effect of running pressure on the rejection rate of sulfate and chloride ions is small,the purity of sodium chloride is greater than or equal to or above 97.5%,which has a great effect on the flux andhigher pressure can increase the membrane flux.Under the condition that the total ion concentration is constant,the concentration of sulfate ion becomes high,and the rejection rate of the nanofiltration membrane is low.Finally,according to the chemical softening process and nanofiltration test results,the daily treatment of ? 10 tons of desulfurization wastewater treatment plant design and pilot test.The device uses a chemical softening-nanofiltration process.The results show that the total hardness of the desulfurization wastewater after the softening is?100mg / l,pH?10 and the conductivity is less than 45 ms / cm.The nanofiltration can be effectively divided into salt.The pilot test can concentrate the wastewater by 2-4times,Secondary nanofiltration effluent sodium chloride purity ? 97.5%.The pilot plant can effectively deal with coal-fired power plant desulfurization wastewater.