No abstract

In this paper, chemical precipitation process is used for the treatment of the desulfurization wastewater generated by the waste gas treatment system of the limestone-gypsum flue gas desulfurization process of a thermal power plant. After one year of operation, the technology is reliable and stable. The removal rate of suspended matter, COD, fluoride, mercury and sulfate reached 99.5%, 98.3%, 87.5%, 99.8% and 85.6% respectively, and the corresponding effluent concentrations were 54 mg/L, 20 mg/L and 9.6 mg/L, 0.04 mg/L, 980 mg/L. Finally, the effluent quality of the system is better than the discharge requirements of “Discharge standard of wastewater from limestone-gypsum flue gas desulfurization system in fossil fuel power plants” (DL/T997-2006). In addition, the total electricity and chemical charges per ton of wastewater treatment were 6.50 yuan, which is lower than most of the engineering project under the same discharge requirements. Therefore, the process has certain engineering advantages.

As one of the most promising processing methods, the microelectrical discharge machining (micro-EDM) process is widely used in industrial production; however, the material removal mechanism of micro-EDM in deionized water has not been clarified due to scale effect. In this paper, the influence of discharge parameters on the discharge crater size was studied by means of a single-pulse discharge experiment using a resistor–capacitor circuit (RC circuit). The variation trend of the discharge crater size with open-circuit voltage and capacitance was discussed based on the experimental results. The results show that the diameter and depth of the discharge crater increases with capacitance and open-circuit voltage due to the increasing discharge duration and the energy density of the discharge plasma. The discharge energy increases with the increase of capacitance and open-circuit voltage, which causes more materials to melt and vaporize, leading to the crater volume becoming larger. This study has reference value for the further application of micro-EDM adopting deionized water as a dielectric.

Aiming to ensure the quality of final effluent, combined with the existing research reports and similar engineering experience, the process of “Coagulation Sedimentation Contact Oxidation MBR” is selected as the main body to treat the wastewater in this paper. After the wastewater treatment system operates normally for one year, the results show that the removal rates of COD, BOD5, SS and chroma can reach 97.8%, 97.7%, 97.4% and 96.0% respectively, and the corresponding effluent concentrations are 96 mg/L, 25 mg/L, 18 mg/L and 20 mg/L, respectively, which meets and is better than the secondary discharge standard of the Integrated Discharge Standard of Water Pollutants in Haihe River Basin of Shandong Province (DB37/675-2007). The process has certain engineering advantages as the quality of wastewater treatment is high and the total cost of electricity and medicament for the wastewater treatment is low.