The Design Of A Novel Pulse Power And Its Application For The Degradation Of HCB Wastewater

The refractory wastewater is difficulty treated by traditional biological treatment technology, so great attention is focused on so called advanced oxidation processes (AOP) that are based on generation of highly reactive species, especially hydroxyl radicals. Pulsed high voltage discharge technology, as one of newly developed AOP, is considered to be an energy efficient method for the production of highly active species, In the past few decades, the pulsed discharge plasma technology has achieved great development in the treatment of toxic organic wastewater, but which has many problems in industrialization including long processing time, high processing cost, instability of pulsed power and unclear of degradation mechanism. So the studies are committed to overcome these problems with the pulsed discharge plasma technology in the paper. The main conclusions are drawn as follows:(1) A novel nanosecond pulse power based on the theory of magnetic pulse compression and SOS effect was developed. The effect of some key parameters on the pulse power output characteristics were discussed through Pspice simulation and laboratory study. The results show that a 51 kV negative pulse was formed which had a pulse width of 120 ns and steep rise time of 40 ns at a load of 50 Q, when the turns of MS was 13, and the winding ratio of PT1 and PT2 were 1:20 and 2:10, respectively. The power will have a good application foreground in environmental treatment by discharge plasma.(2) The matching between generator and reactor is studied for optimizing the pulsed plasma discharge. In term of the idea that the reactor is considered as one-stage capacitor in the switch circuit, one-stage and two-stage magnetic pulse compression system are designed to match the large-scale reactor respectively. The results show that the design switch circuit can well match the large-scale reactor, when the turns of MS1 was 35, the peak voltage of one-stage magnetic pulse compression system was 28 kV; when the turns of MS1 was 33, the peak voltage of two-stage magnetic pulse compression system was 30 kV.(3) It has been demonstrated that pulsed high voltage discharges generated directly in water initiate a variety of active species, in them of the OH·radical is the strongest oxidizing active specie, and H2O2 is the most stable active specie. The results showed that the concentrations of H2O2 increased with increasing the peak voltage and air flow rate. The concentrations of H2O2 increased greatly when air was injected into the reaction region during the discharge process. When the experimental condition was 35kV peak voltage,30Hz frequency and 2cm distance between electrodes, the initial rates of H2O2 were 11.7 and 1.67×10-9mol/s with and without bubbling air, respectively. Energy efficiency of production H2O2 was found to be 6.56 and 0.96×10-11mol/J with and without bubbling air, respectively. The addition of a right amount of TiO2 greatly increased the concentrations of H2O2. The results of the orthogonal experiment show that primary and secondary factors are peak voltage, discharge time, and air flow rate.(4) High performance liquid chromatography (HPLC) has been employed to measure the definite concentration of OH·radicals produced by the novel nanosecond pulse power by determining the hydroxylated derivatives of salicylic acid.200mg/L salicylic acid was used to trap OH·radicals in term of the effective trapping. It was observed that 2.3-dHBA and 2.5-dHBA were produced about in proportions of 30% and 70%, respectively. The repeatability was examined through the R.S.D.s of peak areas. The results showed that the concentrations of OH·increased with increasing the peak voltage, the initial rates of OH·were 4.1,5.7, and 7.7×10-10mol/s at 30,35, and 40 kV without bubbling air, respectively, and the initial rates of OH·were 18.1,22.1, and 26.1×10-10mol/s at 30,35, and 40 kV with bubbling air, respectively. The concentrations of OH·increased greatly when air was injected into the reaction region during the discharge process. Energy efficiency of production OH·without bubbling air was found to be independent of the applied power input parameters and an average value of 3.23×10-12 mol/J was obtained. Energy efficiency of production OH·with bubbling air decreased with increasing the input energy.(5) The degradation of HCB by the pulsed discharge plasma using a needle-plate reactor has been investigated. Effects of some factors were studied, including peak voltages, treatment time, and air flow rate. The degradation reaction of HCB accorded well with pseudo first order kinetics, and the degradation efficiency of HCB increased greatly when air was injected into the reaction region. The peak voltage was an important factor that affected the degradation efficiency of HCB, the degradation efficiency of HCB increased from 48.8% to 91.8% when the peak voltage increased from 20 kV to 40 kV after discharge 90 min. Energy efficiency of degradation HCB decreased with the increase of discharge time, it decreased from 2.01×10-12mol/J to 0.67×10-12mol/J when the discharge time increased from 15 to 90 min with bubbling air, and it decreased from 0.94×10-12mol/J to 0.47×10-12mol/J when the discharge time increased from15 to 90 min without bubbling air.(6) A dynamical model was developed to describe the degradation process of HCB. The data calculated by the model was matched the experimental data well for HCB concentrations. The model is useful for the magnification of the reactor and the propagation application of the technology.