Research Of Multi-needle-plate Pulse Corona Discharge Reactor Structure Optimization And Formaldehyde Degradation

In recent years, as the representative of VOCs(Volatile Organic Compounds), formaldehyde has posed a great threat on people’s physical and mental health and survival environment. Corona discharge synergized photocatalytic technology is regarded as a high degradation efficiency, less by-products and environmental protection way in the degradation of formaldehyde; although the technology has obtained certain research results, it has yet to realize industrial application at present and needs further study.In this paper, multi-needle-plate high-voltage pulse discharge reactor structure optimization and formaldehyde degradation were investigated. The self-made high-voltage pulse corona discharge reactor was adopted in this study; through the research on discharge characteristics of reactor under different electrode structure can optimize the electrode configurations(the needle-plate spacing, the needle-needle spacing), on this basis, the influence on pulse discharge energy efficiency and formaldehyde degradation efficiency of different electrode configurations, electrical parameters(pulse-peak voltage, repetition frequency) and gas injection parameters(gas flow rate, gas direction) was fatherly discussed. Furthermore, the transition metal(Mn, Fe, and Cu) and precious metal(Ag) catalysts were put in the optimized reactor, the effects of pulse corona discharge synergized photo catalysts on formaldehyde degradation, ozone production, CO2 selectivity and energy utilization have been further researched, and then the mechanism of degradation of formaldehyde have been discussed. The results of this study are as follows:(1)Pulse discharge experienced the unstable discharge, stable corona discharge and blocked discharge the three basic processes; compared to the single needle, multi-needle electrode structure has lower corona inception voltage, higher spark breakdown voltage and better discharge stability.(2) The corona discharge has the largest single pulse energy injection and the allowable discharge energy density reaches its maximum when the needle-plate spacing and needle-needle spacing are 20 mm. When the pulse-peak voltage is 17 k V, a repetition frequency of 40 Hz, the gas flow is 0.3L/min and airflow reversed, the efficiency of formaldehyde degradation has achieved the highest, the degradation rate and energy utilization are 86.1%, 3.19g/(k W?h).(3)When pulse corona discharge combined with Mn-Ti, Fe-Ti and Cu-Ti catalysts, the order for formaldehyde degradation is Mn-Ti >Cu-Ti>Fe-Ti>without catalyst, the synergy effect of Mn-Ti catalyst prefers good, compared to the absence of catalyst, formaldehyde degradation rate and energy efficiency are 92.6% and 3.51g/(k W?h), ozone production drops from 175 mg/m3 to 50 mg/m3, the CO2 selectivity rises from 22% to 38%;compared to Mn-Ti catalyst, Ag-Mn-Ti catalyst has further improved and enhanced the effects of formaldehyde degradation, and the effect of photocatalytic has achieved the best under this experimental condition, the formaldehyde degradation rate and energy efficiency are up to 98.6% and 3.65 g/(k W?h), ozone production is 35 mg/m3 and the CO2 selectivity is 48%.All configurations parameters of multi-needle-plate high-voltage pulse corona discharge reactor have been optimized by experiments; and the optimized reactor combined with different photo catalysts to degrade formaldehyde has been studied, thus provide certain theory reference for industrial waste gas degradation by pulse discharge combined with catalysts.