Research On Activation And Conversion Of Carbon Dioxide By Dielectric Barrier Discharge Plasma

The greenhouse effect and its induced global warming are both global environmental issues. Plasma decomposition of carbon dioxide can not only reduce the impact of global warming by consuming the greenhouse gas, but also obtain carbon monoxide and oxygen as by-products, which fully utilize the low-carbon resources. In this paper, the activation and conversion of carbon dioxide using dielectric barrier discharge plasma reactor was investigated. Effects of many factors on conversion of carbon dioxide were investigated to take enhancing conversion of carbon dioxide and yield of carbon monoxide and oxygen into account. The factors included inner electrode form, discharge gap, discharge frequency, input power, gas flow rate and so on. Effect of concentration of carbon dioxide on decomposition reaction of carbon dioxide by plasma was investigated by regarding Helium and Argon as auxiliary gas. Decomposition characteristic of carbon dioxide by dielectric barrier discharge plasma was investigated by selecting four kinds of filler, including zeolite,γ-Al2O3, activated carbon and straws. In the experiment, plasma was combined with catalysts which were Alumina pellets coated with Palladium and Platinum, to attempt to enhance conversion of carbon dioxide and yield of carbon monoxide and oxygen. The main results are summarized as follows:1. Activation and conversion of pure carbon dioxide by dielectric barrier discharge plasma was experimentally investigated. Input power and gas flow rate were important factors influencing conversion of carbon dioxide. Conversion of carbon dioxide and yield of carbon monoxide and oxygen could be enhanced by increasing input power or decreasing gas flow rate within limits. Reactors structures had a certain effect on conversion of carbon dioxide. Compared with bolt as electrode, smooth rod as electrode had more conversion of carbon dioxide. And compared with discharge gap being 3.5 mm, conversion of carbon dioxide was more when discharge gap was 2.0 mm. Effect of discharge frequency on conversion of carbon dioxide was not obvious. Air cooling or circulate water cooling to plasma reactor was helpful to decomposition of carbon dioxide.2. Mixed with Helium or Argon, carbon dioxide was activated and converted by plasma in the experiment. The results are:Increasing input power was not conducive to conversion of carbon dioxide when Helium was used as auxiliary gas. At the same total gas flow rate, with the increased of the ratio of gas flow rate of Helium to that of carbon dioxide, conversion of carbon dioxide increased, but absolute decomposition rate of carbon dioxide decreased. When input power was 140 W, Helium was more beneficial to add to conversion of carbon dioxide than Argon.3. Zeolite and activated Alumina were selected as filler in the experiment. Carbon dioxide activated and converted by filled dielectric barrier discharge plasma was investigated. We found that:Increasing input power or decreasing gas flow rate within limits could enhance conversion of carbon dioxide and yield of carbon monoxide. Compared with discharge filled with zeolite, conversion rate of carbon dioxide were higher by discharge filled with activated Alumina, because activated Alumina could adsorb carbon dioxide to some extent.4. Carbon dioxide activated and converted by plasma combined with catalysts was investigated. We found that:conversion of carbon dioxide was enhanced to some extent by y-Alumina coated with Platinum or Palladium. Because Platinum or Palladium supplied reduction sites for conversion of carbon dioxide, and it reduced activation energy of the reaction. Compared with being filled in reaction zone, catalysts were more beneficial to conversion of carbon dioxide to fill in twilight zone.5. Carbon dioxide activated and converted by plasma combined with solid reducer was investigated. Comparing conversion of carbon dioxide by several discharge forms, the order of excellence of carbon dioxide conversion was:straws, no filling, activated Alumina, activated carbon, zeolite. Although activated carbon contained reductive carbon, conversion of carbon dioxide was relatively low by activated carbon added discharge plasma, because the discharge state was surface discharge, and reaction residence time was short. In this experiment, conversion of carbon dioxide and yield of carbon monoxide reached 30.5%, 25.7%, respectively, when straws was used as filler. Because straws contained reductive carbon and hydrogen, and they participated in the discharge reaction.