Influence of Operating Parameters on Plasma-Assisted Dry Reforming of Methane in a Rotating Gliding Arc Reactor

Abstract

The environmental impact of greenhouse gases such as carbon dioxide and methane can be reduced if they are used as feedstock to synthesize chemical building blocks such as syngas (CO, H 2) via dry reforming. Methane dry reforming is investigated using an Ar/CO2/CH4 rotating gliding arc (RGA) reactor powered by a dual-stage pulsed DC power supply. Tangential gas injection combined with a static magnetic field enabled the rotation and upward displacement of the arc along the conical cathode and the grounded anode, yielding to a larger plasma volume. Different parameters such as peak arc current (0.74 and 1.50 A), total gas flow rate (3.7, 4.7 and 6.7 SLPM), CO2/CH4 ratio (1.0, 1.5, 2.0) and gas inlet preheating (room temperature, 200 °C) were studied to determine the most efficient parameter combination. Gas conversion was measured online using a calibrated mass spectrometer and offline using a gas chromatograph. Noticeable increases in CO2 and CH4 conversions, as well as H2 and CO yields, were obtained when doubling the peak arc current. For the larger peak current, higher H2 yields were obtained at a CO2/CH4=1.0, and the best energy efficiencies were obtained at the lowest specific energy input values. No significant effect of the gas inlet temperature on the conversions or yields was found. Trace amounts of acetylene and ethylene, as well as some carbon deposits were observed as by-products of syngas generation. The low amount of by-products obtained implies a good selectivity for CO and H2, i.e., a cleaner syngas when produced with RGA discharge.

Plasma‐Assisted Reforming of Methane

“…It can alleviate environmental problems such as greenhouse gas emissions and produce value‐added syngas as a chemical feedstock, which is vital in reducing carbon emissions. However, since both CH 4 and CO 2 contain carbon, carbon deposition is inevitable in the PADRM process via the following thermodynamic reactions: [ 31,59 ] $$$$\begin{equation} {\mathrm{CH}}_{4}\to \mathrm{C}+2{\mathrm{H}}_{2}\Delta {H}_{298K}=75\mathrm{kJ}{\mathrm{mol}}^{-1} \end{equation}$$$$ $$$$\begin{equation}{\rm{CO}}_2 + 2{{\rm{H}}}_2 \to {\rm{C}} + 2{{\rm{H}}}_2{\rm{O}} \quad \Delta {H}_{298K} = - 90\ {\rm{kJ}}\;{\rm{mol}}^{ - 1}\end{equation}$$$$ $$$$\begin{equation}2{\rm{CO}} \to {\rm{C}} + {\rm{CO}}_2\quad \Delta {H}_{298K} = - 172.4 \;{\rm{kJ}}\;{\rm{mol}}^{{\rm{ - 1}}}\end{equation}$$$$ $$$$\begin{equation}{\rm{CO}} + {{\rm{H}}}_2 \to {\rm{C}} + {{\rm{H}}}_2{\rm{O}}\quad \Delta {H}_{298K} = - 131 \;{\rm{kJ}}\;{\rm{mol}}^{ - 1}\end{equation}$$$$…”

“…To overcome these problems, RGA discharge between thermal and nonthermal plasmas was introduced. [ 59 ] The RGA reactor is a configuration that makes more efficient use of the energy, it has been reported that the RGA reactor can generate syngas at low temperature (475 °C) without any catalyst with a chemical efficiency (ratio of energy required to carry out the reaction at 25 °C to the used electrical energy) as high as 40%. [ 193 ] However, the structure of the RGA reactor is relatively complex, the catalyst cannot be placed in the plasma area, and the temperature distribution inside the reactor is not uniform.…”

“…It can alleviate environmental problems such as greenhouse gas emissions and produce value‐added syngas as a chemical feedstock, which is vital in reducing carbon emissions. However, since both CH 4 and CO 2 contain carbon, carbon deposition is inevitable in the PADRM process via the following thermodynamic reactions: [ 31 , 59 ] …”

Effect of gas flow rate on breakdown voltage in a rotating gliding arc reactor

“…Rotating gliding arc discharges have been extensively studied for its chemical applications [1,2]. The working principle of RGAs is similar to that of conventional gliding arc discharges (GAD) made of planar diverging electrodes i.e., an arc strikes at the shortest gap between the electrodes when sufficient electric field is given to create breakdown; after initial breakdown, the arc is pushed by the gas downstream thereby elongating the arc [3].…”

A Review about the Recent Advances in Selected NonThermal Plasma Assisted Solid–Gas Phase Chemical Processes

“…Martin-del-Campo et al [133] investigated the CO 2 reforming of methane in a rotating gliding arc (RGA) nonthermal plasma reactor in a pure-plasma condition. The most efficient operating condition was developed by studying the effect of different parameters, in particular peak arc current, total gas flowrate, feed ratio and gas inlet preheating.…”