Reforming of natural gas using an alternating current gliding arc system

Abstract

In this work, the reforming of simulated natural gas was conducted under the alternating current gliding arc system at ambient conditions. The effects of all gaseous hydrocarbons and CO₂ present in the natural gas, process parameters, and O₂ added were investigated. The presence of other gas components (C₂H₆, C₃H₈ and CO₂) in natural gas was found to contribute prominently to the synergistic effects on the overall plasma reaction performance. Especially, CO₂, an oxidative gas, exhibited pronounced effects by enhancing the conversions of all hydrocarbons in the feed, by reducing coke formation, and by lowering specific energy consumption. The results showed that not only did the effects of applied voltage and input frequency strongly influence the stability of the gliding arc discharge, they affect the chemical activation of simulated CO₂-containing natural gas reforming as well. Furthermore, the effect of added oxygen in the feed was tested with using pure oxygen or air as an oxygen source for partial oxidation. The oxygen species derived from the addition of oxygen to the simulated natural gas play an active role in significantly minimizing carbon formation; moreover, they provided improvement in the reactant conversions, product yields, and product selectivities, as well as the decrease in specific energy consumption. Air was best suited for use as the oxygen source in the combined CO₂-containing natural gas reforming and partial oxidation. The innovative concept of integrating non-thermal plasma and microreactor technology offers several advantages, e.g. low reaction temperature, good heat transfer and heat distribution, and short reaction time. Based on this concept, the gliding arc microreactor was first designed to investigate the reforming reaction of natural gas instead of using the conventional gliding arc reaction. For this preliminarily study, methane, a major constituent of natural gas, was used instead of the simulated natural gas in order to reduce the complexity of feed composition. The reforming of methane was conducted under the gliding arc microreactor, with and without catalyst. In the sole plasma system, all operational parameters affected both methane conversion and product selectivities. In the plasma and catalytic system, the temperature distribution within the plasma microreactor has significant role in improving the reaction performance.