Study of CO<inf>2</inf> dissociation in the low current gliding discharge in the reverse vortex flow

Abstract

Summary form only given. If performed with high energy efficiency, plasma-chemical dissociation of carbon dioxide can be a way of converting and storing energy when there is an excess of electric energy, for example generated by solar elements of wind turbines. CO2 dissociation with efficiency of up to 90% was reported [Azizov, R.I., et al., 1985; Fridman, A., 2008] earlier for low pressure microwave discharge in supersonic flow. A new plasma-chemical system uses a low current gliding discharge in the reverse vortex flow of plasma gas. The system is a development of the Gliding Arc in Tornado reactor [Kalra, C.S., et al., 2005; Nunnally, T., et al., 2009; Gustol, A.F., 2011]. The system was used to study dissociation of CO2 in wide ranges of the following experimental parameters: reactor pressure (15-150 kPa), discharge current (50-500 mA), gas flow rate (3-30 liters per minute), and electrode gap length (110 cm). Additionally, the effect of thermal energy recuperation on CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dissociation efficiency was tested. Depending on external parameters, discharge in the system exists in different modes. The first is the glow or arc discharge with small length variation, in which a positive current fluctuation results in a voltage reduction so that the discharge power is almost constant. The second mode is the “gliding arc” discharge, in which a periodical significant discharge elongation results in an increase of discharge resistance, its voltage and power, and a decrease in discharge current. Plasma chemical efficiency of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dissociation is very low (about 3%) in a short discharge at low pressures (about 15 kPa) when it is defined by electronic excitation. The highest efficiency (above 40%) was reached at pressures 50-70 kPa in a long discharge with thermal energy recuperation. It means that the process is controlled by thermal dissociation with subsequent effective quenching. Plasma chemical efficiency was determined from the data of chromatographic analysis and oscilloscope electric power integration, and also was checked calorimetrically by the thermal balance of the system.