Water vapor plasma technology for biomass conversion to synthetic gas

This study presents the results of experimental investigation on the development of water vapor plasma technology for conversion of biomass and destruction of hazardous substances. Similar plasma technology is also foreseen for the synthesis of micro-and nanostructured catalytic coatings for wide range of applications. An experimental DC plasma torch with button type hot cathode and step formed copper anode, operating at atmospheric pressure has been developed, tested and employed. The following main tasks of this research have been solved: (i) experimental facility was constructed and water vapour plasma generation process was practically realized; (ii) thermal and electrical characteristics of water vapour plasma generator were investigated and plasma jet characteristics were established; (iii) the real operating condition of plasma facility was analyzed. This work includes the analysis of operating characteristics of water vapour plasma system which were investigated in the following range of plasma source parameters: power of plasma torch was 25-45kW; arc current was 140-180 A, the arc voltage was 172-231 V, the efficiency was 0.5-0.78, the average temperature of water vapour plasma jet in exhaust nozzle was 2600-3500 K, and the plasma jet velocity was 200-310ms(-1). Holding the temperature above 2300K and water vapour flow rate at 132 l min(-1), it is possible to reach the sufficient conditions for the biomass conversion to syngas. Spectral analysis of plasma jet outflowing from plasma torch exhaust nozzle showed that water vapour plasma contains an increased amount of hydrogen that is usable in many plasma chemical processes. The summarized results can help to calculate and design gasification systems of biomass, to establish optimal parameters for stable operation of plasma generator and regulate the process parameters. (C) 2010 Elsevier B.V. All rights reserved.