Development of ultra-high temperature SHS furnace using atmospheric-pressure microwave steam plasma

The development of superheated steam (SHS) furnace with ultra-high temperature was studied. We have proposed the use of atmospheric-pressure microwave-induced steam plasma as the heat source for SHS furnace. Since the sustainable operation and appropriate temperature distributions of microwave steam plasma play key roles in constructing an SHS furnace, the characteristics of steam plasma were initially investigated. The experimental results revealed that several conditions of microwave discharge existed for stable plasma formation. The limitations of heat-tolerance of a discharge tube, which are attributed to the rise of temperature, were confirmed at low steam flow rate, high input power, and large diameter of a discharge tube. Reducing the diameter of the discharge tube also caused the unstable formation of microwave steam plasma. Then, the furnace was assembled by joining the discharge tube of microwave steam plasma. The flat temperature distributions inside the furnace were observed as strongly affected by the steam flow rate. The proposed furnace could exhibit an ultra-high temperature over 1200 °C. ► We developed superheated steam furnace having ultra-high temperature over 1200 °C ► Microwave steam plasma was used as a heat source for a furnace. ► A discharge tube melted at low steam flow rate, high input power, and large diameter. ► Reducing diameter caused unstable formation of microwave steam plasma. ► Temperature distribution inside a furnace was strongly affected by steam flow rate.