Thermite-Related Technologies for Use in Extreme Geothermal Environments

Thermite and related processes have attracted considerable attentions as highly useful technologies for material and energy supplies in extreme environments such as geothermal and disaster-stricken areas as well as in space exploration. As part of the development of casing pipes used in geothermal power plants started from the 1970s, long ceramic-lined pipes have been obtained via thermite reaction under effective centrifugal force without any additional heat treatment [Centrifugal-Thermite (C-T) process]. The potentials of the ceramic-lined pipes in deeper geothermal utilizations are revalidated in details by reviewing the results obtained through the erosion-corrosion tests carried out under the conditions of high velocities (up to 100 m/s) and various acidities (from pH 2.0 to pH 4.0) of two-phase flows provided by the geothermal field test apparatus at the Onikobe geothermal power plant in Japan. By reducing the FeO content of the ceramic layer processed under proper additives and reactant amounts, the tested ceramic-lined pipes were significantly improved compared to highly corrosion-resistant stainless steels. The technological advantages obtained through the development of the C-T process can show a useful model to promote thermite-related technologies onward.