Thermodynamic and Dynamic Study on the Carbon Deposition on an Iron Surface in a C–H–O System

Abstract

The C–H–O ternary phase diagrams in equilibrium with graphite were developed to determine the gas compositions and boundaries for graphite formation in 500–900 °C. Thermogravimetric calculation results showed that carbon deposition was favored under the conditions of low temperature, high carbon, and low oxygen potential. The carbon deposition with reduced iron was carried out in a syngas of H2 and CO by thermal gravimetric experiments. The results showed that carbon deposition started at 400 °C, accelerated at 600–800 °C, and stopped at 1000 °C. Carbon deposition was accelerated by the presence of H2, which was increased with the CO ratio in the gas mixture, and depressed by the addition of CO2. The reduced iron with large surface area fabricated the carbon deposition. Cementite (Fe3C) was formed as intermediate that accelerated the carbon deposition rate. The C–H–O ternary phase diagrams in equilibrium with Fe3C were also provided.