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

摘要

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 degrees 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 H(2)and CO by thermal gravimetric experiments. The results showed that carbon deposition started at 400 degrees C, accelerated at 600-800 degrees C, and stopped at 1000 degrees C. Carbon deposition was accelerated by the presence of H-2, 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.