Oxidation of B_4C by steam at high temperatures: New experiments and modelling

摘要

The oxidation kinetics of various types of boron carbides (pellets, powder) were investigated in the temperature range between 1073 and 1873 K. Oxidation rates were measured in transient and isothermal tests by means of mass spectrometric gas analysis. It was found that oxidation is strongly influenced by the thermohydraulic boundary conditions and in particular by the steam partial pressure and flow rate. On the other hand, the microstructure of the B_4C samples has a limited influence on oxidation. Very low amounts of methane were produced in these tests. On the basis of the experimental data obtained in the isothermal tests, a new model on boron carbide oxidation was developed. The model self-consistently simulates surface reaction kinetics and mass transport of various species in the multi-component gas phase as rate determining steps of the oxidation process. The model was implemented in the SVECHA/QUENCH code and verified against the transient tests.