Application of random pore model for synthesis gas production by nickel oxide reduction with methane

Abstract

Recently, there is a great interest in the noncatalytic gas–solid reactions between methane, as an environmentally friendly reducing agent, and metal oxides to yield synthesis gas and the related metal at low temperatures. In the present work, reduction of nickel oxide with methane was investigated. It has been proven that it is possible to produce metallic nickel and synthesis gas, simultaneously. The thermogravimetry measurements and instantaneous mass spectrometry analysis of the gaseous products have been performed for the NiO+CH4 reaction. In addition, the complete mathematical model was developed by applying the random pore model to predict the conversion–time profiles at the temperature range of 600–750°C. Some important parameters such as concentration dependency, external mass transfer resistance, solid structural changes, product layer resistance, and pore size distribution have been considered in this sophisticated mathematical model. In addition, the random pore model has been modified for consideration of the bulk flow effect. Results obtained from this kinetic study indicate that the model performs well in predicting the experimental data. However by neglecting the bulk flow effect, there are lower predicted rate constants for this reaction. The analysis of the gaseous products showed that the synthesis gas could be produced with a H2/CO ratio near two.