Kinetic Study and Modeling of Nigerian Sub Bituminous Coal Char Using the Random Pore Technique

Abstract

Inorder to augment for the short supply of energy for industrial purposes, the kinetics of carbon-dioxide gasification of two Nigerian sub bituminous coal chars was studied in this work using a thermogravimetric analyser (TGA). This paper, reports the findings on gasification of typical Enugu (Udi) and Kogi (Okaba) coal of Nigeria in carbon dioxide medium at atmospheric pressure. Proximate and ultimate analysis was performed on the coal samples based on their origin to determine their properties and values. Result shows that Udi coal has a higher heating value as compared to Okaba coal. The effect of the temperature of gasification ranging from 900oC to 1000oC at different concentration of carbon dioxide of 100%, 70% and 40% at atmospheric pressure was studied. The gasification process of coal involves pyrolysis and char gasification. It was found that the reactivity of char gasification increased with the increase of pyrolysis heating rate, which demonstrate the effect of temperature on gasification. A random pore model approach with a novel kinetic scheme was used to describe the behaviour of the coal char. The simulated predictive model result was compared with the observed experimental result, which were in good agreement. Based on the obtained result, it was observed that the rate of carbon conversion increases with increase in concentration of carbon dioxide over time, and vice versa. The activation energy for the coal samples vary depending on their origin and were found to be 97.58kJ/mol and 103kJ/mol for Kogi coal and Enugu coal respectively. Products of coal gasification will serve as a promising fuel alternative.