Post-combustion reactions and modeling

Owing to the presence of carbon, oxygen and hydrogen in many iron and steelmaking processes, vast quantities of combustible gases rich in CO along with {dollar}rm Hsb2{dollar} are often created. To take advantage this potential chemical energy, extra amounts of oxygen may be supplied to the process in order to combust these species, through a practice known as post combustion. Effective post combustion is important in many steelmaking processes.; Post combustion is strongly affected by fluid flow. However, in the presence of carbon and iron at high temperatures reactions known as "de-postcombustion" occur where carbon or Fe is oxidised. These reactions depend on kinetics and fluid flow.; To address the lack of information at high temperature, the kinetics of carbon oxidation by {dollar}rm COsb2{dollar} and {dollar}rm Hsb2O{dollar} has been studied at temperatures between {dollar}rm 1300spcirc C{dollar} and {dollar}rm 1500spcirc C.{dollar} At {dollar}rm 1500spcirc C,{dollar} the graphite-{dollar}rm Hsb2O{dollar} reaction was found to occur at a similar rate to the graphite-{dollar}rm COsb2{dollar} reaction. The overriding importance of internal pore structure was demonstrated in the results, particularly as it develops in the reacted layer during the course of the reaction. Such changes are believed to be responsible for the continuous rate increase observed in non-porous glassy carbon and the consistently higher rates measured in graphite than in coke at high temperatures. The results of this work have also been used to clarify the role of the gas-carbon reaction in the kinetics of FeO reduction in bath smelting slags by solid carbon. Under high stirring conditions in the slag it has been found that the gas-carbon reaction may play a significant role, particularly when coke is the carbonaceous material.; The second component of this study was directed toward understanding the effect of fluid flow on post combustion in the electric arc furnace (EAF). In particular the objective was to determine if computational fluid dynamics (CFD) can be a useful tool for optimising post combustion.; The post combustion degree (PCD) was found to be affected by three main factors, namely the rate of de-postcombustion at the surface, the efficiency of combustion in the lance jet and the degree of recirculation of gases in the furnace. Owing to assumptions made in the de-postcombustion model, the lance flowrate had little effect on the predicted values of PCD. This finding revealed the need to better characterise the relationship between jet momentum and de-postcombustion efficiency. Low combustion efficiencies will adversely affect post combustion efficiency. Increased recirculation of gases in the furnace was also found to reduce the post combustion degree. (Abstract shortened by UMI.)...