Exergy loss minimization for a blast furnace with comparative analyses for energy flows and exergy flows

An optimization model based on material balance and energy balance for a blast furnace iron-making process is established, in which exergy loss minimization is taken as optimization objective. Optimization results are obtained by using sequential quadratic programming method. Effects of coal ratio, top gas temperature, slag basicity and blast parameters on the optimization results are analyzed. The optimization results of the exergy loss minimization objective and the coke ratio minimization objective are analyzed comparatively. The energy flows and exergy flows before and after the optimizations for different objectives are analyzed comparatively. The results show that the total energy flow input, the total exergy flow input and the exergy loss decrease after optimizations. The exergy loss obtained from the optimizations for the exergy loss minimization objective and coke ratio minimization objective decreases by 5.77% and 5.14%, respectively. Above 80% of the total energy input is the energy of fuel and above 80% of the total exergy input is the exergy of fuel. The exergy loss decreases with the increases in coal ratio and blast temperature, and increases with the increases in blast humidity, oxygen enrichment, top gas temperature and slag basicity.