Optimization of gaseous fuel injection for saving energy consumption and improving imbalance of heat distribution in iron ore sintering

It has been widely reported that the sinter strength and heat pattern would be weakened when adopting the low grade solid fuels, such as biomass, semi-coke and anthracite. Moreover, the imbalance of heat distribution in the sintering bed is considered to be problematic on the energy efficiency. To solve the above problems simultaneously, the gaseous fuel segregation method was firstly proposed in this paper. The gaseous fuel was injected to the melting zone from the top and auto-ignited near the solid fuel combustion zone. Firstly, methane concentrations of 0.0% and 0.5% vol. were tested, keeping the total calorific heat input unchanged. The heat pattern in melting zone was recorded by both contact thermocouples and non-contact thermal infrared imager. The results indicated that the methane injection could significantly extend the melting zone from the upstream and raise the sinter strength higher than that of coke sintering, without increasing the energy consumption. Then, the energy saving potential of the novel method was evaluated by reducing the calorific heat input 4, 6 and 8%. Furthermore, in the segregation case, the gaseous fuel injecting concentration was increased in the upper bed to enhance the weak heat pattern, and decreased in the lower bed to avoid the energy waste. It was observed that the melting zone became much more uniform in the infrared images. Finally, the optimum segregation degree of 1.0%/mm was recommended, where the sinter strength grew 2.31%. The present study provides an effective way for optimizing the energy efficiency in the sintering process.