Reduction of CO₂ emissions and energy consumption by improving equipment in direct reduction ironmaking plant

This study aimed to improve equipment in steel industrial in order to save energy, protect the environment, decrease costs, and develop the commercialization improvements. The energy of combustion gases in the reformer box is used to preheat the main air, natural gas, and feed gas in the heat recovery system. The scale-up of process equipment and incorporation of new technologies at the Khouzestan steel company (KSC) in Iran, resulted in their ironmaking plants’ capacity increasing from 550,000 to 800,000 ton/year in 2015. Furthermore, this method could prove profitable for old direct reduction ironmaking plants as well. The modifications include changing the reformer tubes’ diameter to increase the rate of reducing gas flow, increasing the number of process gas compressors from two to three, improving the top gas scrubber capacity, and modifying the shaft furnace refractory thickness to the thin wall. (The internal diameter of the furnace was increased from 5000 to 5130 mm.) To use the flue gas energy, the arrangement, size, and number of tube bundles were altered in heat recovery system (HRS). The reformer and heat recovery system were simulated with Aspen HYSYS software. The simulation results were relatively in good agreement with the experimental data. In this research, practical results with a real implementation in direct reduced ironmaking plant show equipment improvement that can reduce energy consumption and carbon dioxide emissions. The production tonnage increased by 28.15%, and the energy consumption decreased by 13.71%. However, the amount of carbon dioxide in the flue gas decreased by 9.55%. The flue gas exit temperature from HRS dropped by 152.2 °C. The calculation of the net present value (NPV) and present value (PV) shows that the investment cost will be returned in 4 years.