Comprehensive evaluation of hydrogen-rich energy application in iron ore sintering process: Deep function mechanism analysis and process optimization

Applying hydrogen-rich energy such as natural gas to replace coal/coke in the steel industry can efficiently mitigate CO2 emissions and accelerate the process of carbon neutrality. Gas injection sintering technology has been widely used in industry for more than ten years, but the replacement ratio of solid fuels by hydrogen-rich gas has been stagnated at about 15%, the technical breakthrough is urgently needed. This paper discusses the influence of equal/segmented gas injection on sintering indexes based on pilot sintering tests, and the factors limiting gas concentration in this technology are revealed from heat distribution and mineral structure. The results show that the cooling rate of upper layer decreased with 0.8 vol% natural gas injection in 5∼12 min when the coke breeze reduced from 5.6 wt% to 5.3 wt%, which is crucial to improve the total indexes while the indexes of lower layer decreased due to the heat loss. Higher gas concentration will reduce the oxygen partial pressure, which will affect the combustion rate of coke breeze. As the gas gradient increased from 0 to 0.2 vol%, the number and size of pores decreased and the total indexes increased due to the decrease of cooling rate of upper layer from 112 °C/min to 74 °C/min and the hematite of layer-1 disappeared while calcium ferrite increased gradually. For a 360 m2 sintering machine, segmented gas injection can reduce the production cost of $1330000 and 50720 tons of carbon emissions per year compared to the equal concentration injection. The coupled oxygen-gas-steam injection method can accelerate the heat transfer rate without affecting the oxygen partial pressure, so as to achieve a higher fuel replacement ratio, providing a new way of sintering with low cost and low carbon emission.