## 1 Introduction
[25], compared with the BF-BOF process, which emits 2054.33 kg of carbon per ton of steel, the carbon emissions in the hydrogen-rich shaft furnace-electric arc furnace process based on coal gasification and the pure hydrogen shaft furnace-electric arc furnace process based on renewable electricity and water electrolysis have been reduced to 1121.28 kg and 120.92 kg per ton of steel, respectively. [PERSON] et al. [26] established a material and energy model for the production of steel without carbon emissions. The research results reveal that the hydrogen direct reduction iron ore-electric arc furnace process can decrease the carbon emissions of EU steel production exceeding 35%. [PERSON] et al. [27] evaluated the carbon emissions of the hydrogen-based direct reduction from the perspective of the carbon flow of electricity in hydrogen production and found that when the carbon emission intensity of electricity was lower than 120 g CO\({}_{2}\) kWh\({}^{-1}\), the carbon emissions of the HDRSF route were less than that of the natural gas-based direct reduction in the shaft furnace route. The hydrogen reduction of iron ore involves a highly endothermic reaction that necessitates adequate heat supply to sustain the reduction process at high temperatures. Due to the cost implications of using hydrogen in iron ore reduction, alongside efforts to reduce carbon emissions, several scholars have also focused on significant research into energy efficiency, consumption reduction, and process optimization for the HDRSF method. [PERSON] et al. [28] established a thermal equilibrium model of hydrogen metallurgy and calculated that the optimal reduction temperature in hydrogen metallurgy is 1250-1350 K. The utilization of pure hydrogen for reduction can effectively raise the reaction temperature, thereby reducing overall energy consumption. [PERSON] et al. [29] established a mass-energy-exergy calculation model of the reduction section of HDRSFs, analyzed the influence of iron ore preheating temperature on the exergy intensity per ton of DRI, and proposed a furnace top gas recovery process. [PERSON] et al. [30] established a thermal equilibrium model of the reduction section in HDRSFs to explore the energy consumption per ton of DRI at different H\({}_{2}\) and CO ratios within a temperature range of 800-1300 \({}^{\circ}\)C. After the numerical simulation and calculation of the reduction section of HDRSFs, [PERSON] et al. [31] and [PERSON] et al. [32] found that double-row gas injection could enhance the utilization of reducing gas in the shaft furnace and reduce energy consumption. [PERSON] et al. [33] established a thermal balance model of the reduction section of HDRSFs and an optimization model for the utilization of reducing gas, where the utilization of reducing gas after process optimization increased by 26.7%. In summary, the HDRSF process represents a significant technical pathway for the low-carbon production of DRI through hydrogen metallurgy technology, crucial for advancing the green and low-carbon development of the ISI. However, this technology is still in its early stage and requires further in-depth analysis and improvements in the energy utilization and process efficiency. Currently, most energy analysis studies of HDRSFs focus on theoretical calculations of hydrogen metallurgical energy consumption, primarily examining the reduction section while neglecting the impact analysis on the cooling section, leading to incomplete assessments of overall shaft furnace energy utilization. Furthermore, the whole HDRSF process is rarely discussed in the existing literature. Given the current high cost of hydrogen acquisition, it is imperative to design and enhance the overall HDRSF process to achieve energy savings, efficiency improvements, and production cost reductions. Based on the described analysis, in order to further promote the development and improvement of the HDRSF process, the contributions of the present study can be summarized as follows:  
1. The principle of DRI production by HDRSFs is introduced.