Status and prospects of research on HCl removal from blast furnace gas

To address the harm caused by chlorine ions in blast furnace gas, and without altering the fundamental blast furnace ironmaking process, this article conducts an in-depth study focused on various strategies. These include controlling the chloride content in raw materials entering the blast furnace, optimizing the blast furnace operation process, developing pipeline corrosion and blast furnace top gas recovery turbine unit (TRT) scale inhibition technologies, applying alkali dechlorination after TRT, and implementing dry dechlorination before TRT. Regarding chloride source control, it is challenging to significantly reduce HCl generation due to the constraints of the raw materials supplied to the blast furnace and the limitations of the production process. Improving the blast furnace operation process, such as reducing the reduction of roof watering, cannot fully prevent subsequent pipeline corrosion. It may also lead to several adverse consequences, including increased heat energy loss, higher furnace dust production, a shortened service life of the blast furnace roof equipment, and a decline in the sealing performance of the furnace roof. Pipeline anticorrosion technology can extend the pipeline lifespan to some extent, but it is costly and cannot entirely resolve the corrosion issue. Although TRT scale inhibition technology can slow the accumulation of salt scaling on the blades, prolonged use may lead to the formation of pharmaceutical scales. Additionally, the high cost of this technology presents a significant economic burden for large-scale implementation. While post-TRT alkali spray dechlorination effectively protects gas pipelines and equipment after the alkali spray tower, it does not address salt buildup on the TRT blades or the corrosion of gas pipelines between the TRT and the alkali spray tower. This approach may be more suitable for specific applications, such as when space allows and wastewater treatment facilities are available. Fixed-bed dry dechlorination technology is limited by the air velocity of the dechlorinating agent, resulting in the need for large dechlorination towers and frequent replacement of the agent. Additionally, there is a pressure drop in the fixed bed, which can impact the power generation of the TRT. In contrast, pipeline blowing dechlorination allows for flexible adjustment of the blowing volume and pressure of the dechlorinating agent based on actual chlorine content and process requirements, enabling precise control of the dechlorination effect. The pipeline blowing system offers a high degree of automation, simple operation, and easy maintenance, making it suitable for a variety of working conditions. The article also examines the impact of HCl in blast furnace gas on fine desulfurization hydrolysis catalysts, highlighting that HCl causes deactivation of the hydrolysis catalyst, which in turn reduces its effective surface area and catalytic activity. Therefore, reducing HCl content in the gas is crucial for improving the service life and efficiency of the hydrolyzer. Finally, the article proposes directions for future research, including optimizing the performance of dechlorinating agents, reducing costs, and developing more environmentally friendly dechlorination technologies to ensure cleaner use of blast furnace gas and support the sustainable development of the steel industry.