<p>The dripping zone in a blast furnace plays a crucial role in connecting the cohesive zone with the hearth, and its stability significantly impacts low-carbon smelting processes. Based on a detailed anatomical study of a 2200-m³ blast furnace in China, it involves core sampling of the furnace dripping zone and uses scanning electron microscopy to investigate the micro-morphology of potassium (K) and sulfur (S) within this region. The formation process of kalsilite (KAlSiO₄) and CaS inside the furnace is elucidated. The results show that when potassium vapor rises to the upper area of the dripping zone, some of it adsorbs onto the coke pore walls and reacts with the dripping slag and coke ash to form kalsilite. The formation pathways of CaS differ between upper and lower areas of the dripping zone. It forms mainly from the reaction of slag with SO₂ in the gas flow and from the slag–coke interface reaction. The CaS generated from the slag–coke interface reaction is the major source of CaS in the dripping zone. Based on the formation mechanisms of kalsilite and CaS in the dripping zone, it is possible to regulate their formation by adjusting the temperature, slag phase composition, and the content of harmful elements in the raw materials. It provides theoretical insights into the behavior of harmful elements in the blast furnace, offering guidance for steel enterprises to ensure the stable operation of the dripping zone, reduce fuel consumption, and achieve greener production.</p>