Antimony ore fines undergo desulfurization roasting in a rotary kiln before entering the rotary furnace for reduction smelting for several key reasons.

First, antimony ores often contain sulfide minerals such as stibnite (Sb₂S₃); if fed directly into the rotary furnace for reduction, a large amount of sulfur would enter the furnace charge, increasing the sulfur load on the smelting process. Roasting converts sulfides into oxides, ensuring that the subsequent reduction reaction primarily yields metallic antimony rather than antimony sulfide or antimony matte, thereby reducing both reductant consumption and the sulfur content of the slag.

Second, desulfurization helps improve the quality of the crude antimony. During reduction, sulfur tends to combine with antimony or iron to form antimony matte or sulfide inclusions, which lowers the purity of the crude antimony and complicates subsequent refining. Pre-roasting for desulfurization significantly reduces the sulfur content in the resulting crude antimony.

Third, it simplifies flue gas treatment. The SO₂ generated during rotary kiln roasting is relatively concentrated, facilitating acid production or desulfurization treatment; conversely, if desulfurization occurs during reduction in the rotary furnace, the SO₂ mixes with reducing gases like CO, resulting in complex flue gas composition and high treatment costs.

Finally, roasting enhances the operational stability of the rotary furnace. The desulfurized calcine possesses more uniform particle size and composition, leading to steady heat release during reduction and preventing furnace instability caused by the endothermic decomposition of sulfides or the formation of antimony matte. Therefore, desulfurization roasting in a rotary kiln is a crucial pretreatment step in antimony smelting.