Stibnite (Sb₂S₃) is the primary raw material for producing antimony trioxide (Sb₂O₃); three main industrial processes are employed: the dry process, the wet process, and the combined stibnite process.

Dry process: Stibnite is calcined with coke at 1,000°C. The resulting Sb₂O₃ vapor is condensed and collected. Subsequently, the material is reduced to metallic antimony using coke and soda ash (as a flux), followed by oxidation in air to produce Sb₂O₃. While the process is simple and suitable for large-scale production, it entails high energy consumption.

Wet process (hydrochloric acid method): Stibnite reacts with dilute hydrochloric acid to form an SbCl₃ solution. Boiling Na₂CO₃ solution is slowly added until CO₂ evolution ceases. The precipitate is washed with hot water to remove chloride ions (Cl⁻) and dried at 150°C to yield the final product. This method produces high-purity material but requires strict control over residual chloride ions and the treatment of chlorine-containing wastewater.

Stibnite process: Suitable for concentrates with an antimony content exceeding 60%, this method involves mixing the ore with coke and subjecting it to oxidative roasting at 800–1,000°C. The volatilized Sb₂O₃ is rapidly cooled and collected via bag filters to obtain a crude product. This crude product is reduced to metallic antimony using coke and an alkaline flux, then oxidized by passing air through it at high temperatures; the resulting vapor is condensed and collected via bag filters to yield the finished product. Through two-stage oxidation and rapid cooling, this process effectively controls particle size and purity, demonstrates strong adaptability to high-grade concentrates, and ensures stable product quality.

Each of the three processes has distinct advantages: the dry process is suited for large-scale production, the wet process yields high purity, and the stibnite process ensures stable quality. Smelters can select the appropriate process route based on ore grade, environmental regulations, and product positioning.