New Breakthrough in Yellow Phosphorus Deep Processing: Co‑Production of Sodium Hypophosphite, Food‑Grade Phosphoric Acid and Tricalcium Phosphate

Against the backdrop of the phosphorus chemical industry transitioning towards higher refinement and resource efficiency, producing multiple high‑value products from yellow phosphorus has become a key direction for industrial upgrading. This route converts the phosphine off‑gas and calcium phosphite, by‑products of sodium hypophosphite production, into food‑grade phosphoric acid and tricalcium phosphate respectively, achieving a cascaded utilisation of phosphorus elements.

Core process flow:

Yellow phosphorus reacts with liquid caustic soda and quicklime in a reaction unit through a disproportionation reaction to form a sodium hypophosphite solution. After separation and purification, most of the sodium hypophosphite is directly sold as an intermediate product. Meanwhile, the phosphine off‑gas generated during the reaction is further processed via purification, combustion and absorption to obtain food‑grade phosphoric acid. Another by‑product, calcium phosphite, is sent to a dedicated unit and converted into tricalcium phosphate.

Technical highlights:

• Cascaded resource utilisation: The originally troublesome phosphine gas is converted into food‑grade phosphoric acid, and calcium phosphite into tricalcium phosphate, turning waste gas and solid residue into valuable resources.

• Extended product chain: A single production system yields three high‑value phosphorus products, significantly enhancing the overall economic value of yellow phosphorus.

• Environmental benefits: Effective reduction of hazardous off‑gas emissions and solid waste generation, in line with cleaner production requirements for the phosphorus chemical industry.

This process offers a viable pathway for yellow phosphorus producers to move downstream into fine phosphorus chemicals, food additives and bio‑based materials, and is expected to serve as a model for industry transformation and upgrading.