Process Optimization and Mechanism Study for Sulfur Recovery from High-Silica Phosphogypsum via Carbothermal...

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Phosphogypsum (calcium sulfate dihydrate) is a sulfur resource with limitations in traditional sulfuric acid and cement production due to impurities.
• Impurities like phosphorus and fluorine in phosphogypsum affect cement quality and cause kiln ringing.

Purpose of the Study:

• To investigate sulfur recovery and value-added utilization of high-silica phosphogypsum via carbothermal reduction smelting.
• To develop a phosphogypsum ingredient (PGI) system for slag wool production.

Main Methods:

• Carbothermal reduction smelting of a phosphogypsum ingredient (PGI) system with silica, alumina, magnesium oxides, and iron oxides.
• Analysis of desulfurization rate and phase structure under varying temperatures and C/S molar ratios.

Main Results:

• Over 97.44 wt % sulfur recovery achieved at temperatures ≥1300 °C with a C/S molar ratio of 0.5-0.8.
• The molten slag formed an amorphous magnesium-calcium-aluminosilicate structure suitable for slag wool production.
• Desulfurization mechanism elucidated through phase transformation and slag microstructure evolution.

Conclusions:

• Carbothermal reduction smelting is an effective method for high-efficiency sulfur recovery from phosphogypsum.
• The developed PGI system enables the valorization of phosphogypsum into slag wool, addressing waste utilization and resource recovery.
• This approach offers a sustainable alternative to traditional phosphogypsum processing methods.