Process simulation of mineral carbonation of phosphogypsum with ammonia under increased CO2 pressure

- Mineral carbonation of phosphogypsum with ammonia under increased CO2 pressure was simulated by Aspen Plus.
- The sensitivity of many operation conditions were analyzed, and the optimal conditions were selected for its large-scale application.
- The enhanced carbonation section plays the key role for this pressured phosphogypsum carbonation process.
- The phosphogypsum can be completely converted into calcium carbonate after enhanced carbonation section.
- These operation conditions significantly improve the enhanced carbonation temperature, which can help achieve a fast carbonation reaction rate.

The mineral carbonation of phosphogypsum offers many advantages in sequestering CO2, solving the pollution problem of phosphogypsum stacking, and manufacturing high value-added chemical products with low energy consumption and cost. Using the Aspen Plus process simulation software, this work simulates a novel process for the mineral carbonation of phosphogypsum with ammonia under increased CO2 pressure. This process is divided into five sections, namely, pre-carbonation, enhanced carbonation, flash separation, gas phase absorption, and (NH4)2SO4 fertilizer production. With its large-scale application, this new process allows the sensitivity analysis of many operation conditions, identifies the optimal conditions for reducing the ammonia and energy consumption of (NH4)2SO4 fertilizer production, and achieves a high carbonation conversion with a fast reaction rate. The optimal conditions (6 bar enhanced carbonation pressure, 1 bar flash pressure, 38 °C ammonia absorption solution temperature, 1.05 ammonia excess ratio, 1.024 CO2 excess ratio, and 0.94 mass ratio of water to gypsum) yield the highest carbonation conversion, ammonia utilization ratio, and enhanced carbonation temperature of 99.9%, 95.2%, and 138.5 °C, respectively, all of which can help achieve a fast carbonation reaction rate.