Modelling and simulation of inorganic precipitation with nucleation, crystal growth and aggregation: A new approach to an old method

• A process model describing key facets of inorganic precipitation is developed.
• Novel discretised population balance is used to better describe nucleation.
• Thermodynamic model is validated for synthetic struvite solutions.
• Model is used to simulate struvite crystallisation at various operating conditions.

A process model is developed to simulate the recovery of inorganic mineral phosphates through precipitation, incorporating nucleation, crystal growth and aggregation mechanisms. The model includes a detailed description of solution thermodynamics, nucleation, growth and aggregation kinetics, a population balance and dynamic mass conservation. A discretised population balance (DPB) is used to describe changes to the particle size distribution (PSD) caused by nucleation, growth and aggregation. A sigmoid function is incorporated into the DPB to produce a better description of small-particle dynamics. The model is applied in the context of nutrient removal and recovery, with specific focus on a recovery pathway for phosphorus based on chemical precipitation. The model is used here to simulate a mixed suspension, mixed product removal (MSMPR) reactor and explore the relationship between operating conditions and thermodynamics. A validation for the solution thermodynamics portion of the model is also performed and the model is found to successfully predict solution pH.