Study on Exergy Analysis of the Soda Ash Production Process by the Ammonium Sulfate-Soda Method

The exergy calculation, especially chemical exergy calculation, is very intricated in the soda ash production process by the ammonium sulfate-soda method because the gas-liquid reaction and salt precipitation reaction occur simultaneously with the electrolyte ionic reaction in the Na₂SO₄-NH₃-CO₂-H₂O electrolyte system. The main aim of this study is to propose a significant and novel approach to calculate the chemical exergy of an aqueous electrolyte system accompanied by gas-liquid reaction and salt precipitation reaction, based on the Pitzer equation. We simulated the soda ash production process using Aspen Plus and performed exergy analysis based on the thermodynamic data obtained from the simulation. As a result, the exergy destruction of the entire process is 99.945 kW and exergy efficiency is 59.57%. In addition, the units with low exergy efficiency in the process are condenser and absorption towers such as NH₃ absorption tower, carbonation tower, and water washing tower, which are the primary targets of energy saving.