Heuristic Method for Determining C/N Using Inline Process Sensors

Built on extensive process modeling for various solvents, it has been concluded that the pH of solvent is significantly impacted by CO₂ absorbed into solution, and process temperature whilst there is negligible effect from solvent concentrations, solvent impurity and ion strength. In this presentation, inline process measurements of pH and temperature were used as inputs for a heuristic predictive model that provided a reasonable determination of carbon to nitrogen concentration ratios (C/N) in an amine solvent used in a CO₂ capture process. As CO₂ is absorbed by the solvent it becomes more acidic, pH decreases with adjusting for temperature. The C/N model was used to predict solvent carbon loading at the UKy-CAER 0.7 MWe small pilot CO₂ capture plant and a comparative analyses was performed between direct sample concentration analysis and the predictive model output. The average difference between the measured and predicted C/N was 4.6 % and the accuracy of the predicted C/N was comparable to variations among repeated sample analysis. Using the model during process operations will provide reliable, real-time feedback on process performance and solvent quality, allowing for process optimization and reducing the need for time-consuming chemical testing.