Box-Behnken Response Surface Method to Optimize Amine Liquid Purification Process Based on Ion Exchange

Abstract

In the process of recycling MDEA (N-methyldiethanolamine) solution in a terminal decarburization system of CNOOC, the quality of MDEA solution was deteriorated due to the generation and accumulation of impurities such as solid suspended solids and heat stable salts, which led to blockage and unstable operation of pipeline equipment in the decarburization system, thus affecting the CO₂ removal effect of the solution, the Box-Behnken effect surface method was used to design the three main factors of the ion exchange-based amine purification process: the continuous adsorption time of the amine solution, the resin regeneration temperature and the resin regeneration time. Taking the conductivity of the MDEA solution after purification as the response function, a corresponding mathematical model was established to optimize the test method, and the correlation coefficient R² (R²=0.9418) of the regression equation obtained was greater than 0.9, indicating that the predicted value had a high correlation with the experimental value, and the test method was optimized accordingly. The best test conditions obtained were: the continuous adsorption time of amine solution was 50 min, the resin regeneration temperature was 40°C, and the resin regeneration time was 30 min. Under this condition, the conductivity of the purified MDEA solution was 1.56 ms/cm, and the salt content was 0.8%. The experiment was repeated 3 times according to this method, and the salt content of the MDEA solution after purification was ≯0.8%, which met the technological requirements. The Box-Behnken experimental design method was feasible for amine solution purification process optimization screening based on ion exchange, and the predicted value of the mathematical model was consistent with the experimental observation value.