Improving Cracking Severity in an Ethane Thermal Cracker Based on Dynamic Optimization Considering Process Limitations

Abstract

The main goal of this research is to improve cracking severity in an industrial ethane thermal cracker in a domestic plant. In the first step, the considered cracker is modeled based on the mass and energy balance equations considering a molecular kinetic model. To develop an accurate model, a detailed thermal model is adopted to predict the tube skin temperature. To prove the accuracy of the developed model and considered assumptions, the simulation results are compared with the available plant data. In the next step, a sensitivity analysis is performed to investigate the effects of coil outlet temperature and steam to ethane ratio on the cracking severity factors including ethane conversion and production rate. Based on the results of sensitivity analysis although increasing steam to ethane ratio decreases ethane conversion, it improves ethylene yield. Then, a dynamic optimization problem is formulated to maximize ethylene production and minimize production decay during the process run time considering feed temperature, furnace temperature, and steam to ethane ratio as decision variables. The results show that applying the optimal condition to the system improves ethylene production by about 9.44%.