Simulation, Control and Sensitivity Analysis of Thermal Cracking Furnaces of Olefin Unit of Morvarid Petrochemical

Ethylene is one of the most important basic materials in petrochemical industries. It is used as raw material in the production of many chemicals, such as polyethylene and ethylene glycol. The thermal cracking of hydrocarbons, such as ethane, is the most commonly used process for ethylene production. Thermal cracking furnaces provide the required energy for cracking ethane to ethylene. In this research, the cracking furnaces of the Morvarid petrochemical complex was simulated and controlled and sensitivity analysis were performed. For this purpose, firstly the unit was simulated in steady state using Aspen Plus® and after ensuring simulation accuracy, the results were used as the starting point for dynamic simulation in Aspen Dynamic® and the dynamic behavior of the unit was studied. The accuracy of this simulation was satisfactory in dynamic and steady-state forms, so that the average error of stream information compared to the design data were 0.42% and 1.15% for steady-state and dynamic simulation, respectively. Then the feed flow rate stepwise increased to 6.6% of the initial flow rate while the ethylene conversion was controlled at 38.5%. In order to achieve this conversion, the temperature of the thermal cracking furnaces increased to 1131℃ with increasing feed flow rate. With this changes, change of ethylene product flow rate was 0.86 of feedstock changes. Then, the change in the feed composition was investigated whilst the propane concentration in the feed stream was increased gradually as well as the ethane concentration was decreased by 10%. In this case, the mass fraction of propane in the feed flow was changed from 2.52% to 12.52%. Due to these changes and without changing the unit operating condition, finally, the ethylene flow rate decreased 3.3% compared to the primary state.