Improvement Of Hydrocracker Modeling And Comparing Different Quench Schemes

Hydrocracker is an important oil refining technology, and it is always conducted under elevated temperature and pressure. Due to complexity of the process, developing a model to analyze is commonly an effective way. Obvious vaporization is found in a hydrocracker, and when establishing a model, incorporation of it can improve predictive capability. Further, large hydrogen to oil ratio should be provided to control the reactor temperature in a hydrocracker, and employing liquid quench alternative has fundamental significance to the process improvement.In this paper, an improved hydrocracker model was developed by incorporation of vapor-liquid equilibrium, and to get reliable simulated results, the genetic algorithm is implemented to estimate the model parameters on the basis of industrial data. In addition, as the operating condition of the reactor, Peng-Robinson equation of state is implemented to get the two-phase components and properties, also in this equation of state, the interaction coefficients between H2 and hydrocarbons are crucial for the precision of VLE calculation. The results show that the interaction coefficients between H2 and hydrocarbons can be considered as a lumped function of operating temperature and oil properties. Obvious vaporization is observed in the hydrocracker, and 77% of the oil is found in the vapor phase at outlet of the last stage, while it is only 30% at inlet of the first stage. Phase equilibrium also has an important impact on the hydrocracker. Analysis of simulations with and without vapor-liquid equilibrium revealed that there are significant differences in bed temperature profiles, liquid flow rates, liquid compositions and product yields.For reducing down the large compression, purification and circulation of hydrogen, alternative of liquid quench was proposed, and effects of the two quench schemes are compared on basis of the established model. At the same time, model assumptions such as liquid plug flow, full catalyst wetting and full catalyst efficiency were verified. The results indicate that differences in the product yields, average liquid flow rates, hydrogen partial pressures and bed temperatures are not so pronounced under the two schemes. However, the fluid should be compressed, purified and circulated is much less under using liquid quench, so the equipment and operating costs associated with this can be saved.