Ten-lump kinetic model for the two-stage riser catalytic cracking for maximizing propylene yield (TMP) process

Abstract

Modeling Fluid Catalytic Cracking (FCC) riser reactors is of significance to FCC unit control, optimization and failure detection, as well as the development and design of new riser reactors. Under the guidance of catalytic reaction mechanisms and the demands for commercial production, a ten-lump kinetic model was developed for the TMP process in this study. The feedstock and products were divided into ten lumps by reasonably simplifying the reaction network, including heavy oil, diesel oil, gasoline olefins, gasoline aromatics, gasoline saturates, (butane ? propane), butylene, propylene, dry gas and coke. Thirty-five sets of model parameters were estimated with the combined simulated annealing method and the damped least square method. The findings indicated that the model could predict the riser key products and their compositions quite well; thereby it could be useful to the production practice for the TMP process.

Maximization of propylene in an industrial FCC unit

“…Equations (28) and (29) describe the catalyst and gas velocity profiles across the riser [2]. Equations (30) and (31) describe the gas volume fraction, ɛ g , and catalyst volume fraction, ɛ c ; they provide a hydrodynamic constrain such that the summation of the volume fractions is unity. The riser pressure is described by Eq.…”

“…Where propylene is required as a separate lump, this eightlumped model may not be useful. Some kinetic models for the propylene production are based on catalytic cracking, such as the four-lumped model which includes propylene as a component of a gas lump [29]; the ten-lumped model with propylene as a distinct lump [30] and six-lumped model with distinct propylene lump [15]. To maximize the yield of propylene in a lumped kinetic model, propylene has to be a separate lump.…”

“…The ten-lumped model of Du et al [30] and six-lumped model of Ancheyta and Rogelio [15] are most suitable for their ability to have propylene as unique lumps. However, the yields of lumps were obtained at a particular constant temperature; 580 °C [30] and 500 °C [15], instead of progressive temperature profile of the catalyst and vapour phases as it is obtainable in the industrial FCC riser. Specific rate constants for the various cracking reactions and catalyst deactivation in a typical industrial riser also vary along the length of the riser.…”

“…Hence, the upper and lower limits for the following variables are activation energy (0 and 100,000 kJ/kg mol), heat of reaction (0 and1000 kJ/ kg), and frequency factors (0 and 2000 s −1 ). Another reason for opening the limits of the decision variables is to allow for the adjustment of data obtained from the laboratory model to get modified since they are being used on a mathematical model that represents an industrial unit [30].…”

Analysis of Heat and Mass Transfer and Parametric Sensitivity in an Experimental Fixed-Bed Reactor for the Catalytic Cracking of Heavy Hydrocarbons Based on Modeling and Experiments

“…On the other hand, semiempirical models, which have simple calculations, cannot be used for these reactions. , Therefore, the lumping methodology has been utilized for the complex reaction systems involved in the catalytic cracking process. In this way, similar components according to their boiling point and molecular characteristics are categorized into several cuts or lumps. , Many lumping models for catalytic cracking have been proposed and classified into two groups: (1) components are lumped based on the molecular structure characteristics of hydrocarbons, such as the four-lump kinetic model of Ojong et al, the seven-lump kinetic model of Fukuyama and Terai, the eight-lump model of Wang et al., the twelve-lump model of Zong et al., and the seventeen-lump model of Singh et al; (2) components are lumped based on the boiling point or molecular weight range, such as the four-lump kinetic model of Dave et al, Ancheyta-Juárez et al, and by Shayegh et al, the five-lump kinetic model of Sánchez et al and Ancheyta-Juárez et al, , the six-lump model of Ancheyta and Sotelo, Sadighi et al, Xiong et al, John et al, and by Seyed Asaee et al, the seven-lump model of Heydari, and the eight-lump model of Sani et al, You et al, and Sun et al In addition to these two types, in several studies, lumped kinetic models based on the chemical structure and boiling points are mixed, such as the ten-lump kinetic model proposed by Du et al and the nine-lump model by Ebrahimi et al and by Zhang et al Generally, the type of model is selected based on the purpose of the research.…”