Narrow Fraction Model with Secondary Cracking for Low-Severity Thermal Cracking of Heavy Oil

Abstract

Thermal reaction experiments of vacuum residuum were conducted in a micro-batch reactor at 410–480 °C. The product yield variation with time indicated that the secondary cracking reaction mainly occurs in the heavy fraction of the liquid product. A narrow fraction model for low-severity thermal cracking of heavy oil, with the secondary reaction taken into account, was developed. To simplify the reaction network, a pseudo-lump was introduced, which was defined as the fraction generated from the secondary cracking reaction of the heavy fraction (420–540 °C). Furthermore, a sequential method to estimate rate constants in complex models was employed, and the kinetic parameters were estimated by Arrhenius’ law. The model-predicted lump yields agreed well with the experimental values. The ratio of secondary cracking/primary cracking was calculated. The result indicated that, even at the initial stage of the reaction, the ratio in the heavy distillate reaches up to 15–36%; therefore, the secondary cracking reaction cannot be ignored even in low-severity thermal cracking.

Numerical Simulation of the Flue Gas and Process Side of Coking Furnaces

“…However, the product distribution of thermal cracking reaction affects these parameters directly, so it is important to establish an accurate model for the product distribution in thermal cracking of heavy oil, which is suitable for the calculation of apparent velocity and residence time in the furnace tubes. There are many kinetic models proposed for different processes and conditions. − In this work, a 12-lump kinetic model was employed to describe the thermal cracking process …”

Kinetic Model for the Deep-Severity Thermal Reaction in the Coke Drum of Delayed Coking

“…There are many kinetic models developed for the thermal reaction of heavy oil, − which could probably be divided into two categories on the basis of the reaction severity. One is the low-severity or mild reaction lumped model, which is mainly used for the simulation of the low-severity cracking reaction in the coking furnace − or the mild reaction in the soaker process. − In these processes, the overall cracking conversion was usually less than 30–50% and the thermal condensation reaction was ignored. Many of the reported models − are of this category.…”

Progress in kinetic predictions for complex reaction of hydrocarbons: from mechanism studies to industrial applications

“…These well-established and easily-implemented kinetic models have been widely adopted in petrochemical industries and have exhibited credible data and well-behaved simulation results (Elizalde and Ancheyta 2011, 2012, Zhou et al 2011a, Adam et al 2012, Wang et al 2012, Yang et al 2012). However, a few drawbacks remain, such as rough estimations of reaction processes due to rough lumping methods and the lack of a universal model.…”

“…Recently, a number of research interests have pursued the studies of secondary reactions and the exploration of heavy oil resources. For example, the linetic model of secondary reactions of FCC gasoline was studied by Zhou et al (Zhou et al 2011b, Yang et al 2012. Yang et al (2012) also studied the secondary cracking of heavy oil using sequential methods to estimate rate constants in complex models.…”

“…For example, the linetic model of secondary reactions of FCC gasoline was studied by Zhou et al (Zhou et al 2011b, Yang et al 2012. Yang et al (2012) also studied the secondary cracking of heavy oil using sequential methods to estimate rate constants in complex models. For the exploration of heavy oil cracking technology, Longstaff (2012) and Balasubramanian and Pushpavanam (2008) individually developed discrete lumping kinetic models for hydrocracking processes.…”