Multivariable optimization of thermal cracking severity

Self Cite

This work deals with an efficient two-step thermal upgrading process for converting extra-heavy fuel oil to light olefins (ethylene, propylene, and butenes) and fuels (gasoline and diesel fuel). In the first step, mild thermal pretreatment was implemented at different temperatures (360–440 °C) in the liquid phase to obtain a more suitable feedstock for an olefin production unit. Thanks to this cost-effective pretreatment, the upgraded feedstock demonstrated considerable flowability and crackability compared to the initial fuel oil, making the subsequent vapor-phase operation easier to handle at temperatures as high as 800 °C with no severe operational impediments. The quantitative 1H and 13C NMR studies shed light on the enhanced features of the thermally treated feedstock toward lighter and more valuable products. As a result, remarkable olefin production (74.7 or 55.1 wt % light olefins based on the upgraded or the original feedstock) was accomplished in this two-step process. The process could be alternatively stopped at the first stage for maximum liquid fuels (69.3 wt %) with gasoline as the larger constituent. The detailed kinetic investigations of the thermal decomposition of the feedstock using several reliable approaches revealed that the activation energy predictions (42.3–272.9 kJ/mol) by the Kissinger–Akahira–Sunose method almost perfectly matched the trend of a reference Starink model over the whole range of conversion. All model-free methods correlated with a coefficient of determination above 97.9%. Avrami’s theory was further applied to determine the reaction order, and the values were slightly smaller than those from a five-lump kinetic model of the semibatch operation. However, the apparent activation barrier in the reactor was in good correspondence with the range from the microscale nonisothermal decomposition.

Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Two-Step Thermal Cracking of an Extra-Heavy Fuel Oil: Experimental Evaluation, Characterization, and Kinetics

Ghashghaee

Shirvani

2018

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“…The ethylene/propylene production, ethylene selectivity, run length, severity, and total heat duty were the objective functions to be optimized by flow rate, steam ratio, inlet temperature, coil outlet temperature, and pressure. Ghashghaee and Karimzadeh reported a multivariable optimization of the furnace operation and reaction severity in PyroFur . The profit was the objective function, and a case study for a typical liquid furnace has demonstrated that an extra profit can be obtained.…”

Section: Optimal Designmentioning

confidence: 99%

Thermal Cracking of Hydrocarbons for the Production of Light Olefins; A Review on Optimal Process Design, Operation, and Control

Fakhroleslam

Sadrameli

2020

Olefins production plants are large-scale plants, in most of which gaseous and liquid hydrocarbons are cracked to produce light olefins. The complex and large-scale nature of these plants makes it an utmost necessity to design and operate them with the use of computer-aided optimization and control methods. This review paper provides an overview of the reported research works on the optimization and control of different parts of olefin plants. The main research studies are discussed in two main sections: Optimal Design and Process Operation and Control. In the Optimal Design section, the state of the optimal design of cracking furnace systems, cold-end separation systems, and separation columns have been studied. Then in the Process Operation and Control section, the control of cracking furnaces, the control of cold-end separation systems, real-time optimization of olefin plants, cyclic scheduling of cracking furnace systems, production planning of olefin plants, and finally, start-up and shutdown operations in these plants have been extensively reviewed. This paper is a continuation of the three review articles published previously entitled Thermal and Catalytic Cracking of Hydrocarbons for the Production of Light Olefins, the last of which focused on process modeling and simulation.

“…Many studies on steady-state and dynamic optimization of steam cracking furnaces to maximize the total olefin production − are available in the literature. The accuracy of such studies is entirely dependent on a meticulous description of the furnace as a function of the time on stream.…”

Section: Introductionmentioning

confidence: 99%

Incident Radiative Heat Flux Based Method for the Coupled Run Length Simulation of Steam Cracking Furnaces

Zhang

Reyniers

et al. 2017

Due to the significant economic penalty associated with decoking steam cracking furnaces, accurate run length predictions are crucial for assessing their techno-economic performance. Therefore, for the first time, a full coupled run length simulation of an industrial naphtha steam cracking furnace was performed using detailed computational fluid dynamics (CFD) simulations for the furnace side. The results show that the unevenly deposited coke layer within the reactors leads to a redistribution of the thermal power over the time on stream, which is beneficial for the uniformity of the coke growth in the reactor. These effects were not observed in traditional standalone run length simulations, which justifies the high computational cost. However, the high computational cost of these CFD iterations can be overcome by using a novel method which correlates the incident radiative heat flux (IRHF) to the flue gas bridge wall temperature obtained from an overall zero-dimensional heat balance. This so-called IRHF based method provides similar accuracy as the CFD coupled method but at a fraction of the computational cost. The CPU time was decreased by a factor of over 2000, allowing one to move these calculations from a high-performance computing environment to a personal computer. The generality of this method for changing operating conditions or feedstock compositions was also demonstrated by comparing with CFD coupled run length simulations of a set of new cases. With relative errors well below 1%, the IRHF based method is recommended for coupled run length simulations of steam cracking units.