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The steam cracking process is an important asset in the hydrocarbon processing
industry. The main products are lower olefins (ethylene, propylene, butylenes) and
hydrogen, with ethylene being the world’s largest volume organic chemical at a
worldwide capacity of �120 million tonnes per year. Feed stocks are hydrocarbons
(C2+) such as: ethane, LPG,...
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The ethylene production is regarded one of the most significant issues for chemical industries and improving its production operation can bring several benefits. Thus, the market demand for ethylene production has accelerated the improvement of a more rigorous and reliable thermal cracking model of such process. In the present study, developing a r...
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... Figure 19 indicates that the optimized mixing space distribution favors residence times as low as aerodynamically possible for the majority of the forward stages before using "extended" residence time stages toward the rear of the reactor. This leads to a temperature profile where high-temperature conditions are reached very quickly and then held for the remainder of the reaction, which is inline with conventional wisdom [23]. The optimized profile enables a 10% higher primary product yield (see Fig. 19(b)) while simultaneously reducing coking rate by 10% (not shown for brevity). ...
Hard-to-abate industrial processes, such as petrochemicals, have long been considered technically challenging to decarbonize. In response to the urgent demand to eliminate industrial CO2 emissions, a new class of energy-imparting turbomachines has been developed. These devices aim to convert mechanical into internal energy instead of pressurizing the gas, which enables high-temperature gas heating for a variety of applications. This paper is organized into three parts. First, the paper demonstrates the capabilities of the novel, customizable, repeating-stage axial turbo-heater for a hydrocarbon cracking example application. The study presents the new design requirements and working principles of this energy-imparting concept. The radically different objectives compared to a compressor enable ultra-high loading stage designs by avoiding the stability and efficiency constraints imposed on compressors. Within this new design space, the turbo-heater can achieve a loading coefficient ψ ≥ 4.0. Second, detailed numerical simulations of a multistage turbo-reactor with various vaneless space lengths are conducted. This work conclusively demonstrates the robustness of the aerodynamic design to maintain nominal work-input conditions even for the most compact arrangements despite employing a uniform blade design. Finally, having confirmed that the aerothermal restrictions on the vaneless space length can be removed, the designer is free to tailor the design to optimize the chemical reaction by (1) tailoring the residence time distribution (2) homogenizing reaction progress by mixing-out concentration gradients and (3) adjusting the rotational speed to account for variations in the reaction dynamics for different feedstocks.
... Figure 19 indicates that the optimized mixing space distribution favors residence times as low as aerodynamically possible for the majority of the forward stages before using "extended" residence time stages toward the rear of the reactor. This leads to a temperature profile where high-temperature conditions are reached very quickly and then held for the remainder of the reaction, which is inline with conventional wisdom [23]. The optimized profile enables a 10% higher primary product yield (see Fig. 19(b)) while simultaneously reducing coking rate by 10% (not shown for brevity). ...
Hard-to-abate industrial processes, such as petrochemicals and cement production, have long been considered technically challenging to decarbonize. In response to the urgent demand to eliminate industrial CO2 emissions, a new class of energy-imparting turbomachines has been developed. These devices aim to convert mechanical into internal energy instead of pressurizing the gas, which enables high-temperature gas heating (up to 1700 °C) for a variety of applications. This paper is organized into three parts. First, the paper aims to demonstrate the capabilities of the novel, high-capacity, customizable, repeating-stage axial turbo-heater architecture for a hydrocarbon cracking example application. The study presents the new design requirements and working principles of this energy-imparting concept. The radically different objectives compared to a compressor enable ultra-high loading stage designs by avoiding the stability and efficiency constraints imposed on compressors. Within this new design space, the turbo-heater is able to achieve a loading coefficient ψ ≥ 4.0. Second, detailed numerical simulations of a multistage axial turbo-reactor with various vaneless space lengths are conducted. This work conclusively demonstrates the robustness and flexibility of the aerodynamic design despite employing a uniform blade design. It is emphasized that the concept is tolerant to unsteady interstage turbulent disturbances, enabling nominal work-input conditions to be achieved even for the most compact arrangements. Finally, having confirmed that the aerothermal restrictions on the vaneless space length can be removed, the designer is free to tailor the design to optimize the chemical reaction by (1) tailoring the residence time distribution to improve the yield and coking rate (2) homogenizing reaction progress by mixing-out concentration gradients and (3) adjusting the rotational speed to account for variations in the reaction dynamics for different feedstocks.
... Increasing the yield though high gas temperatures and short residence times Conventional process limitation. Indirect surface heat exchange in the radiant section requires the walls to be at a significantly higher temperature than the gas mixture within the reaction tubes, often by 150°C (Van Goethem, 2010). Therefore, the working fluid temperature is fixed by the metallurgical constraints of the tubes as well as by the acute coke deposition rates associated with the elevated metal temperature. ...
Energy consumption in the chemical and petrochemical industries is dominated by the highly energy-intensive, high-temperature hydrocarbon cracking process. This paper offers an attractive solution to potentially decarbonise the cracking industry by direct renewable electrification whilst also improving the efficiency of energy transfer and enhancing the quality of the overall cracking process. Controlled endothermic cracking reactions are generated by direct mechanical energy transfer using a new electric-motor-driven turbo-reactor to replace the fossil-fuelled radiant unit in the conventional cracking plant. This study provides an introduction to the novel concept, focusing on how the unique three-blade-row repeating stage design is exploited in order to drive the efficient energy transfer and transformation processes used to overcome the fundamental limitations of the conventional process. More specifically, this includes increasing the primary product yield, mitigating coke deposition and improving operability. A combination of URANS and high-fidelity LES are presented in order to probe the aerothermal flow physics and interactions in the rotor and diffuser. This study clearly demonstrates how the working principals of the elemental stage can be realised uniformly across the full regenerative turbo-reactor by exploiting the robust and naturally self-adjusting concept. This work highlights the high-level of controllability of the turbomachine, which allows the cracking environment and species selectivities to be tailored during operation, for example, by conducting minor alterations to the rotational speed.
... The formed ethyl radical can be dissociated into ethylene and hydrogen radicals (Equation (3)). Hydrogen radicals attack another ethane molecules and produce a new ethyl radical and hydrogen molecule (Equation (4)) [1,10,23,[26][27][28][29]. ...
... The termination step proceeds via the interaction of two radicals and the formation of saturated or unsaturated molecules (Equations (6)-(11)). Small amounts of heavier hydrocarbons are produced through the termination of the larger radicals formed according to Equation (5) [1,10,23,[26][27][28][29]. ...
Light olefins are the main building blocks used in the petrochemical and chemical industries for the production of different components such as polymers, synthetic fibers, rubbers, and plastic materials. Currently, steam cracking of hydrocarbons is the main technology for the production of light olefins. In steam cracking, the pyrolysis of feedstocks occurs in the cracking furnace, where hydrocarbon feed and steam are first mixed and preheated in the convection section and then enter the furnace radiation section to crack to the desired products. This paper summarizes olefin production via the steam cracking process; and the reaction mechanism and cracking furnace are also discussed. The effect of different operating parameters, including temperature, residence time, feedstock composition, and the steam-to-hydrocarbon ratio, are also reviewed.
... Scope for Reducing the Residence Time. First, metallurgical constraints of the coils limit the maximum tube metal temperature (TMT) to $1150 C [7], thereby lowering the allowable flue gas temperature and hence the heating rate. Figure 4 indicates that at lower temperatures a longer residence time is required (hence lowering the yield). ...
Decarbonising highly energy-intensive industrial processes is imperative if nations are to comply with 2050 greenhouse gas emissions. This is a significant challenge for high-temperature industrial processes, such as hydrocarbon cracking, and there have been limited developments thus far. The novel concept presented in this study aims to replace the radiant section of a hydrocarbon cracking plant with a novel turbo-reactor. Rather than using heat from the combustion of natural gas, the novel turbo-reactor can be driven by an electric motor powered by renewable electricity. Switching the fundamental energy transfer mechanism from surface heat exchange to mechanical energy transfer significantly increases the exergy efficiency of the process. Theoretical analysis and numerical simulations show that the ultra-high aerodynamic loading rotor is able to impart substantial mechanical energy into the feedstock without excess temperature difference and metal temperature magnitude. The required enthalpy rise can be supplied within a reactor volume 500 times smaller than that for a conventional furnace. A significantly lower wall surface temperature, supersonic gas velocities and a shorter primary gas path enable a controlled reduction in the residence time for chemical reactions, which optimises the yield. For the same reasons the conditions for coke deposition on the turbo-reactor surfaces are unfavourable, leading to an increase in plant availability. This study demonstrates that the mechanical work input into the feedstock can be dissipated through an intense turbulent mixing process which maintains an ideal and controlled pressure level for cracking.
... Scope for Reducing the Residence Time. First, metallurgical constraints of the coils limit the maximum tube metal temperature (TMT) to $1150 C [7], thereby lowering the allowable flue gas temperature and hence the heating rate. Figure 4 indicates that at lower temperatures a longer residence time is required (hence lowering the yield). ...
Decarbonising highly energy-intensive industrial processes is imperative if nations are to comply with anthropogenic greenhouse gas emissions targets by 2050. This is a significant challenge for high-temperature industrial processes, such as hydrocarbon cracking, and there have been limited developments thus far. The novel concept presented in this study aims to replace the radiant section of a hydrocarbon cracking plant with a novel turbo-reactor. This is one of the first major and potentially successful attempts at decarbonising the petrochemical industry. Rather than using heat from the combustion of natural gas, the novel turbo-reactor can be driven by an electric motor powered by renewable electricity. Switching the fundamental energy transfer mechanism from surface heat exchange to mechanical energy transfer significantly increases the exergy efficiency of the process. Theoretical analysis and numerical simulations show that the ultra-high aerodynamic loading rotor is able to impart substantial mechanical energy into the feedstock without excess temperature difference and temperature magnitude. A complex shockwave system then transforms the kinetic energy into internal energy over an extremely short distance. The version of the turbo-reactor developed and presented in this study uses a single rotor row, in which a multi-stage configuration is achieved regeneratively by guiding the flow through a toroidal-shaped vaneless space. This configuration leads to a reduction in reactor volume by more than two orders of magnitude compared with a conventional furnace. A significantly lower wall surface temperature, supersonic gas velocities and a shorter primary gas path enable a controlled reduction in the residence time for chemical reactions, which optimises the yield. For the same reasons, the conditions for coke deposition on the turbo-reactor surfaces are unfavourable, leading to an increase in plant availability. This study demonstrates that the mechanical work input into the feedstock can be dissipated through an intense turbulent mixing process which maintains an ideal and controlled pressure level for cracking. Numerical calculations show that the turbulence intensity increases by nearly an order of magnitude relative to that in a industrial radiant reaction tube, which can be favourable for accelerating the chemical kinetics.
The global energy consumption in the chemical and petrochemical industries is dominated by the highly energyintensive hightemperature hydrocarbon cracking process. This paper offers an attractive potential solution to decarbonise the cracking industry by renewable electrification whilst also improving the efficiency of energy transfer and enhancing the quality of the overall cracking process. Controlled endothermic cracking reactions are generated by direct mechanical energy transfer using a new electricdriven turboreactor to replace the fossilfuelled radiant unit in the conventional cracking plant. This study provides an introduction to the novel concept, focusing on how the unique threebladerow repeating stage design is exploited in order to drive the efficient energy transfer and transformation processes used to overcome the fundamental limitations of the conventional process, more specifically by increasing the yield and mitigating coke deposition. A combination of URANS and highfidelity LES are presented in order to probe the aerothermal flow physics and interactions in the rotor and diffuser. This study clearly demonstrates how the working principals of the elemental stage can be realised uniformly across the full regenerative turboreactor by exploiting a robust and naturally selfadjusting concept. This work highlights the highlevel of controllability of the turbomachine, allowing the cracking environment to be tailored during operation, for example, by conducting minor alterations to the rotational speed.
