Using molecular dynamics simulations to study the non-thermal effects of microwave radiation on the mechanism of char gasification

Su, Jian; Zhao, Deng; Feng, Haoyuan; Wu, Tianyu; Liu, Hua; Wang, Huashan; Guo, Shuai; Liu, Hui

doi:10.1016/j.renene.2022.11.125

Cited by 9 publications

(5 citation statements)

References 49 publications

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“…More specifically, the electromagnetic field consists of mutually orthogonal fluctuating electric and magnetic fields. However, the electric field force is several orders of magnitude greater than the Lorentz (magnetic) force, given the intensity of the electric/magnetic field of the actual electromagnetic waves and the speed of molecular motion [26]. As a result, we neglect the magnetic field (as is common in MD simulations) and focus on the effect of the electric field.…”

Section: The Expression Of Ir Energy Form In MD Simulationmentioning

confidence: 99%

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Atomic-scale insight into arc plasma radiation-induced gassing materials ablation: photothermal decomposition behavior

Cao,

Li,

Zhang

et al. 2024

J. Phys. D: Appl. Phys.

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In this study, we present a novel computational atomistic study of the photothermal decomposition behavior of arc plasma on radiation-induced gassing materials, studying a polyamide 66 (PA66) system using reactive force field (ReaxFF) molecular dynamics (MD). We determine the infrared (IR) vibrational frequency of the PA66 permanent molecular dipole using MD and then computationally impose an electric field at the same frequency to simulate photothermal decomposition by IR, verifying our observations with gas chromatography-mass spectrometry (GCMS) of experimental decomposition. MD indicates that photothermal decomposition reaction is dominated by either cleavage at low temperature or cyclization at high temperature. At low temperature, initial chain scission takes place at the two amide C-N, and the remaining chains break down into a variety of molecular fragments and free radicals. Further increasing the temperature stabilizes a variety of branched chain structures via cyclization, debranching and polymerization, with further cleavage forming hydrocarbons and volatile small molecule gases. Overall, H2, CO, H2O, alkanes and alkenes are the main gaseous products and cyclic structures (especially nitrogen-containing three-membered ring) are the main solid products during the photothermal decomposition of PA66, and their formation results from a variety of complex chemical reactions. The results of MD cover the experimental observations of GCMS, demonstrating that this computational methodology helps us understand the molecular breakdown mechanisms of arc plasma radiation-induced gassing materials. We also discuss the physical mechanism by which the main gas can accelerate arc quenching, and the importance and necessity of using electric fields to simulate IR photothermal decomposition of arc-induced ablation.

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Section: The Expression Of Ir Energy Form In MD Simulationmentioning

confidence: 99%

“…This patch has been approved by the developers and will be included in the next release. It introduces the ability to impose a periodic electric field in ReaxFF to ensure proper charge transfer, which was mentioned in previous reports [26,36] which unfortunately were not accompanied by publicly available source code.…”

Section: Model Constructionmentioning

confidence: 99%

Atomic-scale insight into arc plasma radiation-induced gassing materials ablation: photothermal decomposition behavior

Cao,

Li,

Zhang

et al. 2024

J. Phys. D: Appl. Phys.

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“…24 Plasmas can be easily distinguished from solids, liquids, or gases owing to the presence of charged species in plasmas, making them highly reactive. 25 Charged electrons collide with gas molecules at high energies, forming a plasma that is sometimes called the fourth state of matter. Thermal plasma is used in waste processing, which is characterized by very high temperatures and energy densities.…”

Section: Introductionmentioning

confidence: 99%

Sustainable Plasma Gasification Treatment of Plastic Waste: Evaluating Environmental, Economic, and Strategic Dimensions

Rida Galaly,

Van Oost,

Dawood

2024

ACS Omega

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The conversion of waste to energy is an essential process in the Middle East, especially in Saudi Arabia, where it plays a crucial role in waste management. The annual analysis of the decomposition hazards of the landfills in the city of Makkah showed that they ranged from 168,000 Mg in 1994 to 297,000 Mg in 2022. The emission costs of pollution ranged from 4 million in 1994 to 7 million in 2022. The number of gas emissions of plastic waste accumulating in the analyzed landfill has increased from 128,000 Mg in 1994 to 227,000 Mg in 2022. The thermal plasmas used were produced by air plasma torches, which are an essential part of plasma reactors. The operational characteristics of air plasma torches were investigated at a flow rate of 10−30 g/s, including current−voltage characteristics, applied power, applied flow rate, average temperatures of the exiting plasma jet ranging from 15,000 to 19,000 K, average velocity of the exiting plasma jet (1677.3−2763.2) m/s, wavelength of the emitted radiation ranging from 153 to 193 nm, and the corresponding beam lengths ranging from 400 to 450 mm. The proposed plasma gasification is the greenest method for processing plastic waste in the light of ecological, economic, and strategic visions with an amount of recovered pyrolysis oil in the year 2022 of 3.17 × 10 5 tons with an equivalent energy of 12.55 × 109 MJ, with an output efficiency value equal to 81%. A roadmap for the economic and environmental visions was introduced, where the economic return on investment (ROR%) was 80%, the payback period (PBP) was 1.2 years, and the gross profit reached 129%.

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“…In recent years, the application of molecular dynamics (MD) simulations based on the reactive force field (ReaxFF) has proven successful in modeling the combustion and pyrolysis characteristics of complex compounds such as coal [16], biomass [17], and charcoal [18,19]. This methodology has provided a deeper understanding of the reaction processes.…”

Section: Introductionmentioning

confidence: 99%

Reactive Force Field Molecular Dynamics Investigation of NH3 Generation Mechanism during Protein Pyrolysis Process

Guo,

Wang,

Zhu

et al. 2024

Molecules

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The mechanism of ammonia formation during the pyrolysis of proteins in biomass is currently unclear. To further investigate this issue, this study employed the AMS 2023.104 software to select proteins (actual proteins) as the model compounds and the amino acids contained within them (assembled amino acids) as the comparative models. ReaxFF molecular dynamics simulations were conducted to explore the nitrogen transformation and NH3 generation mechanisms in three-phase products (char, tar, and gas) during protein pyrolysis. The research results revealed several key findings. Regardless of whether the model compounds are actual proteins or assembled amino acids, NH3 is the primary nitrogen-containing product during pyrolysis. However, as the temperature rises to higher levels, such as 2000 K and 2500 K, the amount of NH3 decreases significantly in the later stages of pyrolysis, indicating that it is being converted into other nitrogen-bearing species, such as HCN and N2. Simultaneously, we also observed significant differences between the pyrolysis processes of actual proteins and assembled amino acids. Notably, at 2000 K, the amount of NH3 generated from the pyrolysis of assembled amino acids was twice that of actual proteins. This discrepancy mainly stems from the inherent structural differences between proteins and amino acids. In proteins, nitrogen is predominantly present in a network-like structure (NH-N), which shields it from direct external exposure, thus requiring more energy for nitrogen to participate in pyrolysis reactions, making it more difficult for NH3 to form. Conversely, assembled amino acids can release NH3 through a simpler deamination process, leading to a significant increase in NH3 production during their pyrolysis.

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Using molecular dynamics simulations to study the non-thermal effects of microwave radiation on the mechanism of char gasification

Cited by 9 publications

References 49 publications

Atomic-scale insight into arc plasma radiation-induced gassing materials ablation: photothermal decomposition behavior

Atomic-scale insight into arc plasma radiation-induced gassing materials ablation: photothermal decomposition behavior

Sustainable Plasma Gasification Treatment of Plastic Waste: Evaluating Environmental, Economic, and Strategic Dimensions

Reactive Force Field Molecular Dynamics Investigation of NH3 Generation Mechanism during Protein Pyrolysis Process

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