Flow behaviors and heat transfer characteristics of liquid film during the pyrolysis process of molten plastics using OpenFOAM

Yin, Leilei; Jia, Yuanjie; Guo, Xingtong; Chen, Dezhen; Jin, Zechen

doi:10.1016/j.ijheatmasstransfer.2018.12.098

Cited by 8 publications

(11 citation statements)

References 20 publications

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“…The observed devolatilization rate is largely affected by internal transport phenomena, besides the intrinsic kinetics. Indeed, due to the fast reaction kinetics of pyrolysis and gasification [122,166], the internal heat and mass transfer may become the rate-limiting steps [161,167] (especially because plastics have shown poor heat and mass transfer characteristics [52,168], even in the molten phase [169]).…”

Section: Internal Transport Limitationsmentioning

confidence: 99%

“…The focus of the discussions above was based on the gas-solid-only assumption. However, the same challenges and opportunities are expected for the situations in which the presence of liquid is considered, e.g., for the molten plastic droplet [237,238], the fluidization agents covered by the molten plastic layer [45], and the falling film reactors [67,169,239].…”

Section: Numerical-based Correlationsmentioning

confidence: 99%

“…If the presence of a liquid phase is considered, the role of other forces in the momentum transfer between the phases depends on the operation. For the falling film systems, only the drag force is important and other forces are not usually assessed [169,239,271]. However, non-drag forces become more important in the case of the presence of liquid in the system [242] for the bubbly or droplet regimes.…”

Section: Non-drag Forcesmentioning

confidence: 99%

“…Consequently, the VOF method can be a better approach to simulate these situations, e.g., for the rotary kiln pyrolysis [310]. A similar situation-i.e., large interface between the gas and liquid phase-is observed also in the falling film systems [67,169,311]. One of the drawbacks of this method is the required high-resolution spatial discretization to track the surface in the cells, which increases the computational costs.…”

Section: Eulerian-eulerianmentioning

confidence: 99%

“…They also further investigated, experimentally and numerically, the heat transfer characteristics of the molten plastic (PE, PP, PS, and their mixture) [67] for the same reactor configuration. To increase the precision of their simulation, in another research, they modified the VOF method to include the effect of the drag force [169]. They used the air-water system for the initial studies and then implemented the framework for the molten plastic pyrolysis.…”

Section: Eulerian-eulerianmentioning

confidence: 99%

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Multi-Scale Modeling of Plastic Waste Gasification: Opportunities and Challenges

et al. 2022

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Among the different thermo-chemical recycling routes for plastic waste valorization, gasification is one of the most promising, converting plastic waste into syngas (H2+CO) and energy in the presence of an oxygen-rich gas. Plastic waste gasification is associated with many different complexities due to the multi-scale nature of the process, the feedstock complexity (mixed polyolefins with different contaminations), intricate reaction mechanisms, plastic properties (melting behavior and molecular weight distribution), and complex transport phenomena in a multi-phase flow system. Hence, creating a reliable model calls for an extensive understanding of the phenomena at all scales, and more advanced modeling approaches than those applied today are required. Indeed, modeling of plastic waste gasification (PWG) is still in its infancy today. Our review paper shows that the thermophysical properties are rarely properly defined. Challenges in this regard together with possible methodologies to decently define these properties have been elaborated. The complexities regarding the kinetic modeling of gasification are numerous, compared to, e.g., plastic waste pyrolysis, or coal and biomass gasification, which are elaborated in this work along with the possible solutions to overcome them. Moreover, transport limitations and phase transformations, which affect the apparent kinetics of the process, are not usually considered, while it is demonstrated in this review that they are crucial in the robust prediction of the outcome. Hence, possible approaches in implementing available models to consider these limitations are suggested. Finally, the reactor-scale phenomena of PWG, which are more intricate than the similar processes—due to the presence of molten plastic—are usually simplified to the gas-solid systems, which can result in unreliable modeling frameworks. In this regard, an opportunity lies in the increased computational power that helps improve the model’s precision and allows us to include those complexities within the multi-scale PWG modeling. Using the more accurate modeling methodologies in combination with multi-scale modeling approaches will, in a decade, allow us to perform a rigorous optimization of the PWG process, improve existing and develop new gasifiers, and avoid fouling issues caused by tar.

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