A comprehensive pyrolysis model for lignocellulosic biomass particles with a special emphasis on the anisotropic characteristics

Li, Fangzhou; Wu, Kai; Ke, Yang; Ge, Zefeng; Feng, Jie; Zhang, Huiyan

doi:10.1016/j.fuel.2023.127635

Cited by 5 publications

(5 citation statements)

References 48 publications

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“…For both lengths, the dimensional change of the radial and tangential directions caused a change in the overall geometric shape of particles from cylinders to elliptic cylinders. Conversely to the modeling studies, the particles did not show a noticeable deviation in radial and transverse dimensions between the top/bottom and the middle of the particles. , …”

Section: Resultscontrasting

confidence: 71%

“…Conversely to the modeling studies, the particles did not show a noticeable deviation in radial and transverse dimensions between the top/bottom and the middle of the particles. 19,104 Also, above 480 °C, cracks and fissures in the particles started to become profound. It was observed that they commonly started on the growth rings of the wood, causing layering of the structure and deformation in the radial direction (see Figure S19).…”

Section: General Structural Changesmentioning

confidence: 99%

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Part 1─Impact of Pyrolysis Temperature and Wood Particle Length on Vapor Cracking and Char Porous Texture in Relation to the Tailoring of Char Properties

Maziarka,

Kienzl,

Dieguez-Alonso

et al. 2024

Energy Fuels

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Pore size distribution is a key parameter in the performance of biobased pyrolytic char in novel applications. In industrial-scale production, the size of feedstock particles typically exceeds a few millimeters. For such particle sizes, it is a challenge to tailor the final properties of the char based only on the process conditions (experimental and modeling-wise). Pyrolysis studies of single particles larger than a few millimeters provide data sets useful for modeling and optimization of the process. Part 1 of this research focused on the pyrolysis of single particles of beech wood, secondary cracking, and its effect on the char porous texture. It contains a quantitative assessment of the effects of five conversion temperatures (from 300 to 840 °C) and two particle dimensions (Ø8 × 10 mm and Ø8 × 16 mm) on the composition of the pyrolysis vapors and pore morphology of the char. Results from real-time temperature and mass changes are presented along with release profiles of 15 vapor constituents measured by infrared spectroscopy. Furthermore, characterization of the collected bio-oil (using GC-MS/FID) and the textural hierarchical structured char (through N 2 and CO 2 adsorption, Hg porosimetry, and scanning electron microscopy (SEM)) was performed. Cracking of vapors above 500 °C was compound-specific. The polyaromatic hydrocarbons (PAHs) yield, between 680 and 840 °C, increased 5 times for 10 mm particles and 9 times for 16 mm ones. Besides temperature, PAH yield was suspected to correlate with particle length and PAHs/soot deposition in the micropores. Results showed that the macropores accounted for over 80% of the total pore volume, regardless of the temperature and particle length. Increasing the particle length by 60% caused a reduction in the specific surface area (ca. 15% at 840 °C) of the resulting char, mainly due to a reduction in microporosity. Based on the findings, the production conditions for a specific char application are suggested. The obtained data will be used in Part 2 of this research, devoted to subsequent CFD modeling of the process.

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Section: Resultscontrasting

confidence: 71%

Section: General Structural Changesmentioning

confidence: 99%

Part 1─Impact of Pyrolysis Temperature and Wood Particle Length on Vapor Cracking and Char Porous Texture in Relation to the Tailoring of Char Properties

Maziarka,

Kienzl,

Dieguez-Alonso

et al. 2024

Energy Fuels

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“…The changes in the particle geometry with conversion (e.g., shrinking) are relevant for the accurate description of changes in structure and thermo-physical parameters; hence indirectly, the conversion route. , Despite their occurrence in real systems, the available studies do not explain unambiguously the impact of these phenomena. Some modeling studies included geometric deformation, with a presumption of its beneficial impact. ,,, However, other studies showed that omitting its implementation still leads to reliable outcomes in terms of the predicted temperature and mass loss profile. ,, Despite the presumed beneficial effect of implementing geometric deformation in the model, none of the studies so far have conducted a direct validation of the model results against experimentally obtained data of bulk density and porosity change.…”

Section: Introductionmentioning

confidence: 99%

“…Some modeling studies included geometric deformation, with a presumption of its beneficial impact. 22,29,41,42 However, other studies showed that omitting its implementation still leads to reliable outcomes in terms of the predicted temperature and mass loss profile. 11,29,43 Despite the presumed beneficial effect of implementing geometric deformation in the model, none of the studies so far have conducted a direct validation of the model results against experimentally obtained data of bulk density and porosity change.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, both phenomena should be assessed independently for precise quantification of their impact. The modeling studies of single particle conversion include secondary vapor reactions, but rarely distinguish between intrinsic and external effects or include them both. ,,,− The secondary vapor reactions, under favorable conditions, lead to the formation of secondary carbon (soot), where the polyaromatic hydrocarbon (PAH)-triggered mechanism is considered to be the most reliable. , If it occurs intrinsically, the phenomenon can have a non-negligible effect on the composition and structure of the material, thereby impacting the final application of the resultant char. However, the literature modeling studies that assess the intrinsic effects of the secondary reactions are missing, especially regarding their effect on the char particle structure.…”

Section: Introductionmentioning

confidence: 99%

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Part 2─Tailoring of Pyrolytic Char Properties with a Single Particle CFD Model with a Focus on the Impact of Shrinking, Vapor Cracking, and Char Permeability

Maziarka,

Kienzl,

Dieguez-Alonso

et al. 2024

Energy Fuels

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The prediction of the structural properties of biobased carbonaceous materials of pyrolytic origin (chars) with only base feedstock properties and process conditions still poses a challenge that hinders char tailoring for novel applications. CFD modeling of single biomass particle conversion can help solve this issue since it allows for the quantification of relations between parameters that are difficult to measure. A model for char tailoring must include a validated representation of the structural changes coupled to all other relevant phenomena occurring during conversion. Part 2 of this study focuses on finding the description of the mentioned aspects to achieve the highest precision of prediction of the structural changes in char by a CFD model. The investigation in Part 2 is composed of three cases focused on accurate description and prediction of (1) bulk density and porosity, (2) secondary vapor reactions on yields and soot formation, and (3) permeability, as well as the outflux and conversion of evolved vapors. The experimental results from Part 1 and the literature data were used to find appropriate descriptions of phenomena and assess the accuracy of the model. The model results indicate that for both particle lengths (10 and 16 mm), a high accuracy of prediction of base structural parameters was achieved. The average prediction error for temperatures between 400 and 840 °C of bulk density was 31 ± 15 kg/m 3 , and the porosity was 1.8 ± 1.1 vol %. The results also show a low error in the prediction of bulk product yields (dry basis) over the mentioned temperature range, which were: for char 2.8 ± 1.1 wt %, for the condensable fraction 6.5 ± 3.3 wt %, and for the pyrolysis gas 4.1 ± 1.9 wt %. The distribution of secondary char formation was found to be nonuniform below 500 °C. The changes in permeability had a minor influence on the vapor outflux but a non-negligible effect on the soot formation, especially at 840 °C. The results indicate a need for further improvement of the primary degradation model to increase the accuracy of the effect of soot formation on the char structure.

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A comparative thermodynamic assessment of microwave-assisted and conventional pyrolysis of biomass in poly-generation systems using coupled numerical and process simulations

Li,

Lin

et al. 2024

Energy Conversion and Management

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A comprehensive pyrolysis model for lignocellulosic biomass particles with a special emphasis on the anisotropic characteristics

Cited by 5 publications

References 48 publications

Part 1─Impact of Pyrolysis Temperature and Wood Particle Length on Vapor Cracking and Char Porous Texture in Relation to the Tailoring of Char Properties

Part 1─Impact of Pyrolysis Temperature and Wood Particle Length on Vapor Cracking and Char Porous Texture in Relation to the Tailoring of Char Properties

Part 2─Tailoring of Pyrolytic Char Properties with a Single Particle CFD Model with a Focus on the Impact of Shrinking, Vapor Cracking, and Char Permeability

A comparative thermodynamic assessment of microwave-assisted and conventional pyrolysis of biomass in poly-generation systems using coupled numerical and process simulations

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