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Ghasemi Monfared, Z., Hellström, J. G. & Umeki, K. (2024). The Impact of Discrete Element Method Parameters on Realistic Representation of Spherical Particles in a Packed Bed. Processes, 12(1), Article ID 183.
Open this publication in new window or tab >>The Impact of Discrete Element Method Parameters on Realistic Representation of Spherical Particles in a Packed Bed
2024 (English)In: Processes, E-ISSN 2227-9717, Vol. 12, no 1, article id 183Article in journal (Refereed) Published
Abstract [en]

Packed bed reactors play a crucial role in various industrial applications. This paper utilizes the Discrete Element Method (DEM), an efficient numerical technique for simulating the behavior of packed beds of particles as discrete phases. The focus is on generating densely packed particle beds. To ensure the model accuracy, specific DEM parameters were studied, including sub-step and rolling resistance. The analysis of the packed bed model extended to a detailed exploration of void fraction distribution along radial and vertical directions, considering the impact of wall interactions. Three different samples, spanning particle sizes from 0.3 mm to 6 mm, were used. Results indicated that the number of sub-steps significantly influences void fraction precision, a key criterion for comparing simulations with experimental results. Additionally, the study found that both loosely and densely packed beds of particles could be accurately represented by incorporating appropriate values for rolling friction. This value serves as an indicator of both inter-particle friction and friction between particles and the walls. An optimal rolling friction coefficient has been thereby suggested for the precise representation for the densely packed bed of spherical char particles.

Place, publisher, year, edition, pages
MDPI, 2024
Keywords
packed bed, discrete element method, rolling friction, void fraction, sub-steps, wall effect
National Category
Fluid Mechanics and Acoustics Energy Engineering
Research subject
Energy Engineering; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-103794 (URN)10.3390/pr12010183 (DOI)
Funder
Swedish Energy Agency, P46974-1
Note

Validerad;2024;Nivå 2;2024-01-17 (joosat);

Full text: CC BY 4.0 License

Available from: 2024-01-17 Created: 2024-01-17 Last updated: 2024-01-17Bibliographically approved
Dossow, M., Klüh, D., Umeki, K., Gaderer, M., Spliethoff, H. & Fendt, S. (2023). Electrification of gasification-based biomass-to-X processes - a critical review and in-depth assessment. Energy & Environmental Science
Open this publication in new window or tab >>Electrification of gasification-based biomass-to-X processes - a critical review and in-depth assessment
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2023 (English)In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706Article, review/survey (Refereed) Epub ahead of print
Abstract [en]

To address the impacts of climate change, it is imperative to significantly decrease anthropogenic greenhouse gas emissions. Biomass-based chemicals and fuels will play a crucial role in substituting fossil-based feedstocks and reducing emissions. Gasification-based biomass conversion processes with catalytic synthesis producing chemicals and fuels (Biomass-to-X, BtX) are an innovative and well-proven process route. Since biomass is a scarce resource, its efficient utilization by maximizing product yield is key. In this review, the electrification of BtX processes is presented and discussed as a technological option to enhance chemical and fuel production from biomass. Electrified processes show many advantages compared to BtX and electricity-based processes (Power-to-X, PtX). Electrification options are classified into direct and indirect processes. While indirect electrification comprises mostly the addition of H2 from water electrolysis (Power-and-Biomass-to-X, PBtX), direct electrification refers to power integration into specific processing steps by converting electricity into the required form of energy such as heat, electrochemical energy or plasma used (eBtX). After the in-depth review of state-of-the-art technologies, all technologies are discussed in terms of process performance, maturity, feasibility, plant location, land requirement, and dynamic operation. H2 addition in PBtX processes has been widely investigated in the literature with process simulations showing significantly increased carbon efficiency and product yield. Similar studies on direct electrification (eBtX) are limited in the literature due to low technological maturity. Further research is required on both, equipment level technology development, as well as process and system level, to compare process options and evaluate performance, economics, environmental impact and future legislation.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2023
National Category
Energy Systems Chemical Process Engineering Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-103854 (URN)10.1039/d3ee02876c (DOI)2-s2.0-85181966035 (Scopus ID)
Note

Funder: German Federal Ministry of Economic Affairs and Climate Action (03EE5044B); German Federal Ministry ofEducation and Research (01DD21005);

Full text license: CC BY-NC

Available from: 2024-01-25 Created: 2024-01-25 Last updated: 2024-01-25
Khasevani, S. G., Nikjoo, D., Chaxel, C., Umeki, K., Sarmad, S., Mikkola, J.-P. & Concina, I. (2023). Empowering Adsorption and Photocatalytic Degradation of Ciprofloxacin on BiOI Composites: A Material-by-Design Investigation. ACS Omega, 8(46), 44044-44056
Open this publication in new window or tab >>Empowering Adsorption and Photocatalytic Degradation of Ciprofloxacin on BiOI Composites: A Material-by-Design Investigation
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2023 (English)In: ACS Omega, E-ISSN 2470-1343, Vol. 8, no 46, p. 44044-44056Article in journal (Refereed) Published
Abstract [en]

Binary and ternary composites of BiOI with NH2-MIL-101(Fe) and a functionalized biochar were synthesized through an in situ approach, aimed at spurring the activity of the semiconductor as a photocatalyst for the removal of ciprofloxacin (CIP) from water. Experimental outcomes showed a drastic enhancement of the adsorption and the equilibrium (which increased from 39.31 mg g–1 of bare BiOI to 76.39 mg g–1 of the best ternary composite in 2 h time), while the kinetics of the process was not significantly changed. The photocatalytic performance was also significantly enhanced, and the complete removal of 10 ppm of CIP in 3 h reaction time was recorded under simulated solar light irradiation for the best catalyst of the investigated batch. Catalytic reactions supported by different materials obeyed different reaction orders, indicating the existence of different mechanisms. The use of scavengers for superoxide anion radicals, holes, and hydroxyl radicals showed that although all these species are involved in CIP photodegradation, the latter play the most crucial role, as also confirmed by carrying out the reaction at increasing pH conditions. A clear correlation between the reduction of BiOI crystallite sizes in the composites, as compared to the bare material, and the material performance as both adsorbers and photocatalyst was identified. 

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2023
National Category
Physical Chemistry Materials Chemistry
Research subject
Energy Engineering; Experimental Physics; Waste Science and Technology
Identifiers
urn:nbn:se:ltu:diva-103204 (URN)10.1021/acsomega.3c06243 (DOI)
Funder
The Kempe Foundations, SMK-1974Knut and Alice Wallenberg FoundationBio4Energy
Note

Validerad;2023;Nivå 2;2023-12-11 (joosat);

License full text: CC BY

Available from: 2023-12-11 Created: 2023-12-11 Last updated: 2023-12-11Bibliographically approved
Jayawickrama, T. R., Chishty, M. A., Haugen, N. E., Babler, M. U. & Umeki, K. (2023). The effects of Stefan flow on the flow surrounding two closely spaced particles. International Journal of Multiphase Flow, 166, Article ID 104499.
Open this publication in new window or tab >>The effects of Stefan flow on the flow surrounding two closely spaced particles
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2023 (English)In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 166, article id 104499Article in journal (Refereed) Published
Abstract [en]

The aim of the work was to study the effects of neighboring particles with uniform Stefan flow in particle–fluid flows. Particle-resolved numerical simulations were carried out for particles emitting a uniform Stefan flow into the bulk fluid. The bulk fluid was uniform and isothermal. The Stefan flow volume emitted from the two particles is equal, such that it represents idealized conditions of reacting particles. Particles were located in tandem arrangement and particle distances were varied between 1.1 and 10 particle diameters (). Three particle Reynolds numbers were considered during the simulations ( and 14), which is similar to our previous studies. Three Stefan flow velocities were also considered during simulations to represent inward, outward, and no Stefan flow. The drag coefficient of the particles without Stefan flow showed that the results fit with previous studies on neighbor particle effects. When the particle distance is greater than 2.5 diameters (), the effects of Stefan flow and neighboring particles are independent of each other. I.e. an outward Stefan flow decreases the drag coefficient () while an inward Stefan flow increases it and the upstream particle experience a higher  than the downstream particle. When , the effect of Stefan flow is dominant, such that equal and opposite pressure forces act on the particles, resulting in a repelling force between the two neighboring particles. The pressure force showed a large increase compared to the viscous force at these distances. The effect of Stefan flow is weakened at higher Reynolds numbers. A model was developed for the calculation of the drag coefficient. The model, which reproduce the results from the numerical simulations presented above, is a product of independent models that describe the effects of both neighboring particles and two distinguished effects of the Stefan flow.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Drag coefficient, Stefan flow, Neighboring particles, Boundary layer, Multiphase reactive flow
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-97645 (URN)10.1016/j.ijmultiphaseflow.2023.104499 (DOI)2-s2.0-85159152810 (Scopus ID)
Funder
Swedish Research Council, (2018-05973, 2015-05588)EU, Horizon 2020, (764697)
Note

Validerad;2023;Nivå 2;2023-05-29 (joosat);

Funder: Swedish for Gasification Center; Research council of Norway (267916)

Licens fulltext: CC BY License

Available from: 2023-05-29 Created: 2023-05-29 Last updated: 2023-09-06Bibliographically approved
Kreitzberg, T., Phounglamcheik, A., Haugen, N. E., Kneer, R. & Umeki, K. (2022). A Shortcut Method to Predict Particle Size Changes during Char Combustion and Gasification under regime II Conditions. Combustion Science and Technology, 194(2), 272-291
Open this publication in new window or tab >>A Shortcut Method to Predict Particle Size Changes during Char Combustion and Gasification under regime II Conditions
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2022 (English)In: Combustion Science and Technology, ISSN 0010-2202, E-ISSN 1563-521X, Vol. 194, no 2, p. 272-291Article in journal (Refereed) Published
Abstract [en]

In most industrial applications, combustion and gasification of char progresses under regime II conditions. Unlike in other regimes, both particle size and density change simultaneously in regime II due to non-uniform consumption of carbon inside the particles. In this work, mathematical predictions of diameter changes in regime II were made by a one-dimensional simulation tool, where transient species balances are resolved locally inside the particle. This simulation is computationally expensive and usually not appropriate for the implementation in comprehensive CFD simulations of combustion or gasification processes. To overcome this restraint, an alternative shortcut method with affordable computation time has been developed and validated against the detailed model. This method allows the calculation of diameter changes during combustion and gasification from precalculated effectiveness factors. Additionally, the change of particle size has been investigated experimentally in a single particle converter setup. Therein, particles are fixed on a sample holder placed in the hot flue gas of a flat flame burner. Size and temperature trends are optically assessed by a 3CCD camera.

Place, publisher, year, edition, pages
Taylor & Francis, 2022
Keywords
combustion, gasification, char conversion, biomass, particle size change
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-76792 (URN)10.1080/00102202.2019.1678919 (DOI)000492714600001 ()2-s2.0-85074512914 (Scopus ID)
Funder
Bio4EnergySwedish Research CouncilThe Kempe FoundationsThe Research Council of Norway, 267916
Note

Validerad;2022;Nivå 2;2022-03-01 (sofila);

Funder: German Research Foundation (215035359); Swedish Center for Biomass Gasification

Available from: 2019-11-20 Created: 2019-11-20 Last updated: 2022-07-04Bibliographically approved
Yu, J., Xia, W., Areeprasertc, C., Ding, L., Umeki, K. & Yu, G. (2022). Catalytic effects of inherent AAEM on char gasification: A mechanism study using in-situ Raman. Energy, 238, part C, Article ID 122074.
Open this publication in new window or tab >>Catalytic effects of inherent AAEM on char gasification: A mechanism study using in-situ Raman
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2022 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 238, part C, article id 122074Article in journal (Refereed) Published
Abstract [en]

Despite a small proportion of mineral in coal, inherent alkali and alkaline earth metals (AAEM) catalytically affected thermal conversion of coal. The gasification of raw and leached coal char was investigated by using an operando microscopic Raman spectroscopy to explore the effect of content and chemical form of the inherent AAEM on morphology and carbon structure evolution of a single particle during in-situ char gasification. The removal of water-soluble and ion-exchangeable AAEM reduced the R0.5 of SF, NM and YN char by 53.31%, 49.09% and 35.02%, respectively. As a result, the shrinkage of leached coal char progressed slower than that of the raw coal char. Besides, both water-soluble and ion-exchangeable AAEM accelerated char gasification because of an inhibition of the orderly evolution of carbon structure. Higher gasification temperature weakened the catalytic performance of ion-exchangeable AAEM. With the consumption of carbon, carbon microcrystalline structure of the residual char tended to be ordered, which led to a decrease in active free carbon sites for gasification reaction. Kinetic analysis indicated both water-soluble and ion-exchangeable AAEM reduced the activation energy of SF, NM and YN char by 20.97, 20.82 and 9.38kJ∙mol-1, respectively, and the effect of ion-exchangeable AAEM was more significant.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
gasification, operando Raman, in-situ characterization, catalytic mechanism
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-87104 (URN)10.1016/j.energy.2021.122074 (DOI)000701789000013 ()2-s2.0-85115180165 (Scopus ID)
Note

Validerad;2021;Nivå 2;2021-09-23 (alebob);

Forskningsfinansiär: National Natural Science Foundation of China (21878093); National Key R&D Program of China (2017YFB0602601); Fund of Shanghai Science and Technology Committee (20230742400, 20PJ1402800); Fundamental Research Funds for the Central Universities (JKB012011013)

Available from: 2021-09-17 Created: 2021-09-17 Last updated: 2021-12-13Bibliographically approved
Umeki, K. (2022). Dataset - Self-Heating of Biochar during Postproduction Storage by O2 Chemisorption at Low Temperatures.
Open this publication in new window or tab >>Dataset - Self-Heating of Biochar during Postproduction Storage by O2 Chemisorption at Low Temperatures
2022 (English)Data set, Primary data
Abstract [en]

Biochar is attracting attention as an alternative carbon/fuel source to coal in the process industry and energy sector. However, it is prone to self-heating and often leads to spontaneous ignition and thermal runaway during storage, resulting in production loss and health risks. This study investigates biochar self-heating upon its contact with O2 at low temperatures, i.e., 50–300 °C. First, kinetic parameters of O2 adsorption and CO2 release were measured in a thermogravimetric analyzer using biochar produced from a pilot-scale pyrolysis process. Then, specific heat capacity and heat of reactions were measured in a differential scanning calorimeter. Finally, a one-dimensional transient model was developed to simulate self-heating in containers and gain insight into the influences of major parameters. The model showed a good agreement with experimental measurement in a closed metal container. It was observed that char temperature slowly increased from the initial temperature due to heat released during O2 adsorption. Thermal runaway, i.e., self-ignition, was observed in some cases even at the initial biochar temperature of ca. 200 °C. However, if O2 is not permeable through the container materials, the temperature starts decreasing after the consumption of O2 in the container. The simulation model was also applied to examine important factors related to self-heating. The results suggested that self-heating can be somewhat mitigated by decreasing the void fraction, reducing storage volume, and lowering the initial char temperature. This study demonstrated a robust way to estimate the cooling demands required in the biochar production process.

Keywords
biochar, self-heating, thermal runaway, O2 chemisorption, large-scale storages, packed-bed simulation
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-88668 (URN)
Available from: 2022-01-04 Created: 2022-01-04 Last updated: 2022-01-21
Dal Belo Takehara, M., Llamas, A. D., Chishty, M. A., Umeki, K. & Gebart, R. (2022). Effect of acoustic perturbation on particle dispersion in a swirl-stabilized pulverized fuel burner: Cold-flow conditions. Fuel processing technology, 228, Article ID 107142.
Open this publication in new window or tab >>Effect of acoustic perturbation on particle dispersion in a swirl-stabilized pulverized fuel burner: Cold-flow conditions
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2022 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 228, article id 107142Article in journal (Refereed) Published
Abstract [en]

Inter-particle distance and particle dispersion during gasification of biomass have been found to significantly affect soot emission. Consequently, enhanced particle dispersion decreases energy losses and the risk for blockages of downstream equipment, increasing the efficiency and reliability of entrained flow reactors (EFRs). In this work, we investigated the interactions between imposed acoustic oscillations and particle dispersion under non-reacting conditions in a co-axial burner for a lab-scale EFR. A flow of air, laden with pulverized stem wood particles (Norwegian Spruce) of three different sizes (63–112 μm, 200–250 μm, and 500–600 μm), was forced axially through the burner center tube at Reynolds numbers ranged from 800 to 1700, and loading ratio of 0.7–4.2. The influences on particle dispersion from variations of the Strouhal number (0.12–0.6), the pressure amplitude at synthetic jet cavity (0.5–4.0 kPap-p), the swirl number (0–2.3), and the center jet velocity (1.9–3.9 m s−1) were investigated. Post-processed shadowgraph images revealed the influence of acoustic perturbations, which generate large structures with high particle concentration for both swirling and non-swirling conditions. Time-averaged contour maps showed a significantly higher particle dispersion, quantified as dispersion angle, for higher values of forcing amplitude and swirl numbers, with a stronger influence from the forcing amplitude, especially at lower Stokes number.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Biomass, Acoustic excitation, Particle-laden flow, Particle dispersion, Gas-particle coaxial jets
National Category
Fluid Mechanics and Acoustics
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-88606 (URN)10.1016/j.fuproc.2021.107142 (DOI)000749923000004 ()2-s2.0-85121808061 (Scopus ID)
Funder
Swedish Energy Agency, 47485-1The Kempe Foundations, SMK-1632
Note

Validerad;2022;Nivå 2;2022-01-01 (johcin)

Available from: 2021-12-29 Created: 2021-12-29 Last updated: 2023-09-05Bibliographically approved
Dal Belo Takehara, M., Chishty, M. A., Umeki, K. & Gebart, R. (2022). Pulverized biomass flame under imposed acoustic oscillations: Flame morphology and emission characteristics. Fuel processing technology, 238, Article ID 107484.
Open this publication in new window or tab >>Pulverized biomass flame under imposed acoustic oscillations: Flame morphology and emission characteristics
2022 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 238, article id 107484Article in journal (Refereed) Published
Abstract [en]

Forced intermittent combustion with periodical variations of pressure, velocity, and air-fuel ratios is a promising method to increase efficiency and reduce emissions from combustion and gasification applications. In this work, flame characteristics and emissions from a pulverized biomass burner are investigated under oscillations induced by an acoustically-driven synthetic jet. Instantaneous images of incandescent light emitted from flame were captured using high-speed cameras. The images were analyzed to identify the liftoff distance, flame length, and shape. The flame liftoff distance decreased under excited conditions, notably at high forcing amplitude applied to small particle size distribution (63-112 μm). In such conditions, acoustic forcing increases particle dispersion as presented in the previous work, providing conditions for earlier ignition due to enhanced fuel-air mixing besides reducing CO emissions. Flue gas emissions were influenced mainly by the particle size distribution, from which the 63-112 μm particle size presented the lowest values of CO and highest levels of NO emissions. The results presented stable flame edge positions for the particle size of 63-112 μm, while wide range particle distributions (0–600, 0-400 μm) had strong fluctuations, indicating high flame instability. The experimental work adds new insights regarding acoustic excitation in swirl burners, which could be used to optimize pulverized fuel combustion.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Pulverized solid biomass, Acoustic excitation, Swirl stabilized burner, Particle-laden flow, Flame
National Category
Other Mechanical Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-93053 (URN)10.1016/j.fuproc.2022.107484 (DOI)000893047000004 ()2-s2.0-85138799832 (Scopus ID)
Funder
Swedish Energy Agency, 47485-1The Kempe Foundations, SMK-1632
Note

Validerad;2022;Nivå 2;2022-09-15 (joosat);

Available from: 2022-09-15 Created: 2022-09-15 Last updated: 2023-09-05Bibliographically approved
Llamas, Á. D., Guo, N., Li, T., Gebart, R. & Umeki, K. (2022). Rapid change of particle velocity due to volatile gas release during biomass devolatilization. Combustion and Flame, 238, Article ID 111898.
Open this publication in new window or tab >>Rapid change of particle velocity due to volatile gas release during biomass devolatilization
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2022 (English)In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 238, article id 111898Article in journal (Refereed) Published
Abstract [en]

Our earlier study showed significant differences in average particle velocity between simulation and experimental results for devolatilizing biomass particles in an idealised entrained flow reactor [N. Guo et al., Fuel, 2020]. This indicates that the simulations do not accurately describe the physicochemical transformations and fluid dynamic processes during devolatilization. This article investigates the reasons for these discrepancies using time-resolved analyses of the experimental data and complementary modelling work. The experiments were conducted in a downdraft drop-tube furnace with optical access, which uses a fuel-rich flat flame (CH4 O2 CO2) to heat the particles. Gas flow was characterized using particle image velocimetry, equilibrium calculations and thermocouple measurements. High-speed images of devolatilizing Norway spruce (Picea Abies) particles were captured and analysed using time-resolved particle tracking velocimetry methods. The data were used to estimate the balance of forces and fuel conversion. Thrust and “rocket-like” motions were frequently observed, followed by quick entrainment in the gas flow. Rocketing particles were, on average, smaller, more spherical and converted faster than their non-rocketing counterparts. These differences in conversion behaviour could be captured by a particle-size dependent, 0-D devolatilization model, corrected for non-isothermal effects. The results from this investigation can provide a basis for future modelling and simulation work relevant for pulverized firing technologies.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Biomass devolatilization, TR-PTV, In-situ measurements, Rocket effect, Non-isothermal modelling
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-88625 (URN)10.1016/j.combustflame.2021.111898 (DOI)000735744600001 ()2-s2.0-85121437396 (Scopus ID)
Note

Validerad;2022;Nivå 2;2022-01-01 (johcin)

Available from: 2021-12-30 Created: 2021-12-30 Last updated: 2022-01-28Bibliographically approved
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