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Numerical Modeling of Cyclone Gasification
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.ORCID-id: 0000-0001-7184-839x
2018 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The current work aims to make a numerical model for an engineering design of anindustrial cyclone gasifier called as the Hortlax plant with capacity of providing 2.4 (MWth)of district heating as well as 1.3 (MW) of electricity. The model is needed to be able not onlyto predict the gasifier flow field with a suitable accuracy but also to investigate a largenumber of design alternatives with limited computer resources.The time-dependent single-phase flow field in a cyclone at first was simulated by usingseveral popular turbulence models including standard k-epsilon and SST models withcurvature correction, SSG-RSM and LES Smagorinsky models. The goal was to find the mostappropriate turbulence modeling as a foundation for the further works. Averaged andfluctuating parts of the simulated velocity component profiles from different turbulencemodels were compared with each other and the LDA measurements from literature.Comparison showed that the SSG-RSM can be the best alternative for the future simulations.An isothermal time-dependent Eulerian-Lagrangian particle modeling was implemented asthe second step for simulating particle-laden cold flow in the Hortlax gasifier. The impacts ofparticle-to-gas coupling on the pressure and velocity of the flow and particles motion insidethe gasifier were studied. The model could reasonably predict the particle tracking aspresented in the experimental results from the literature. High temperature of the gas flowinside the gasifier had quite important effects on the reduction of swirl and turbulenceintensity especially in the core region, pressure and particle behaviors. However, the presenceof solid particles did not influence the swirl intensity and turbulence significantly.The Hortlax gasifier was moreover experimentally studied in order to optimize thegasification plant efficiency, and understand the effect of operating. The air stoichiometricratio was varied to find the optimal condition for the plant. Moreover, the gasification processwas modeled using adiabatic thermodynamic equilibrium to see how far the process is fromequilibrium condition. Five different commercially available fuels were also studied usingequilibrium calculations. It was found that the gasifier is needed to work under the processtemperature of 1000 °C and stoichiometric ratio of 0.3, since at higher temperature the ash ismelted that is seriously avoided in the cyclone gasifier. Accordingly, the amount of undesiredmethane in the produced gas is quite high and the gasification efficiency is relatively lowaround 56%. Although the process does not reach equilibrium, it was seen thatthermodynamic equilibrium could compare the fuels performance almost close to theexperiments.

Ort, förlag, år, upplaga, sidor
Luleå: Luleå tekniska universitet, 2018. , s. 30
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Nationell ämneskategori
Energiteknik
Forskningsämne
Energiteknik
Identifikatorer
URN: urn:nbn:se:ltu:diva-70753ISBN: 978-91-7790-193-8 (tryckt)ISBN: 978-91-7790-194-5 (digital)OAI: oai:DiVA.org:ltu-70753DiVA, id: diva2:1245140
Handledare
Tillgänglig från: 2018-09-05 Skapad: 2018-09-04 Senast uppdaterad: 2020-01-23Bibliografiskt granskad
Delarbeten
1. Turbulence Modelling of a Single-Phase Flow Cyclone Gasifier
Öppna denna publikation i ny flik eller fönster >>Turbulence Modelling of a Single-Phase Flow Cyclone Gasifier
2017 (Engelska)Ingår i: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 9, nr 9, s. 779-799, artikel-id 79329Artikel i tidskrift, Editorial material (Refereegranskat) Published
Abstract [en]

The current work aims to make a foundation for an engineering design of a cyclone gasifier to be able not only to predict its flow field with a suitable accuracy but also to investigate a large number of design alternatives with limited computer resources. A good single-phase flow model that can form the basis in an Euler-Lagrange model for multi-phase flow is also necessary for modelling the reacting flow inside a cyclone gasifier. The present paper provides an objective comparison between several popular turbulence modelling options including standard k-ε and SST with curvature corrections, SSG-RSM and LES Smagorinsky models, for the single-phase flow inside cyclone separators/gasifiers that can serve as a guide for further work on the reacting multi-phase flow inside cyclone gasifiers and similar devices. A detailed comparison between the models and experimental data for the mean velocity and fluctuating parts of the velocity profiles are presented. Furthermore, the capabilities of the turbulence models to capture the physical phenomena present in a cyclone gasifier that affects the design process are investigated.

Ort, förlag, år, upplaga, sidor
Scientific Research Publishing, 2017
Nyckelord
Cyclone Gasifier, Turbulence Modelling, Swirling Flow Pattern, Secondary Flow
Nationell ämneskategori
Energiteknik Strömningsmekanik och akustik
Forskningsämne
Energiteknik; Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-66442 (URN)10.4236/eng.2017.99047 (DOI)
Anmärkning

Validerad;2017;Nivå 1;2017-11-10 (andbra)

Tillgänglig från: 2017-11-07 Skapad: 2017-11-07 Senast uppdaterad: 2020-01-23Bibliografiskt granskad
2. Modeling of Particle-Laden Cold Flow in a Cyclone Gasifier
Öppna denna publikation i ny flik eller fönster >>Modeling of Particle-Laden Cold Flow in a Cyclone Gasifier
2018 (Engelska)Ingår i: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 141, nr 2, artikel-id 021302Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Isothermal transient Eulerian–Lagrangian simulation of the turbulent gas–solid flow in a cyclone gasifier with two inlet tubes at 890 °C has been performed. The single-phase gas flow is modeled using SSG Reynolds stress turbulence model. Ten thousand representative solid particles of different sizes are injected from each inlet continuously at every second of simulation time. Particles are finally stopped as soon as they arrive at the outlet or reach the bottom plate of the gasifier. The effect of particle-to-gas coupling on the pressure and velocity of the flow and particles motion inside the gasifier is studied. The numerical approach can reasonably predict the impact of particle load on the gas flow as presented in the experimental results. Single particles are traveled throughout the transient gas flow field by using Lagrangian approach. High temperature of the gas flow inside the gasifier has significant effects on the swirl intensity reduction, damping the turbulence in the core region, pressure, and particle behaviors. However, the presence of solid particles does not have a notable influence on the swirl intensity and turbulence.

Ort, förlag, år, upplaga, sidor
The American Society of Mechanical Engineers (ASME), 2018
Nationell ämneskategori
Teknik och teknologier Energiteknik Strömningsmekanik och akustik
Forskningsämne
Energiteknik; Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-70480 (URN)10.1115/1.4040929 (DOI)000452773200012 ()2-s2.0-85052003087 (Scopus ID)
Anmärkning

Validerad;2018;Nivå 2;2018-08-31 (svasva)

Tillgänglig från: 2018-08-17 Skapad: 2018-08-17 Senast uppdaterad: 2020-01-23Bibliografiskt granskad

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