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Modeling in Biomass Harvesting, Biomass Pyrolysis and Producer Gas Cleaning
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.ORCID iD: 0000-0002-1881-2686
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biomass is a viable alternative in order to mitigate the environmental effectscaused by the aggressive use of fossil feedstock during the last century.This thesis builds around the idea of a biofuel production process that iscomprised of biomass production, biomass gasication, gas cleaning andfuel production. Biomass production includes microalgae synthesis followedby harvesting to supply microalgae to the gasication process. In the gasi-cation process, the prepared microalgae is dried, pyrolyzed and gasiedto obtain a producer gas containing syngas and impurities. The producergas is cleaned from the impurities and fed to a fuel production unit, e.g. amethanation process.This thesis investigates three distinct aspects related to this processscheme, namely the occulation of microalgae as part of harvesting, biomasspyrolysis as a part of gasication, and sulfur removal from the producer gasas a part of gas cleaning.The investigation of occulation focuses on secondary phenomena thataccompany the aggregation and breakup of the suspended particles, namelyrestructuring, decay of oc strength and settling. For the study of theconsidered phenomena, a population balance model is developed.Slow pyrolysis of biomass is studied on both the reactor scale and thepellet scale. A model for a rotary drum reactor, using principles of isoconversionalanalysis, is developed for the study of dierent biomass feedstock.The proposed model allows for deriving a preliminary reactor design withminimal experimental input data. A one-dimensional nite volume schemeis developed for the investigation of pyrolysis on the pellet scale. The proposedscheme accounts for convective and diusive heat and mass transfer,and is tested against analytical solutions and commercial software packages.Sulfur removal by metal oxides in a packed bed is studied on both thesystem level and the process level. Criteria for the selection of metal oxidesand the design of packed bed units are derived. A detailed analysis isundertaken to study the reaction of H2S with ZnO in a packed bed, wherethe nano-particles of ZnO experience void formation and outward growth.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. , p. 80
Series
TRITA-CBH-FOU ; 2019:65
Keywords [en]
PBE modeling of flocculation; Pyrolysis in Rotary Kilns; Pellet Pyrolysis; Gas Cleaning; Desulfurization.
National Category
Chemical Process Engineering
Identifiers
URN: urn:nbn:se:kth:diva-263085ISBN: 978-91-7873-367-5 (print)OAI: oai:DiVA.org:kth-263085DiVA, id: diva2:1366405
Public defence
2019-11-28, Kollegiesalen, Brinellv. 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 2019-10-29

Available from: 2019-10-29 Created: 2019-10-29 Last updated: 2019-11-06Bibliographically approved
List of papers
1. Mechanisms behind overshoots in mean cluster size profiles in aggregation-breakup processes
Open this publication in new window or tab >>Mechanisms behind overshoots in mean cluster size profiles in aggregation-breakup processes
2018 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 528, p. 336-348Article in journal (Refereed) Published
Abstract [en]

Aggregation and breakup of small particles in stirred suspensions often shows an overshoot in the time evolution of the mean cluster size: Starting from a suspension of primary particles the mean cluster size first increases before going through a maximum beyond which a slow relaxation sets in. Such behavior was observed in various systems, including polymeric latices, inorganic colloids, asphaltenes, proteins, and, as shown by independent experiments in this work, in the flocculation of microalgae. This work aims at investigating possible mechanism to explain this phenomenon using detailed population balance modeling that incorporates refined rate models for aggregation and breakup of small particles in turbulence. Four mechanisms are considered: (1) restructuring, (2) decay of aggregate strength, (3) deposition of large clusters, and (4) primary particle aggregation where only aggregation events between clusters and primary particles are permitted. We show that all four mechanisms can lead to an overshoot in the mean size profile, while in contrast, aggregation and breakup alone lead to a monotonic, "S" shaped size evolution profile. In order to distinguish between the different mechanisms simple protocols based on variations of the shear rate during the aggregation-breakup process are proposed.

Place, publisher, year, edition, pages
Academic Press, 2018
Keywords
Population balance modeling, Colloidal aggregation, Shear aggregation, Aggregate breakup, Restructuring, Flocculation, Fractal aggregates, Turbulence
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-233260 (URN)10.1016/j.jcis.2018.05.064 (DOI)000440127000036 ()29885609 (PubMedID)2-s2.0-85048509507 (Scopus ID)
Funder
Swedish Research Council, 2012-6216
Note

QC 20180817

Available from: 2018-08-17 Created: 2018-08-17 Last updated: 2019-10-29Bibliographically approved
2. Modeling of slow pyrolysis of various biomass feedstock in a rotary drum using TGA data
Open this publication in new window or tab >>Modeling of slow pyrolysis of various biomass feedstock in a rotary drum using TGA data
2018 (English)In: Chemical Engineering and Processing, ISSN 0255-2701, E-ISSN 1873-3204, Vol. 129, p. 95-102Article in journal (Refereed) Published
Abstract [en]

Design and optimization of biomass gasification faces the challenge of feedstock variation. Specifically, design calculations require kinetic rate expressions for the given feedstock, whose rigorous determination is demanding and often exceeds available recourses in an early development stage. In this work, we model the slow pyrolysis of biomass for the production of biochar. The aim is to predict the conversion of raw biomass to biochar as a function of the process conditions. Here, we will show that TGA data processed with an isoconversional method is enough to obtain an effective rate expression which allows for predicting the behavior of the biomass at an arbitrary temperature evolution. Such rate expressions can then be used in the process model to simulate conversion of raw biomass to biochar. To illustrate the feasibility of this approach we consider four vastly different biomass, namely spruce wood, pulp, lignin and xylan–lignin, undergoing slow pyrolysis in an indirectly heated rotary kiln reactor. The results of our modeling are compared to experimental data obtained from a 500 kW pilot plant pyrolyzer and to a more detailed process model.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Biomass pyrolysis, Isoconversional, Process model, Rotary drum
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-228722 (URN)10.1016/j.cep.2018.05.002 (DOI)000435059000012 ()2-s2.0-85047165839 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20180530

Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2019-10-29Bibliographically approved
3. 1D finite volume scheme for simulating gas-solid reactions in a porous spherical particle
Open this publication in new window or tab >>1D finite volume scheme for simulating gas-solid reactions in a porous spherical particle
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:kth:diva-263084 (URN)
Note

QC 20191104

Available from: 2019-10-29 Created: 2019-10-29 Last updated: 2019-11-06Bibliographically approved
4. A Medium-Scale 50 MWfuel Biomass Gasification Based Bio-SNG Plant: A Developed Gas Cleaning Process
Open this publication in new window or tab >>A Medium-Scale 50 MWfuel Biomass Gasification Based Bio-SNG Plant: A Developed Gas Cleaning Process
2015 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, no 6, p. 5287-5302Article in journal (Refereed) Published
Abstract [en]

Natural gas is becoming increasingly important as a primary energy source. A suitable replacement for fossil natural gas is bio-SNG, produced by biomass gasification, followed by methanation. A major challenge is efficient gas cleaning processes for removal of sulfur compounds and other impurities. The present study focuses on development of a gas cleaning step for a product gas produced in a 50 MWfuel gasification system. The developed gas cleaning washing process is basically a modification of the Rectisol process. Several different process configurations were evaluated using Aspen plus, including PC-SAFT for the thermodynamic modeling. The developed configuration takes advantage of only one methanol wash column, compared to two columns in a conventional Rectisol process. Results from modeling show the ability of the proposed configuration to remove impurities to a sufficiently low concentrations - almost zero concentration for H2S, CS2, HCl, NH3 and HCN, and approximately 0.01 mg/Nm(3) for COS. These levels are acceptable for further upgrading of the gas in a methanation process. Simultaneously, up to 92% of the original CO2 is preserved in the final cleaned syngas stream. No process integration or economic consideration was performed within the scope of the present study, but will be investigated in future projects to improve the overall process.

National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-172500 (URN)10.3390/en8065287 (DOI)000357489700033 ()2-s2.0-84933558353 (Scopus ID)
Note

QC 20150825

Available from: 2015-08-25 Created: 2015-08-25 Last updated: 2019-10-29Bibliographically approved
5. Removal of hydrogen sulfide with metal oxides inpacked bed reactors - a review from modelingperspective with practical implications
Open this publication in new window or tab >>Removal of hydrogen sulfide with metal oxides inpacked bed reactors - a review from modelingperspective with practical implications
(English)Manuscript (preprint) (Other academic)
Keywords
Hydrogen sulfide; Metal oxides; Gas cleaning; Packed bed modeling
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:kth:diva-263082 (URN)
Note

QC 20191104

Available from: 2019-10-29 Created: 2019-10-29 Last updated: 2019-11-04Bibliographically approved
6. Numerical investigation of the outward growth of ZnS in the removal of H2S in a packed bed of ZnO
Open this publication in new window or tab >>Numerical investigation of the outward growth of ZnS in the removal of H2S in a packed bed of ZnO
2017 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 158, p. 328-339Article in journal (Refereed) Published
Abstract [en]

Sulfidation of zinc oxide is a viable option for the removal of hydrogen sulfide from raw syngas and biogas. Recent experiments showed that sulfidation of nanoscopic zinc oxide particles leads to an outward growth and the formation of voids inside the particles. In this work, we derive a micro-scale model to describe this phenomenon. The model accounts for nucleation and growth of voids inside the particles, diffusion of Zn and O through the product layer, and deposition of the solid product at the particle surface as a result of the reaction between ZnO and H2S. The model is thus opposite to the well known shrinking core model where an inward growth of the product layer is assumed. To explore the effect of the outward growth on the dynamics of a packed bed adsorber the micro-scale model is combined with a macro-scale model that accounts for intra-pellet diffusion and convection along the packed bed. In the limit of fast nucleation and growth of voids inside the zinc oxide particles, the micro-scale model shows a qualitatively similar conversion profile to the shrinking core model, while when nucleation controls an inflection point in conversion profile is found. On the macro-scale, the outward growth can cause the clogging of pores inside the pellets which prevents the pellets from reaching full conversion. This leads to shorter breakthrough times of the packed bed due to the sealing of unreacted zinc oxide. Our results thus provide a possible explanation of the incomplete conversion of zinc oxide in packed beds.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Gas-solid reaction, Syngas cleaning, H2S removal, ZnO sulfidation, Outward growth, Hollow particles
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-199459 (URN)10.1016/j.ces.2016.10.038 (DOI)000389068900033 ()2-s2.0-84993996109 (Scopus ID)
Note

QC 20170123

Available from: 2017-01-23 Created: 2017-01-09 Last updated: 2019-10-29Bibliographically approved

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1213141516171815 of 32
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