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Energy and Exergy Analysis of High Temperature Agent Gasification of Biomass
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.ORCID iD: 0000-0002-1837-5439
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
2014 (English)In: Energies, ISSN 1996-1073, Vol. 7, no 4, 2107-2122 p.Article in journal (Refereed) Published
Abstract [en]

A chemical equilibrium model was developed to predict the product composition of a biomass gasification system using highly preheated air and steam. The advantages and limitations of this system were discussed from a thermodynamic viewpoint. The first and second law analyses have been conducted for various preheating temperatures and steam/biomass mass (S/B) ratios. The results demonstrated that the chemical energy output of the produced syngas is highest when the S/B ratio is 1.83 under the conditions used in this study. However, higher S/B ratios have a negative effect on the energy and exergy efficiencies. Higher preheating temperatures increase the chemical energy of the produced syngas and the two efficiencies. The peak values for the energy and exergy efficiencies are 81.5% and 76.2%, respectively. Based on the calculated limitation values, where the highest chemical energy (exergy) of the produced syngas and maximum achievable efficiencies are determined, a thermodynamically possible operating region is suggested.

Place, publisher, year, edition, pages
2014. Vol. 7, no 4, 2107-2122 p.
Keyword [en]
biomass gasification, high temperature agent, Aspen model, exergy
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-147061DOI: 10.3390/en7042107ISI: 000336217000013ScopusID: 2-s2.0-84899138296OAI: diva2:728922

QC 20140625

Available from: 2014-06-25 Created: 2014-06-23 Last updated: 2014-07-11Bibliographically approved
In thesis
1. Computational Fluid Dynamics Modeling of Biomass Gasification in Fixed-bed Reactors Using Highly Preheated Agent
Open this publication in new window or tab >>Computational Fluid Dynamics Modeling of Biomass Gasification in Fixed-bed Reactors Using Highly Preheated Agent
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biomass gasification is considered to be one of the most promising energy recovery technologies for the widespread utilization of biomass. Mathematical models have been developed to understand the gasification process inside gasifiers. As the oldest type of gasifier, fixed-bed gasifiers have been widely studied by using zero-dimensional and one-dimensional models; however, only a limited number of two-dimensional models for this type of reactor can be found in existing literature.

The primary goal of this thesis is to develop a two-dimensional computational fluid dynamics (2-D CFD) model for fixed-bed gasifiers that considers the complex kinetic mechanisms, the flow field, and a series of chemical reactions inside gasifiers. The model was evaluated for both downdraft and updraft fixed-bed gasifiers through comparison with existing data from a demonstration-scale high temperature agent gasification (HTAG) system. The results demonstrated that this model can reasonably predict the performance of fixed-bed gasifiers when high-temperature air/steam is used as the gasifying agent. The performances of fixed-bed gasifiers were also discussed under the framework of HTAG technology. This CFD model is a potentially powerful tool for analyzing the performance sensitivity of a fixed-bed gasifier, which will further aid in the design and operation of this type of system.

Biomass should be produced in an ecologically and economically sustainable manner. Therefore, the optimization of the gasification process was further studied to improve gasification performance and efficiency. A zero-dimensional kinetic-free model was introduced based on an updraft fixed-bed gasifier. A thermodynamic analysis was conducted based on the first and second laws of thermodynamics for various S/B ratios and preheating temperatures of the gasifying agent. A practical operating region for the HTAG process was proposed for industrial applications.

According to the results, the HTAG technology relies on an external heat source and uses super-heated air combined with steam; this results in a limited need for feedstock combustion and produces syngas with a high H2 fraction and a low tar content. Based on energy and exergy efficiency analyses from a HTAG application, plasma melting of municipal solid waste (MSW), HTAG technology is demonstrated to be preferable from environmental and energy (exergy) efficiency perspectives.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. x, 63 p.
biomass, high temperature agent gasification, CFD modeling, exergy efficiency
National Category
Engineering and Technology Energy Systems
Research subject
Energy Technology
urn:nbn:se:kth:diva-147988 (URN)ISBN 978-91-7595-207-9 (ISBN)
Public defence
2014-08-29, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20140711

Available from: 2014-07-11 Created: 2014-07-11 Last updated: 2014-07-11Bibliographically approved

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Wu, YueshiYang, WeihongBlasiak, Wlodzimierz
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