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Internal Tar/CH4 Reforming in Biomass Dual Fluidised Bed Gasifiers towards Fuel Synthesis
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. (Bioenergy - gasification)
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Production of high-quality syngas from biomass gasification in a dual fluidised bed gasifier (DFBG) has made a significant progress in R&D and Technology demonstration. An S&M scale bio-automotive fuel plant close to the feedstock resources is preferable as biomass feedstock is widely sparse and has relatively low density, low heating value and high moisture content. This requires simple, reliable and cost-effective production of clean and good syngas. Indirect DFBGs, with steam as the gasification agent, produce a syngas of high content H2 and CO with 12-20 MJ/mn3 heating value. The Mid Sweden University (MIUN) gasifier, built for research on synthetic fuel production, is a dual fluidised bed gasifier. Reforming of tars and CH4 (except for methanation application) in the syngas is a major challenge for commercialization of biomass fluidised-bed gasification technology towards automotive fuel production. A good syngas from DFBGs can be obtained by optimised design and operation of the gasifier, by the use of active catalytic bed material and internal reforming. This thesis presents a series of experimental tests with different operation parameters, reforming of tar and CH4 with catalytic bed material and reforming of tar and CH4 with catalytic internal reformer.

 

The first test was carried out to evaluate the optimal operation and performance of the MIUN gasifier. The test provides basic information for temperature control in the combustor and the gasifier by the bed material circulation rate.

 

 After proven operation and performance of the MIUN gasifier, an experimental study on in-bed material catalytic reforming of tar/CH4 is performed to evaluate the catalytic effects of the olivine and Fe-impregnated olivine (10%wtFe/olivine Catalyst) bed materials, with reference to non-catalytic silica sand operated in the mode of dual fluidised beds (DFB). A comparative experimental test is then carried out with the same operation condition and bed-materials but when the gasifier was operated in the mode of single bubbling fluidised bed (BFB). The behaviour of catalytic and non-catalytic bed materials differs when they are used in the DFB and the BFB. Fe/olivine and olivine in the BFB mode give lower tar and CH4 content together with higher H2+CO concentration, and higher H2/CO ratio, compared to DFB mode. It is hard to show a clear advantage of Fe/olivine over olivine regarding tar/CH4 catalytic reforming. 

 

In order to significantly reduce the tar/CH4 contents, an internal reformer, referred to as the FreeRef reformer, is developed for in-situ catalytic reforming of tar and CH4 using Ni-catalyst in an environment of good gas-solids contact at high temperature.  A study on the internal reformer filled with and without Ni-catalytic pellets was carried out by evaluation of the syngas composition and tar/CH4 content. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases from 25 g/m3 down to 5 g/m3 and the CH4 content from 11% down below 6% in the syngas.

 

The MIUN gasifier has a unique design suitable for in-bed tar/CH4 catalytic reforming and continuously internal regeneration of the reactive bed material. The novel design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas composition. 

 

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2014. , 61 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 187
Keyword [en]
Allothermal gasification, Bio-automotive fuels, Biomass gasification, Catalytic bed-material, Dual fluidised bed, Ni-catalyst, Syngas cleaning, Tar removal, Tar/CH4 reforming
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-22984ISBN: 978-91-87557-58-3 (print)OAI: oai:DiVA.org:miun-22984DiVA: diva2:746821
Public defence
2014-05-19, N109, Holmgatan 10, Sundsvall, 10:32 (English)
Opponent
Supervisors
Projects
Gasification-based Biorefinery for Mechanical Pulp Mills
Available from: 2014-09-15 Created: 2014-09-15 Last updated: 2015-03-13Bibliographically approved
List of papers
1. Review of syngas production via biomass DFBGs
Open this publication in new window or tab >>Review of syngas production via biomass DFBGs
2011 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, Vol. 15, no 1, 482-492 p.Article, review/survey (Refereed) Published
Abstract [en]

Production of high-quality syngas from biomass gasification in a dual fluidised bed gasifier (DFBG) has made a significant progress in R&D and Technology demonstration. An S&M scale bio-automotive fuel plant close to the feedstock resources is preferable as biomass feedstock is widely sparse and has relatively low density, low heating value and high moisture content. This requires a simple, reliable and cost-effective production of clean and good quality syngas. Indirect DFBGs, with steam as the gasification agent, produces a syngas of high content H2 and CO with 12-20 MJ/mn3 heating value. A good quality syngas from DFBGs can be obtained by optimised design and operation of the gasifier, by the use of active catalytic bed materials including internal reforming of tars and methane, and finally by a downstream cleaning process. This article reviews the whole process from gasification to high quality syngas. © 2010 Elsevier Ltd. All rights reserved.

Keyword
Allothermal gasification; Bio-automotive fuels; Biomass; Gasifier and syngas
National Category
Other Environmental Engineering
Identifiers
urn:nbn:se:miun:diva-12205 (URN)10.1016/j.rser.2010.09.032 (DOI)000284863100032 ()2-s2.0-78149409758 (Scopus ID)
Available from: 2010-11-03 Created: 2010-11-03 Last updated: 2014-09-16Bibliographically approved
2. Experimental test on a novel dual fluidised bed biomass gasifier for synthetic fuel production
Open this publication in new window or tab >>Experimental test on a novel dual fluidised bed biomass gasifier for synthetic fuel production
2011 (English)In: Fuel, ISSN 0016-2361, Vol. 90, no 4, 1340-1349 p.Article in journal (Refereed) Published
Abstract [en]

This article presents a preliminary test on the 150 kWth allothermal biomass gasifier at MIUN (Mid Sweden University) in Härnösand, Sweden. The MIUN gasifier is a combination of a fluidised bed gasifier and a CFB riser as a combustor with a design suitable for in-built tar/CH4 catalytic reforming. The test was carried out by two steps: 1) fluid-dynamic study; 2) measurements of gas composition and tar. A novel solid circulation measurement system which works at high bed temperatures is developed in the presented work. The results show the dependency of bed material circulation rate on the superficial gas velocity in the combustor, the bed material inventory and the aeration of solids flow between the bottoms of the gasifier and the combustor. A strong influence of circulation rate on the temperature difference between the combustor and the gasifier was identified. The syngas analysis showed that, as steam/biomass (S/B) ratio increases, CH4 content decreases and H2/CO ratio increases. Furthermore the total tar content decreases with increasing steam/biomass ratio and increasing temperature.  The biomass gasification technology at MIUN is simple, cheap, reliable, and can obtain a syngas of high CO+H2concentration with sufficient high ratio of H2 to CO, which may be suitable for synthesis of Methane, DME, FT-fuels or alcohol fuels. The measurement results of MIUN gasifier have been compared with other gasifiers. The main differences can be observed in the H2 and the CO content, as well as the tar content. These can be explained by differences in the feed systems, operating temperature, S/B ratio or bed material catalytic effect etc..

Keyword
allothermal gasification, biofuel, biomass, gasifier, syngas
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-12907 (URN)10.1016/j.fuel.2010.12.035 (DOI)000287652300004 ()2-s2.0-79951921720 (Scopus ID)
Projects
Development of BTL towards small scale automotive fuel plants
Available from: 2010-12-29 Created: 2010-12-29 Last updated: 2014-09-15Bibliographically approved
3. Simulation of biomass gasification in a dual fluidized bed gasifier
Open this publication in new window or tab >>Simulation of biomass gasification in a dual fluidized bed gasifier
2012 (English)In: Biomass Conversion and Biorefinery, ISSN 2190-6815, E-ISSN 2190-6823, Vol. 2, no 1, 1-10 p.Article in journal (Refereed) Published
National Category
Bioenergy
Identifiers
urn:nbn:se:miun:diva-16182 (URN)10.1007/s13399-011-0030-2 (DOI)2-s2.0-84978021765 (Scopus ID)
Available from: 2012-05-07 Created: 2012-05-04 Last updated: 2017-07-04Bibliographically approved
4. Internal tar/CHreforming in a biomass dual fluidised bed gasifier.
Open this publication in new window or tab >>Internal tar/CHreforming in a biomass dual fluidised bed gasifier.
Show others...
2015 (English)In: Biomass Conversion and Biorefinery, ISSN 2190-6815, Vol. 5, 355-366 p.Article in journal (Refereed) Published
Abstract [en]

An internal reformer is developed for in situ catalyticreforming of tar and methane (CH4) in allothermal gasifiers.The study has been performed in the 150 kW dual fluidised bed (DFB) biomass gasifier at Mid Sweden University(MIUN). The MIUN gasifier is built for research onsynthetic fuel production. Reduction of tars and CH4 (exceptfor methanation application) in the syngas is a major challengefor commercialization of biomass fluidised-bed gasificationtechnology towards automotive fuel production. The MIUN gasifier has a unique design with an internal reformer, where intensive contact of gas and catalytic solids improves the reforming reactions. This paper presents an initial study on the internal reformer operated with and without Ni-catalytic pellets, by evaluation of the syngas composition and tar/CH4 content. A novel application of Ni-catalyst in DFB gasifiers is proposed and studied in this work. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases down to 5 g/m3 and the CH4 content down below 6 % in the syngas. The tar content can be decreased further to lower levels, with increased gas contact to the specific surface area of the catalyst and increased catalyst surface-to-volume ratio. The new design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas quality.

Keyword
Biomass gasification, Syngas cleaning, Tar removal, Tar/CH4 reformning, Dual fluidised bed, Ni-catalyst
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-23247 (URN)10.1007/s13399-014-0151-5 (DOI)2-s2.0-84978026015 (Scopus ID)
Note

Published online 2nd Oct 2014.

Available from: 2014-10-17 Created: 2014-10-17 Last updated: 2016-09-22Bibliographically approved

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