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Characterization of particulate matter from atmospheric fluidized bed biomass gasifiers
Linnaeus University, Faculty of Science and Engineering, School of Engineering.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Through biomass gasification, biomass can be converted at high temperature to a product gas rich in carbon monoxide, hydrogen, and methane. After cleaning and upgrading, the product gas can be converted to biofuels such as hydrogen; methanol; dimethyl ether; and synthetic diesel, gasoline, and natural gas. Particulate matter (PM) is formed as a contaminant in the gasification process, and the aim of this work was to develop and apply a method for sampling and characterization of PM in the hot product gas.

 

A particle measurement system consisting of a dilution probe combined in series with a bed of granular activated carbon for tar adsorption was developed, with the aim of extracting a sample of the hot product gas without changing the size distribution and composition of the PM. The mass size distribution and concentration, as well as the morphology and elementary composition, of PM in the size range 10 nm to 10 µm in the product gas from a bubbling fluidized bed (BFB) gasifier, a circulating fluidized bed (CFB) gasifier and an indirect BFB gasifier using various types of biomass as fuel were determined.

 

All gasifiers and fuels displayed a bimodal particle mass size distribution with a fine mode in the <0.5 µm size range and a coarse mode in the >0.5 µm size range. Compared with the mass concentration of the coarse mode the mass concentration of the fine mode was low from all gasifiers. The evaluation of the results for the fine-mode PM was complicated by condensing potassium chloride for the CFB gasifier when using miscanthus as fuel and by condensing tars for the indirect BFB gasifier when using wood C as fuel. The mass concentration of the coarse-mode PM was higher from the CFB gasifier than from the two BFB gasifiers. The coarse-mode PM from the BFB gasifier when using wood A as fuel was dominated by char. In the CFB gasifier the coarse-mode PM was mainly ash and bed material when using all fuels. The coarse-mode PM from the indirect BFB gasifier when using wood C as fuel was mainly ash.

Place, publisher, year, edition, pages
Växjö, Kalmar: Linnaeus University Press , 2011.
Series
Linnaeus University Dissertations, 50/2011
Keyword [en]
biomass gasification, fluidized bed, particulate matter, particle morphology, particle elementary composition
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
URN: urn:nbn:se:lnu:diva-11473ISBN: 978-91-86491-80-2OAI: oai:DiVA.org:lnu-11473DiVA: diva2:412937
Public defence
2011-05-27, Wicksell, Linnéuniversitetet, 351 95 Växjö, Växjö, 10:00 (English)
Opponent
Supervisors
Available from: 2011-04-27 Created: 2011-04-27 Last updated: 2011-05-02Bibliographically approved
List of papers
1. Method for High-Temperature Particle Sampling in Tar-Rich Gases from the Thermochemical Conversion of Biomass
Open this publication in new window or tab >>Method for High-Temperature Particle Sampling in Tar-Rich Gases from the Thermochemical Conversion of Biomass
2010 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 24, no 3, 2042-2051 p.Article in journal (Refereed) Published
Abstract [en]

The thermochemical conversion of biomass produces compounds in both gas and particle phases that may be regarded as contaminants. These contaminants include both particulate matter (e.g., fly ash, soot, and fragmented nonvolatilized material) and volatilized metals and tars that condense and form particulate matter during cooling. In this study a method for high-temperature particle sampling in tar-rich gases from the thermochemical conversion of biomass was developed and tested. Both a bed of granular activated carbon and a denuder were used for tar adsorption. First, the transport efficiency of particles was determined both theoretically and experimentally using a K2SO4 reference aerosol, and the losses were found to be smaller in the denuder than in the bed of granular activated carbon. The adsorption capacity was then tested using a model aerosol of K2SO4 and diethyl-hexyl-sebacate (DEL-IS). The adsorption capacity of the bed of granular activated carbon was found to be higher than that of the denuder. The adsorption capacity was also tested using a model aerosol of K2SO4 particles and tar-rich gas from a laboratory-scale gasifier. As for DEHS, the result indicated that the capacity of the bed of granular activated carbon was higher than that of the denuder; it was also found that the adsorption was incomplete when the tar concentrations increased. In addition, the bed of granular activated carbon was successfully tested during experiments using a 100 kW circulating fluidized bed gasifier. The results indicate that the tar adsorption capacity is dependent not only on the total tar concentration but also on the tar composition

Place, publisher, year, edition, pages
American Chemical Society, 2010
Keyword
FLUIDIZED-BED COMBUSTION; AEROSOL-PARTICLES; ASH FORMATION; HOT GAS; GASIFICATION; ADSORPTION; THERMODENUDER; GASIFIER
National Category
Energy Engineering
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:lnu:diva-6918 (URN)10.1021/ef9012196 (DOI)
Projects
CHRISGAS
Available from: 2010-07-31 Created: 2010-07-31 Last updated: 2013-04-10Bibliographically approved
2. Physical and Chemical Characterization of Aerosol Particles Formed during the Thermochemical Conversion of Wood Pellets Using a Bubbling Fluidized Bed Gasifier
Open this publication in new window or tab >>Physical and Chemical Characterization of Aerosol Particles Formed during the Thermochemical Conversion of Wood Pellets Using a Bubbling Fluidized Bed Gasifier
2007 (English)In: Energy Fuels, ISSN 0887-0624, Vol. 21, no 6, 3660-3667 p.Article in journal (Refereed) Published
Abstract [en]

Product gas obtained through biomass gasification can be upgraded to hydrogen-rich synthesis gas. The synthesis gas can be further converted to liquid or gaseous fuels. However, the raw product gas contains both gas- and particle-phase impurities that can negatively affect both catalysts and hot-gas filters used for upgrading and cleaning. The present study aimed to characterize, both physically and chemically, aerosol particles formed during the steam- and oxygen-blown biomass gasification of wood pellets in an atmospheric 20 kW bubbling fluidized bed (BFB) gasifier. The product gas from the gasifier was sampled upstream from the cyclone at 500 °C. The particle number size distribution determined using a scanning mobility particle sizer (SMPS) was bimodal, with modes at 20–30 and 400 nm, mobility equivalent diameters (dB). The total mean number concentration of particles with dB = 15–670 nm was approximately 7 × 10^5 particles/cm3; however, the concentration of particles with dB < 80 nm fluctuated. The particle mass size distribution determined using a low-pressure impactor (LPI) was bimodal, and the total mass concentration of particles with aerodynamic diameters (dae) < 5 µm was 310 mg/m3. Microscopy analysis of particulate matter on the lower LPI stages, expected to sample particles with dae < 0.4 µm, revealed structures approximately 10 µm in diameter. In addition, the mass concentration of particles with dae < 0.5 µm determined using a LPI was higher than that estimated using a SMPS, possibly because of the bounce-off or re-entrainment of coarser particles from higher LPI stages. Elementary analysis of the particulate matter indicated that it was dominated by carbon. The collected particulate matter was stable when heated in nitrogen to 500 °C, indicating that the carbon was not present as volatile tars but more likely as char or soot. The particulate matter collected on all LPI stages contained a small percentage of ash (noncarbonaceous inorganic material), with calcium as the dominant element.

Place, publisher, year, edition, pages
American Chemical Society, Washington DC, 2007
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:vxu:diva-2764 (URN)doi:10.1021/ef7002552 (DOI)
Available from: 2007-12-14 Created: 2007-12-14 Last updated: 2011-04-27Bibliographically approved
3. Characterization of Particulate Matter from a Circulating Fluidized Bed Gasifier Using Different Types of Biomass
Open this publication in new window or tab >>Characterization of Particulate Matter from a Circulating Fluidized Bed Gasifier Using Different Types of Biomass
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This study characterized the particulate matter (PM) formed during gasification of different types of biomass in a circulating fluidized bed gasifier at atmospheric pressure. Two systems were used to sample the PM, and both on- and offline analysis techniques were used to characterize the PM. Four different instruments were used to measure the particle mass size distribution and concentration in the size range 0.01–30 µm. The agreement between the instruments was good, and the particle mass size distributions upstream of any cleaning device were bimodal, dominated by the coarse mode (>0.5 µm). The particle mass concentration of the fine mode (<0.5 µm) varied, depending on which biomass was used. The variation in particle mass concentration of the coarse mode was less, and was due to different loads of bed material and various ash contents in the biomass. The morphological analysis of the PM showed that the char content was low and that the PM was dominated by ash and bed material. The coarse-mode PM was rich in magnesium and calcium, while potassium and chlorine were prevalent in the fine-mode PM. The elementary composition of the PM varied between the different types of biomass used and heavy metals, that is, zinc and lead, were detected in low concentrations when using demolition wood as fuel.

Keyword
Biomass gasification, particulate matter
National Category
Industrial Biotechnology
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:lnu:diva-11264 (URN)
Available from: 2011-03-29 Created: 2011-03-29 Last updated: 2016-01-11Bibliographically approved
4. Characterization of Particulate Matter in the Hot Product Gas from Indirect Steam Bubbling Fluidized Bed Gasification of Wood Pellets
Open this publication in new window or tab >>Characterization of Particulate Matter in the Hot Product Gas from Indirect Steam Bubbling Fluidized Bed Gasification of Wood Pellets
Show others...
2011 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, no 4, 1781-1789 p.Article in journal (Refereed) Published
Abstract [en]

This study characterized the particulate matter (PM) formed during the indirect steam bubbling fluidized bed gasification of wood pellets at atmospheric pressure. A system including a dilution probe, a bed of granular activated carbon, and a thermodenuder was used to sample the PM at high temperature with the aim of separating it from condensing inorganic vapors and tars. The particle mass size distribution was bimodal with a fine mode in the <0.5-μm size range and a dominating coarse mode in the >0.5-μm size range. The coarse mode was representatively characterized while condensing inorganic vapors and tars complicated the evaluation of the results for the fine-mode PM. Morphological analysis of the PM indicated that the char content was low. The inorganic fraction was dominated by potassium and chlorine for fine-mode PM and calcium and silicon for coarse-mode PM.

Keyword
Biomass gasification, particulate matter
National Category
Industrial Biotechnology
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:lnu:diva-11261 (URN)10.1021/ef101710u (DOI)
Available from: 2011-03-29 Created: 2011-03-29 Last updated: 2014-02-25Bibliographically approved
5. Characterization of particulate matter in the hot product gas from atmospheric fluidized bed biomass gasifiers
Open this publication in new window or tab >>Characterization of particulate matter in the hot product gas from atmospheric fluidized bed biomass gasifiers
2011 (English)In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 35, no Supplement 1, 71-78 p.Article in journal (Refereed) Published
Abstract [en]

This study compares the characteristics of particulate matter (PM) in the hot product gas from three different atmospheric fluidized bed biomass gasifiers: a bubbling fluidized bed (BFB) gasifier, a circulating fluidized bed (CFB) gasifier, and an indirect BFB gasifier (the latter integrated with a CFB boiler). All gasifiers displayed a bimodal particle mass size distribution with a fine mode in the <0.5 μm size range and a coarse mode in the >0.5 μm size range. Compared with the mass concentration of the coarse mode the mass concentration of the fine mode was low in all gasifiers. For both the BFB and CFB gasifiers the fine-mode PM had a similar inorganic composition, indicating an origin from the ash and the magnesite bed material used in both gasifiers. In the indirect BFB gasifier the fine-mode PM was instead dominated by potassium and chlorine, and the tar fraction properties evoked tar condensation in the sampling system that affected mainly the fine-mode PM. The coarse-mode PM in the BFB gasifier was dominated by char fragments abraded from the pyrolyzed wood pellets. In the CFB gasifier the coarse-mode PM was mainly ash and magnesite bed material that passed through the process cyclone. In the indirect BFB gasifier the coarse-mode PM was mainly ash, probably originating both from the BFB gasifier and the CFB boiler.

Keyword
Biomass gasification, particulate matter
National Category
Bioenergy
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:lnu:diva-11263 (URN)10.1016/j.biombioe.2011.02.053 (DOI)
Available from: 2011-03-29 Created: 2011-03-29 Last updated: 2016-05-23Bibliographically approved

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