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Study of the activity of catalysts for the production of high quality biomass gasification gas – with emphasis on Ni-substituted Ba-hexaaluminates
Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The fossil hydrocarbons are not inexhaustible, and their use is not without impact in our need of energy, fuels and hydrocarbons as building blocks for organic materials. The quest for renewable, environmentally more friendly technologies are in need and woody biomass is a promising candidate, well provided in the boreal parts of the world. To convert the constituents of wood into valuable gaseous products, suitable for the end use required, we need a reliable gasification technology. But to become an industrial application on full scale there are still a few issues to take into account since the presence of contaminants in the process gas will pose several issues, both technical and operational, for instance by corrosion, fouling and catalyst deactivation. Furthermore the downstream applications may have very stringent needs for syngas cleanliness depending on its use. Therefore, the levels of contaminants must be decreased by gas cleanup to fulfil the requirements of the downstream applications.

One of the most prominent problems in biomass gasification is the formation of tars – an organic byproduct in the degradation of larger hydrocarbons. So, tar degrading catalysts are needed in order to avoid tar related operational problems such as fouling but also reduced conversion efficiency. Deactivation of catalysts is generally inevitable, but the process may be slowed or even prevented. Catalysts are often very sensitive to poisonous compounds in the process gas, but also to the harsh conditions in the gasifier, risking problems as coke formation and attrition. Alongside with having to be resistant to any physical and chemical damage, the catalyst also needs to have high selectivity and conversion rate, which would result in a more or less tar-free gas. Commercial tar reforming catalysts of today often contain nickel as the active element, but also often display a moderate to rapid deactivation due to the causes mentioned.

Place, publisher, year, edition, pages
Linnaeus university , 2016. , 72 p.
Keyword [en]
bioenergy, catalysis, tars, steam reforming, gasification, hexaaluminate
Keyword [sv]
bioenergi, katalys, tjäror, ångreformering, förgasning, hexaaluminat
National Category
Bioenergy Other Chemical Engineering
Research subject
Technology (byts ev till Engineering), Bioenergy Technology; Natural Science, Chemistry
Identifiers
URN: urn:nbn:se:lnu:diva-55702OAI: oai:DiVA.org:lnu-55702DiVA: diva2:954376
Presentation
2016-09-06, Sal N1017, hus N, Växjö, Växjö, 09:15 (English)
Opponent
Supervisors
Available from: 2016-08-25 Created: 2016-08-22 Last updated: 2016-08-25Bibliographically approved
List of papers
1. High temperature water-gas shift step in the production of clean hydrogen rich synthesis gas from gasified biomass
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2011 (English)In: Biomass and Bioenergy, ISSN 0961-9534, Vol. 35, no Supplement 1, S123-S131 p.Article in journal (Refereed) Published
Abstract [en]

The possibility of using the water-gas shift (WGS) step for tuning the H2/CO-ratio in synthesis gas produced from gasified biomass has been investigated in the CHRISGAS (Clean Hydrogen Rich Synthesis Gas) project. The synthesis gas produced will contain contaminants such as H2S, NH3 and chloride components. As the most promising candidate FeCr catalyst, prepared in the laboratory, was tested. One part of the work was conducted in a laboratory set up with simulated gases and another part in real gases in the 100 kW Circulating Fluidized Bed (CFB) gasifier at Delft University of Technology. Used catalysts from both tests have been characterized by XRD and N2 adsoption/desorption at −196 °C.

In the first part of the laboratory investigation a laboratory set up was built. The main gas mixture consisted of CO, CO2, H2, H2O and N2 with the possibility to add gas or water-soluble contaminants, like H2S, NH3 and HCl, in low concentration (0–3 dm3 m−3). The set up can be operated up to 2 MPa pressure at 200–600 °C and run un-attendant for 100 h or more. For the second part of the work a catalytic probe was developed that allowed exposure of the catalyst by inserting the probe into the flowing gas from gasified biomass.

The catalyst deactivates by two different causes. The initial deactivation is caused by the growth of the crystals in the active phase (magnetite) and the higher crystallinity the lower specific surface area. The second deactivation is caused by the presence of catalytic poisons in the gas, such as H2S, NH3 and chloride that block the active surface.

The catalyst subjected to sulphur poisoning shows decreased but stable activity. The activity shows strong decrease for the ammonia and HCl poisoned catalysts. It seems important to investigate the levels of these compounds before putting a FeCr based shift step in industrial operation. The activity also decreased after the catalysts had been exposed to gas from gasified biomass. The exposed catalysts are not re-activated by time on stream in the laboratory set up, which indicates that the decrease in CO2-ratio must be attributed to irreversible poisoning from compounds present in the gas from the gasifier.

It is most likely that the FeCr catalyst is suitable to be used in a high temperature shift step, for industrial production of synthesis gas from gasified biomass if sulphur is the only poison needed to be taken into account. The ammonia should be decomposed in the previous catalytic reformer step but the levels of volatile chloride in the gas at the shift step position are not known.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
Biomass gasification; Synthesis gas, Water-gas shift, FeCr catalyst, Catalyst poisons, Slipstreams
National Category
Natural Sciences
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:lnu:diva-14060 (URN)10.1016/j.biombioe.2011.04.052 (DOI)
Projects
CHRISGAS
Available from: 2011-09-09 Created: 2011-09-09 Last updated: 2016-08-25Bibliographically approved
2. Nickel-substituted bariumhexaaluminates as novel catalysts in steam reforming of tars
Open this publication in new window or tab >>Nickel-substituted bariumhexaaluminates as novel catalysts in steam reforming of tars
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2015 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 140, 1-11 p.Article in journal (Refereed) Published
Abstract [en]

This work investigates the performance of Ba–Ni-hexaaluminate, BaNixAl12 − xO19, as a new catalyst in thesteam-reforming of tars. Substituted hexaaluminates are synthesized and characterized. Steam reforming testsare carried out with both a model-substance (1-methylnaphthalene) and a slip-stream from a circulatingfluidized bed gasifier. The water–gas-shift activity is studied in a lab-scale set-up. Barium–nickel substitutedhexaaluminates show a high catalytic activity for tar cracking, and also shows activity for water–gas-shift.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Catalysis, Gasification, Steam-reforming, Water–gas-shift, Tar-cracking, BaNi-hexaaluminates
National Category
Energy Engineering Bioenergy
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:lnu:diva-46183 (URN)10.1016/j.fuproc.2015.07.024 (DOI)000363354000001 ()2-s2.0-84941562585 (ScopusID)
Available from: 2015-09-09 Created: 2015-09-09 Last updated: 2016-09-23Bibliographically approved

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