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Effect of gas phase alkali species on tar reforming catalyst performance: Initial characterization and method development
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.ORCID iD: 0000-0002-5395-599X
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.ORCID iD: 0000-0001-9391-7552
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2015 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 154, 95-106 p.Article in journal (Refereed) Published
Abstract [en]

In thermochemical conversion of biomass to synthesis gas and biofuels, the effect of varying gas phase alkali concentrations on tar reforming catalyst performance in combination with gas phase sulfur and chlorine is largely unknown. The current study demonstrates a new methodology for investigating gas phase alkali adsorption and presents results for early stage adsorption on a Ni-based catalyst under realistic industrial conditions. The experiments were carried out using pine pellets as feedstock in a setup consisting of a 5 kW atmospheric bubbling fluidized bed gasifier, a high temperature hot gas filter and a catalytic reactor - all operating at 850 °C. A potassium chloride solution was atomized with an aerosol generator, and the produced submicrometer KCl particles were continuously introduced to the catalytic reactor where they rapidly evaporated to form KCl (g). The accurate dosing of gas-phase alkali was combined with elimination of transient effects in catalytic performance due to catalyst sintering and S adsorption, and results for K uptake in relation to sulfur uptake were obtained. Different KCl levels in the gas phase demonstrates different initial uptake of K on the catalyst surface, which at low K coverage (θK) is approximately linearly proportional to time on stream. The results also show a clear suppressing effect of sulfur adsorption on potassium uptake. Indications of a slow approach to K equilibration on the catalyst were observed. The potential of the developed methodology for detailed studies under close to industrial conditions is discussed.

Place, publisher, year, edition, pages
2015. Vol. 154, 95-106 p.
Keyword [en]
Alkali, Biomass gasification, Ni catalyst, Potassium, Sulfur, Tar reforming, Adsorption, Catalysts, Chlorine compounds, Fluidization, Fluidized beds, Gasification, Nickel, Sintering, Tar, Bubbling fluidized bed, Linearly proportional, Ni catalysts, Potassium chloride solutions, Thermochemical Conversion, Gases
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-167687DOI: 10.1016/j.fuel.2015.03.027ISI: 000353893200012Scopus ID: 2-s2.0-84926632320OAI: oai:DiVA.org:kth-167687DiVA: diva2:816107
Funder
Swedish Energy Agency
Note

QC 20150602

Available from: 2015-06-02 Created: 2015-05-22 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications
Open this publication in new window or tab >>Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Reliable energy supply is a major concern and crucial for development of the global society. To address the dependency on fossil fuel and the negative effects of this reliance on climate, there is a need for a transition to cleaner sources. An attractive solution for replacing fossil-based products is renewable substitutes produced from biomass. Gasification and pyrolysis are two promising thermochemical conversion technologies, facing challenges before large-scale commercialization becomes viable. In case of biomass gasification, tar is often and undesired by-product. An attractive option to convert tar into syngas is nickel-based catalytic steam reforming (SR). For biomass pyrolysis, catalytic SR is in early stages of investigation as a feasible option for bio-crude conversion to syngas.

The focus of the thesis is partly dedicated to describe research aimed at increasing the knowledge around tar reforming mechanisms and effect of biomass-derived impurities on Ni-based tar reforming catalyst downstream of gasifiers. The work focuses on better understanding of gas-phase alkali interaction with Ni-based catalyst surface under realistic conditions. A methodology was successfully developed to enable controlled investigation of the combined sulfur (S) and potassium (K) interaction with the catalyst. The most striking result was that K appears to lower the sulfur coverage and increases methane and tar reforming activity. Additionally, the results obtained in the atomistic investigations are discussed in terms of naphthalene adsorption, dehydrogenation and carbon passivation of nickel.

Furthermore, the thesis describes research performed on pyrolysis gas pre-conditioning at a small-industrial scale, using an iron-based catalyst. Findings showed that Fe-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way for generating a hydrogen-enriched gas without the need for bio-crude condensation.

Abstract [sv]

Tillförlitlig energiförsörjning är en stor utmaning och avgörande för utvecklingen av det globala samhället. För att ta möta beroendet av fossil råvara och de negativa effekter som detta beroende medför för klimatet finns ett stort behov av en övergång till renare energiråvaror. En attraktiv lösning är att ersätta nuvarande fossil råvara med produkter från biomassa. Förgasning och pyrolys är två lovande teknologier för termokemisk omvandling av biomassa. Kommersialisering av dessa teknologier är inte helt problemfritt. I fallet förgasning så behöver, bl.a. oönskade tyngre kolväten (tjära) hanteras innan den producerade orenade produktgasen kan användas i syntesgastillämpningar. Ett effektivt alternativ för detta är gaskonditionering vid höga temperaturer, baserade på katalytisk ångreformering med en nickelkatalysator. Katalytisk ångreformering är en möjlig teknik för omvandling av bioråvara, producerad från pyrolys av biomassa, till syntesgas.

Avhandlingen fokuserar delvis på att beskriva den forskning som utförts för att öka kunskapen kring mekanismer för tjärreformering och effekterna av föroreningar från biomassan på en nickelkatalysator nedströms förgasare. Arbetet bidrar till en bättre förståelse av hur alkali i form av kalium (K) i gasfasen upptas, jämviktas och växelverkar med ytan hos nickelkatalysatorn under fullt realistiska förhållanden. Inledningsvis utvecklades en metod för att möjliggöra kontrollerade studier av den kombinerade effekten av S och K, vilken inkluderar exakt dosering av alkali till en produktgas, eliminering av transienter i katalysatoraktiviteten samt katalysatorkarakterisering. Det mest lovande resultatet är att K både sänker ytans svavelinnehåll och ökar aktiviteten för omvandlingen av metan och tjära. För att ytterligare fördjupa kunskaperna i mekanismerna för tjärnedbrytning utfördes experimentella och teoretiska ytstudier på en enkristallnickelyta med naftalen som modellförening. Resultat avseende naftalenadsorption, dehydrogenering av naftalen och kolpassivering av nickelytan diskuteras.

Därutöver så beskriver avhandlingen den forskning som utförts inom förkonditionering av pyrolysgas med en järnkatalysator för varsam deoxygenering av biooljan och vätgasproduktion. Detta utfördes vid en småskalig industriell anläggning. De experimentella studierna visar att den undersökta järnkatalysatorn resulterar i en vätgasberikad gas och att den är en potentiell kandidat för tillämpning i ett förkonditioneringssteg.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 126 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:36
Keyword
tar reforming, biomass gasification, Ni-based catalyst, potassium, sulfur, pyrolysis gas, bio-crude conditioning, gas conditioning, Fe-based catalyst, tjärreformering, biomassaförgasning, Ni-baserad katalysator, kalium, svavel, pyrolysgas, konditionering bio-råolja, gaskonditionering, Fe-baserad katalysator
National Category
Chemical Process Engineering Other Chemical Engineering
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-213368 (URN)978-91-7729-509-9 (ISBN)
Public defence
2017-09-29, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170830

Available from: 2017-08-30 Created: 2017-08-30 Last updated: 2017-09-07Bibliographically approved

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Moud, Pouya H.Lanza, RobertoEngvall, Klas

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