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Author:Kaisalo, Noora
Title:Coking of steam reforming catalysts in biomass gasification conditions
Höyryreformointikatalyyttien koksaantuminen biomassan kaasutusolosuhteissa
Publication type:Master's thesis
Publication year:2012
Pages:viii + 91 + [2]      Language:   eng
Department/School:Kemian laitos
Main subject:Teknillinen kemia   (Kem-40)
Supervisor:Niemelä, Marita ; Lehtonen, Juha
Instructor:Kihlman, Johanna ; Karinen, Reetta
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  2035   | Archive
Keywords:coke
steam reforming
gas cleaning
koksi
höyryreformointi
kaasunpuhdistus
Abstract (eng): In the literature part of this master thesis, the coking problem in catalytic hot gas cleaning of biomass gasification gas is discussed.
The feed, catalyst, temperature and pressure affect coking.
Increasing H2O/C ratio decreases coking rate, whereas the effect of sulfur is not clear.
The unsaturated and aromatic compounds in the feed form coke easily.
Nickel catalysts tend to coke more than noble metal catalysts.
Smaller nickel crystal size decreases coking rate.
The support affects the dispersion of active metal and thus also the crystal size.
In addition, acid sites on the support increase coking of the catalyst.
Different coke types were reviewed and special attention was paid to whisker coke because of its destructive nature.

In the experimental part of this master thesis, coking of three different catalysts is studied using simulated biomass gasification gas.
The experiments were carried out in a pressurized plug flow reactor at different temperatures at pressure of 4 bar (a).
A reactor with four catalyst compartments was used.
The catalysts used were two nickel catalysts and one noble metal catalyst.
In addition, SiC and Al2O were used as inerts.
Experiments were carried out with two different water concentrations in the gas.
Experiments with 100 ppm of H2S in the feed were performed to see the effect of sulfur on coking.
The coked catalysts were inspected with microscope and characterized by TPO and elemental analysis.
The thermodynamic equilibrium limit for coking was calculated by HSC program and the experimental results were compared to thermodynamic calculations.
Abstract (fin): Diplomityön kirjallisessa osassa käsitellään koksaantumisongelmaa biomassan kaasutuskaasun katalyyttisessa kuumapuhdistuksessa.
Koksaantumiseen vaikuttavat syöttö, katalyytti, lämpötila ja paine.
H2O/C-suhteen kasvattaminen hidastaa koksaantumisnopeutta, mutta rikin vaikutus puolestaan ei ole selvä.
Tyydyttymättömät ja aromaattiset yhdisteet syötössä muodostavat koksia helposti.
Nikkelikatalyytit koksaantuvat helpommin kuin jalometallikatalyytit, mutta nikkelikiteiden pieni koko hidastaa koksaantumista.
Katalyytin kantaja vaikuttaa aktiivisen metallin dispersioon ja siten kidekokoon.
Lisäksi kantajan happamat paikat nopeuttavat koksaantumista.
Erityyppisiä kokseja tarkasteltiin, ja erityisesti keskityttiin whisker-koksiin koska sen on todettu hajottavan katalyytteja.

Diplomityön kokeellisessa osassa tutkittiin kahden nikkelikatalyytin ja yhden jalometallikatalyytin koksaantumista simuloidulla biomassan kaasutuskaasulla.
Kokeet tehtiin paineellisella tulppavirtausreaktorilla eri lämpötiloissa ja neljän barin paineessa.
Kokeissa käytettiin reaktoria, jolla voitiin testata neljä eri katalyyttia kerralla.
Kokeissa käytettiin kahta eri syötön vesipitoisuutta.
Rikin vaikutusta koksaantumiseen selvitettiin kokeilla, joissa syötössä oli mukana 100 ppm H2S:a.
Koksaantuneita katalyytteja tutkittiin mikroskoopilla, ja koksia karakterisoitiin TPO:lla ja alkuaineanalyysilla.
Koksaantumiselle laskettiin termodynaaminen tasapainoraja HSC-ohjelmalla, ja koetuloksia verrattiin termodynaamisiin laskelmiin.
ED:2012-05-21
INSSI record number: 44602
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