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High-pressure catalytic combustion of gasified biomass in a hybrid combustor
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.ORCID iD: 0000-0002-2992-6814
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2005 (English)In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 293, no 1-2, 129-136 p.Article in journal (Refereed) Published
Abstract [en]

Catalytic combustion of synthetic gasified biomass was conducted in a high-pressure facility at pressures ranging from 5 to 16 bars. The catalytic combustor design considered was a hybrid monolith (400 cpsi, diameter 3.5 cm, length 3.6 cm and every other channel coated). The active phase consisted of 1 wt.% Pt/gamma-Al2O3 With wash coat loading of total monolith 15 wt.%. In the interpretation of the experiments, a twodimensional boundary layer model was applied successfully to model a single channel of the monolith. At constant inlet velocity to the monolith the combustion efficiency decreased with increasing pressure. A multi-step surface mechanism predicted that the flux of carbon dioxide and water from the surface increased with pressure. However, as the pressure (i.e. the Reynolds number) was increased, unreacted gas near the center of the channel penetrated significantly longer into the channel compared to lower pressures. For the conditions studied (lambda = 46, T-in = 218-257 degrees C and residence time similar to 5 ms), conversion of hydrogen and carbon monoxide were diffusion limited after ignition, while methane never ignited and was kinetically controlled. According to the kinetic model surface coverage of major species changed from CO, H and CO2 before ignition to O, OH, CO2 and free surface sites after ignition. The model predicted further that for constant mass flow combustion efficiency increased with pressure, and was more pronounced at lower pressures (2.5-10 bar) than at higher pressures (> 10 bar).

Place, publisher, year, edition, pages
2005. Vol. 293, no 1-2, 129-136 p.
Keyword [en]
catalytic combustion, gasified biomass, platinum, high pressure, catalytically stabilized combustion, CHEMKIN
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-7571DOI: 10.1016/j.apcata.2005.07.003ISI: 000232436200014Scopus ID: 2-s2.0-24644491216OAI: oai:DiVA.org:kth-7571DiVA: diva2:12638
Note
QC 20100916Available from: 2007-11-06 Created: 2007-11-06 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Kinetic modelling of autoignition phenomena
Open this publication in new window or tab >>Kinetic modelling of autoignition phenomena
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

To fully understand the elementary reactions behind the ignition of automotive fuels the interaction between the fuel components must be known. The ignition initiation is most often caused by loss of an H radical from a reactive fuel molecule, for example n-heptane. The formed alkyl radical is prone to react with oxygen under lean conditions. However, it can also abstract hydrogen from other fuel molecules, hence activating more unreactive species. This type of reactions is called cooxidation reactions and including it in combustion mechanisms improve ignition delay predictions in a wide range of experiments, for Primary Reference Fuel mixtures and toluene/heptane mixtures. Example of such reactions are

C7H15• + C8H18 = C7H16+ C8H17•

C7H15OO• + C8H18 = C7H15OOH+ C8H17•

Adding cooxidation reactions also significantly improves prediction of the general trend of auto-ignition phasing as function of operating conditions in Homogeneous Charge Compression Ignition, HCCI, engine combustion.

The effect of NO addition on engine combustion has also been studied in this work. A novel strategy to control ignition onset in HCCI engines is to retain exhaust gases in the cylinder to control the cylinder temperature. While this not only controls the engine temperature it also introduces NOx in the cylinder. The NO will advance ignition onset by several crank angle degrees at concentrations below 10 ppm. This is because NO activates HO2 in the reaction: HO2• + NO = OH• + NO2. At higher concentrations the ignition onset is not as advanced and in the PRF case even retarded. This is because NO has cool flame-inhibiting effects.

Kinetic modelling can also be used to predict combustion efficiency in catalytic combustors for power generation. It was shown that at high pressures the number of free sites decreases which limits the combustion efficiency. Thus a hybrid concept could be used where only a fraction of the air and fuel is burned catalytically.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 53 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:65
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4516 (URN)978-91-7178-778-1 (ISBN)
Presentation
2007-11-15, 591, KTH, Teknikringen 42, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101109Available from: 2007-11-06 Created: 2007-11-06 Last updated: 2010-11-09Bibliographically approved
2. Catalytic Combustion in Gas Turbines: Experimental Study on Gasified Biomass Utilization
Open this publication in new window or tab >>Catalytic Combustion in Gas Turbines: Experimental Study on Gasified Biomass Utilization
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Environmental and geopolitical concerns encourage societies towards the utilization of renewable energy sources (RES). Photovoltaic and wind power can produce electricity directly, although their intermittent characteristic negatively affects the security and safety of the energy supply chain; moreover, in order to be viable it is necessary to establish energy storage systems and to find mechanisms to adapt the power distribution grid to larger production variability. In contrast, biomass (a carbon neutral fuel if adequately managed) can be stored, is relatively widely available, and after simple treatments can be gasified and ready to be used for power production. Correspondingly, gas turbines are a well-established technology that first became relevant in industrial applications and power production since 1940’s. The use of biomass in gas turbines is an important step forward towards more sustainable power production; however, this combination presents some technical challenges that have yet to be overcome.

Gasified biomass is generally a gas with low or medium heating value that is usually composed of a mixture of gases such as CO, H2, CH4, CO2, and N2 as well as other c60*6nents in small fractions. Its firing in standard gas turbine combustors might be unstable at certain load conditions. Moreover, gasified biomass contains undesirable compounds; in particular the nitrogen-containing compounds that may produce elevated NOx emissions once the biomass is burned.

Catalytic combustion is an alternative for using gasified biomass in a gas turbine, and it is investigated in this study. Using catalytic combustion is possible to burn such a mixture of gases under very lean conditions, extending the normal flammability limits, reducing the maximum temperature of the reaction zone, and thus reducing the thermal NOx formation. It also reduces the vibration levels, and it is possible to avoid fuel-NOx formation using alternative catalytic techniques, such as Selective Catalytic Oxidation (SCO).

In the present study the feasibility of using catalytic combustion in a gas turbine combustor is evaluated. The tests performed indicate the necessity of using hybrid combustion chamber concepts to achieve turbine inlet temperatures levels of modern gas turbines. The different catalytic burning characteristic of H2, CO and CH4 was evaluated and different techniques were applied to equalize their burning behaviour such as the diffusion barrier, and partially coated catalyst. Fuel-NOx is another subject treated in this work, where a Selective Catalytic Oxidation (SCO) technique is applied reaching up to 42% of fuel NOx reduction. Finally, the use of Catalytic Partial Oxidation (CPO) of methane was experimentally investigated.

In this study, two one-of-a-kind test facilities were used directly, namely the high-pressure test facility and the pilot scale test facility. This gives a unique characteristic to the study performed. Finally, the catalytic combustion approach allows the utilization of gasified biomass with some restrictions depending on whether it is a Catalytic Lean, Catalytic Rich or Catalytic Partial Oxidation (CPO) approach.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xiv, 152 p.
Series
TRITA-KRV, ISSN 1100-7990 ; 14:01
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-144102 (URN)978-91-7595-048-8 (ISBN)
Public defence
2014-04-11, Sal B1, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency, 5110-2003-06929/2152-1
Note

QC 201140409

Available from: 2014-04-09 Created: 2014-04-09 Last updated: 2014-04-11Bibliographically approved

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