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CLIMIT-Forskning, utvikling og demo av CO2-håndtering

Fundamentals of Pressurized Oxy-fuel Combustion for Natural Gas Semi-Closed Combined Cycles

Alternative title: Grunnlag for trykksett oksy-brensel-forbrenning for naturgassfyrte delvis lukka kombinerte syklusar

Awarded: NOK 9.1 mill.

To mitigate climate change and maintain an ambitious CO2 reduction target in a fossil fuel dominated society, Carbon Capture and Storage (CCS) must be implemented. Several technologies have been developed to capture CO2 from the exhaust of combustion processes. The oxy-fuel combustion method is based on burning fuel with oxygen instead of air which provides an exhaust gas with a high CO2 concentration, making its capture less energy consuming. Oxy-fuel gas turbine engines that generate electricity are today not available commercially because the technology is still new and its development cost high. The most complex component of an engine is the combustion chamber which operates under high pressure, and it is critical to understand and being able to predict combustion in such a new oxy-fuel environment in order to design and build such engines. In OXYFUN the objectives are to develop advanced tools based on a high-pressure combustion facility (HIPROX - ECCSEL), dedicated advanced laser-based technique as a unique tool to perform the measurements inside the flame, and improve adapted numerical models. There is a lack of both detailed experimental data in the core of the flame and validation of the models in oxy-fuel combustion in general, and particularly under high pressure. OXYFUN has assigned one postdoc and one PhD in each of these aspects. For the experimental part, a collaboration with CORIA-Normandie Université (France), has been engaged to adapt and further develop a novel measurement method based on advanced laser Raman spectroscopy specifically designed for high temperature gases with high CO2 concentrations. The objective is to master a measurement technique able to build flame database that can be used as validation in Computational Fluid Dynamics (CFD). A combustor adapted to the high-pressure facility HIPROX to accommodate the high intensity laser beam to penetrate without damaging the optical windows has been designed, manufactured, and delivered. The postdoc has been hosted by the project partner CORIA-Normandie Université (France), for training and further development of the technique in 2021. The measurement technique developed has shown the capability of measuring temperature and species concentration based on the Raman signal from CO2 anywhere in the flame on a "single shot" basis, i.e., able to resolve turbulent phenomena. The laser and optical setup has also been applied around the high pressure facility, but unfortunately first tests did not occur due to the delayed delivery of the custom manufactured "pockels cell", one of the major optical components of the developed measurement technique. The complete Laser Raman diagnostic is now complete and ready to be applied. A phd student on numerical simulation has now completed and submitted the thesis for evaluation, with defence planned early 2023. She has done model development and simulations with the computer code OpenFoam. She has studied different approaches in handling reactions in small turbulent eddies in the combustion model. Results are presented at meetings/conferences 2018-2019. The student was on a 6 months visit at Cambridge University, with funding from CLIMIT Personal Grant. Here, she has conducted simulations with EDC and participated in a cooperation where different models are compared with experimental data for a case of rich CO2 combustion. The results are presented at the International Symposium on Combustion in 2020 and published in the Proceedings journal. Subsequently, she has worked on a new model for turbulent combustion; published in Combustion Theory and Modelling. Further work is presented in a manuscript submitted for evaluation in a journal. Compared to earlier models, the new model gave better results for temperature and chemical species within the investigated turbulent flame. In lack of experimental data for oxy-combustion, she has tested the model against data for turbulent premixed combustion. In a separate study, included in the thesis, the model is used for oxy-combustion. A short study on the application of the principles of semi-closed oxy-fuel cycle transposed to hydrogen fired gas turbine has also been performed by power process cycle simulation and was published in the international journal "Energy". It is shown that when the principle is applied, it is not necessary to develop expensive advanced burner technology to handle pure hydrogen as fuel, and therefore make possible the use of older generation combustors. The fundamental basis of this concept is therefore validated and can be taken to further development stage for proof of concept. OXYFUN also participated in spreading knowledge and information about oxy-fuel combustion in professional networks and the CCS community. The project has been affected by the COVID pandemic with delayed employment of the postdoc, restrictions and delays during the visiting period in France, and in the delivery of a critical custom-made equipment.

Being a Researcher project, OXYFUN has improved the competence of the combustion group at SINTEF and NTNU, in the fields of advanced measurement methods in high temperature turbulent reacting flows and the modelling of these flames. For the 3 academic candidates who will enter their professional careers, they have been faced with state-of-the-art research problems and methods, and an understanding of CO2 capture from power generation. Through the publications produced by the project, an increased attention has been drawn to the community on the oxy-fuel CO2 capture for gas turbine power generation as a CCS technology. In total, there has been active collaboration with visiting stays in 3 international research groups: (CORIA-Université (FR), Loeben (AT), and Cambridge University (UK). These collaborations will be pursued and will potentially lead to new reseacrh projects (one already been applied for as a KSP in Norway in 2022).

The project aims at advancing the fundamental knowledge required to design and operate high-pressure oxy-fuel combustion. Semi-closed oxy-fuel gas turbine cycles is a promising technology for natural-gas fired power production with carbon capture. Combustion in a O2/CO2 oxidizer mixture has shown properties very different from those of air combustion, and pressurized combustion in a gas turbine differs from coal combustion at atmospheric pressure in a boiler. An experimental study on flame configurations relevant for practical gas-turbine applications will be conducted. Advanced non-intrusive laser based methods like Particle Image Velocimetry, Laser Induced Fluorescence, or Laser Raman Spectroscopy will provide fine temporal and spatial resolutions of motion and composition of the pressurized flame, giving data sets of high quality and originality. Different stability modes and influence of combustion as a function of burner oxidizer O2/CO2 concentration ratio will be studied. In the computational part, the effects of turbulence on the chemistry will be investigated. With the strong variations in motions and time scales, chemical reactions will proceed substantially different from those of laminar flames and simple reactors. The default turbulent combustion model for industrial CFD is the Eddy-Dissipation Concept (EDC) developed by B.F. Magnussen and co-workers at NTNU and SINTEF. Some studies in literature indicate that effects of the longer chemical time scales in CO2/O2 combustion compared to air combustion calls for further development of the model, and this will be investigated and dealt with. Furthermore, the EDC will be further developed for use with Large-Eddy simulations (LES). Both activities will be performed in parallel and interactions between these will be privileged by amongst other, carefully define the boundary and inlet conditions and thus provide proper validation of simulations in gas turbine relevant conditions.

Publications from Cristin

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CLIMIT-Forskning, utvikling og demo av CO2-håndtering