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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.

Objectives: Approximately 60% of the world CO2 emissions come from combustion in the energy and industry sectors. 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 rapidly. Several technologies have been developed to capture CO2 from the exhaust of combustion processes. One of them, called oxy-fuel combustion 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. This type of combustion is more challenging and has been far less studied than the conventional air based combustion. The OXYFUN project aims at understanding the microscopic physical and chemical mechanisms of oxy-fuel combustion occurring in a gas turbine engine used for producing electricity from natural gas. Technical content: A particular characteristic of a gas turbine engine is that combustion takes place under high pressure. In OXYFUN a high-pressure combustion facility (HIPROX) and advanced laser-based techniques will be used to perform measurements inside the flame (1 post-doc task) and numerical simulation tool will be developed to model the combustion in detail (1 PhD task). Added value of the project: Oxy-fuel gas turbine engines are today not available commercially because the technology is still new and its development cost high. By better understanding and being able to predict the complex physical-chemical phenomena of high pressure oxy-fuel combustion, the project will allow to establish knowledge and reliable tools to develop and engineer efficient and low emission thermal power engine with CO2 capture. Research challenges: Advances in combustion research has principally focussed on air based combustion. In comparison, very little research has considered oxy-fuel combustion and even less under high pressure. There is therefore a lack of both detailed experimental data in the core of the flame and validation of the models. This project assigns one postdoc and one PhD studies in each of these aspects. For the experimental part, a collaboration with the French research group CORIA will allow to use and test a novel measurement method based on advanced laser Raman spectroscopy specifically designed for high temperature gases with high CO2 concentrations. The collaboration will attempt to provide unique temperature measurements in the heart of the turbulent flame and will be completed with measurements of velocity and turbulence. The experimental database obtained will be used in the parallel PhD study for validation and improvement of the coupled kinetic and turbulence models in Computational Fluid Dynamics (CFD). Results and progress of the project: The phd student started in January 2018. She has completed coursework and 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 visit at Cambridge University (6 months) in 2019, 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 in an article in the journal «Proceedings of the Combustion Institute». Subsequently, she has worked on a new model for turbulent combustion; a manuscript with results is submitted for review in a journal (October 2021). Compared to earlier models, the new model gave better results for temperature and chemical species within the investigated turbulent flame. A study on the application of the principles of semi-closed oxy-fuel cycle transposed to hydrogen fired gas turbine performed in 2018 by power process cycle simulation has been published in the peer-reviewed journal "Energy". It is shown that when the Exhaust Gas Recycle concept is applied to a gas turbine, it is not necessary to develop expensive advanced burner technology to handle pure hydrogen as fuel, and therefore make retrofit application possible. 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 manufactured delivered and is ready for use. A postdoc partly funded by NTNU has been employed (delayed Nov. 2020 due to the pandemic). He has been visiting project partner CORIA (France), for training and experiments for most of 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 as a single shot, ie able to resolve turbulent phenomena. The technique will be applied in 2022 in HIPROX under pressure.

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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.

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CLIMIT-Forskning, utvikling og demo av CO2-håndtering