RADIATIVE HEAT TRANSFER FEATURES OF TECHNOLOGICAL INTEREST IN COMBUSTION PROCESSES WITH HIGH LEVEL OF FLUE GAS RECIRCULATION

The reduction of greenhouse gas emissions is essential to mitigate the impact of energy production from fossil fuels on the environment. Oxyfuel technology is a process developed to reduce emissions from power stations by removing nitrogen from air and burning the fossil fuels in a stream of pure oxygen. The remaining oxidiser is composed of recycled flue gas from the furnace to reduce temperatures. The product of this system is a flue gas with very high carbon dioxide concentration enabling more efficient capture and storage. Accurate modelling of oxyfuel is essential to gain better understanding of the combustion fundamentals and obtain accurate predictions of properties within the furnace that cannot be measured. Heat transfer to the furnace walls will be affected due to the different composition of the gases in the furnace. Carbon dioxide has higher heat capacity than nitrogen. Water vapour and carbon dioxide also exhibit absorption spectra of radiation in the infra-red region of the spectrum relating to wavelengths observed in combustion. Accurate CFD modelling of radiative heat transfer in oxyfuel combustion will require improvements to the radiative properties model to account for the spectral nature of radiation. In addition the impact of the solid fuel particles, soot and ash are considered. Several different radiative properties models have been tested to assess the impact on the predicted radiation and temperatures under air and oxy firing conditions. The results for radiation transferred to the walls are highly dependent upon the model chosen and the need for an accurate radiative properties model for oxyfuel firing, such as the full-spectrum k-distribution method is demonstrated.

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The impact of radiative heat transfer in combustion processes and its modeling – with a focus on turbulent flames

Fuel ◽

10.1016/j.fuel.2020.118555 ◽

2020 ◽

Vol 281 ◽

pp. 118555

Author(s):

Fengshan Liu ◽

Jean-Louis Consalvi ◽

Pedro J. Coelho ◽

Frédéric Andre ◽

Mingyan Gu ◽

...

Keyword(s):

Heat Transfer ◽

Radiative Heat Transfer ◽

Radiative Heat ◽

Turbulent Flames ◽

Combustion Processes ◽

The Impact

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Effect of flue gas recirculation on heat transfer in a supercritical circulating fluidized bed combustor

Archives of Thermodynamics ◽

10.1515/aoter-2015-0022 ◽

2015 ◽

Vol 36 (3) ◽

pp. 61-83 ◽

Cited By ~ 18

Author(s):

Artur Błaszczuk

Keyword(s):

Heat Transfer ◽

Fluidized Bed ◽

Flue Gas ◽

Circulating Fluidized Bed ◽

Furnace Chamber ◽

Flue Gas Recirculation ◽

Heat Transfer Behavior ◽

Transfer Behavior ◽

Bed Material ◽

Gas Recirculation

Abstract This paper focuses on assessment of the effect of flue gas recirculation (FGR) on heat transfer behavior in 1296t/h supercritical coal-fired circulating fluidized bed (CFB) combustor. The performance test in supercritical CFB combustor with capacity 966 MWth was performed with the low level of flue gas recirculation rate 6.9% into furnace chamber, for 80% unit load at the bed pressure of 7.7 kPa and the ratio of secondary air to the primary air SA/PA = 0.33. Heat transfer behavior in a supercritical CFB furnace between the active heat transfer surfaces (membrane wall and superheater) and bed material has been analyzed for Geldart B particle with Sauter mean diameters of 0.219 and 0.246 mm. Bed material used in the heat transfer experiments had particle density of 2700 kg/m3. A mechanistic heat transfer model based on cluster renewal approach was used in this work. A heat transfer analysis of CFB combustion system with detailed consideration of bed-to-wall heat transfer coefficient distributions along furnace height is investigated. Heat transfer data for FGR test were compared with the data obtained for representative conditions without recycled flue gases back to the furnace through star-up burners.

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Radiative Heat Transfer Modeling Using the CW and SLW Models in Gas Mixtures With Soot

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D ◽

10.1115/imece2012-87653 ◽

2012 ◽

Cited By ~ 1

Author(s):

Fabiano Cassol ◽

Rogério Brittes ◽

Francis Henrique Ramos França ◽

Ofodike A. Ezekoye

Keyword(s):

Heat Transfer ◽

Radiative Heat Transfer ◽

Radiative Heat ◽

Radiation Heat Transfer ◽

Homogeneous Medium ◽

Advantages And Disadvantages ◽

Spectral Integration ◽

Complex Dependence ◽

Benchmark Solution ◽

Combustion Processes

This paper presents the computation of radiative heat transfer in a slab filled with a participating medium composed of CO2, H2O, and soot. The HITEMP 2010 spectral database is employed to obtain the necessary parameters for the prediction of radiative transfer in the non-isothermal, homogeneous medium. The spectral integration is performed with the spectral line weighted-sum-of-gray-gases (SLW) and the cumulative wavenumber (CW) models and compared with the line-by-line (LBL) benchmark solution. Since radiation heat transfer can sometimes be the dominant heat transfer mechanism in combustion processes, it is important to understand how the predicted thermochemical state depends on the radiation model for the composition, taking into account the complex dependence of the properties with the spectrum. The contribution of this work is to compare two detailed spectral model that are available in the literature and determine advantages and disadvantages in some practical, illustrative examples.

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