Pressurized oxy-combustion with low flue gas recycle: Computational fluid dynamic simulations of radiant boilers

Xia, Fei; Yang, Zhiwei; Adeosun, Adewale; Gopan, Akshay; Kumfer, Benjamin M.; Axelbaum, Richard L.

doi:10.1016/j.fuel.2016.04.023

Cited by 56 publications

(19 citation statements)

References 40 publications

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“…However, for second generation oxy-fuel technology, or pressurized oxy-fuel combustion (POFC) technology, the whole system runs under pressure, and hence the work losses due to the pressure fluctuations can be substantially reduced. Together with this feature, many other advantages can also be achieved by deploying POFC [6][7][8] including: (1) recovering latent heat from flue gas; (2) increasing the convective heat transfer for a given mean velocity; (3) reducing the boiler size and equipment costs; (4) avoiding air ingress, thus ensuring the production of high purity of CO2 in the flue gas and a relatively low purification cost; and (5) reducing the cost of flue gas recirculation fan and the CPU system.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen and sulfur conversion during pressurized pyrolysis under CO 2 atmosphere in fluidized bed

Duan

Anthony

et al. 2017

Fuel

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Pressurized oxy-fuel combustion (POFC) is a promising technology for CO2 capture from coal-fired power plants, offering both high efficiency and a low penalty. However, the high partial pressure of CO2 in a POFC furnace has important impacts on fuel-N and fuelS conversion during the coal pyrolysis process, and understanding this will help to achieve further control of SOx/NOx. In this study, coal pyrolysis experiments were conducted in a pressurized fluidized bed with the pressure range of 0.1-0.7MPa under N2 and CO2 atmosphere. The gaseous products were monitored by a Fourier transform infrared spectroscopy analyzer (FTIR) and the char residue was characterized by an X-ray photoelectron spectroscopy (XPS) analyzer in order to acquire the species information for S-containing and N-containing compounds. Results show that the enrichment of CO2 in the local atmosphere enhances the fuel-N conversion to HCN in the pyrolysis process, which serves as a favorable precursor to N2O. The generation of HCN and NH3 increase simultaneously with the increase of overall pressure. SO2 concentration in the gaseous product is relatively low, and as the pressure increases, the concentration decreases slightly due to CO reduction of SO2 to COS. Sulfur content in the char decreases as the pressure goes from 0.1MPa to 0.7MPa indicating higher CO2 pressure accelerates the decomposition of sulfur compounds in the coal, which is further confirmed by the XPS results.

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Section: Introductionmentioning

confidence: 99%

Nitrogen and sulfur conversion during pressurized pyrolysis under CO 2 atmosphere in fluidized bed

Duan

Anthony

et al. 2017

Fuel

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“…However, all of the above models were designed for atmospheric oxy‐fuel combustion; and no WSGG model exists for a pressurized oxy‐fuel condition. Thus, Xia et al still used the atmospheric WSGG model in their calculation of a pressurized oxy‐fuel combustion boiler. Nevertheless, a recent study showed that non‐ideal results occur when the atmospheric WSGG models were applied to pressurized conditions.…”

Section: Introductionmentioning

confidence: 99%

New weighted-sum-of-gray-gases model for typical pressurized oxy-fuel conditions

et al. 2017

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Summary Pressurized oxy‐fuel combustion technology has received considerable attention due to its ability to improve the overall system efficiency and to control CO2 emissions. The characteristics of radiation heat transfer are significant for pressurized oxy‐fuel gas mixture and different from those under atmospheric conditions. Therefore, to calculate the radiation characteristics of pressurized oxy‐fuel gas mixture quickly and accurately, new weighted‐sum‐of‐gray‐gases (WSGG) model for pressurized oxy‐fuel conditions was first presented in this paper, which was applied in 3 typical high pressure conditions: 5, 10, and 15 bar. The new WSGG model correlations were suitable for pressurized conditions with a molar ratio range of 0.125‐2, temperature range of 400‐2500 K, and path length range of 0.1‐20 m. Calculations for a variety of typical pressurized oxy‐fuel combustion cases showed that the new WSGG model can accurately predict the radiation characteristics and heat transfer characteristics of the gas mixtures compared with the SNB model benchmark. In addition, the application of the previous atmospheric WSGG models yielded non‐ideal results under pressurized conditions. Consequently, the new model can provide efficient and accurate radiation heat transfer results for pressurized oxy‐fuel conditions and can be used to design pressurized oxy‐fuel combustion furnaces or boilers.

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“…296 which indicates that the contribution of the wall to the measurement of flame radiation 297 becomes negligible, and the measured surface incident radiation can be directly used to 298 approximate flame radiation. Optically dense systems include pilot-and large-scale coal combustion systems operating under elevated pressure [10,23,41]. Since the particle number density almost increases proportionally with pressure for a given thermal input and stoichiometric ratio, the optical thickness is also approximately proportional to pressure.…”

Section: An Approach To Estimate Flame Radiationmentioning

confidence: 99%

“…Also, determination of flame radiation through computational calculations remains a subject with high uncertainty in practical combustion systems [16][17][18][19]. This is principally due to the complexity associated with determining the key radiative properties, such as the local absorption and scattering coefficients of optically active gaseous components and, more importantly, those of various particulates (coal, char, ash, and soot) [20][21][22][23][24].…”

Section: Introduction 51mentioning

confidence: 99%

An approach to estimating flame radiation in combustion chambers containing suspended-particles

Yang

Adeosun

Kumfer

et al. 2017

Fuel

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Thermal radiation often plays a key role in heat transfer between flames and the surrounding environment. Therefore, reliable measurement of flame radiation is indispensable in the study of combustion. While the measurement of radiative flux from flames is straightforward in an open environment, it is challenging to do so in a confined chamber, due to the influence of the walls. Radiation emitted by the walls and the reflection of flame radiation off the walls can interfere with measurements of flame radiation. For wall surfaces that are at high temperature or highly reflective, the error in the flame radiation measurement can be significant. In this paper, a theoretical analysis was carried out to study the contribution of wall emission and wall reflection to the incident radiation measured by radiometers. The results reveal that for a typical lab-scale air-fired flame, the contribution of wall emission and wall reflection to the measured incident radiation can be as high as 55% for a refractory-lined wall and 40% for a water-cooled wall. A convenient approach is proposed to distinguish flame radiation from the measured incident radiation. The approach is based on measurements of surface incident radiation and net radiative heat flux through the wall. The approach can be applied to optically thin systems (most labscale and some pilot-scale atmospheric pressure combustion systems) and optically dense systems (typically pressurized large-scale combustion systems). CFD simulations were 41 also performed for two coal-fired combustors, one which represents optically thin and the 42 other optically thick systems, to validate the theoretical model and the approach to 43 estimating flame radiation. Good agreement was observed between CFD results and the 44 3 theoretical model results, and the proposed approach to estimation of flame radiation was 45 found to have reasonable accuracy. 46

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Pressurized oxy-combustion with low flue gas recycle: Computational fluid dynamic simulations of radiant boilers

Cited by 56 publications

References 40 publications

Nitrogen and sulfur conversion during pressurized pyrolysis under CO 2 atmosphere in fluidized bed

Nitrogen and sulfur conversion during pressurized pyrolysis under CO 2 atmosphere in fluidized bed

New weighted-sum-of-gray-gases model for typical pressurized oxy-fuel conditions

An approach to estimating flame radiation in combustion chambers containing suspended-particles

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