Modeling Issues in CFD Simulation of Brown Coal Combustion in a Utility Furnace

Tian, Zhao Feng; Witt, Peter J.; Schwarz, M. Philip; Yang, William

doi:10.1260/1757-482x.2.2.73

Cited by 9 publications

(19 citation statements)

References 19 publications

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“…Up till now, none of the solid fuel combustion submodels has been validatd for pressurized oxy-combustion environment. In the present work, the sub-models that have been extensively validated under atmospheric pressure oxy-coal combustion environment are used[4,[29][30][31][32][33][34]. It has been shown that RANS is able to provide reasonable agreement between experiments and CFD simulations under atmospheric pressure oxy-combustion condistions.…”

mentioning

confidence: 99%

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

Xia

Yang

Adeosun

et al. 2016

Fuel

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Oxy-fuel combustion is considered a promising technology for carbon capture, utilization, and storage (CCUS). One of the primary limitations on full-scale implementation of this technology is the significant increase in the cost of electricity due to a large reduction in plant efficiency and high capital costs. Recently a new concept, namely staged, pressurized oxy-combustion, has been developed in which the flue gas recycle is reduced significantly by means of fuel-staged combustion. At higher pressure the latent heat of condensation of the moisture in the flue gas can be utilized in the Rankine cycle, further increasing the plant efficiency. As determined through ASPEN Plus modeling, this approach increases the net plant efficiency by more than 6 percentage points, compared to first-generation oxy-combustion plants. The early stages of the system involves burning coal in high oxgen concentration, which means the flame temperature is extremely high. New boilers designs are required to handle these extreme conditions. In the present papr, a unique burner and boiler has been designed via computational fluid dynamics (CFD) to effectively and safely burn coal under conditions of elevated pressure and low flue gas recycle. The enclosed jet theory was used to design a combustion system with slow mixing and no external recirculation, which helped minimize flame impingement and ash deposition. A cone-shaped geometry was utilized to minimize the effects of buoyancy in the down-fired, axial-flow system. A 1540 MWth SPOC system was simulated based on this design and the results showed that a relatively uniform distribution of wall heat flux can be acheieved and the peak wall heat flux was under a manageable level even though local gas temperature are extremely high.

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confidence: 99%

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

Xia

Yang

Adeosun

et al. 2016

Fuel

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“…Turbulence is modeled using the standard k –ε turbulence model. This was chosen after testing a number of turbulence models for coal combustion in a non-swirl burner, gas–particle flows through rectangular jets inclined to a cross-flow, and brown coal combustion in a furnace . The second case is representative of air and coal particle flows through the slot burners used in the tangentially fired furnace.…”

Section: Cfd Model Descriptionmentioning

confidence: 99%

“…In our previous work, , the CFD model used here was validated by comparing the FGET, concentration of flue gas components, total boiler heat supply, and wall incident heat fluxes to power plant measurements. Additionally, validation of submodels for gas–particle flows, coal and volatile combustion, and turbulence , was performed on simpler flows, where more detailed measurements could be taken under controlled operating conditions.…”

Section: Cfd Model Descriptionmentioning

confidence: 99%

“…Additionally, validation of submodels for gas–particle flows, coal and volatile combustion, and turbulence , was performed on simpler flows, where more detailed measurements could be taken under controlled operating conditions. Readers requiring further information on the CFD model used in this work are referred to the detailed description of the model and current furnace operating conditions with wet brown coal that are given in our previous studies. , …”

Section: Cfd Model Descriptionmentioning

confidence: 99%

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Combustion of Predried Brown Coal in a Tangentially Fired Furnace under Different Operating Conditions

Tian

Witt²,

Schwarz³

et al. 2012

Energy Fuels

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A major challenge in the use of brown coal in Victoria, Australia, for power generation is its high moisture content, which results in high greenhouse gas emissions. Predrying technologies for coal are one option being considered for use in browncoal-fired power plants in Victoria to reduce greenhouse gas emissions. Using a validated computational fluid dynamics (CFD) model, this study investigates the combustion of predried brown coal in a 375 MW tangentially fired furnace that was designed for raw or non-predried brown coal. Different operating arrangements of the fuel gas for the predried coal with various moisture contents are proposed and assessed. When predried brown coal is burned with 55% or lower moisture content, the CFD results indicate that additional gas needs to be added to the fuel gas to maintain the original mass flow rate and reduce the heat flux in the furnace. Arrangements with additional air or recirculated flue gas added to the fuel gas are proposed and tested for predried coal with 55, 45, 35, 25, and 15% moisture contents. The increase in the furnace temperature for the recirculated flue gas arrangement is smaller than that of the additional air arrangement, and stack loss is expected to be smaller than for additional air cases. The temperature distributions and wall heat fluxes in the boiler for the recirculated flue gas cases are similar to that of the raw coal combustion case. Therefore, use of recirculated flue gas is proposed as an option for future operation of the furnace with predried coal. Nevertheless, further studies are essential to understand the technical and financial feasibility of using flue gas to maintain the fuel gas flow rate.

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“…(2) evaporation/drying model, (3) devolatilisation model, (4) char combustion model, (5) turbulence model, (6) turbulence-reaction interaction model (gas phase reaction models), (7) radiation model, (8) soot model, (9) NOx model, (10) SOx model, (11) slagging model. Figure 2, adapted from Tian et al (2010a) shows some sub-models available in the commercial CFD code ANSYS/CFX 14.…”

Section: Introductionmentioning

confidence: 99%