Combined control of secondary air flaring angle of burner and air distribution for opposed-firing coal combustion

Luo, Rui; Fu, Jiapeng; Li, Na; Zhang, Yafei; Zhou, Qulan

doi:10.1016/j.applthermaleng.2015.01.008

Cited by 24 publications

(7 citation statements)

References 21 publications

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“…The particles in the sampled fly ash continue burn in the thermal gravimetric analyzer (TGA). The burnout can be calculated by the following formula [28,[30][31][32]:…”

Section: Of 14mentioning

confidence: 99%

“…In this paper, a swirling burner with real-time adjustable inner secondary air flaring angle is proposed and built on a laboratory scale. Although some related works [20,28] have been conducted about the burner adjustable flaring angle influence mechanism and combined control with air distribution, its application under various load and fuel rich/lean combustion conditions is still not reported. The effects of burner flaring angle on fuel rich/lean combustion and low load combustion are separately studied by combustion experiments in a laboratory-scale opposed-firing furnace.…”

Section: Introductionmentioning

confidence: 99%

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Combustion Characteristics and NOx Emission through a Swirling Burner with Adjustable Flaring Angle

et al. 2018

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A swirling burner with a variable inner secondary air (ISA) flaring angle β is proposed and a laboratory scale opposed-firing furnace is built. Temperature distribution and NOx emission are designedly measured. The combustion characteristics affected by variable β are experimentally evaluated from ignition and burnout data. Meanwhile, NOx reduction by the variable β is analyzed through emissions measurements. Different inner/outer primary coal-air concentration ratios γ, thermal loads and coal types are considered in this study. Results indicate that β variation provides a new approach to promote ignition and burnout, as well as NOx emission reduction under conditions of fuel rich/lean combustion and load variation. The recommended β of a swirling burner under different conditions is not always constant. The optimal βopt of the swirling burner under all conditions for different burning performance are summarized in the form of curves, which could provide reference for exquisite combustion adjustment.

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“…The particles in the sampled fly ash continue burn in the thermal gravimetric analyzer (TGA). The burnout can be calculated by the following formula [28,[30][31][32]:…”

Section: Of 14mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Combustion Characteristics and NOx Emission through a Swirling Burner with Adjustable Flaring Angle

et al. 2018

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“…Similar studies of large boiler swirl burners have shown that the flame height increases as the ratio of secondary air increases (Wang et al, 2018). For the study of the air distribution of a slightly less powerful burner (900 kW), Luo et al (2015) also believed that the reasonable secondary air ratio was beneficial to the increase of the combustion temperature. In smaller restricted spaces, the required burner power is usually less than 100 kW.…”

Section: Introductionmentioning

confidence: 96%

Effect of Air Quantity Distribution Ratio on Flame Height of Flue Gas Self-Circulation Burner

Xie

Cui

Qiu

et al. 2020

JAFM

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It is a difficult scientific problem of applied fluid mechanics that the flame is too long and does not match the furnace chamber in a small restricted heating space. This paper aims to investigate the effect of the air quantity distribution ratio on the flame height of a flue gas self-circulation burner. In order to obtain a better combustion emission effect and a shorter flame height, a burner head structure with a small flue gas selfcirculation was designed. Numerical simulation was employed to investigate the effect of the different distributions of central air, swirling air and secondary air on flame height. The periodic boundary condition model was adopted and the numerical model was compared and validated by experiment. Correlation analysis was used to determine the influence of the air inlet ratio of each part on the flame height and recirculating flue gas ratio (RFGR). The results show that the influence of different air quantity distributions on flame length is very significant. A reasonable central air ratio is a necessary condition for the good combustion of this flue gas self-circulation burner. Secondary air can effectively increase the RFGR, and flame height was significantly shorter with the increase of RFGR, but when it increased to more than 12%, the flame length was basically no longer shortened. On the premise of stable combustion, when the ratio of central air, swirling air and secondary air are respectively 25%, 35% and 40%, the shortest flame length is achieved. This work reveals an influence mechanism of the flame height of a small burner with a flue gas circulation structure. These results can provide theoretical support and an engineering design basis for the short flame problem in a small restricted space.

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“…At the moment, the three most common combustion technologies used in coal-fired power plants are opposed-fired, tangential-fired, and down-fired. Because of its flame organisation independence, limitless boiler shape, and low gas temperature deviation in the horizontal flue gas pass, opposedfired boilers are frequently utilised [19]. However, low-load flame stability and NO x emissions remain the primary challenges in design and operation [19].…”

Section: Introductionmentioning

confidence: 99%

Optimisation of Solid Fuel In-furnace Blending for an Opposed-firing Utility Boiler: A Numerical Analysis

Rahman

2022

CFDL

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Continuous research on the clean and effective use of coal is still necessary as coal will continue to play a key role in global energy supply for the foreseeable future. Hence, in the current study, the optimisation of in-furnace coal blending for one of Malaysia's opposed-firing utility boilers was numerically executed on the basis of hydrodynamics and combustion characteristics. The predicted FEGT from the numerical model was validated against the actual FEGT from the coal-fired power plant, revealing a difference of less than 10 %. Four (4) coal blended cases were tested, which included both bituminous (bit) and sub-bituminous (sub-bit) coals. The findings demonstrate that due to the difference in density between bit and sub-bit coals, the hydrodynamic performance is predicted to significantly improve when sub-bit coal is injected at the bottom burner as opposed to the upper burner. In terms of kinetics, the higher volatile matter (VM) of sub-bit coal in contrast to bit coal has been postulated to release a substantial amount of volatiles and improve the combustibility of bit coal. Furthermore, enhanced oxygen release from sub-bit coal volatiles can aggravate the gas-solid heterogeneous reaction during bit coal char combustion. As a result of the bottom burner's high temperature, it has been discovered that introducing sub-bit coals into those burners speeds up VM release and char combustion, which increases the rate of combustion. Thus, when combustibility rises, the peak temperature position moves downward, reducing the likelihood of delayed combustion and, consequently, the risk of heat exchanger pendant failure and ash deposition. In a furnace with a relatively long coal residence time, a considerable fraction (>20 %) of high gross calorific value (GCV) sub-bit coal (>5800 kcal/kg) is predicted to produce two peak flame temperatures exceeding 1600°C owing to the likelihood of enhanced char which created delayed combustion. Therefore, a furnace condition with a comparatively shorter coal residence time may aid in the rapid evacuation of residual char from the combustion/burner zone and minimise the potential for delayed combustion. Nonetheless, residual char escape may exacerbate the emission problem by releasing considerable unburned carbon. Overall, the current numerical model has the potential to be a reliable and cost-effective tool for investigating the combustion characteristics of coal blends in a power plant boiler.

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Combined control of secondary air flaring angle of burner and air distribution for opposed-firing coal combustion

Cited by 24 publications

References 21 publications

Combustion Characteristics and NOx Emission through a Swirling Burner with Adjustable Flaring Angle

Combustion Characteristics and NOx Emission through a Swirling Burner with Adjustable Flaring Angle

Effect of Air Quantity Distribution Ratio on Flame Height of Flue Gas Self-Circulation Burner

Optimisation of Solid Fuel In-furnace Blending for an Opposed-firing Utility Boiler: A Numerical Analysis

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