Effect of an Acoustic Field on the Combustion of Coal Particles in a Flat Flame Burner

The effects of an acoustic field on the enhancement of coal combustion are investigated. A flat flame burner using methane-air mixtures as the fuel is used for the experiments. Micronized coal particles 20–70 μm in diameter are injected into the burning gas stream at the same velocity as the gas. The light intensity emitted from the flame, temperature and pictures of the flame with and without an acoustic field are recorded. The nominal values of the intensity of the acoustic field are between 140–160 dB and the frequency is between 500–3500 Hz. A definite increase in the rate of combustion of the coal particles is observed with the application of an acoustic field. The enhancement can be seen from the increased light intensity of the flame and the flame width. This paper presents the data and a discussion of light intensity emitted by the flame as a function of acoustic parameters.

Download Full-text

The determination of burning velocities of slow flames

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1955.0050 ◽

1955 ◽

Vol 228 (1174) ◽

pp. 297-322 ◽

Cited By ~ 16

Keyword(s):

Carbon Monoxide ◽

Burning Velocity ◽

Flame Temperature ◽

Excess Energy ◽

Flat Flame ◽

Straight Line ◽

Flame Burner ◽

Line Relationship ◽

Propane Butane

Measurements of the burning velocities of methane, ethane, propane, butane, ethylene, carbon monoxide and cyanogen mixtures with air, in the range about 4 to 8 cm, are made by the flat-flame burner method with an accuracy of 2 to 3%. The results can be represented by a straight-line relationship between composition and burning velocity except for carbon monoxide which is sensitive to the percentage of water vapour present. Extrapolated values agree well with recent measurements of faster flames. Measurements are also made on binary mixtures with air of the gases, including hydrogen. The mixture law holds except with mixtures containing carbon monoxide. Limits of inflammability are also determined and the burning velocities at the limits average 3⋅6 cm/s. The mixtures obey the Le Chatelier rule accurately, except for carbon monoxide mixtures. The burning velocities of the hydrocarbons can be represented approximately by a straight-line relationship with the heat generated and with the maximum flame temperature, but correlation is best when thermal conductivity is introduced. At a given velocity the excess energy maintained by the flame appears to be constant for all the hydrocarbons investigated, except methane, which behaves slightly differently. The burning velocities of the hydrocarbons are controlled by a reaction which provides reasonable values of the activation energies and probably precedes the sudden development of chain branching.

Download Full-text

Study on the mechanisms of ultrafine particle formation during high-sodium coal combustion in a flat-flame burner

Fuel ◽

10.1016/j.fuel.2016.01.033 ◽

2016 ◽

Vol 181 ◽

pp. 1257-1264 ◽

Cited By ~ 27

Author(s):

Zhenghang Xiao ◽

Tiankun Shang ◽

Jiankun Zhuo ◽

Qiang Yao

Keyword(s):

Coal Combustion ◽

Ultrafine Particle ◽

Particle Formation ◽

High Sodium ◽

Flat Flame ◽

Flame Burner

Download Full-text

Large Eddy Simulation on the Effects of Coal Particles Size on Turbulent Combustion Characteristics and NOx Formation Inside a Corner-Fired Furnace

Journal of Energy Resources Technology ◽

10.1115/1.4048864 ◽

2020 ◽

Vol 143 (8) ◽

Author(s):

Wenjing Sun ◽

Wenqi Zhong ◽

Jingzhou Zhang ◽

Tarek Echekki

Keyword(s):

Large Eddy Simulation ◽

Coal Combustion ◽

Flame Temperature ◽

Particle Dispersion ◽

Combustion Characteristics ◽

Pulverized Coal ◽

Nox Formation ◽

Eddy Simulation ◽

Coal Particles ◽

Large Eddy

Abstract The effects of pulverized coal particles’ sizes on the coal combustion characteristics are numerically studied in a laboratory-scale tangentially fired furnace. The turbulent gas flow and the coal particle motion are solved by employing the large eddy simulation (LES) and the discrete phase model (DPM). The mixture fraction probability density function (MF-PDF) is coupled to simulate the non-premixed pulverized coal combustion. It is found that the coal combustion efficiency is positively affected by the dispersion of coal powders. The particle dispersion and the coal combustion are augmented by the intensive impingement caused by the corner-injected flow. Large coal particles, with their greater inertia, enhance particle agglomerations, which limit the combustion of volatile and char. Accordingly, the average flame temperature decreases with the growing particle sizes. Also, the O2 concentration increases slightly because of the incomplete coal combustion, and the CO2 concentration decreases gradually. In contrast, the CO concentration increases markedly in the furnace center due to the presence of a reducing atmosphere. The NO concentration exhibits an exponential decline with the increased particle size. A relatively stable combustion and a relatively low NOx formation are acquired inside such a corner-fired furnace when the particle Stokes number is a little greater than 1.

Download Full-text

A Model of the Enhancement of Coal Combustion Using High-Intensity Acoustic Fields

Journal of Energy Resources Technology ◽

10.1115/1.2905912 ◽

1991 ◽

Vol 113 (4) ◽

pp. 277-285 ◽

Cited By ~ 9

Author(s):

S. Yavuzkurt ◽

M. Y. Ha ◽

G. Koopmann ◽

A. W. Scaroni

Keyword(s):

Mass Transfer ◽

Heat And Mass Transfer ◽

Acoustic Field ◽

High Intensity ◽

Coal Combustion ◽

Sound Pressure ◽

Pulverized Coal ◽

Acoustic Fields ◽

Coal Particles ◽

Sound Pressure Levels

A model for the enhancement of coal combustion in the presence of high-intensity acoustic fields has been developed. A high-intensity acoustic field induces an oscillating velocity over pulverized coal particles otherwise entrained in the main gas stream, resulting in increased heat and mass transfer. The augmented heat and mass transfer coefficients, expressed as space and time-averaged Nusselt and Sherwood numbers for the oscillating flow, were implemented in an existing computer code (PCGC-2) capable of predicting various aspects of pulverized coal combustion and gasification. Increases in the Nusselt and Sherwood numbers about 45, 60 and 82.5 percent at sound pressure levels of 160, 165 and 170 dB for 100-μm coal particles were obtained due to increase in the acoustic slip velocity associated with the increased sound pressure levels. The main effect of the acoustic field was observed during the char combustion phase in a diffusionally controlled situation. A decrease in the char burn-out length (time) of 15.7 percent at 160 dB and 30.2 percent at 170 dB was obtained compared to the case with no sound for the 100-μm coal particles.

Download Full-text