Numerical analysis on effect of furnace scale on heat transfer mechanism of coal particles in pulverized coal combustion field

Abstract

To investigate the effect of the furnace scale on the heat transfer mechanism of coal particles, numerical simulations of coal combustion fields in three different scale furnaces (915 MW th actual large scale boiler, 2.4 MW th and 0.76 MW th test furnaces) were conducted. High accuracy of simulation methods was validated with the measured data. From the comparison of numerical simulations between three different scale furnaces, it was clarified that the particle residence time with high particle temperature for a small scale furnace is shorter than that for a large scale furnace even if the particle residence time passing the high temperature gas is the same. This is caused by the insufficient heat gain of particles for a small scale furnace due to the lower radiation heat transfer because of the thinner flame thickness in the small furnace. The sphericity of ash particles from small scale furnaces is lower than that for large scale furnaces due to the shorter particle residence time with high particle temperature. These findings should be considered when the usability of coal brands for actual large scale boilers is evaluated by the fly ash properties from a small scale experimental furnace.

Radiative heat transfer in strongly forward scattering media of circulating fluidized bed combustors

“…This agreement may be attributed to low particle load (0.01 kg/ m 3 ) in the ABFBC under consideration. Use of isotropic scattering assumption in pulverized fuel (PF) furnaces with the same order of magnitude particle load [13,14] has also been found to lead to fairly accurate results, as reported in recent literature [15][16][17][18][19][20][21][22][23]. However, in some of these studies, isotropic scattering was found to underestimate wall heat fluxes, mostly due to fly ash [17], compared to measurements [18,19].…”

“…(22) and (23) for Henyey-Greenstein phase function was recently suggested [26]. Only the forward cos…”

A complete review based on various aspects of pulverized coal combustion

“…They further added that both CO 2 and temperature predictions improved by considering radiation. Hashimoto and Watanabe studied how heat transfer mechanism is affected by furnace scale and investigated heat transfer mechanism in 915 MW large boiler 2.4 MW and 0.76 MW test furnaces. They reported that small‐scale furnace has shorter residence time due to the higher temperature of the particles than the large‐scale furnace.…”

Effect of different fuel NO models on the prediction of NO formation/reduction characteristics in a pulverized coal combustion field

“…Numerical simulations of pulverized coal combustion fields are useful to archive such understanding [e.g., . Recently, numerical simulations of actual large-scale boilers have been conducted by some researchers [e.g., [7][8][9][10]. Numerical simulations for predicting NOx formation characteristics in coal combustion fields have also been conducted [e.g., [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”