The transition of heterogeneous–homogeneous ignitions of dispersed coal particle streams

Yuan, Yongfeng; Li, Shuiqing; Li, Gengda; Wu, Ning; Yao, Qiang

doi:10.1016/j.combustflame.2014.03.008

Cited by 137 publications

(73 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The combustion setup represents a typical entrained flow reactor [11,[24][25][26] for particle combustion combined with an optical device to measure particle temperature and diameter (assuming a spherical particle) by sizing pyrometry with simultaneous measurement of infra-red radiation by two different detectors. A fiber spectrometer was employed to measure the thermal radiation from particles in the region 1.…”

Section: Introductionmentioning

confidence: 99%

Char particle emissivity of two coal chars in oxy-fuel atmospheres

Graeser

Schiemann

2016

Fuel

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Char particle emissivity of two coal chars in oxy-fuel atmospheres

Graeser

Schiemann

2016

Fuel

View full text Add to dashboard Cite

“…The devolatilisation and char oxidation rates, ignition delays and burnout times of burning solid fuel particles largely depend on the surrounding conditions [1,2]. The hot gas temperature, rapid heating ratesand oxygen concentration contribute to discrepantignition delaysand flame intensities [3,4].Fast pyrolysis increases the soot production from solid fuel particles, particularly at high temperatures, whensoot is relatively more reactive [5,6].Such reactivity, along with the high volume fraction of soot particles,greatly influences thecombustion performance inindustrialapplications,because sooty flamesradiate large amounts of heat. In general,pulverised solid fuel particles immediately reach high temperatures during combustion, forming a sooty flame with release of volatile matter, tar, soot and ash in the early stages [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…1).The reactor dimensions of (45×45×800)mm3 , equipped with a guard heater insulator. The honeycomb burner produced a high surrounding gas from the bottom To analyse particle combustion behaviours, the velocities of the the leftward-flowing streams are constant in all experiments honeycomb flow straightener installed above the burner maintained a laminar gas flow , which maintained a cold carrier gas at 298 K,was placed .This layout allowed a cross-flow configuration in the reactor.…”

mentioning

confidence: 99%

Flame structures and ignition characteristics of torrefied and raw sewage sludge particles at rapid heating rates

Mock

Lee

Choi

et al. 2017

Fuel

View full text Add to dashboard Cite

Torrefactionis a promising method for improving the quality of pulverised solid fuel, as itincreases the flame stability,radiative heat transfer and energy density of the fuel.Raw sewage sludge contains less fixed carbon and more ash compounds than other biomasses; consequently, it has poorenergy quality witha long ignition delay and forms arelatively low, sooty flame. In this study,we directly investigate the combustion behavioursof particles with varying degrees of torrefaction by burning them at 1340 K.Thetorrefied particles were prepared at different temperatures(473 K or 573 K) for different residence times (10minor 30min).The experimental parameters examined were the size range of the particles (150-215μmand 255-300 μm)and the O 2 percentage(10-40%).The particles wereentrained from a 3 cold carrier gas into a hot gas stream, igniting a volatile flame that was extinguished a few millisecondslater. These temporal variations in the burning particles weredetected byin-situ high speed photography (7000 frames/s).Thetorrefactiondegree affected the flame structure and varied the ignition delay, due to the mismatched reactivity and soot formation at rapid heating rates. The mosttorrefied sludge particlesexhibited a relatively luminous volatile cloudand a large flame, while preserving the duration of volatile combustion. These observations confirm theimproved pulverised combustion of the torrefied sludge particles. We also obtained valuable flame parameters (radius, intensity and combustion time) of the differentlytorrefied sludge particles.

show abstract

“…With regard to the ignition and burnout behaviours of coal, most previous studies concentrated on the influences of coal rank, particle size, temperature, etc. As an example, Yuan et al observed the transition of heterogeneous‐homogeneous ignitions of dispersed coal particle streams using the ICCD technology, detecting that the heterogeneous ignition occurred in lower temperatures at 1200 K and the hetero‐homogeneous ignition existed in cases of 1500 K or 1800 K, while the pure homogeneous ignition mode could only occur theoretically at high temperatures and low O 2 for high‐volatile coals. In addition, it has been reported that finer particles are more likely to ignite as a one‐step process with the heterogeneous ignition and burn out rapidly, whereas coarser particles incline to show a volatile flame prior to heterogeneous oxidation and hold a dramatic increase in burnout times .…”

Section: Introductionmentioning

confidence: 99%

The competitive reaction mechanism between oxidation and pyrolysis consumption during low‐rank coal combustion at lean‐oxygen conditions: A quantitative calculation based on thermogravimetric analyses

Wang

Xin

et al. 2018

Can J Chem Eng

View full text Add to dashboard Cite

The evolution of the oxidation-pyrolysis competitive mechanism during low-rank coal combustion at lean-oxygen conditions determines the development of the coalfield fires and the burning loss rate of the coal resource. In the present work, the mass increments of oxygen-chemisorption were measured and calculated firstly. An abstract shrinking core model was built for distinguishing the oxidation and pyrolysis pathways. On this basis, the consumption rates of oxidation and pyrolysis were respectively calculated with the TGA data obtained under the lean-oxygen gradient of 21-0 %. The results demonstrate that the oxidation path gradually delays in temperature while the pyrolysis exhibits great temperature stability as the oxygen concentration decreases. Besides, the significant transition of the competitive consumption mechanism exists below 9 % for the oxidation phase before ignition and 5 % for the combustion phase after ignition, respectively. Two temperature indicators of T C1 and T C2 for guiding the optimal fire extinguishing schemes based on the actual oxygen concentrations and temperatures are proposed. Furthermore, 1 % is identified as the limiting oxygen concentration for the development of the coalfield fires where the ignition mechanisms of both the HST and WD coal transform into the homogeneous ignition. The WD lignite, which always maintains the coke state as the burnout mechanism, holds higher reactivity but wider dispersion degrees of combustion compared with the HST sub-bituminous coal.

show abstract

The transition of heterogeneous–homogeneous ignitions of dispersed coal particle streams

Cited by 137 publications

References 21 publications

Char particle emissivity of two coal chars in oxy-fuel atmospheres

Char particle emissivity of two coal chars in oxy-fuel atmospheres

Flame structures and ignition characteristics of torrefied and raw sewage sludge particles at rapid heating rates

The competitive reaction mechanism between oxidation and pyrolysis consumption during low‐rank coal combustion at lean‐oxygen conditions: A quantitative calculation based on thermogravimetric analyses

Contact Info

Product

Resources

About