Explosion energy of methane/deposited coal dust and inert effects of rock dust

甲烷/沉积煤尘爆炸能量及岩尘惰性影响

Fuel, Volume 228, 15 September 2018, Pages 112-122

Yifan Song, Bouras Nassim, Qi Zhang

摘要：In order to study the processes of lifting, dispersing and igniting of a dust

layer behind the local gas explosion as well as their suppression, premixed

methane local explosion igniting deposited coal/inert rock dust at the bottom

of a tube are simulated. The two-phase combustion mechanism is obtained that

the deposited dust is kicked up by the leading pressure wave, developing an

uneven dust cloud filling in the tube, and then the gas flame ignites the dust

cloud to form the composite flame. The rock dust lain on the tunnel ground has

a significant suppression effect on the explosion overpressure, flame

temperature and velocity of methane with coal dust. When the rock dust

proportion in coal dust is 90%, the peak values of overpressure, flame

temperature and flame velocity of the hybrid coal dust/rock dust/methane

explosion are 0.6, 0.78 and 0.55 times of those of coal dust/methane explosion,

respectively. The rock dust with the particles of smaller size has a remarkable

suppression effect on explosion flame. When the rock dust proportion in the

coal dust is 70%, the peak explosion overpressure and the flame velocity under

suppression of the 12 µm rock dust are 10% and 11% lower than those of the

31 µm rock dust, respectively.

 

Assessment of gas and dust explosion in coal mines by means of fuzzy fault tree analysis

基于模糊故障树分析的煤矿瓦斯与煤尘爆炸评估

International Journal of Mining Science and Technology, In press, corrected proof, Available online 31 July 2018

Shulei Shi, Bingyou Jiang, Xiangrui Meng

摘要：During the past decade, coal dust and gas explosions have been the most two serious

types of disasters in China, threatening the lives of miners and causing

significant losses in terms of national property. In this paper, an evaluation

model of coal dust and gas explosions was constructed based on a fuzzy fault

tree by taking the Xingli Coal Mine as a research site to identify the risk

factors of coal dust and gas explosions. Furthermore, the hazards associated

with such explosions were evaluated for this particular coal mine. After

completing an on-site investigation, the fuzzy probabilities of basic events

were obtained through expert scoring, and these expert opinions were then

aggregated as trapezoidal fuzzy numbers to calculate the degrees of importance

of all basic events. Finally, these degrees of importance were sorted.

According to the resulting order, the basic events with higher probabilities

were determined to identify key hazards in the daily safety management of this

particular coal mine. Moreover, effective measures for preventing gas and coal

dust explosions were derived. The fuzzy fault tree analysis method is of high

significance in the analysis of accidental coal mine explosions and provides

theoretical guidance for improving the efficiency of coal mine safety

management in a scientific and feasible manner.

 

The quantitative studies on gas explosion suppression by an inert rock dust deposit

惰性岩尘沉积抑制气体爆炸量化研究

Journal of Hazardous Materials, Volume 353,5 July 2018, Pages 62-69

Yifan Song, Qi Zhang

摘要：The traditional defence against propagating gas explosions is the application of

dry rock dust, but not much quantitative study on explosion suppression of rock

dust has been made. Based on the theories of fluid dynamics and combustion, a

simulated study on the propagation of premixed gas explosion suppressed by

deposited inert rock dust layer is carried out. The characteristics of the

explosion field (overpressure, temperature, flame speed and combustion rate) at

different deposited rock dust amounts are investigated. The flame in the

pipeline cannot be extinguished when the deposited rock dust amount is less

than 12 kg/m3. The effects of suppressing gas explosion become weak when the

deposited rock dust amount is greater than 45 kg/m3. The overpressure decreases

with the increase of the deposited rock dust amounts in the range of

18–36 kg/m3 and the flame speed and the flame length show the same trends. When

the deposited rock dust amount is 36 kg/m3, the overpressure can be reduced by

40%, the peak flame speed by 50%, and the flame length by 42% respectively, compared

with those of the gas explosion of stoichiometric mixture. In this model, the

effective raised dust concentrations to suppress explosion are 2.5–3.5 kg/m3.

 

Construction of a 36 L dust explosion apparatus and turbulence flow field comparison with a standard 20 L dust explosion vessel

36 L粉尘爆炸实验装置的构建及其湍流流场与标准20 L粉尘爆炸容器的比较

Journal of Loss Prevention in the Process Industries, Volume 55, September 2018, Pages 113-123

Diana Castellanos, Victor Carreto, Trygve Skjold, Shuai Yuan, Chad Mashuga

摘要：By modifying the dispersion system and the ignition delay time, and hence the flow

field and turbulence intensity during the combustion process, various 20 L dust

explosion vessels have been calibrated to give results comparable to the 1 m3

vessel as prescribed in the former ISO standard (ISO-6184, 1985). However, the

results obtained from experiments conducted in the two vessels do not always

agree for the same dust. There can be several reasons for this discrepancy:

turbulence decays faster in the 20 L vessel compared with the 1 m3 vessel, the

energetic ignition sources used in standardized tests may overdrive the

combustion process in the 20 L vessel, and the interaction between the flame

front, including radiation emitted from the flame, and the vessel walls is more

pronounced for the smaller vessel. This paper details an approach for

calibrating a new 36 L dust explosion vessel by utilizing principles for

factorial design and analyzing the decay of turbulence following the transient

dispersion of the dust clouds by means of computation fluid dynamics (CFD). In

the present work, the CFD simulations were used to examine transient injection

of air into the 20 L and 36 L vessels, in conjunction with experimental data

reported for the 20 liter spherical vessel. Although the vessels considered

here had slightly different shapes, sizes, dispersion systems and operating

conditions, the simulated turbulence levels were similar at the time of

explosion. In addition, the estimates for the laminar burning velocity (SL)

obtained using experimental results from the 20 L and 36 L vessels, and

assuming the validity of a correlation for the turbulent burning velocity (ST),

were also in good agreement. The experimental procedure and multi-variable

calibration of the 36 L vessel has been successfully validated by comparing the

explosion parameters, such as maximum explosion pressure (Pmax) and

size-corrected maximum rate of pressure rise (KSt) to values obtained for the

same fuels in a standard 20 L vessel. Furthermore, the experimental results

obtained for niacin and cornstarch in the 36 L vessel were in excellent

agreement with accepted reference values from literature. It is expected that

the same methodology can be used for calibrating other equipment with different

configurations where transient turbulence decay has a strong effect on the

explosions.

 

Influence of specific surface area on coal dust explosibility using the 20-L chamber

基于20-L爆炸容器的比表面积对煤尘爆炸性的影响

Journal of Loss Prevention in the Process Industries, Volume 54, July 2018, Pages 103-109

Isaac A. Zlochower, Michael J. Sapko, Inoka E. Perera, Connor B. Brown, Naseem S. Rayyan

摘要：The relationship between the explosion inerting effectiveness of rock dusts on coal

dusts, as a function of the specific surface area (cm2/g) of each component is

examined through the use of 20-L explosion chamber testing. More specifically,

a linear relationship is demonstrated for the rock dust to coal dust (or

incombustible to combustible) content of such inerted mixtures with the

specific surface area of the coal and the inverse of that area of the rock

dust. Hence, the inerting effectiveness, defined as above, is more generally

linearly dependent on the ratio of the two surface areas. The focus on specific

surface areas, particularly of the rock dust, provide supporting data for

minimum surface area requirements in addition to the 70% less than 200 mesh

requirement specified in 30 CFR 75.2.