Thermal degradation of bituminous coal with both model-free and model-fitting methods

Lei

et al. 2019

Energies

Liquid nitrogen is a vital medium during the extinguishing and chilldown process of coal spontaneous combustion in coal mine goafs. In this paper, the heat and mass transfer of liquid nitrogen in a loose medium was investigated. A laboratory system including a temperature sensing system was designed and built to explore the effects of different nitrogen injection positions and angles on the chilldown effect. The results indicate that after liquid nitrogen injection, the temperatures in the liquid nitrogen flow area and the bottom of the model can be quickly reduced to −196 °C, which was the best chilldown effect zone. With the vaporization of the liquid nitrogen, the cryogenic nitrogen gradually diffused. At 20,000 s, the bottom temperature was about –63 °C, the middle was –30 °C, and the upper was 0 °C. When the model angle was 0°, the effective chilldown zone was the largest. As the angle increased, the effective chilldown volume and holding time decreased significantly. The model angle had a greater impact on the chilldown. For the position of nitrogen injection, the inlet was set slightly farther from the gas outlet’s position, leading to a larger coverage for the liquid nitrogen and cryogenic nitrogen chilldown. This study can provide a theoretical basis for the flow and chilldown of nitrogen injection in goafs.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

An Experimental Study on the Heat and Mass Transfer of Liquid Nitrogen in a Loose Medium

Lei

et al. 2019

Energies

“…ermogravimetric analysis (TGA) is an important approach to examining the pyrolytic property of coal [19]. A thermogravimetric analyzer was used to analyze the pyrolytic property of the three coal dust samples.…”

Section: Coal Sample Preparationmentioning

confidence: 99%

Experimental Study on the Ignition Sensitivity and Explosion Severity of Different Ranks of Coal Dust

Wang

Meng

et al. 2019

Shock and Vibration

is study is conducted to examine the ignition sensitivity and explosion severity differences among different ranks of coal dust and reveal the causes underlying these differences. A G-G furnace, a Hartmann tube, and a 20 L explosion tank are used to test MIT, MIE, P max , (dp/dt) max , and other parameters of three different ranks of coal dust. SEM analysis is carried out on the coal dust before and after explosion to compare and trace their microstructure changes. e results indicate that the lower the rank of the coal, the more likely the dust cloud to be ignited, the faster the explosion flame propagated, and the greater the explosion severity. e main drivers behind the ignition sensitivity and explosion severity differences among different ranks of coal dust are the volatile content and pyrolytic property of the coal.

“…Oil shale belongs to unconventional oil and gas resources. It is a kind of sedimentary rock containing heterogeneous solid combustible organic matter in mineral skeleton and having fine schistosome [2,3]. China's oil shale reserves exceed 700 billion tons and are equivalent to nearly 50 billion tons of shale oil, thereby exhibiting a huge, comprehensive development and utilization value.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Multiple Explosions during the Development and Utilization of Oil Shale Dust

Liu

et al. 2019

Shock and Vibration

Oil shale is a kind of high-combustion heat mineral; in the process of exploitation, storage, and utilization, oil shale dust has the risk of explosion. e explosion characteristics and flame propagation behavior of oil shale dust are worth studying. e difference between the multiple explosion behaviors of oil shale dust was investigated with the use of a 20 L explosive spherical tank and a dust MIE experimental device. e explosion characteristics and microstructure changes of the explosive products in multiple explosions were examined. e experimental results show that the maximum explosion pressure (P max ) dropped, and simultaneously, the minimum ignition energy (MIE), the explosion time (t), and the maximum rate of pressure rise ((dp/dt) max ) increased as the explosions continued. Furthermore, the oil shale continued exploding until the third explosion. Some original oil shale dust (OOSD) and explosive residues were analyzed using a scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectrometer. e SEM images of the explosive residues indicate a high fragmentation degree and well-developed pore structure during the entire multiexplosion process. Oxygen-containing functional groups, the aliphatic C-H bond, and the aromatic C-H bond in oil shale dust all participated in the oil shale dust explosion process.