Variation Law for Minimum Ignition Temperature of Coal Dust Layer
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摘要: 为研究煤尘层最低着火温度随煤样变质程度、煤尘粒径及煤尘层厚度的变化规律,采用煤尘层最低着火温度测定系统进行实验研究,结果表明:随着煤样由褐煤到无烟煤变质程度逐渐增大,煤尘层最低着火温度由290℃上升到400℃以上,同时,褐煤、长焰煤、不粘煤、气煤煤尘层着火时观察到明显的火焰。随着煤尘粒径不断减小,不同煤质的煤尘层最低着火温度明显减小,煤尘层厚度为15 mm时,随着煤尘粒径由0.5 mm减小至0.075 mm,不同煤质煤尘层最低着火温度分别减小了31.0%、26.7%、28.1%、25.8%、28.6%、27.8%、18.9%和15.0%,煤尘粒径影响作用十分显著。随着煤尘层厚度的增大,不同煤质在不同粒径下的煤尘层最低着火温度都减小,其中无烟煤的变化最不明显。Abstract: In this paper we studied the variation of the minimum ignition temperature of coal dust layer with its metamorphism, particle size and thickness using the minimum ignition temperature measurement system.The results showed that, with the gradual increase of its degree of metamorphism, the minimum ignition temperature of coal dust layer varied from 290℃ to above 400℃; and that when the coal dust layer of lignite, long flame coal, non-stick coal, gas coal were ignited, an obvious flame was observed; and that, as the coal dust particle size decreased, the minimum ignition temperature of different kinds of the coal dust layer exhibited a significant reduction trend.It was found that when the thickness of the layer is 15 mm, with the particle size decreasing from 0.5 mm to 0.075 mm, the minimum ignition temperature decreased by 31.0%, 26.7%, 28.1%, 25.8%, 28.6%, 27.8%, 18.9% and 15.0%, respectively, indicating a very obvious effect of the coal dust particle size.With the increase of the layer's thickness, the minimum ignition temperature of different kinds of the coal dust layer exhibited a decreasing trend, while the trend of anthracite was the least significant.
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图 2 煤尘层最低着火温度测定装置结构
Figure 2. Structure of coal dust layer MIT tester
1.Thermocouple height adjustment knob; 2.Spring; 3.Heater base; 4.Recording thermocouple on hot plate surface; 5.Hot plate surface; 6.Heater; 7.Metal ring; 8.Control thermocouple on hot plate surface; 9.Dust layer thermocouple; 10.Heater leads
表 1 8种煤质的煤尘层最低着火温度
Table 1. Coal dust layer MIT of 8 kinds of coal quality
No. Coal quality Particle size/mm Thickness/mm Minimum ignition temperature/℃ Ignition type Ignition time/min 1 Lignite 0.2 5 290 a 18 2 Long flame coal 0.2 5 310 a 22 3 Not sticky coal 0.2 5 330 a 18 4 Gas coal 0.2 5 320 a 20 5 Coking coal 0.2 5 340 c 11 6 Lean coal 0.2 5 360 c 9 7 Meagre coal 0.2 5 370 c 13 8 Anthracite 0.2 5 >400 No fire >30 -
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