变氧体积分数条件下烟煤自燃传热特性研究

Study on heat transfer characteristics of bituminous coal spontaneous combustion under variable oxygen volume fraction condition

为了研究变氧体积分数条件下烟煤的热传导特性,以长焰煤、中黏煤、气肥煤3种煤样作为研究对象,采用LFA457激光导热仪对3种煤样的热扩散系数、比热容和导热系数进行测量,研究煤样在3种不同氧气体积分数(5%、13%、21%)条件下的热传导特性。煤样分别在3种不同氧气体积分数下从室温加热升温到300℃,检测从30~300℃之间煤的热物性参数的变化规律。通过分析不同氧气体积分数条件下的热传导特性发现,随着氧气体积分数的增加,热扩散系数的临界温度逐渐朝着低温区域移动;当温度超过临界温度时,同一温度下的比热容随着氧气体积分数的增大而减小,而导热系数的变化受热扩散系数的影响较大。通过对温度敏感性的分析发现,温度在达到临界温度之前,氧气体积分数对热物性参数的影响较小;而在温度超过临界温度以后,氧气体积分数的影响开始变大。

In order to study the heat transfer characteristics of bituminous coal under the condition of variable oxygen volume fraction,the long-flame coal,medium-clay coal and gas-fat coal were used.Three kinds of coal samples were used as the research objects.The LFA457 laser thermal conductivity meter was used to measure the thermal diffusivity,specific heat capacity and thermal conductivity of the coal samples.And the coal samples were studied in three different oxygen concentrations(5%,13%,21%).The coal samples were heated from room temperature to 300℃ under three different oxygen volume fractions,and the changes in thermal physical parameters of coal from 30-300℃ were detected.By analyzing the heat conduction characteristics under different oxygen volume fraction conditions,with the increase of oxygen volume fraction,the critical temperature of the thermal diffusivity steadily moved into the low temperature area.When the temperature rises over the critical temperature,the specific heat capacity at the same temperature decreases as oxygen volume fraction rises,whereas the change in thermal conductivity is determined by thermal diffusivity.The analysis of temperature sensitivity reveals that the effect of oxygen volume fraction on the thermal property parameters is small before the temperature reaches the critical temperature;while the effect of oxygen volume fraction starts to become larger after the temperature exceeds the critical temperature.