原煤和氧化煤的低温氧化特性

Characteristics of low-temperature oxidation of raw and oxidized coals

为研究原煤和氧化煤的低温氧化特性,以潘集矿煤样为研究对象,将原煤在90℃空气环境中恒温氧化150 min制备氧化煤样。采用程序升温实验装置测定了170℃以下原煤和氧化煤低温氧化阶段不同温度下的CO浓度,并基于CO浓度分阶段计算了原煤和氧化煤的表观活化能。此外,通过电子自旋共振设备测定了180℃以下原煤和氧化煤低温氧化过程中的自由基浓度。结果表明:原煤和氧化煤的CO浓度和表观活化能均随着温度的升高而增大,且表现出明显的阶段性特征;原煤和氧化煤的CO浓度和表观活化能在50~60℃范围内产生交叉;50℃以下,氧化煤的CO浓度大于原煤,表观活化能小于原煤;超过60℃,氧化煤的CO浓度小于原煤,表观活化能大于原煤。原煤的自由基浓度随着温度的升高而增大,氧化煤的自由基浓度随着温度的升高先降低后升高;相同温度下,氧化煤的自由基浓度大于原煤,但其自由基浓度的变化速率小于原煤。

To investigate the characteristics of low-temperature oxidation of raw and oxidized coals,coal samples from Panji coal mine in Anhui province were taken as the research object,and oxidized coal was artificially prepared by putting raw coal into incubator at 90℃for 150 minutes.The temperature-programmed experiment was conducted to investigate the CO concentration,and the apparent activation energy during low-temperature oxidation(below 170℃)was calculated based on CO concentration.The free radical concentration of raw and oxidized coals below 180℃was measured by electron spin resonance(ESR)experiment.The experimental results show that the CO concentration and apparent activation energy of both raw and oxidized coals increase with the elevated temperature.Meanwhile,the CO concentration and apparent activation energy of raw coal cross with that of oxidized coal between 50 and 60℃.The CO concentration of oxidized coal is higher than that of raw coal below 50℃,whereas the apparent activation energy is lower.When the temperature exceeds 60℃,the CO concentration of oxidized coal is lower than that of raw coal,whereas the apparent activation energy is higher.The free radical concentration of raw coal increases with the increase of temperature,but the free radical concentration of oxidized coal first decreases and then increases.The free radical concentration of oxidized coal is higher than that of raw coal at the same temperature;however,the change rate of free radical concentration is lower.