半焦氧化过程中反应活化能的变迁

The Transition of the Activation Energy of Semi-coke During Its Oxidation Process

使用热天平考察了 5种半焦的本征氧化反应活性。这 5种半焦是由大同煤、神木煤、蔚县煤、湔江煤和台湾石油焦在 90 0℃下热解 7min制得的 ,使用分布活化能模型(DAEM)描述了半焦在氧化过程中的活化能变迁。大同煤半焦初期活化能最小 ,随着碳损失率的增加 ,活化能增加 (反应初期增加较快 ) ,反应后期达到峰值后下降。湔江煤半焦活化能则是在反应初期活化能很高 (达 2 5 0kJ/mol) ,其初始下降较快 ,在碳损失为 0 .2后其下降趋势变缓。而对于其它三种半焦 ,均在反应初期与反应后期其活化能分别经历两个峰 ,在此之间变化比较平缓。各种半焦活化能的变迁规律不同 ,反映了其内部性质的不同。与煤焦相比 ,石油焦半焦的内部结构比较均一。

The activation energy of five kinds of semi-coke during its eigen oxidation in air was investigated by using a thermogravimetric balance. These semi-cokes were prepared from Datong coal, Shenmu coal, Yuxian coal, Jianjiang coal and Taiwan petroleum coke by pyrolysis for 7 minutes at a temperature of 900 ℃. A distributed activation energy model (DAEM) was employed to describe the transition of activation energy of semi-cokes during an oxidation process. Initially, the activation energy of Datong coal semi-coke assumes a minimum value. With an increase in carbon loss rate the activation energy will increase (the increase at initial period of reaction is relatively rapid), and decrease on reaching a peak value at a later period of reaction. The activation energy of Jianjiang coal semi-coke is very high at the initial period of reaction (as high as 250 kJ/mol). It decreases rather rapidly at first, but tends to decrease slowly when the carbon loss is assessed at 20%. As for the semi-coke of the other three kinds of coal their activation energy will experience respectively two peaks at the initial and later period of reaction with a relatively mild change between the two peaks. The different transition mechanisms of the activation energy specific to various kinds of semi-coke reflect their different internal qualities. As compared with coal cokes, the semi-coke of petroleum coke exhibits a relatively uniform internal structure.