Experimental investigation of the transformation. and release to gas phase of potassium and chlorine during straw pyrolysis
Experimental investigation of the transformation. and release to gas phase of potassium and chlorine during straw pyrolysis
复制标题
DOI：
10.1021/ef000104v
复制
发表时间：
2000-11-01
期刊：
影响因子：
5.3
通讯作者：
Sander, B
中科院分区：
文献类型：
--
作者：
Jensen, PA;Frandsen, FJ;Sander, B
当秸秆进行热处理时，初始过程是热解，在热解时，一些K和Cl可以挥发，这可能导致存款形成和反应器安全壳腐蚀的问题。采用实验室间歇反应器研究了初始升温速率约为50 ℃/s时K和Cl的释放和转化随温度的变化。为了便于解释间歇反应器实验的热力学平衡计算在还原条件下进行，和扫描电子显微镜（SEM）和浸出调查进行了秸秆和焦炭样品。实验表明，氯的释放分两步进行，当温度从200 ℃升高到400 ℃时，约有60%的氯释放出来，而大部分余氯在700 ~ 900 ℃之间释放出来。低于700 ℃时，没有观察到显著的钾释放;高于该温度时，钾释放逐渐增加，直到1050 ℃时约25%的钾释放。在热解过程中，大部分K从原始结合位点释放，并且未转化为气相的部分作为KCl和K2 CO 3的再沉积离散颗粒、硅酸钾或结合到有机基质中而存在。钾在约700 ℃下初始释放到气相中是由沉积的KCl颗粒蒸发引起的。加热速率和样品尺寸对氯向气相的释放有很大影响。
When straw undergoes thermal treatment the initial process is a pyrolysis at which some K and Cl can be volatilized, and this may result in problems with deposit formation and corrosion of the reactor containment. A laboratory batch reactor was applied to study the release and transformation of K and Cl as a function of temperature, at an initial heating rate of approximately 50 degreesC/s. To facilitate the interpretation of the batch reactor experiments thermodynamic equilibrium calculations at reducing condition were conducted, and SEM (scanning electron microscopy) and leaching investigations were carried out on straw and char samples. The experiments showed that chlorine was released in two steps, about 60% was released when the temperature increased from 200 to 400 degreesC and most of the residual chlorine was released between 700 and 900 degreesC. Below 700 degreesC no significant potassium release was observe; above that temperature it increased progressively until about 25% potassium release at 1050 degreesC. During pyrolysis most K was released from the original binding sites, and the part that was not transformed to gas phase existed as redeposited discrete particles of KCl and K2CO3, as potassium silicates, or bound to the organic matrix. The initial release of potassium to the gas phase at approximately 700 degreesC was caused by evaporation of deposited KCl particles. The release of Cl to the gas phase was strongly affected by heating rate and sample size.