【作者】 窦余信；

【导师】 陈雪莉；

【作者基本信息】 华东理工大学 ， 化学工艺， 2011， 硕士

【摘要】 稻草中氯的含量较高,在热转化利用过程中氯易析出,从而产生诸如高温金属腐蚀、受热面污染及炉内结渣聚团等问题。基于此,本文对稻草在300℃-900℃热解过程中氯的析出特性进行了实验研究和模拟计算,并对热解过程中氯的析出机理进行了深入分析。稻草在低于600℃热解时,氯的析出率随热解温度的升高而增大,但增大趋势越来越缓,600℃时氯的析出率约为30%,其析出主要有两条途径：一是所含氯化钾与热解中产生的水合质子反应形成HCl析出,二是所含有机氯的快速反应析出。热解固体产物半焦中的氯主要有两种存在形式：绝大部分是以离子键形式存在,受热处理方式影响较小,难以析出；少部分则是以物理吸附的方式存在于半焦中。热解温度在600℃-900℃间时,氯的析出量随温度升高而逐渐增大,到900℃时0.5h内有约70%的氯析出,并且析出较慢,到达析出平衡需一定的时间；热解半焦中的氯含量在热解温度300℃-900℃间呈现先增后减的趋势,最大值出现在600℃左右。运用FactSage软件对稻草热解过程中氯的析出进行计算,发现温度低于600℃时氯几乎不析出,少量析出以HCl为主；高于600℃氯开始以气态KCl、(KCl)2及HCl形式大量析出,随温度升高气态KCl的比例越来越大并成为析出的主要形式；到850℃时氯基本析出完全；在氯析出过程中增大压力将抑制氯的析出,而气氛中水分的增加能促进氯的析出。更多还原

【Abstract】 Because of the high chlorine content, thermal conversion processes of rice straw will encounter many problems, such as corrosion of metals at high temperature, pollution in the heating surface, slag aggregation in the furnace and so on. Thus, the regularity of chlorine releasing during pyrolysis from 300℃to 900℃was discussed based on the results of experiment and Factsage software. Moreover, the precipitation mechanism of chlorine releasing during pyrolysis was analyzed.When straw was pyrolysed below 600℃, the chlorine releasing rate increased with pyrolysis temperatures ranging from 300℃to 600℃, but the increasing trend became gentle. About 30% of chlorine was released at 600℃in the following two ways:one way is that the chlorine in KCl reacts with hydrated proton produced in pyrolysis and then is released in the form of HC1, and another way is that organic chlorine in straw is released by chemical reaction. The chlorine in semi-char has two existence forms. Most exists by ionic bond, the removal of which has almost nothing to do with thermal treatment methods. The remaining is in the semi-char by physical adsorption. When straw was pyrolysed from 600℃to 900℃, the chlorine releasing rate increased, and about 70% of the total chlorine was released at 900℃in half an hour. The chlorine contents of semi-char increased at first and then decreased with pyrolysis temperatures ranging from 300℃to 900℃, and the maximum value was at 600℃.The calculated results of Factsage software showed that the chlorine almost did not release below 600℃; HC1 was the major form of the releasing of little chlorine. Above 600℃, chlorine began to release in the form of gaseous KCl, (KCl) 2 and HCl, and with the raising of temperature, gaseous KCl gradually became the major form of chlorine releasing. At 850℃, there was no chlorine left in the semi-char. When increasing the pressure, it would inhibit the chlorine releasing rate, while increasing the moisture in the atmosphere, it would promote the precipitation of chlorine.更多还原