【作者】 刘亮；

【导师】 周孑民；

【作者基本信息】 中南大学 ， 热能动力工程， 2011， 博士

【摘要】 城市污水污泥的处理已成为困扰各国的环境问题,焚烧法和热解法具有资源化和能源化等优点,被认为是两种有前途的热化学处理方法,在发达国家广泛应用。随着经济的迅速发展,污泥的处理处置越来越受到关注,因此,污水污泥的高效洁净焚烧已成为我国城市污水污泥处理亟需研究的课题。本文采用热量计、差热天平、加热炉、扫描电子显微镜(SEM)、能谱分析(EDX)及X衍射分析仪(XRD)等分析仪器对污泥及其混煤的热解、燃烧过程进行研究,探讨污泥及其混煤燃烧热解机理,分析燃烧过程的反应动力学特性,对焚烧后的灰渣进行了形貌与物相结构分析。对城市污水污泥干燥特性的研究表明：不同厚度、比表面积大小及外部加热干燥条件均影响到污泥的干燥特性。随着料层的减薄,比表面积的增加,污泥干燥速度变快,干燥时间变短,收缩效果变好,过热干燥效果优于饱和干燥。用非等温热重分析法进行了污泥的热解特性实验,分析了污泥在升温过程中的基本失重规律。研究显示：污泥的热解过程可用气固反应动力学方程表示为：dα/dτ=AeRT(1-α)n,并得出了污泥热解表观动力学参数。发现r(α)=(1-α)2、f(α)=(1-α)0.2是最适合描述污泥热解反应峰前峰后的机理方程。在空气氛围下对城市污水污泥进行燃烧实验,计算了相关的燃烧特性参数,并对污泥燃烧、热解特性进行了比较,发现：在第一温度段(20-330℃)燃烧曲线与热解曲线基本上相同或接近；第二温度段(330-450℃)热解曲线衰减快于燃烧曲线,而在第三温度区(450℃～550℃),由于污泥中高分子有机物的分解燃烧,燃烧曲线衰减更快。实验中还发现氮气氛围下污泥残重要高于空气氛围,说明氧气的存在能够加快污泥的热解。对污泥掺混不同比例煤粉的试样进行热重法试验研究发现：在混合试样的热解燃烧过程中,两组分之间不会相互影响,挥发分的释放过程可以认为是两母本试样挥发分释放的总和；混合试样的燃烧曲线位于污泥和煤粉燃烧曲线之间。在煤中掺入城市污泥后,混合试样和煤相比其着火温度减少,但综合燃烧性能却下降。混烧表现出的着火和燃尽等某些特性要优于污泥或煤单独燃烧时的燃烧特性,因而将污泥掺混煤燃烧是可行的,但在进行污泥的掺混燃烧时应合理组织掺混比例。利用热分析方法提出了燃料燃烧特性综合判别指数S’,可以对燃料的燃烧特性及其燃尽性能进行初步预测,并通过Arrhenius定律求出了各混合试样的动力学参数。污泥焚烧及其混煤燃烧后产生的固体残留物的熔融特性,对焚烧炉的运行会产生多方面的影响。本文在高温熔融炉上对污泥及其混煤进行焚烧试验研究,通过电子扫描显微镜和能量分散光谱仪对焚烧过程中的试样结构和形貌特征进行描述；发现混合试样随着污泥含量的增加,灰分熔融性4个特征温度依次降低,渣样由较松散的煤渣型向熔融状的泥渣型转化；随着温度的升高,灰渣中逐渐出现晶体结构；Na、K元素的含量减少,这与发生的分解反应有关(蒸发分解)。试样中有毒重金属含量较少或未检出,说明生活污水污泥受污染程度较轻。通过X射线衍射仪分析可知：石英Si02、赤铁矿Fe203、硅化钙CaSi(或碳硅石SiC)是所有试样渣的主体组成部分；随着温度的升高,部分渣样中有莫来石(Al6Si2O13)结晶体生成。更多还原

【Abstract】 Sewage sludge has become a serious environmental problem besetting each country. Because of its advantage of energy recovery and resources recycle, combustion (incineration) and pyrolysis has become two promising disposal methods, which have received wide application in the developed countries. With rapid development of the economy, the treatment and disposal of sewage sludge have been paid attention to by more and more peoples in China. Therefore, how to ensure efficient and clean combustion (incineration) of sewage sludge becomes an emergent subject which needs further research.In this dissertation, the pyrolysis of sewage sludge was systematically investigated under different atmospheres of nitrogen and oxygen in the thermogravimetry which can obtain the kinetic parameters by means of a mathematical model, different heating rates being used. The characteristics of samples were detected by calorimeter, proximate analyzer, and the SEM and XRD techniques were used to identify the morphology and mineralogy characteristics of the ash residue respectively.The surface area and dry temperature of sludge have important influence on dry characteristics. As the surface area of sludge increases, the dry pace becomes fast, dry time shortened, at the same time its shrink influence change well too, the overheated dry demonstrates better influence than the saturation one.The thermogravimetric characteristics of sewage sludge were studied under non-isothermal heating in nitrogen media. The thermogracimetric process can be described as a gas-solid reaction equation, da/dτ=AeE/RT(1-α)n.The apparent kinetics parameters of sewage sludge were calculated using Coats-Redfen integral method and they fitted well with experimental values. Mathematical models of sewage sludge were obtained to describe the pyrolytic decomposition kinetics mechanics in different temperature regions.The combustion characteristics indexes at difference heating rates were obtained by experiments of sewage sludge which were carried out in oxidative atmosphere. Two or three different behaviors were observed when comparing the combustion curves with the corresponding pyrolysis curves. Sludge have a combustion curve that is close to the corresponding pyrolysis curve in the 20-330℃temperature range and then show a slower decay at 330-450℃, but at 450-550℃temperature range strong decay at probably as a consequence of the combustion of the car formed. The facts, the higher burnout ratio of sludge in oxidative atmosphere, indicated that the oxygen accelerates the decomposition rate in comparison to the pyrolysis.An experimental investigation on the combustion characteristics of the blends of Lanba’s coal and Changsha’s sewage sludge is conducted by TG dynamic runs at 20℃/min in the temperature range 20～1200℃. The investigation reveals that the curve of blend basically locates between the curves of sewage sludge and coal. Although the sludge-coal blends show an intermediate behavior between sludge and coal, the sewage sludge and coal have basically maintained their respective devolatilisation characteristic, and devolatilisation releasing process can be considered as total devolatilisation of two parent samples. In a way, the ignition and burnout behaviors of blends samples are better than the parent samples. This showed that the co-combustion of coal and sludge (their blends) were feasible, if the weight percentage of sludge in the blend can be controlled properly. A comprehensive discrimination index S’is being suggested, which reflects the combustion and burn-out properties. The Arrhenius activation energy corresponding to the co-combustion of the blends was evaluated by non-isothermal kinetic analysis.Slagging characteristics of sludge-coal blends is one of the main factors which influence the safety and economy of incineration boiler. The sintered ash of sludge-coal blends, after having been incinerated in a high temperature furnace at different temperatures, have been studied by scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX) and X-ray diffractometry (XRD). The results showed that the melting temperature of the ash decreases with the increase the content of sludge ash in blended ash. At the same time, appearances of blended ash is gradually close the sludge ash, in which in situ visual observation and SEM morphology indicate that fusion occurs for the residue. X-ray diffractometer analysis shows that the crystalline material will presented with the sintered temperature increasing. Energy dispersive X-ray microanalysis results show that the content of atriums and kaliums reduce with the sintered temperature increasing, due to the vaporizations of alkali metal. The fact, there are few content of heavy metals in sewage sludge, indicated that there is significant difference between industrial sludge and sewage sludge. X-ray diffractometer crystallization phase results show that quartz, hematite and calcium silicide form in the residue of sludge-coal blends, whereas mullite will be presented in few residue at higher temperature.更多还原