【作者】 侯海盟；

【导师】 吕清刚； 李诗媛；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 热能工程， 2013， 博士

【摘要】 城市下水污泥(以下简称污泥)焚烧处理具有减量化、稳定化、无害化和资源化的优点,是污泥处置方法中最彻底的处置方式。但是污泥焚烧处理过程中,会产生NOx、SO2、HCl、CO、重金属及二嗯英等污染物,直接排放会对环境产生严重危害。污泥具有特殊的燃料特性,导致其具有与煤和生物质不同的燃烧特性和污染物排放特性。因此,对城市下水污泥焚烧及污染物排放特性进行研究具有重要的理论价值,对污泥焚烧处理具有很高的应用价值。本论文主要针对污泥在循环流化床(CFB)内焚烧及污染物排放特性进行研究。通过在不同试验装置上的试验及理论分析计算,研究污泥的燃烧过程,焚烧过程中主要气体污染物的排放特性以及重金属的迁移和转化特性,探讨湿污泥循环流化床一体化焚烧工艺污泥干化和焚烧过程中污染物排放特性,为污泥流化床焚烧技术的工程应用提供理论和试验依据。具体研究内容如下：1.研究污泥燃烧特性及动力学特性。利用热重分析法对污泥燃烧过程进行研究,并对加入不同辅助燃料对污泥燃烧的影响进行探索。研究结果表明污泥与煤或生物质燃烧过程明显不同,挥发分析出和燃烧阶段及挥发分和固定碳燃尽阶段均是主要失重区间,存在两个明显失重峰。污泥着火温度低,但其燃烧速率较低,导致综合燃烧性能和燃尽性能较差。掺混煤或生物质燃烧会在不同程度上改善污泥的燃尽特性和综合燃烧特性。2.在15kW循环流化床试验台内研究干污泥焚烧过程中NOx、SO2、HCl等污染物的排放特性。设计并搭建15kW循环流化床试验台,进行不同运行参数条件下污泥焚烧试验,探索主要气体污染物的排放特性。本试验台上的研究结果表明,随着焚烧温度的升高,NO、SO2和HCl排放浓度均会增加,N2O浓度会降低；增大过量空气系数会促进NO和N2O的生成；提高二次风比率可以降低N2O和NO的排放浓度,但对不同含水率的污泥效果不同；污泥含水率增大会促进N2O和HCl排放,而降低NO的浓度；污泥焚烧过程中NO和N2O排放浓度较高,但燃料氮的转化率低于燃煤过程；未加入石灰石时,SO2排放浓度较高,HCl排放浓度超过标准限值,加入石灰石可以有效地进行炉内脱硫脱氯。3.在15kW循环流化床试验台内研究污泥中磷对石灰石脱硫的影响。针对不同含P量的污泥焚烧石灰石脱硫过程,进行试验研究与热力学平衡计算,探讨P对石灰石脱硫的影响。计算结果表明污泥焚烧时CaO首先与含P化合物反应,剩余部分CaO才参与脱硫反应。试验结果得到与计算结果相同的趋势,及污泥含P量高会影响石灰石脱硫效果。但试验表明仅有部分CaO会优先与含P化合物反应,而且单位摩尔P消耗的CaO量低于计算结果,即热力学平衡计算高估了P的影响。在计算脱硫石灰石加入量时,需要考虑这种作用。4.研究污泥焚烧过程中重金属的形态和分布。通过化学热力学平衡计算计算,研究污泥焚烧过程中Cu、Cd、Cr、Mn、Pb、Zn等重金属元素形态和分布,探讨S和C1对其转化的影响以及吸附剂的化学吸附效果。计算结果表明,污泥焚烧过程中Cd、Cu、Pb的挥发性较强,而Cr、Mn和Zn的挥发性较弱；由于生成了熔沸点较低的金属氯化物,C1会促进Cd、Cu、Pb、Mn和Zn的挥发；S会与Cd和Pb结合生成硫酸盐,对其具有一定的吸附作用；Al203和SiO2都对Cd和Pb有一定吸附作用,S和C1会影响其吸附效果。5.研究湿污泥循环流化床一体化焚烧系统中污泥干化和焚烧过程中污染物排放。流化床干化试验台中湿污泥干化试验结果表明,干化乏气中主要气体污染物为NH3、CH4、C3H8、C7H8和C2H60,其中NH3浓度较高,且随着干化温度升高而增大；干化乏气冷凝水呈碱性,COD、NH3-N和NH4+浓度较高。针对100吨/日循环流化床一体化污泥焚烧工艺进行了排放特性试验,结果表明在80%负荷和满负荷条件下系统均可连续、稳定运行,燃烧效率在98.5%以上,干化器污泥干化效果较好；烟气中CO、NOx、SO2、HCl、Hg、Cd、Pb及二嗯英等污染物浓度均满足国家标准,固体灰渣中重金属浸出毒性远低于标准限值。提出了干化乏气直接通入炉膛焚烧的工艺,并进行初步验证实验。更多还原

【Abstract】 Sewage sludge incineration with the advantages of volume reduction, stabilization, harmlessness and energy recovery, is considered to be the most thorough way among the methods of sludge disposal. During the process of sewage sludge incineration, if the emissions of NOx, SO2, HCl, CO, heavy metals and other secondary pollutants are not effectively controlled, serious environmental pollution will occur. Due to its special fuel properties, incineration and pollutants emission characteristics of sewage sludge are different from those of coal and biomass. Therefore, it is theoretically important to study incineration characteristics and pollutants emission and control of sewage sludge, which is also with application value for the disposal of sewage sludge incineration.In this paper, incineration characteristics and pollutants emission of sewage sludge in circulating fluidized bed (CFB) are investigated. Along with theoretical analysis, a series of experiments in different devices were conducted in order to explore the sewage sludge combustion behaviors, the gaseous emission of sewage sludge incineration in CFB, and the speciation transformation and distribution of heavy metals. Pollutants emission of sewage sludge during the drying and incineration process in the integrated incineration system for wet sewage sludge in CFB is also studied. The detailed contents are as follows.1. The combustion characteristics and kinetics of sewage sludge were studied by thermo-gravimetric analysis. The results show that there are obvious differences between the combustion of sludge and coal or biomass. During sludge combustion, both the stages of volatile volatilization and combustion and the burn-out stage of residue volatile and fixed carbon are the main combustion processes. The ignition temperature of sewage sludge is low, but its combustion rate is also low, leading to poor combustion and burnout performance, which could be remarkably improved by adding coal or biomass.2. The emission characteristics of NOx, SO2and HCl during sewage sludge incineration in CFB were explored. Sewage sludge combustion experiments under different operation conditions were carried out in a15kW CFB experimental system. The results reveal that the concentrations of NO, SO2and HCl increases as the combustion temperature increases, while N2O concentration decreases. The concentrations of N2O and NO reduce with the increase in the secondary air ratio, and the effect is different between sewage sludge with different moisture content. Increasing sewage sludge moisture content leads to substantial increase in the emissions of N2O and HCl, and decrease in NO emission. Compared with coal, higher nitrogen oxides emissions but lower fuel-N conversion ratios are obtained during sewage sludge combustion. Emissions of SO2and HCl can be effectively controlled by limestone injection.3. The effect of phosphorus in sludge on desulfurization of limestone was investigated through experiments and chemical thermodynamic analyses. Chemical thermodynamic analyses show that CaO would react first with phosphoric oxide during sewage sludge incineration, and then the remaining parts may be involved in desulfurization. The same tendency is found by desulfurization experiments. However, during experiments only parts of CaO will react first with phosphoric oxide, and the amount of CaO occupied by unit mole of phosphorus is much lower than analyses results, which mean chemical thermodynamic analyses overestimate the effect of phosphorus. Such effect should be taken into account when the Ca/S ratio is to be decided for sulfur capture.4. The speciation transformation and distribution of heavy metals during sewage sludge incineration were researched by the chemical thermodynamic analyses. The results indicate that Cd, Cu and Pb are transformed to other volatile forms easily during sewage sludge incineration, while Cr, Mn and Zn are not so easy. Cl will promote the volatilizations of Pb, Cd, Cu, Mn and Zn due to the formation of metal chlorides, and S will react with Cd and Pb forming sulfates. Al2O3and SiO2have a good adsorption of Cd and Pb, which will be restrained by Cl and S.5. Pollutants emission of sewage sludge in the drying and incineration process in integrated incineration system for wet sewage sludge in CFB was studied. Experimental results of sewage sludge drying in a fluidized bed demonstrate that the main emitted gases emission in drying process are identified to be NH3, CH4, C3H8, C7H8and C2H6O. Among them, NH3concentration is high, which increases with the increase in incineration temperature. The condensate from drying gases is alkaline, and the concentrations of COD, NH3-N and NH4+are relatively high. The results of incineration test on100t/d integrated incineration system for sewage sludge in CFB show that continuous and stable operation at full load has been achieved with the combustion efficiency of over98.5%in the incinerator and the good drying performance in the drier. The concentrations of CO, NOx, SO2, HCl, Hg, Cd, Pb and dioxin-like pollutants in flue gas are lower than the emission standard limit. The leaching toxicity of heavy metals in fly ash and bottom ash are much lower than the identification standards for hazardous wastes.更多还原