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城市生活垃圾与煤矸石混烧及其HCl排放特性研究
李晓云
学位类型硕士 ; 学位论文 ; 硕士 ; 学位论文
导师吴晋沪
2016-05
学位授予单位中国科学院大学
学位授予地点北京
学位专业化学工程
关键词城市生活垃圾 煤矸石 混烧 氯源 氯化氢
摘要近年来,中国城市生活垃圾(Municipal Solid Waste,简称MSW)年产量迅速增长,引起了严重的环境问题。由于减容、减量、能源回收等优势,焚烧法已成为垃圾处理的主要发展方向之一。但垃圾焚烧厂设备投资和操作费用较高,能量转化效率较低,二噁英和重金属等二次污染严重导致其发展备受争议。与之相比,利用现有循环流化床煤矸石电站,采取MSW与煤矸石混烧的方式,不仅可降低MSW处理投资成本,提高焚烧发电稳定性和效率,降低垃圾焚烧过程的二次污染,还可利用MSW挥发分含量高,易于着火的特点,改善煤矸石的着火和燃烧性能,是一种非常具有潜力的MSW和煤矸石协同处理方式。 然而,煤矸石与MSW燃烧特性相差较大,且MSW中氯含量较高,混烧可能导致HCl排放风险增加。为此,本文从燃烧特性、燃烧动力学、HCl排放特性和脱氯剂的脱氯作用四个方面对煤矸石与MSW混烧过程展开了研究: (1)利用热重差热联用仪(TG-DSC)考察了煤矸石、MSW及其不同比例混合物的燃烧特性。结果表明,掺烧MSW可显著降低燃料的脱挥发分温度和燃点,改善煤矸石的着火特性。燃烧特性指数随着掺烧比的增加呈现先降低后增加的趋势,当MSW掺混比达到30 wt.%以上时,混合燃料的燃烧特性相比单独煤矸石会已发生明显改变。不同混烧阶段及掺烧比例下,煤矸石与MSW存在不同的相互作用。在脱挥发分阶段,当MSW掺混比小于30 wt.%时,由于混合及空气量不足等原因,混烧存在抑制作用;但在固定碳起始燃烧阶段,当MSW掺混比大于20 wt.%时,MSW的存在可促进混合燃料的固定碳提前燃烧。 (2)采用Coats-Redfern法及一阶反应模型分析了不同掺混比条件下,混合燃料脱挥发分阶段及固定碳燃烧阶段的活化能变化。结果表明,脱挥发分阶段的活化能随MSW掺混比增加而增加,固定碳燃烧阶段的活化能降低,提高了混合燃料固定碳燃烧阶段的反应活性。 (3)利用高温管式炉燃烧系统,考察了不同氯源PVC、NaCl及MSW与煤矸石混烧过程中HCl的排放规律。结果表明,PVC或NaCl的掺混量较少时,煤矸石的存在可抑制PVC中的HCl的析出,同时会显著促进NaCl中HCl的析出。随着掺混比增大,上述作用逐渐减弱。MSW与煤矸石混烧时,会促进HCl的析出,增大烟气中HCl的浓度。 (4)采用石灰石作为脱氯剂,考察了煤矸石与MSW混烧过程的脱氯性能。结果表明,石灰石脱氯效率随温度的升高先增加后减小,燃烧温度为700 oC左右时,石灰石的脱氯效率最大,为32.62 %;随着Ca/(S+0.5Cl)摩尔比增加,石灰石的脱氯率逐渐增加,当Ca/(S+0.5Cl)摩尔比达到12:1后,进一步增加钙氯比对脱氯效率的改善影响较小。
其他摘要Recently, the annual production of municipal solid waste (MSW) increases sharply, which leads to serious environmental problems. Much more attention has been paid on the disposal of MSW through incineration due to its harmlessness, volume reduction and recycling. However, incineration has high capital investment, low combustion efficiency and high pollutants emission. Compared to that, co-firing MSW with coal gangue in the existing coal gangue CFB boiler, which has high combustion efficiency, broad fuel adaptability and complete pollutants removal equipment, may utilize MSW with low capital cost, high efficiency and less pollutions. Besides, MSW has high volatile content and can be ignited easily, which may improve the ignition and combustion characteristics of coal gangue. Hence, co-combustion of coal gangue and MSW is a highly potential way for collaborative utilization of coal gangue and MSW. However, there is a big difference in combustion characteristics between coal gangue and MSW. Besides, MSW has high chlorine content, which may give a risk of HCl emission. Hence, the co-combustion of coal gangue and MSW is investigated from four aspects including the co-combustion characteristics,combustion kinetics, the hydrogen chloride emission characteristics and the hydrogen chloride emission control. (1) The combustion characteristics of coal gangue, MSW and their various blends were investigated by the Thermogravimetric Analyzer-Differential Scanning calorimeter (TGA-DSC). The results show that the MSW blending can decreases the volatile release temperature and ignition temperature significantly and improve coal gangue ignition characteristic. The comprehensive combustion characteristic parameter decreased firstly and then increased with the increasing of MSW blending ratio. When the MSW blending ratio is above 30 wt.%, the combustion characteristic of co-fuels changes obviously compared to coal gangue. There are different interactions between coal gangue and MSW during co-combustion. During volatile release and combustion stage, there is inhibiting interaction between coal gangue and MSW due to the mix and the lack of air, when the MSW blending ratio was lower than 30 wt.%. While, during the fixed carbon combustion stage, MSW may promote the initial combustion of fixed carbon, when the MSW blending ratio is larger than 20 wt.%. (2) The first order model and Coats-Redfern method are adopted to investigate the blending of MSW on the thermal reactivity of coal gangue. The results investigated that the activation energy for the devolatilization stage increased with the increasing of MSW blending ratio, while the opposite for fixed carbon combustion stage, which improve the thermal reactivity during fixed carbon combustion stage for co-fuels. (3) The high-temperature tube furnace combustion system is adopted to investigate the hydrogen chloride emission rules for the co-combustion of coal gangue with PVC, NaCl and MSW. The results show that the chlorine in PVC can be inhibited to be released by coal gangue during co-firing, while that in NaCl can be promoted to be released. Besides, the inhibition and promotion effects decrease with the increasing of MSW blending ratio. During co-combustion of coal gangue and MSW, HCl is promoted to be released and the HCl concentration in flue gas increases. (4) Based on the above research results, the effect of CaCO3 addition on the controlling of HCl emission was analyzed. It can be found that the chlorine retention increased firstly and then decreases with the increasing of combustion temperature. The best combustion temperature for controlling HCl emission by CaCO3 is 700 oC, where there is the largest chlorine retention 32.62 %. The chlorine retention increased with the increasing Ca/(S+0.5Cl) molar ratio. However, when the Ca/(S+0.5Cl) molar ratio reached 12:1, the improvement of chlorine retention ratio by CaCO3 is not significant.
作者部门热化学转化事业部
公开日期2016-06-30
学位类型硕士 ; 学位论文 ; 硕士 ; 学位论文
语种中文
文献类型学位论文
条目标识符http://ir.qibebt.ac.cn/handle/337004/9778
专题热化学转化团队
作者单位中国科学院青岛生物能源与过程研究所
推荐引用方式
GB/T 7714
李晓云. 城市生活垃圾与煤矸石混烧及其HCl排放特性研究[D]. 北京. 中国科学院大学,2016.
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