【作者】 韩颖慧；

【导师】 赵毅；

【作者基本信息】 华北电力大学 ， 热能工程， 2012， 博士

【摘要】 本文查阅了大量烟气同时脱硫脱硝技术及其吸收剂研究的文献并进行了综述；以次氯酸钠和添加剂为基础原料制备了两种多元复合活性吸收剂SHC和SHF,通过逐级放大的方式,在固定床、小型流化床、烟气循环流化床以及工业化装置上分别进行了一系列半干法烟气同时脱硫脱硝实验研究,提出了一种利用烟气循环流化床(CFB)增湿活化过程向床体喷淋该吸收剂的半干法同时脱硫脱硝新工艺。通过脱除产物分析及同时脱除反应的热力学研究,探讨了多元复合活性吸收剂烟气CFB同时脱硫脱硝的机理。通过活性添加剂的筛选,以NaCIO和添加剂A及A’为基础原料,制备了两种多元复合活性吸收剂SHC和SHF。扫描电镜(SEM)、X-射线能谱(EDS)、离子色谱(1C)和X-射线衍射(XRD)表征结果显示,多元复合活性吸收剂比表面积大、活性高。脱除实验表明,SHC和SHF可将烟气中难溶于水的NO快速氧化为高价态,从而实现SO2和NOx的高效同时脱除。通过固定床正交实验,确定了影响多元复合活性吸收剂脱硫脱硝的主要影响因素。在自制的小型流化床上进行了动态条件下多元复合活性吸收剂的同时脱硫脱硝实验,研究了多元复合活性吸收剂浓度、增湿水pH、Ca/(S+N)、入口温度等因素对脱除效率的影响。根据小型流化床的实验结果,在烟气循环流化床装置上进行了同时脱硫脱硝实验,考察了吸收剂浓度、组分配比,增湿水pH值、Ca/(S+N)、反应温度、烟气湿度、烟气含氧量等多种因素对同时脱硫脱硝效率的影响,确定了最佳工艺条件,在此条件下,SHC的同时脱硫和脱硝效率可分别达到96.5%和73.5%,SHF的同时脱硫和脱硝效率可分别达到96.1%和67.2%,且脱除效率数据精密度高,表明本文提出的半干法烟气同时脱硫脱硝运行稳定,具有较高的工业化应用价值。利用多种测试技术和化学分析方法对同时脱硫脱硝的反应产物进行了分析。结果表明,SHC为吸收剂时,SO2和NO、的主要脱除产物为硫酸钙和硝酸钙,其次为亚硫酸钙和亚硝酸钙；SHF为吸收剂时,脱硫和脱硝产物分别为硫酸钙和硝酸钙,表明其氧化能力高于SHC。由上述产物分析结果可以推断,增湿水中的多元复合活性吸收剂可首先快速将NO氧化为NO2,其后与SO2一起被Ca(OH)21吸收,实现了同时脱除。脱除反应的热力学研究也证实了这一结论。利用实验室开发的多元复合活性吸收剂,在河北某电厂200MW锅炉烟气循环流化床装置上进行了现场工业化试验研究。通过考察多元复合活性吸收剂浓度、增湿水pH值、吸收剂组分配比、Ca/(S+N)、近绝热饱和温度、循环倍率等因素对脱除效率的影响,确定了最佳工况条件,获得了较高的同时脱除效率。工业化应用表明,本文开发的具有自主知识产权的新型烟气治理技术具有操作简便、低费用、低能耗及同时脱除烟气中多污染物的特点,经济、环境和社会效益显著,具有重要的应用前景。基于烟气CFB脱硫脱硝反应的各种工况条件,利用FLUENT计算软件对烟气CFB内流场和温度场进行了数值模拟,为工业化应用设计提供了依据。更多还原

【Abstract】 The current status of the researches about flue gas simultanteous desulfurization and denitrification and the absorbents were reviewed by consulting a large number of literatures in this dissertation. Two multicomposite active absorbents, named SHC and SHF respectively, were prepared from sodium hypochlorite and different additives. Meanwhile, a new semi-dry process of simultaneous desulfurization and denitrification were proposed by spraying the multicomposite acitive absorbents into a flue gas circulating fluidized bed (CFB) using the humidifying activation, and a series of experimental studies of semi-dry flue gas desulfurization and denitrification simultaneously were carried out in a fixed bed, fluidized bed, CFB, and in the industrial pilot plant respectively, by amplifing the condition step by step. Through the analysis of removal products and the investigations of thermodynamic processes, the mechanism of simultaneous desulfurization and denitrification in a CFB by the multicomposite active absorbents were disclosured.By screening of additives on activity, NaCIO and additives A and A’were determined as the basic raw materials for prepared the two multicomposite active absorbents SHC and SHF. Scanning electron microscopy (SEM), X-ray spectroscopy (EDS), ion chromatography (IC) and X-ray diffraction (XRD) characterization results indicate that multicomposite active absorbents have large surface areas and high activities. The removal experiments show that SHC and SHF can rapidly oxidize NO, which is difficult to dissolve in the water, and then achieve high simultaneous removal efficiencies of SO2and NOx.Through the orthogonal experiment in fixed bed, the main impact factors of multicomposite active absorbents on simultaneous desulfurization and denitrification were determined.Then, the dynamic experiments of simultaneous desulfurization and denitrification by the multicomposite active absorbents were performed in a small-scale fluidized bed, and various effect of absorbent concentration, pH, Ca/(S+N), inlet temperature and et al. on the removal efficiencies were also studied.According to the experimental results of small-scale fluidized bed, and further amplification of experimental conditions, the experiments of simultaneous desulfurization and denitrification in the flue gas circulating fluidized bed were carried out, and various factors such as the absorbent concentration, molar ratio, pH of humidified water, Ca/(S+N), reaction temperature, gas humidity, oxygen content of flue gas and so on the efficiencies of simultaneous desulfurization and denitrification were investigated, therefore, the optimum conditions were confirmed. At the optimum condition, the efficiencies of desulfurization and denitrification by SFIC can achieve96.5%and73.5%, respecitively; meanwhile, the efficiencies of desulfurization and denitrification by SHF can reach96.1%and67.2%, respecitively. In addition, the high precise data of removal efficienies showed that the proposed semidry flue gas simultaneous desulfurization and denitrificaiton process runs stable, and has broad application prospects.The reaction products were analyzed by using a variety of modern testing techniques and chemical analysis. The results showed that, the removal products of SO2and NO by SHC are mainly calcium sulfate and calcium nitrate, respecitively, followed by calcium sulfate and calcium nitrite; while for SHF, its desulfurization and denitrification products are calcium sulfate and calcium nitrate, respecitively, which means the oxidizability of SHF is higher than that of SHC. Though the above results of products, it can be inferred that NO can be rapidly oxidized to NO2by multicomposite active absorbents, and then absorbed by Ca(OH)2with SO2, thus the simultaneous removal were achieved. These conclusions can also be confirmed by the thermodynamic analysis.A pilot-scale test were implemented in a flue gas circulating fluidized bed combined with200MW boiler unit of a power plant in Hebei by the multicomposite active absorbent. By examining various effect of the absorbent concentration, pH of humidified water, molar ratios of absorbent, Ca/(S+N), near-adiabatic saturation temperature, circulation rate and et al. on the removal efficiencies, the optimal operating conditions were determined, on which a higher removal efficiencies of SO2and NO were reached. The results of the pilot-scale tests showed that the new flue gas treatment technology with independent intellectual property rights developed in the dissertation has the merits of simple operation, low cost, low energy dissipation and simultaneous removal of multi-pollutants from flue gas, which can generate significant economic, environmental and social benefits and has a broad application.Based on FLUENT computing platforms, the flue gas flow field and temperature field in the CFB were simulatied under a variety of operating conditions on both SO2and NO removal process, which can provide a basis for the industrial application.更多还原