超临界机组过热器氧化皮化学清洗技术研究

发布时间：2018-09-01 12:14

【摘要】：近年来火电厂因过热器氧化皮引起的超温、爆管和汽轮机叶片冲蚀问题日益严重和普遍,研究开发过热器氧化皮化学清洗技术是解决这一问题的有效途径之一。过热器的化学清洗比锅炉本体的化学清洗有着更高、更复杂的技术难度,从腐蚀角度看有以下两个方面的特点增加了腐蚀控制的难度。第一,过热器管垢量大、微观结构差异大、垢质密实,需要使用更高的清洗介质浓度和更长的清洗时间,甚至需要二次或三次清洗,由此增加了控制腐蚀速率和腐蚀总量的难度,特别是铁素体钢的均匀腐蚀和点蚀。第二,过热器材质复杂,包含铁素体钢及奥氏体不锈钢,如12Cr1MoV、T22、T91、TP347等,为了控制化学清洗过程中金属的腐蚀,通常向酸液中加入缓蚀剂,但缓蚀剂对不同金属材质的缓蚀效果存在差异,因此,化学清洗过程中所有金属材质的腐蚀控制难度较大。此外,目前过热器化学清洗过程中仍采用传统的挂片失重法来评价化学清洗过程中材料的腐蚀速度,但该方法只能得到化学清洗结束后整个清洗过程的平均腐蚀速度,不能实时地对清洗过程中的腐蚀情况进行监测。本文根据腐蚀电化学原理,开发出了适合过热器化学清洗环境的腐蚀在线监测系统及腐蚀监测电极,并通过腐蚀实验验证了腐蚀在线监测系统的可靠性。通过对现场氧化皮脱落、爆管案例的调查研究和对实际管样氧化皮进行实验研究分析,获得不同材质过热器氧化皮剥离规律,同时分析氧化皮厚度对机组寿命和锅炉效率的影响,进而确定过热器氧化皮进行化学清洗的条件,以指导电厂根据过热器氧化皮情况选择化学清洗时机。
[Abstract]:In recent years, the problem of overtemperature, tube burst and erosion of steam turbine blade caused by oxidation skin of superheater in thermal power plant has become more and more serious and widespread. It is one of the effective ways to solve this problem by researching and developing chemical cleaning technology of oxidation skin of superheater. The chemical cleaning of the superheater has higher and more complex technical difficulties than the chemical cleaning of the boiler body. From the point of view of corrosion, the characteristics of the following two aspects increase the difficulty of corrosion control. First, the superheater tubes have a large amount of scale, large microstructure differences, dense scale, need to use a higher concentration of cleaning media and longer cleaning time, and even need a second or third cleaning, Therefore, it is more difficult to control the corrosion rate and the total corrosion amount, especially the uniform corrosion and pitting corrosion of ferrite steel. Second, the superheater is made of complex materials, including ferrite steel and austenitic stainless steel, such as 12Cr1MoVT22T91T91TP347. In order to control the corrosion of metals during chemical cleaning, corrosion inhibitors are usually added to the acid solution. However, the corrosion inhibition effect of the inhibitor on different metal materials is different, so it is difficult to control the corrosion of all metal materials in the chemical cleaning process. In addition, in the chemical cleaning process of superheater, the traditional weight loss method is still used to evaluate the corrosion rate of the material in the chemical cleaning process, but this method can only get the average corrosion rate of the whole cleaning process after the chemical cleaning. No real-time monitoring of corrosion during cleaning. According to the principle of corrosion electrochemistry, a corrosion on-line monitoring system and corrosion monitoring electrode suitable for chemical cleaning environment of superheater have been developed in this paper. The reliability of the on-line corrosion monitoring system has been verified by corrosion experiments. Through the investigation and analysis of the cases of the exfoliation of the oxidation skin in the field and the case of the tube burst and the experimental study and analysis on the actual tube sample, the law of the exfoliation of the oxide skin of the superheater of different materials is obtained. At the same time, the influence of oxidation thickness on unit life and boiler efficiency is analyzed, and the conditions for chemical cleaning of superheater oxidation coating are determined, so as to guide the power plant to choose the time of chemical cleaning according to the condition of superheater oxidation coating.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM621

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