Ban Heng, Li Zuoping
Department of Mechanical and Aerospace Engineering, Utah State University, 4130 Old Main Hill, Logan, Utah 84341, USA.
Rev Sci Instrum. 2009 Nov;80(11):115107. doi: 10.1063/1.3262500.
Fireside corrosion in coal-fired power plants is a leading mechanism for boiler tube failures. Online monitoring of fireside corrosion can provide timely data to plant operators for mitigation implementation. This paper presents a novel sensor concept for measuring metal loss based on electrical capacitance. Laboratory-scale experiments demonstrated the feasibility of design, fabrication, and operation of the sensor. The fabrication of the prototype sensor involved sputtering deposition of a thin metal coating with varying thickness on a ceramic substrate. Corrosion metal loss resulted in a proportional decrease in electrical capacitance of the sensor. Laboratory experiments using a muffle furnace with an oxidation environment demonstrated that low carbon steel coatings on ceramic substrate survived cyclic temperatures over 500 degrees C. Measured corrosion rates of sputtered coating in air had an Arrhenius exponential dependence on temperature, with metal thickness loss ranging from 2.0 nm/h at 200 degrees C to 2.0 microm/h at 400 degrees C. Uncertainty analysis indicated that the overall measurement uncertainty was within 4%. The experimental system showed high signal-to-noise ratio, and the sensor could measure submicrometer metal thickness changes. The laboratory experiments demonstrated that the sensor concept and measurement system are capable of short term, online monitoring of metal loss, indicating the potential for the sensor to be used for fireside corrosion monitoring and other metal loss measurement.
燃煤电厂的炉侧腐蚀是导致锅炉管失效的主要原因。对炉侧腐蚀进行在线监测可为电厂操作人员提供及时的数据，以便实施缓解措施。本文提出了一种基于电容测量金属损耗的新型传感器概念。实验室规模的实验证明了该传感器在设计、制造和运行方面的可行性。原型传感器的制造包括在陶瓷基板上溅射沉积不同厚度的薄金属涂层。腐蚀导致的金属损耗使传感器的电容成比例降低。使用具有氧化环境的马弗炉进行的实验室实验表明，陶瓷基板上的低碳钢涂层在超过500摄氏度的循环温度下仍能存活。在空气中测量的溅射涂层腐蚀速率与温度呈阿仑尼乌斯指数关系，金属厚度损失范围从200摄氏度时的2.0纳米/小时到400摄氏度时的2.0微米/小时。不确定度分析表明，总体测量不确定度在4%以内。实验系统显示出高信噪比，该传感器能够测量亚微米级的金属厚度变化。实验室实验表明，该传感器概念和测量系统能够对金属损耗进行短期在线监测，这表明该传感器有潜力用于炉侧腐蚀监测和其他金属损耗测量。
