Tan Houzhang

水冷壁高温腐蚀倾向判断及H 2 S近壁面许用浓度研究

为预防日益严重的锅炉水冷壁高温腐蚀，在300 MW燃煤锅炉上研究了近壁面气氛分布规律，结合不同气氛下水冷壁材料12Cr1MoV的高温腐蚀动力学试验数据，预测了不同温度、气氛、腐蚀层开裂周期下的高温腐蚀速率，从而提出不同运行时间下锅炉水冷壁腐蚀的倾向判断标准；建立了腐蚀速率与H 2 S浓度、腐蚀时间和腐蚀层开裂周期的关系式，并以腐蚀膜开裂周期12 h和24 h为例，求得了近壁面气氛的许用浓度。研究结果表明，近壁面硫化氢（H 2 S）浓度与一氧化碳（CO）浓度成正比，而与氧气（O 2 ）浓度成反比；高温腐蚀速率与时间符合抛物线关系，与温度符合阿雷尼乌斯定律；只要将近壁面气氛控制在对应的H 2 S许用浓度范围以内，就可以预防严重高温腐蚀的发生。

Coupled LBM-FVM-CA simulation of particledeposition and removal processes on tubes

A numerical model was proposed to simulate the fouling processes on the tubes, which contained the evolution of the fouling shape and the particle deposition/removal mechanisms. Firstly, the coupled lattice Boltzmann method (LBM) and finite volume method (FVM) was established to simulate the air flow. The flow around the tubes was simulated by the LBM due to its convenience in complex boundary conditions. The downstream flow was simulated by the FVM to save the computational source. A reconstruction operator was derived for the information transfer from macroscopic parameters to multiple-relaxation-time LBM. The cellular automata model, energy conservation model and moment analysis were included to simulate the particle motion, collision, deposition and removal. Then, because the time step in the simulation was several orders of magnitude shorter than the real fouling time, a time ratio was proposed for the conversion between simulation and real time. Finally, the evolutions of the fouling shapes along with time for different particle diameters and inlet velocities were simulated and analyzed. The results showed that the proposed coupled model can be used to study the particle deposition, removal and the changing of the fouling layers. When the mass concentration was the same, the fouling of small particle grew faster. The fouling area grew exponentially with time. It grew rapidly in the beginning, then grew slower and finally reached an asymptotic balance value. When the particle concentration was specified, the fouling rate first grew with and then decreased with the increasing inlet velocity. Therefore, there was a velocity range in which the fouling rate was high. As for the shape of the fouling layer, the removal was severe on the windward side, but the direct impaction of the particles formed the cone-shaped fouling layers. The cone-shape changed the air flow and stopped the deposition on the windward side. The fouling layers grew on the entire leeward side of the tubes and finally stopped when the removal was equal to the deposition. The simulated fouling shape was compared with the real picture of the fouling on a tube of an economizer and the fouling shapes on the leeward side coincided well with each other. The growth of the fouling mass was also compared with the existing experiment. The simulated mass had the same trend with the experiment. This demonstrated that the time ratio can be used to convert the time scale. The distribution of the particle sizes and the properties of the real particles should be considered in the future works.

A Fuzzy Appraisement-based Applied Study on High-temperature Corrosion of a Thermal Power Plant

Targeting at the fuzziness and uncertainty among the factors affecting high-temperature corrosion, tests and analyses were conducted based on the fuzzy mathematical theory and by use of the Fuzzy analytic hierarchy process¿FAHP¿. By discriminating the pair wise membership degree of all affecting factors and combining the in-situ tests, a fuzzy matrix reflecting the consistency between thinking judgment and objective reality was constructed. The weighting indexes of all factors affecting high-temperature corrosion of the water wall of a certain thermal power plant were quantified. The factors most affecting high-temperature corrosion of the water wall of the plant were discovered and combustion adjustment was made correspondingly. During the shutdown inspection after operating for half a year, it was found that the high-temperature corrosion phenomenon of the water wall was basically removed.Targeting at the fuzziness and uncertainty among the factors affecting high-temperature corrosion, tests and analyses were conducted based on the fuzzy mathematical theory and by use of the Fuzzy analytic hierarchy process?FAHP?. By discriminating the pair wise membership degree of all affecting factors and combining the in-situ tests, a fuzzy matrix reflecting the consistency between thinking judgment and objective reality was constructed. The weighting indexes of all factors affecting high-temperature corrosion of the water wall of a certain thermal power plant were quantified. The factors most affecting high-temperature corrosion of the water wall of the plant were discovered and combustion adjustment was made correspondingly. During the shutdown inspection after operating for half a year, it was found that the high-temperature corrosion phenomenon of the water wall was basically removed.