基于多场动力行为分析的电除尘器系统模型与控制

Electrostatic precipitator is mainly used for pollution control of flue gas, but its consuming huge electric energy is a serious problem, and it is very necessary to perform energy-saving optimal control for electrostatic precipitator. The optimal control is based on the object model of electrostatic precipitator control system, yet this model can not be achieved by far due to difficulties in measuring outlet concentrations of middle zones and in describing complex separating process. In order to establish the object model, the finite volume method is employed to analyze dynamic behavior of dust particle which motion is affected by multiple fields, such as electric field, flow field, diffusion field, etc. Consequently, the dynamic parameter of collection efficiency formula is determined, and the real-time estimation of middle concentrations is realized. According to the particle dynamic analysis, middle concentrations are considered as the model input, and the Takagi-Sugeno fuzzy model of the electrostatic precipitator with multiple cascaded zones is established, moreover, this fuzzy model is also considered as the object model of electrostatic precipitator control system. By using the fuzzy model, the particle separating process can be described mathematically. Furthermore, on the basis of the fuzzy model, the weighted quadratic objective function, which consists of the deviation of final outlet concentration and total electric power, is established, and the energy-saving optimal control is performed. As a result, the minimal total electric power consumed by electrostatic precipitator is obtained while satisfying the outlet concentration requirement.

电除尘器作为治理烟气污染的主要设备，工作过程中存在电能消耗大的问题，对其进行节能优化控制有着重要意义。而建立电除尘器控制系统对象模型是开展节能优化控制的基础，但电除尘器建模目前面临中间级出口浓度无法测量、复杂物理过程难以描述的困难。为建立电除尘器控制系统对象模型，本项目利用有限体积元方法对电场、流场、扩散场等多个场作用下颗粒的动力行为进行了分析，确定了除尘效率公式中的动力参数，实现了对中间级出口浓度的实时估计，并基于对颗粒动力行为的分析，将中间级出口浓度引入到模型输入，通过建立多区级联电除尘器的Takagi-Sugeno模糊模型，作为控制系统对象模型，实现了对复杂除尘过程的数学描述。并以该模型为基础，通过建立包含烟气出口浓度偏差和总功率的加权二次型目标函数，开展了电除尘器节能优化控制，在满足烟气出口浓度限定的条件下实现了电除尘器电能消耗的极小化。

搭建了缩尺板的电除尘器实物模型，并针对不同芒刺电极，测量了不同电压下其对应的收尘极电流密度分布和伏安特性曲线，计算了芒刺类电极对应的电场强度和空间电荷密度，仿真得到了粉尘颗粒在电除尘器中的运动轨迹，初步掌握了多场作用下粉尘颗粒的动力行为规律，为电除尘器本体放电极选型、收尘极面积设计提供了理论依据；在此基础上，进一步确定了除尘效率公式中的电场特性参数，使得能够通过除尘效率对中间级烟气出口浓度进行估计。研制了大功率电除尘软稳高压电源和高精度电晕电流测量装置，并实际应用到了某钢厂烧结机机头除尘器。采用神经网络建立了电除尘器的数学模型，通过分析电除尘器实际运行数据，最终确定了输入级烟气入口浓度、输出级烟气出口浓度、烟气流速、四个除尘区二次电压和二次电流、四个除尘区的平均火花击穿电压共14个变量作为模型输入，而输出级烟气出口浓度则作为模型唯一的输出。利用所建立的电除尘器数学模型，实现了对各级除尘区烟气出口浓度的估计，且为了验证所确定的除尘效率公式中电场特性参数的合理性，还将模型计算得到的中间级烟气出口浓度估计与除尘效率公式计算得到的中间级烟气出口浓度估计进行了对比，结果表明，除尘效率公式的估计结果在合理范围之内。基于所建立的电除尘器数学模型，开展了电除尘器的节能优化控制，建立了包含烟气出口浓度偏差与总功率的加权二次型目标函数，并采用遗传算法，搜索得到了使目标函数最小的各除尘区二次电压值，将搜索得到的各除尘区二次电压值作为给定，实际设置到了除尘器各高压电源中，运行结果表明，能够在满足烟气出口浓度限定的条件下有效降低电除尘器的总功率。

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