Thermoelectric Phenomana in High-Temperature and High-Pressure Electrostatic Precipitator and Performance Improvement

高温烟气中飞灰颗粒的有效脱除是实现整体煤气化联合循环(IGCC)等先进高效煤炭利用系统的重要技术之一，为此考虑了陶瓷过滤系统。另一方面，高温电除尘器系统也有很高的可能性用于IGCC的气体净化，但在这种情况下，需要高压条件才能保持电晕放电。本研究的目的是阐明温度和压力对高温高压电除尘器中各种电和热现象的分离影响，并获得开发高效高温高压电除尘器所需的基础知识。为此，构建了一维圆柱形中线细丝电除尘器，分别推导了温度和压力对各种电学和热学现象的影响，阐明了它们对电除尘性能的耦合效应.高温下除尘效率的急剧下降可以定性地解释为中心电极附近离子生成率的降低、颗粒荷电率的降低和运动粘度较高的颗粒漂移速度的降低，这一结果可以用平均自由程对温度的依赖关系来很好地解释.放电模式应该已经从电晕模式更改为辉光模式。因此，为了保持高温电除尘器的高性能和低能耗，施加高压是绝对必要的。

Efficient removal of fly ash particles from high temperature flue gas is one of the most important technologies to be developed for realizing advanced high efficiency coal utilization systems such as an integrated coal gasification combined cycle (IGCC), and ceramics filtering systems have been considered for this purpose. On the other hand, high-temperature electrostatic precipitator systems also have a high possibility to be used for gas clean-up in IGCC.But in this case, high-pressure condition should be required to maintain corona discharge. The purpose of this study is to clarify separated effects of temperature and pressure on various electric and thermal phenomena in the high-temperature and high-pressure electrostatic precipitator and to obtain fundamental knowledges necessary to develop a highly efficient high-temperature and high-pressure electrostatic precipitator. For this purpose, one-dimensional cylindrical electrostatic precipitator with a thin wire electrode at the centerline has been constructed and effects of temperature and pressure on various electric and thermal phenomena have been derived separately and then coupled effect of them on precipitation performances have been clarified.Drastic decrease of collection efficiency at high temperature can be qualitatively explained by decrease of ion formation rate near the center electrode, decrease of particle charging rate and decrease of particle drift velocity with high kinematic viscosity and this result can be well explained by the dependency of mean free path on the temperature. The discharge mode should have changed from corona to glow mode. So, applying high pressure is definitely necessary to maintain high performance and low energy consumption in a high-temperature electrostatic precipitator.