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

从高温烟气中有效地去除飞灰颗粒是实现先进的高效煤炭利用系统（例如整体煤气化联合循环（IGCC））所要开发的最重要的技术之一，并且陶瓷过滤系统已经被考虑用于该目的。另一方面，高温静电除尘系统也有很大的可能性用于IGCC中的气体净化，但在这种情况下，需要高压条件来维持电晕放电。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单独影响，并获得开发高效高温高压电除尘器所需的基础知识。为此目的，一个本文建立了一个中心线为细线电极的三维圆柱形电除尘器，分别导出了温度和压力对各种电、热现象的影响，阐明了它们对除尘性能的耦合作用，并定性地解释了高温下除尘效率的急剧下降是由于中心附近离子形成速率的降低高运动粘度的颗粒荷电率降低，漂移速度降低，这一结果可以用平均自由程对温度的依赖性来解释。放电模式应从电晕模式变为辉光模式。因此，在高温电除尘器中施加高压是保持高性能和低能耗的必要条件。

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.