The removal of nanoparticles from hot gas streams is a challenging task. However, there is a huge potential for heat recovery from waste gas incineration, glass furnaces, ceramic, metallurgical, pyrolytic and many other high temperature processes. A prototype application is the separation of nanoparticles formed by condensation in thermal post-combustion processes, in order to achieve efficient heat recovery at high temperatures.

This case study evaluates the performance of a high-temperature electrostatic precipitator (HT-ESP) between 400 and 800 °C for both discharge polarities. The tube-type ESP with 150 mm diameter and 1500 mm length is operated isothermally. Two electrode designs are tested by separating flame-generated iron oxide nanoparticles from a flue gas atmosphere. The total number concentration in the raw gas is around 2·10⁷ cm⁻³ with a temperature-dependent mode diameter of 20–40 nm.

Between 400 and 600 °C very high separation efficiencies around 99.998% (number-based) were found with just 1.5 s of residence time and negative polarity, using a wire discharge electrode. In fact, the separation is more efficient than at room temperature which is explained by particle charging with free electrons leading to an exceptionally high particle charge. At 700 °C and 800 °C, thermionic emissions become more relevant for ESP operation. In this range the best separation efficiencies of 99.96% and 99.5% respectively were obtained using a rod discharge electrode operated below the corona onset voltage. The specific input of energy required for 99% separation efficiency at any temperature is less than 250 J/m³.

These findings clearly prove that HT-ESPs are a feasible and highly performing alternative for nanoparticle removal from hot gases at up to 800 °C.

从热气流中去除纳米颗粒是一项具有挑战性的任务。然而，废气焚烧、玻璃熔炉、陶瓷、冶金、热解和许多其他高温工艺的热回收潜力巨大。一个原型应用是分离在热后燃烧过程中通过冷凝形成的纳米颗粒，以实现高温下的有效热回收。

本案例研究评估了高温静电除尘器 (HT-ESP) 在 400 和 800 °C 之间对于两种放电极性的性能。直径为 150 mm、长度为 1500 mm 的管式 ESP 等温运行。通过从烟道气中分离火焰产生的氧化铁纳米颗粒来测试两种电极设计。原始气体中的总数浓度约为 2·10 ⁷  cm ^-3，与温度相关的模态直径为 20-40 nm。

在 400 和 600 °C 之间，使用线放电电极发现了大约 99.998%（基于数量）的非常高的分离效率，停留时间仅为 1.5 秒，负极性。事实上，这种分离比在室温下更有效，这可以通过用自由电子进行粒子充电来解释，从而导致异常高的粒子电荷。在 700 °C 和 800 °C 时，热电子发射与 ESP 运行更加相关。在这个范围内，使用低于电晕起始电压的棒状放电电极分别获得了 99.96% 和 99.5% 的最佳分离效率。在任何温度下实现 99% 分离效率所需的特定能量输入低于 250 J/m³。

这些发现清楚地证明了 HT-ESP 是一种可行且高性能的替代方法，可在高达 800 °C 的温度下从热气体中去除纳米颗粒。