Mist Removal Performance of a Novel Electrostatic Precipitation Type Mist Eliminator, With a Narrow Gap and High Gas Velocity, for Use in Coal-Fired Power Plants

Abstract

To remove fine particles from a wet flue gas desulfurization (FGD) system in a coal-fired power plant, we develop a flat-plate type wet electrostatic mist eliminator (EME), with a narrower gap and higher gas velocity than that of a conventional electrostatic precipitator. Particle collection and pressure drop performance tests are conducted at the laboratory scale for the EME with a single-channel geometry and collection area of 0.5 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at various gas velocities and applied voltages. The results are compared to those achieved for a chevron-type mist eliminator. The pilot EME, which is designed based on the laboratory-scale device, has a collection area of 4.6 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and tested at a fixed velocity of 4 m/s, with and without the chevron-type ME. Its long-term performance is evaluated for approximately 400 min. Mists smaller than 10 μm are generated, including CaCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> particles, and an optical particle counter and United States Environmental Protection Agency M5 method are used to measure the particle collection efficiency. The collection efficiency of the laboratory-scale EME at 4 m/s is approximately three times higher than that of the chevron-type ME, whereas the pressure drop is only 8% of that of the chevron-type ME. The particle emission from the pilot scale EME with multiple channels is 2 mg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , which decreased to 1.4 mg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> when it is combined with the chevron-type ME. Although the initial particle collection efficiency of the pilot scale EME (71.2%) decreases to 60.5%, the efficiency recovered to almost the initial state after 10 min of water cleaning at 43.5 L/min.