Mist removal performance of a novel electrostatic precipitation type mist eliminator with a narrow gap at high velocity for coal-fired power plant

Abstract

To remove fine particles from a wet FGD (Flue gas desulfurization) in coal-fired thermal power plants, we developed a flat-plate type wet electrostatic mist eliminator (EME) with narrow gap and high gas velocity, compared to conventional electrostatic precipitation (ESP) design for the thermal power plants. The particle collection and pressure drop performance tests of the lab scale EME having single channel geometry with a collection area of 0.5 m2 were conducted at various gas velocities and applied voltages, and also compared to those with the Chevron type mist eliminator. The pilot scale EME designed from the lab scale with collection area (4.6 m2) was tested at a fixed velocity of 4 m/s with and without the Chevron type ME, and its long term performance was evaluated for approximate 400 minutes. Mists smaller than $\mathbf{10}\ \mu \mathbf{m}$ including CaCO3 were generated and an optical particle counter and EPA test method 5 were used to measure particle collection efficiency and emission concentration. Experimental results showed that collection efficiency of the lab scale EME at 4 m/s was approximately 3 times higher than that with the Chevron type, while pressure drop was only 8% of it. Particle emission from the pilot scale EME with multiple channels was 2 mg/m3 and decreased to 1.4 mg/m3 when it combined with the Chevron. Even though the initial particle collection efficiency of the pilot scale EME, 71.2%, was decreased to 60.5%, the efficiency was recovered almost to the initial state after 10 min water cleaning with 43.5 L/min.