Separating Al2O3 particles from high-speed flue gas by an induced flow recirculation in two-stage electrostatic precipitator

Abstract

Although fly ash is known to be harmful to human health, fly ash is full of metals and compounds that are useful in certain applications. Aluminum oxide is one of the economic compounds in fly ash emitted from coal-fired power plants where electrostatic precipitators (ESPs) are commonly used to collect fly ash. The collection efficiency of an ESP decreases rapidly when the passing airflow velocity increases and could get even worse because of particle reentrainment when rapping the collecting electrode for cleaning purposes. This paper presents how the flow recirculation, induced by square-wave structure, prevents the collection efficiency from dropping too fast by suppressing particle reentrainment. The results show that the ESP comes with the square-wave collecting electrode (ESP-SW) has higher collection efficiency than that comes with the traditional flat-plate collecting electrode (ESP-FP), and the difference gets larger when the airflow velocity increases. The particle reentrainment rate of the ESP-SW is up to 22% lower than that of the ESP-FP. Furthermore, when the airflow velocity goes higher, the square-wave collecting electrode collects more and more percentage of particles, while the flat-plate collecting electrode collects a fewer and fewer percentage of particles.