Experimental investigation on the characteristics of ash layers in a high-temperature wire–cylinder electrostatic precipitator

Abstract

Abstract The high-temperature electrostatic precipitator (ESP) is a potentially efficient method for hot-gas cleaning in advanced technologies, e.g., the coal-staged conversion poly-generation system and IGCC. This paper investigates the characteristics of the ash layer on the internal surface of the anode pipe of a wire–cylinder ESP at temperatures ranging from 350 °C to 700 °C, including ash deposition forms, growth of ash layer and the effect of ash layer on back corona discharge. There are four typical ash deposition forms: the belt form, the slope with ribs form, the slope form and the slope with a thick bottom edge form. Ash layer thickness generally decreases with increasing height. When T ⩽ 500 °C, ash belts form under low port voltages, and with increasing port voltage, they will overlap each other to form ash ribs. When T ⩾ 500 °C, particles are deposited in the smooth slope form if the port voltage is great enough. When T ⩾ 700 °C, a thick bottom ash edge occurs. Ash deposition forms can vary under different operating conditions. As the operating time increases, the thickness growth rate at a given point decreases, and the ash layer height increases because of the repulsive electrical force between the ash layer and the particles. Back corona discharge always occurs on the thickest portion of the ash layer first. The back corona discharge onset voltage decreases nearly linearly with increasing ash layer thickness, from 19,787 V to 17,197 V as the maximum thickness of the ash layer increases from 0.34 to 2.02 mm when T = 500 °C, U p = 17,200 V and m in = 650 mg/N m 3 .