Electrostatic Precipitator Penetration Function for Pulverized Coal Combustion

ABSTRACT

The penetration of fly ash particles through an electrostatic precipitator (ESP) was measured as a function of particle size in the range of 0.02–0.7 μm (divided into 32 mobility channels) with a combination of an electrostatic classifier (DMA) and a condensation nucleus counter (CNC), but in the size range of 1.0–10 μm with the Berner type low-pressure impactor (BLPI). The measurements were carried out at a 300 MW power plant firing Polish bituminous coal during several operating conditions for coal combustion and ESP, data being acquired by both instruments and ranges. Gas composition (NO_x, SO₂, CO₂, CO, and O₂) was monitored by gas analyzers located downstream from the ESP. The ESP's operating voltage and currents were recorded. Electrical mobility distributions were measured with prime apparatus, the DMPS system. These data were reduced to the desired number size distributions with the commercial TSI-algorithm. D50-method was applied to impactor data. Fractional penetration curves were calculated from the size distributions channel by channel as the ratio of outlet concentration to that at inlet, respectively. Penetration functions appeared to depend on the boiler load, ESP voltages, and the operation of coal mill. The highest penetration was achieved with highest boiler load. The penetration dependence as a function of particle size was bimodal, reproducible, and compared against the conventional theories. Bimodal structure of the penetration curve was detected first when the first section of the ESP had low current density, and reproduced when the last section of ESP was turned totally off in an experiment to imitate the electrical conditions of the first experiment. These data add consistently to the experimental studies previously made with an industrial sized ESP. However, the resolution of the instrumentation of this study is better and confirms the doubts of theoretical suspicion against the conventional Deutsch model and its variants.