Single and two-stage electrostatic demisters for biomass pyrolysis application

摘要

Single-stage and two-stage tubular electrostatic precipitators were designed. A nitrogen stream containing very fine droplets of fogging oil was forced through the electrostatic precipitator chamber. It was found that 98.6 wt% of the oil droplets present in the turbulent jet were mechanically collected on the inner walls of the test chamber. When the electrode was energized at 13 kV, 92.37 wt% of the droplets that had not been mechanically separated were collected in single-stage mode. The collection efficiency was increased to 93.18 wt%, when the electrostatic precipitator was operated in two-stage mode. Voltage-current (V-I) characteristics of the single-stage and two-stage electrostatic precipitators were studied in detail for different test conditions. Nitrogen impurities played a major role in determining the V-I characteristics. They became less relevant with the introduction of mist in the nitrogen stream, presumably due to the presence of water vapor in the gas. The two-stage tubular electrostatic precipitator was scaled up and tested on a fluidized bed pilot plant used for the pyrolysis of biomass. A droplet collection efficiency of 95 wt% was observed. Such demis-ters will extend, to the product recovery train, the process intensification gains of short residence time processes such as fast pyrolysis.