Ari Laitinen

Bipolar charged aerosol agglomeration with alternating electric field in laminar gas flow

Abstract This paper presents the results of an experimental study for a method of increasing the efficiency of electrostatic precipitators for the collection of fly ash particles of submicron size. An alternating electric field was used to induce agglomeration of bipolarly charged particles (bipolar AC-agglomeration). A bench-scale AC-agglomeration test apparatus with bipolar corona charger was constructed. Test aerosol was generated from vegetable oil. The total mass loading was 0.2 gm−3 (5 × 106 particles cm−3), mass median diameter was 0.5 μm. Count median diameter was 0.2 μm, and geometrical standard deviation was 1.8. Residence time in the agglomerator was 4.8 s and the agglomerator field was 5.0 kV cm−1 (rms). Systematic experiments were conducted to investigate the agglomeration efficiency of the system. The percentage decrease in number concentration of 0.1–1.0 μm sized particles was found to be between 17 and 19%.

Spray Charging of Droplets in a Wet Scrubber

Abstract The experimental setup was designed to study the effect of natural charging of droplets during spraying (called spray electrification or spray charging) in a wet scrubber. The influence of nozzle material, liquid feed rate, and liquid composition on the specific charge (charge per unit volume of liquid) formed in spraying was measured. It was found that the nozzle material has no measurable effect on this specific charge. Increasing the liquid feed rate increases the specific charge significantly. Increasing solute (NaCl or NaOH) concentration increases the conductivity that decreases the formed specific charge. The same correlation between the specific charge and conductivity was also observed with real scrubbing liquids. It is proposed that the specific charge depends only on the value of liquid conductivity, not on liquid composition. The conductivity of the tested scrubbing liquids was high enough to suppress the formation of a high specific charge during spraying.

Preformed spray scrubber: Comparison of precipitation mechanisms for charged fine particles

Fine particle removal is studied by measurements in a laboratory scale preformed spray scrubber. Particles are charged in a corona charger.