An efficient wet electrostatic precipitator for removing nanoparticles, submicron and micron-sized particles

An efficient wire-to-plate single-stage wet electrostatic precipitator (WESP) was designed and tested to control nanoparticles, submicron and micron-sized particles emitted from semiconductor manufacturing processes. Tungsten-wires of 0.36 mm in diameter were used as discharge electrodes and a fixed voltage of-15 kV was supplied to generate the electric field and corona ions. Fine water mist at room temperature was used to quench the high temperature exhaust gas to enhance particle condensation growth and improve the collection efficiency of nanoparticles. Experimental results showed that without fine water mist, nanoparticle collection efficiency was 67.9-92.9%, which was greatly enhanced to 99.2-99.7% when the WESP was operated with fine water mist. A predictive method was developed to calculate the particle collection efficiency equation η(%) in the form as η(%) = [1-exp(-α(N_De)^β + γ)] × 100%, in which α, β and γ are regression coefficients and N_De is the Deutsch number. Good agreement was obtained between present predictions and experimental data. For longer term operation, the periodic wall-cleaning water was used to clean discharge electrodes and collection electrodes regularly. In the field tests, the total collection efficiencies (40 ≤ d_p ≤ 8100 nm) of the WESP were found to maintain greater than 98.7% and 97.3% for continuous operation for 35 and 22 day at fab A and fab B, respectively.