A Novel Approach for Computing Particle Collection Efficiency of Electrostatic Scrubber

Abstract

One of the major causes of air pollution is the presence of particulate matter such as dust, mist, smoke, or vapour in the atmosphere in amounts that may be harmful to human, plant or property. Particles which are submicron in size tend to remain entrained in the gas stream. To collect particles of such small size with high efficiency electrostatic charging of the particles is done. The electrostatic scrubber uses charged collector droplets to collect the dust particles of same or opposite polarity. Following Coulomb’s Law, the small particles get attracted towards the water droplets. These collector droplets, after the deposition of the dust particles, are removed from the apparatus and simultaneously fresh droplets enter the system. This electrostatic system shows far better performance as compared to other conventional scrubbers. The main advantages of using an electrostatic scrubber are low water consumption, low power consumption, low operation cost and low wear and tear. Thus in past, several authors have simulated and studied the performance and collection efficiency of the system using stream function and finite element method, which makes it difficult to understand and calculate the path followed by the dust particles. Thus here we use an alternate method of plotting these trajectories and thus calculating the dust collection efficiency in a simplified manner using Runge-Kutta method. These trajectories are plotted by calculating the co-ordinates of the dust particle and the collector droplet at each instant of time for different set of conditions. And the collection efficiency is calculated by taking the ratio of number of particles depositing on the collector to the number of particles entering the system. This collection efficiency is studied with respect to various parameters, such as collector radius, Coulomb number, Stokes number, keeping all others constant. The graphs showing these particle trajectories and collection efficiency relations have been presented.