You need to study the Ideal Gas Laws to understand the relationships between gas volume, density and velocity. An EP works by inducing a strong electrical field between discharge and collection electrodes. Dust carried in the gas stream passing between these oppositely charged electrodes itself becomes charged and is collected on the collection electrode from where it is periodically knocked off into the collection hopper at the bottom of the EP by the rapping devices.

I understand that flow of exit gases at preheater may be calculated by Q = velocity * cross sectional area of duct But I do not know the formula for velocity and density. Please explain the same. Secondly, please explain how an EP functions.

I am afraid I cannot see many merits to this suggestion. It is common practice to condition (humidify and cool) the gases before entering the ESP by spraying droplets of water into the gas stream in a conditioning tower. This might indeed lead to 80 per cent of the dust load dropping out in the conditioning tower. However in your kiln, the suggestion is not to spray into a tower that will act as an expansion chamber but into the gas riser. You will also cool and contract the volume of the gases which will have the effect of increasing the draft at the kiln inlet leading to the possibility of higher dust losses from the kiln. I could not advise such a modification and believe that a much more detailed examination of the problem is required.

Our ESP on our long dry kiln (2520tpd) is out of order. A certain company has recommended instead of the ESP to install a water fogging system(droplet size = 10 micron) into the riser pipe of this kiln claiming that 80 per cent of dust passing with exit gases before the ID fan can be suppressed that way. Can you advise us on the merits and/or disadvantages of such a system.