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.

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.

What do you know about consuming SPL in cement kilns in North America. What are the environmental concerns with this. There are kilns burning SPL on North America. I believe that one of the plants at Harleyville was doing this. If there are any environmental concerns it is that the pot liners absorb some heavy metals in the electrolysis process and that this might lead to emissions of these materials. The SPL will also contain high levels of NaF and this will significantly affect clinker chemistry and kiln operations but not necessarily emissions. The sodium and fluoride should all be retained in the clinker.

There are kilns burning SPL on North America. I believe that one of the plants at Harleyville was doing this. If there are any environmental concerns it is that the pot liners absorb some heavy metals in the electrolysis process and that this might lead to emissions of these materials. The SPL will also contain high levels of NaF and this will significantly affect clinker chemistry and kiln operations but not necessarily emissions. The sodium and fluoride should all be retained in the clinker.