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?

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.

I own a 400tpd cement plant. Because of a recent reshuffle in government, the state is now asking us prove our pollution free state of running. How can I prove the technology is a pollution free one.

You need to begin the process of obtaining ISO 14001 certification for environmental management systems. There are various consulting companies who should be able to help you with this process.