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 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.

We would like to know the effect of removal of an ESP outside casing insulation if the prevailing ambient temperature is 40 degrees Centigrade and rainfall is scarce, ie dry weather, and is it possible to get a decrease in gas temperature inside the filter by this action or there are going to be some operational problems?

There will certainly be operational problems if you remove the insulation from your ESP. The temperature of the inner walls of the ESP will then become equal to the ambient temperature of 40 degrees C. This will be below the acid dew point of the gases passing through the ESP and you will have condensation on the inner walls and internal fittings of the ESP. You will then suffer from severe corrosion problems and will have to replace the internal fittings of the ESP on a regular basis.
My recommendation would be to adjust the raw mix chemistry to raise the LSF and AM and compensate for these changes. This will reduce the amount of baghouse fines required and therefore the ZnO additions. The mineralising effect of the ZnO will allow a higher LSF kiln feed to be combined in the kiln. At the same time C₃S and C_{3A content in clinker and cement will be increased offseting the retardation effects of the ZnO.}

Our government is starting to limit NO_x emissions from cement kilns and the regulation, as I heard, was more severe than in the European countries. I think the best way for reducing NO_x emission with no further cost is to use fuels that contain the lower nitrogen content, especially coal and residual fuels. Am I correct?

The NO_x emissions arise from two sources: (i) the nitrogen in the fuel as you say, and (ii) "thermal" NO_x from the breakdown of atmospheric nitrogen at the high temperatures in the burning zone. Usually the thermal NO_x is much higher than the fuel NO_x and the best way to reduce NO_x emissions is to reduce this thermal NO_x. Low NO_x burners reduce the temperatures in the flame and produce less NOx by using less primary air. Low NO_x calciners burn some of their fuel in a depleted oxygen environment to cause NOx degradation by the following reaction: NO + CO -> 0.5N₂ + CO₂. These are the best way sto reduce the NO_x emissions of the kiln.

We will appreciate your support clarifying the following points:
1-False air effect upon the (increase/decrease) of dust load in a closed system of air swept type ball mill (between the mill outlet duct-seperator-cyclones-filter-stack). Also, will the dust resistivity increase/decrease?

In an air-swept mill false air is usually introduced at the bottom of the ascension pipe in order to ensure there is sufficient volume, density and velocity of air to lift the ground material up the ascension pipe and through the separator. The amount of dust being carried up the ascension pipe is the same, however the volume of air is greater therefore the overall effect is a dilution of the dust load. In principle the false air will cause a reduction of the temperature and this will reduce the resistivity of the dust improving the electrostatic precipitation.

Do you think that pre-dedusting in a raw mill circuit by means of cyclone with a separation efficiency of 91-93 will have negative influence on the raw mill bag filter or ESP in regard to the fact that after pre-dedusting only rather fine grain and rather low quantity of dust will enter the filter? Could it become difficult to clean the bags due to fine dust getting deeper into the pores of the filter bag and could the fine dust have negative influence on the ESP?

I cannot foresee that reduces the load of dust entering a filter will have any detrimental effect on its performance. Certainly no problem with an ESP. Your point regarding fine dust blinding the cloth of fabric filters maybe valid, but I would be surprised.

We will appreciate your support clarifying the following points:
1-False air effect upon the (increase/decrease) of dust load in a closed system of air swept type ball mill (between the mill outlet duct-separator-cyclones-filter-stack). Also, will the dust resistivity increase/decrease?

In an air-swept mill false air is usually introduced at the bottom of the ascension pipe in order to ensure there is sufficient volume, density and velocity of air to lift the ground material up the ascension pipe and through the separator. The amount of dust being carried up the ascension pipe is the same, however the volume of air is greater therefore the overall effect is a dilution of the dust load. In principle the false air will cause a reduction of the temperature and this will reduce the resistivity of the dust improving the electrostatic precipitation.