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.

I would like to raise question with regard to the impact of strontium (Sr) to EP efficiency. From our experience, there is a negative correlation between Sr concentration to EP efficiency. When Sr increased, dust emission increased too. Our Sr content in limestone rock varies from 183 to 1382mg/kg. Or, do you suspect from another elements such as organic matters as well as high dust resistivity, too?

Your experience with strontium is very interesting and I have not heard of it before. The performance of your ESP will also be affected by organic matter and the resistivity of the dust. The key question then becomes are these variables independent of one-another? I know of no reason why strontium would increase the resistivity of the dust.

We've been faced with a problem that the collecting efficiency of the electrostatic precipitators lowers remarkably since having started to use sewage sludge as the secondary material. I'm not sure where the cause is from. Is there any possibility of causing such problem by using sewage sludge, and which kind of components that sewage contains can affect the performance of ESP? As the reference, we've been experienced in the same problem when we used TPA sludge(Telephtalic Acid) two years ago.

I have not heard of this phenomenon before. The resistivity of the dust exiting the preheater must be changed when burning these sludges. I hope all the sewage sludge is being burnt in the kiln and the problem is not caused by organic residues entering the ESP. If so then the problem can only be associated with volatiles derived from the sludge entering the ESP with the dust. The most likely source is chlorides from the sludge. You should also check carefully that the problem is not caused by mercury from the sludge. If so then you have a big problem.

I'm working in a cement plant established at 1984, two lines with dry processing technology, the plant faces so many conflicts, major parts are not from the source company, for example the dust separator doesn't work at all, so many efforts carried out with no result, also the computerised analysis system with daily production reports does not work either. The plant uses oil for heating up, there is a factor normally set at 1.64 which is a standard in cement production, but now it has been elevated to 1.90. After how many years how could the 1.64 could be increased to 1.90.

The factor of 1.64 you refer to is the raw mix to clinker factor taking into consideration dust losses from the preheater. If you have very high dust losses then this factor might need to be higher. However to justify a factor of 1.90 the dust losses will need to be in the region of 30 per cent of the feed to the top of the preheater. If this is the case and your dust collector is not working the pollution must be terrible.

Is silicosis a potential hazard in cement manufacturing? If so, what kind of protective measures should be taken?

Whether silicosis is a hazard of cement manufacturing depends on whether there is free silica in the raw materials. However, whether there is free silica or not workers should avoid breathing any dust into their lungs. Dust mask should be worn wherever there are high dust levels. There is no free silica in the cement final product.

I study about hexavalent chromium and its source in portland cement production. Before I have studied about this and measured total chromium by ICP analysis method. Now I want to study portland cement samples for determination and quantification of soluble and insoluble hexavalent chromium and find the main source of this pollutant and if possible to control such effects.

The main source of hexavalent chromium in Portland cement and the dust associated with its manufacture are magnesite chrome refractories used to line the burning zone of cement rotary kilns. For this reason the use of these refractories has been discontinued in many parts of the world, but they are still used in some regions.

We have a 1000tpd FLS kiln with a five-stage preheater. We are having a lot of clinker dust formation which is causing great wear at the kiln hood. What would you recommend to get rid of the clinker dust.

It is difficult to diagnose the problem over the internet, however these problems are often caused by inefficient combustion of the fuel in the main burner, long flames and poor heat flux in the kiln. I suggest you increase the axial primary to the maximum and see if that helps.