I am a consultant to the petroleum coke industry. There is a lot of talk that high sulphur pet coke (7-8 per cent) is a low cost feed to cement plants that meets US emission standards. The theory is that the suphur is thoroughly consumed or bound up by the limestone and converted to calcium sulphate. I have been recently asked by a US cement plant contemplating burning coke for more specific information in order for them to meet their EPA permit. Do you have anything re solid scientific statistics of the SO_x formation in cement kilns when burning coke??

There are a number of case studies of cement kilns burning petcoke and having no SO_x emission problems. It is correct that the predominantly alkaline feed absorbs any SO₂ in the kiln exhaust gases due to the intimate contact between the gases and the feed in the preheater cyclones. There is a greater potential for SO_x emissions with long kilns (ie without preheaters).

I have been looking for a small bagging machine to bag our duct collect powder. In conversation with an individual I was told that bagging requiremnets were about to change. That the old plastic lined bags were going to be replaced by hermetically seal bags...are you aware of anything like that in the works?

I'm not aware of this development, but I'm sure it depends where in the world you are working. In Europe the big coming issue is hexavalent chrome. This has to be guaranteed to be less that 2 ppm and to ensure that ferrous sulphate is added to the cement to reduce any chrome. Unfortunately the effectiveness deteriorates over time and therefore shelf-life issues raise their head. This could very well be the reason why there is a move towards hermetically sealed bags.

We have ESP at the kiln system. It is also used for raw mill system. System is sent ESP's feedback to kiln feeding silo. There are two homogeneous silos and two stockage silos. Material is sent from ESP to homogeneous silos. So, my question is that, I am thinking to feed the ESP's feedback directly to preheater system but this line will be entered to system after weighfeeder. We have got line to feed this material before weighfeeder but it causes to reduce of fresh feeding. In this way I want to increase clinker production with same feeding amount. What do you think?

Your idea is a very good one. There are plants that do exactly what you propose. This has the advantage that the chemistry of the kiln feed is more stable because it is not destabilised by slugs of ESP dust being added to the homegenisation silo when the raw mill is not running. I am not sure that you will get more output but the kiln operation and clinker quality should be more stable.

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.

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). 2 - 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 filterbag 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 may be valid, but I would be surprised.

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.