Kiln Material Bypass

Does anyone know of a plant that installed a "material bypass" on their kiln or know anything about that technology?

A normal alkali bypass wastes hot gas but what I am calling "material bypass" is to waste hot meal from the bottom stage cyclone.  It should be a cheap and relatively effective method for us to help reduce our volatile cycle since our Hot meal SO3 content is typically 5 - 8% (occasionally hitting 12% in the past!!) and up to 1% Cl.

Over the years I have heard rumors of its existence but never any proof or details.  Now I am considering installation at our plant it would be good for me to have a technical exchange with a plant that is already doing it rather than re-inventing the wheel.

Chemically I am sure it will work.  The important thing is how it is done - safe and reliable extraction and cooling are the key.  Possible methods - Plattco valve leading to water cooled screw, or eductor (air cooling) or potential direct contact with water spray (perhaps similar to how dust or flyash is often "conditioned")

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Re: Kiln Material Bypass

As for us we do have traditional by-pass. It is effective thing.

But I think that the way to start is alkali-sulphur-chlorine optimization first.

By-pass installation itself is not cheap!

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Re: Kiln Material Bypass

I don't know your plant, but as rule the dust coming from the dedusting system at the end of the kiln line is rich in SO3 and Cl.

You can carry out this dust out of the process, is not too hot, and is easy to handle.

 Also this dust you can added to masonry cements as a Filler.

 This is a cheap way to take alkalies out of the system.

I hope this helps.

Best Regards

Germán

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Re: Kiln Material Bypass

Wasting hot meal from the bottom stage cyclone will work just as well as wasting hot gas wth its load of dust and evaporated volatiles. What is important is that the material which is wasted contains the concentrated volatiles. This is why bypasses (of any description) are most effective for chloride - the chloride concentrates to a much higher degree than the sulphate.

From your hot meal SO3 and Cl levels it sounds to me as if your problem is high SO3 rather than chloride. 1% Cl in hot meal is not unusual. I would recommend that you optimise the combustion in your main burner to reduce SO3 volatility rather than wasting anything (gas or material) through a bypass.

Dr Michael Clark

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