4 posts
TimePosted 16/01/2009 09:55:44
Giovanni says

Raw mill drying problem

We have a Ball mill, the average moisture of the mix is ca 4-5% but during strong raining season it comes up to 8%!

Hot gas coming from the kiln is not enough to dry the material, we have also installed a hot gas generator (HGG) to  use in case of kiln shutdown.

 My question:

Is it safe to try to run with both kiln hot gas and hot gas coming from the HGG?

HGG and kiln hot gas are connected to the same duct.

Thanks in advanced!


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57 posts
TimePosted 19/01/2009 15:08:25

Re: Raw mill drying problem

The only problem I can see is to ensure that enough air can be drafted through your hot gas generator.

You should check the mill fan to be sure it can take both gas from kiln and from HGG.

 Gas repartition may also be a concern (i.e how to determnie what amount will be taken from HGG and what amount from kiln). This depends on the specificities of your gas circuit (flaps, booster fans, etc...)


14 posts
TimePosted 21/01/2009 22:28:10

Re: Raw mill drying problem

Depending on your preheater arrangement there may be the possibility to operate a 5-stage preheater during the dry season and a 4-stage preheater during the wet season by feeding the raw meal to the riser of the lower preheater stage resulting in higher preheater off-gas temeperature.

This would reduce the capital cost for installing a hot gas generator.

This way operation is done in some cement plants.

Best regards,



6 posts
TimePosted 22/01/2009 05:47:18
Soni says

Re: Raw mill drying problem

Dear Sir,

To some extend I agree with the idea expressed by Mr. Wizi  by draw hot gases operating 5 stage PH in normal days and from 4th stage PH during rains.

However to comment more realistic concern are requested better to put the problem in totality along with basic plant set up like 5stage  or 4 stage PH and plant capcity etc.


R P Soni