Ted Krapkat
537 posts
TimePosted 10/11/2008 04:41:28

Volatility of Fluoride


 Does anybody have any practical experience with the volatility of fluoride in the preheater?

 We are currently burning 1 - 2tph of Spent Cell Liner (SCL) waste from a local aluminium refinery. This material contains ~10% fluoride.

 We have tested our clinker and found that the above usage rates of SCL increase the fluoride level from ~200ppm (no SCL) to ~1000ppm (2t/h SCL)

 The literature seems to suggest that this is a modest level of fluoride, with most sources quoting maximum levels of  2000ppm (0.2%) in clinker, with respect to cement performance (particularly setting times) and up to 5000ppm (0.5%) with respect to build-up problems.

Our own mass balance data for fluoride (performed some years ago before the use of SCL) tends to suggest that fluoride is not substantially enriched in either the hotmeal or kiln dust streams.(at least not at levels of ~200ppm in the clinker)

Does anybody have any experience with fluoride-related buildups or other process/operational problems associated with fluoride?



Ted Krapkat (Plant Chemist)

Cement Australia - Gladstone Plant



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Michael Clark
321 posts
TimePosted 10/11/2008 16:58:41

Re: Volatility of Fluoride


Your experience seems to be in line with experience reported from elsewhere. Fluoride does not enter into a pronounced cycle in the kiln or concentrate particularly in the hot meal. “Stickiness” in hot meal is sometimes reported. Fluoride additions, in combination with sulphate are used to mineralise clinker formation in kilns.

Best regards

Dr Michael Clark


Ted Krapkat
537 posts
TimePosted 11/11/2008 01:17:43

Re: Volatility of Fluoride


Thanks for confirming my initial thoughts. At the low rates (2 - 3t/h) of SCL we are forced to use (limited by clinker sodium equiv.) the effect of fluoride on blockages in our process is probably of little concern.






Raj Sahu
198 posts
TimePosted 11/11/2008 11:31:29
Raj Sahu says

Re: Volatility of Fluoride

Dear Mr.Ted,

Could you please tell me what is alkali concentration you get in SCL.