66 posts
TimePosted 04/04/2011 08:04:52
fjalali says

Alk-S Balance in Clk

Hi Experts,

I was looking at a White cement plant’s raw feed chemical analysis with:

SO3: 0.24%

Na2O: 0.14%

K2O: 0.14%

That uses natural gas with a nominal zero sulfur content as fuel, which produces a clinker with:

SO3: 0.6%

Na2O: 0.13%

K2O: 0.16%

What can be the source of sulfur in Clk? Is it the accumulation cycle or the natural gas has some sulfur?

Thanks for your help.


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Ted Krapkat
536 posts
TimePosted 05/04/2011 01:11:15

Re: Alk-S Balance in Clk

Hello Fjalali,

Yes, although 98% of the sulphur in raw natural gas is removed during processing, sulphur-containing odorants such as mercaptans are also added to help detect gas leaks, so processed natural gas will contain traces of sulphur.

However I don't think this small amount of sulphur would account for the large difference between raw feed and clinker SO3 contents you have described above.   (Do you know the sulphur content of the natural gas being fired at this plant?)

Assuming a normal raw feed to clinker ratio of about 1.55,  there should only be (0.24 * 1.55) = 0.37% SO3 in the clinker, rather than the 0.6% reported.

The SO3 recirculation cycle would not explain this either because, as long as the values you have given above are averages over a long period, and there are no other material inputs or removals from the kiln system, input SO3 should equal output SO3.

This also applies to Na2O and K2O, but the results you provided show that there is  an even more puzzling discrepancy in the balance of these two oxides.

Again, assuming a raw feed to clinker ratio of about 1.55,  both the Na2O and K2O content of the clinker should be;- 1.55 * 0.14 = 0.22% 

However the clinker Na2O is only 0.13% (less than the raw feed!!) while the clinker K2O is just 0.16%.

Taking all this information into account, I suspect that the discrepancies you observed are due to:-

 1. Analysis results are not based on averages taken over a long enough period.


 2. Errors in the analyses.





66 posts
TimePosted 06/04/2011 10:11:20
fjalali says

Re: Alk-S Balance in Clk

Hi Ted,

Thanks for your explanation. Regarding the natural gas the source company claims that it does not have any sulfur.

The analysis is from batch analysis not long term but they claim it is representative of long term results, meaning they always get the same ratio of sulfur and alkalis in their raw feed and produced clinker.

If they have errors in their analysis I am not aware of it.

Can the sulfur in the fuel source be at a level that results in such sulfur level in the clinker? Should the alkalis always be (1.55 x Alkali in raw feed)?

Thanks for your help.


Juliano P.Q.Minh
26 posts
TimePosted 07/04/2011 03:20:34

Re: Alk-S Balance in Clk

Dear Sir 

As your fomular, i tried to calculae the SO3 absorbed into the Clinker. The analyses (bases on X-ray) is normally more than the calculated result:

  0.49 (analyses result) > 1.55*0.21 (from kilnfeed) = 0.33 (calculated result)

 This is statistics result within 1 week.

Could you explain by clearly, pls?? Thanks!!