SO2 emission control

Dear All

Recently, the SO2 emission in our kiln was quite high even in direct or compound mode. Can you please share me some info related to the SO2:

What are the main sources of SO2 emission of kiln stack?

Does AFR (rubber wastes, rice husk, solid hazardous wastes..) impact to the SO2 emission?

Does fuel (coal) or burning process impacts to the SO2 emission?

Measures to control the SO2 emission?

Thanks for your sharing

Tam Nguyen

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re SO2 emission control

Hello Tam,

SO2 emissions in a properly-operated cement kiln with a reasonable alkali/SO3 balance are due primarily to increased levels of sulphides and organic sulphur-containing compounds in the raw meal. 

By 'properly-operated' I mean that the kiln oxygen should be continuously maintained at a level which prevents the formation of more than about 100-200ppm CO in the kiln inlet. Oxygen is required to ensure that SO2 can be converted to SO4-2 in the form of alkali sulphates, which can exit the kiln within the clinker. Both of these things are important because if the alkali /SO3 balance is  extremely low (ie excess SO3) and/or there is insufficient O2 in the kiln inlet, it is more likely that SO2 emissions will be higher. High levels of chloride can also combine with alkalis in the lower preheater and so reduce the amount of alkalis available to remove SO3 from the kiln.

Sulphur in fuels and in AFRs introduced through the main burner is normally  "scrubbed out" of the gas stream by the high levels of calcium oxide in the hot meal dust. In addition there is likely to also be some additional scrubbing of SO2 in the conditioning tower, raw mill and raw meal baghouse because of the high levels of fine CaCO3 in this dust. Therefore very little SO2 is emitted as a result of sulphur introduced through the main burner or calciner burners. However, as mentioned earlier, this is contingent on having a good alkali/SO3 balance, low chloride input and sufficient O2 at the kiln inlet.

AFRs containing sulphur (such as petcoke and rubber) should therefore not impact strongly on the SO2 emissions as long as these materials are fired in the main burner or calciner burners, and the Alkali/SO3 balance is adjusted to ensure the excess SO3 is removed from the kiln as alkali sulphates in the clinker.

The following link points to an excellent document by the Portland Cement Association, which explains the formation and control of SO2 emissions in cement kilns;-

http://luisreyher.files.wordpress.com/2011/09/sn2460.pdf

Regards,
Ted.

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re SO2 emission control

Dear Mr.Krapkat,

Thank you for your sharing.

Regards,

Tam

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