stage 3 cyclone coating

Sir,

Can some one explain why like this??

Ours is a 4000 t/d double stream 4 stage preheater , ILC kiln with 7 rows statonery grate and remaing grate cooler.we continuously run the alkali bypass system.Coal is the fuel. our top side 3rd stage cyclone when inspected in the shutdown found feather like coating the whole of cyclone (1st stage cyclone is the bottom one) The coating sample shows as follows.

LOI 5.50%           Fe203; 3.51%    K2O 1.466%

SIO2 6.87%        CAO 45.62%      R2O 1.131%

AL2O3 3.78%     MGO: 0.92%     CHLORIDES  0.9341%

SO3 31.20%     NA2O 0.166%

Hot Raw meal result shows Chlorides about 0.7358% So3 about 1.02% and R20 About 1.0%.

Pl suggest.

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re stage 3 cyclone coating

Hello,

Based on the analysis you've given, the sample probably contains mostly gypsum and possibly some sulphospurrite. It's likely that your alkali bypass is preferentially removing alkali chlorides and leaving a higher proportion of the sulphur behind. This remaining SO3 can then combine with CaO to form these minerals.

Do you have an analysis of both your hot meal and bypass dust?

 

Regards,

Ted.

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re stage 3 cyclone coating

Sir,

 Here is the alkali dust result and hot rawmeal result taken today.

Hot rawmeal chloride % 0.7531

                       SO3 % 1.51

                       R2O  %1.007

Alkali dust:

LOI 6.28% ,SIO2 19.19%, AL2O3  3.32%, FE2O3  4.25%, CAO 57.06%, MGO 1.06%

SO3 :3.26%,NA2O : 0.273%, K2O :2.881 %, R20 :2.169%  CL2  2.4000%

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re stage 3 cyclone coating

Hello,

Thank you for your analyses.

Both the hot meal and bypass dust have a very low molar Alk/SO3 ratio. (0.30 and 0.03 respectively)

This means that a large proportion of the sulphur in both these streams is not bound to alkalis.  This 'uncombined' sulphur is therefore free to move up the preheater in the gas stream where, at the right temperature, it can then react with incoming CaO and SiO2 to form deposits of Anhydrite (CaSO4) and Sulphospurrite. (4CaO.2SiO2.CaSO4)

The chemical analysis of your preheater buildup is consistent with a mineral composition of;-

 ~27.5% Sulphospurrite (4CaO.2SiO2.CaSO4)

~44.6% Anhydrite (CaSO4)

~12.6% Calcite (CaCO3)

~0.4% Thenardite (Na2SO4)

~0.4% Arkanite (K2SO4)

~2.0% Sylvite (KCl)

~4.2% Free Lime

(Note that these values are only an estimate based on the chemical data alone and are not necessarily accurate. The only way to know for sure is to have a sample tested by XRD for the actual mineralogical composition.)

 

What is the O2 and CO content of your kiln inlet gases?  Insufficient O2 will increase the volatility of SO3 within the calciner/preheater.

Also, what is the sulphur content of your coal?

 

Regards.

Ted.

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