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Technical Cement Forum / VERY HIGH FREE LIME

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xxxx 31/01/2013 08:25:46

VERY HIGH FREE LIME

DEAR ALL

WE R FACING A LOT OF HIGH FREE LIME PROBLEM IN CLINKER (AS HIGH AS 3 TO 4%)

THERE IS NO CO FORMATION , BURNER PIPE IN THE CENTRE , FLAME MOMENTUM IS 1800 %M/S.

LITRE WEIGHT 1120-1160

KILN NOT DUSTY AT ALL.

LSF IN KILN FEED 93.5 TO 93.7

SM 2.25-2.27

AM IS 1.22-1.25

CLINKER IS HAVING BROWN MATERIAL INSIDE WNILE THE OUTSIDE LAYER IS BLACK.

PREHEATER DRAFTS ARE NORMAL.

IF I SUSPECT ON QUARTZ & CALCITE ETC. THAN IT IS ALSO GIVE IMPACT ON THE VRM GRINDING EFFICIENCY BUT THERE IS NO UNDICATION OF THE SAME.

MY RAW MEAL IS 17% ON 90 MIC & LESS THAN 2% ON 212 MIC.

FUEL IS 80% PETCOKE & 20% SOUTH AFRICAN COAL WITH 3.5% RETENTION ON 90 MIC.

SO3 IN THE HOT MEAL IS AROUND 1.5-1.6%.

THE ONLY INDICATION IS VERY HIGH CALCINATION IN THE HOT MEAL (98-99%).

TO REDUCE THIS CALCINATION I HAVE TRIED TO REDUCE FUEL BUT KILN BECOMES DUSTY .

NOW HOW TO CHECK THE QUARTZ & CALCITE IN THE LABORATORY THAT I DO NOT KNOW?

MINE IS AN ILC KILN WITH 5 STAGE PH (3.3*50M) 200 MM REFRACTORTY.

PLEASE DO SUGGEST TO OVERCOME THE PROBLEM.

THANKS

SIDHANT

Raj Sahu 01/02/2013 10:23:20

One of the possible reason is coarse grain quartz and calcite minerals in limestone.It has been reported that 1% quartz above 45 micron may increase 0.93% free lime and 1% calcite above 125 micron may increase 0.56% free lime.The content of the coarse particles (crystal grain size of quartz and calcite minerals) in your raw mix/lime stone is determined by using Optical Microscopy.

If you found your calcite grain size is coarser than 125 micron then finer grinding of raw mix may help to reduce free lime.

xxxx 01/02/2013 11:49:37

Dear Mr Sahu

thanks a lot for the response but if quartz & calcite is the possible problem than it should also reflect in the raw mill (VRM) output & operation along with wear in the internals

But we do not find any change in the mill output,power & wear etc.

Is it the kiln shorte\r dimensions which makes it very sensitive to free lime?

Is very high calcination (> 98%) in the hot meal gives some idea about the problem?

Please do reply.

Sidhant

GSMS 01/02/2013 13:44:44

The high free lime may be due to incomplete combustion. That is why you are getting high calcination. The fuel is burning in Pre-heater instead of Kiln. The possible reasons are.

Chek your CO percentage with portable gas analyser. May be the analyser reading is wrong.

Check and confirm the fuel quantity shown in your CCR display with actual quantity.

Try to adjust ID fan draft. May be due to high draft than required draft.

Try to adjust the TAD openings.

May be this will solve your problem.

Please do reply after you made adjustments.

Best of luck.

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