44 posts
TimePosted 16/04/2010 03:34:24
hongminh says

Preheater temperature.

Dear Experts,

My factory is face to face with the phenomenon of preheater temperature increased, espescially in meal chute and exhaust gas of C1( from kiln inlet).

Normally my kiln operating with parameters follow :

- Raw mix ratio : LSF : 100; MS : 2.55; MA : 1.45.

                         finess : 12 - 14%

- Kiln feed : 275 t/h.

- kiln speed : 3.5 - 3.7 rpm

- Meal chute temp : 850 - 860 degree C.

- NOx : 900 - 1100 ppm.

- coal finess : 3 - 4%.

- Kiln inlet O2 : 2 - 4%.

But some days ago :

- Raw mix, coal, kiln feed not change.

-  Meal chute temp : 880 - 920 degree C.

-  NOx : 500 - 700 ppm.

- Kiln inlet O2 : 2 - 4%.

- kiln speed : 3.2 - 3.5 rpm. 

- kiln has dust.

When we have to try to reduce meal chute temperature then kiln cooling down also.

Now we operated kiln with low speed (2.8 - 3 rpm and sometime it goes down to 2.5 rpm because CaOf increase) the kiln rpm increasing also.

If anybody has experience about this problem please explain to me to solve this problem.

- Why meal chute temp increased?

- why it has clinker dust when meal chute temp increased?

- Why NOx reduced when meal chute temp increased? 

Thank in advance,




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Michael Clark
312 posts
TimePosted 16/04/2010 16:07:57

Re: Preheater temperature.

To summarise: (i) NOx has reduced, (ii) kiln speed has been reduced, (iii) kiln has dust, (iv) meal chute temperatures have risen. This sounds to me that there are reducing burning conditions explaining why the NOx has reduced and the kiln has dust (also why there is high free CaO in clinker on occasion). The higher meal chute temp might be caused by unburnt fuel being carried out of the calciner into the bottom stage cyclone and continuing to burn in the meal chute. If a sample is taken from the meal chute can you see it "sparkling" as you bring the sample into the air? The unburnt fuel might be the result of, or a cause of the reducing burning conditions. You need to check coal fineness in the first instance.


technical cement forms
68 posts
TimePosted 16/04/2010 17:07:19

Re: Preheater temperature.


   In addition to What Dr Michael Clark  said, Have you checked the alkali and sulphur concentration from the meal chute .Higher concentration of any of these may be one of the reason.Also what about the kiln bag filter dust ,Whether you are taking it directly to the kiln at the time of Raw mill stoppage..All these  changes you notice in Clinker HM LSF and are the causes of  kiln operation...As  you said there s change in clinker size (Dusty cooler)which affect the precalciner always.Also Check there is no abnormal coating at the kiln Inlet.Coal fineness also  looks a bit too high.



15 posts
TimePosted 17/04/2010 06:50:54
Engr.Amin says

Re: Preheater temperature.

Dear HongMinh,

                      It is very surprising for me that the LSF of Raw Mix is upto 100, why it is so necessary that you have too much LSF in Raw Meal. with high SM. 

What i understand from your's problem, Mr. M. Clark has clearly communicate you the possible reasons. Please also check the preheater velocity may be there is some short cuircuting, if the O2 at kiln inlet is actual.