Thanks for your reesponse on our cracking problems. We have ordered a new cone and in the mean time we have welded the effected part and have used dye penetration test for finding the magnitude of crack. But what in I am interested is the reasons;thats why such cracks develop, either due to misappropriate operating, startup /shutdown procedures. improper jackingup the mill at the startup time, overdue servicing of trunion etc. Or only due to matelurgical/ casting failure. Furthermore please let me have the diagnoses procedure/test for the above.

The main reasons why these cracks occur are due to the high stresses that the mill end castings are subjected to and therefore metal fatigue. Most suppliers have taken steps to reduce metallurgical or casting failures as much as possible, but pre-delivery inspection and testing would be one step. Many problems are caused insufficient care by the maintenance department when welding, grinding the mill shell, or cutting bolts/drilling holes for fixing bolts. Of course there are steps you can take to during operation to mitigate against these cracks developing, (i) broken wear protection plates must be replaced immediately, (ii) temperature monitoring. Ultimately there is no alternative to frequent and rigorous inspection.

What is function of preheater immersion pipe? What is the behavior of material inside cyclone if immersion pipe is missing ? If we have any immersion pipe missing it will effect on decarbonation degree or not ?

The function of the vortex finder is the improve the material separation efficiency in the preheater cyclones. If the vortex finder is not there then separation efficiency and preheater performance will decline. Yes, it will affect the decarbonation degree … some decarbonated material will pass back up the preheater and recarbonate. The biggest effects will be on fuel consumption and kiln output.

I want to know about calculation mathods of gas & material flow in preheater, pc, kiln, cooler. Further, can you advise why we are getting brown clinker problem in our 2000tpd off-line calciner kiln from which we are recently producing 2500tpd while having 90-91 LSF, 2.26 SM, 1.4 AM.& kiln feed residue up to 22 per cent. How we can improve our clinker quality?

The calculation of gas and material flow in the preheater relies on the principles of stoichoimetry (to assess the combustion gas products from the fuel) and the conservation of mass. In principle what goes into the kiln must come out somewhere and will allow you to prepare a mass balance for the kiln. With regard to the brown clinker you are producing this is most probably caused by having reducing burning conditions in the burning zone of the kiln. This is very bad for clinker quality and fuel efficiency of the kiln. Almost certainly the problem is with the kiln burner and might be solved by adjustment. You must be sure that you maintain at least one per cent oxygen at the kiln inlet.

I have to ask you a question with regards to the chlorides and kiln-preheater operations. The Cl in our limestone is approx 0.003-0.007. However, I have to go down a bench in the quarry and the chlorides down there are like 0.027 based on one of the samples (the high chlorides as a result of the sea bed interface). My quarry is actually being exhausted and I am forced to go down there to buy some time till town and country planning approve new quarry lands. What we have is a VA design with a pair of 1st Stage Cyclone, one 2nd stage cyclone and three shaft stages. They went with this design as it lends itself to the least possibility of plugging. This leads me to the question....How forgiving is a shaft stage preheater?

I can't tell you whether your shaft preheater will forgive the higher chloride input....no-one can and that's why no-one writes it in a manual! It depends on may factors including the other kiln chemistry parameters and the way you operate the kiln. However, I appreciate you need some confidence to go forward. I suggest going ahead but make preparations to break the external alkali cycle of the kiln. That will involve taking some of the kiln dust out of the kiln. Hopefully that will be sufficient to allow the kiln to operate smoothly with the raw materials from the lower level.

I want to know about calculation methods of gas and material flow in preheater, pc, kiln, cooler. Further, can you advise why we are getting brown clinker problem in our 2000tpd off-line calciner kiln from which we are recently producing 2500tpd while having 90-91 LSF, 2.26 SM, 1.4 AM and kiln feed residue up to 22 per cent. How we can improve our clinker quality?

The calculation of gas and material flow in the preheater relies on the principles of stoichoimetry (to assess the combustion gas products from the fuel) and the conservation of mass. In principle what goes into the kiln must come out somewhere and will allow you to prepare a mass balance for the kiln. With regard to the brown clinker you are producing this is most probably caused by having reducing burning conditions in the burning zone of the kiln. This is very bad for clinker quality and fuel efficiency of the kiln. Almost certainly the problem is with the kiln burner and might be solved by adjustment. You must be sure that you maintain at least one per cent oxygen at the kiln inlet.

Why does false air infiltration from the bottom stage of a preheater tower increase tower temperature, but in top stage decrease the tower temperature. The preheater system is SLC-S supplied by Fuller. We understand this is a common phenomenon for any other system like ILC, SLC or SLC.

I have not observed this phenomenon, however it is perhaps connected with the additional draft that is required to keep the kiln hood under suction when there is inleak in the bottom stage of the preheater. This would cause the thermal energy from the calciner to be drawn up the preheater. Conversely when the inleak is in the cyclones above the calciner then the inleak makes no difference to the draft on the calciner.

I understand that flow of exit gases at preheater may be calculated by Q = velocity * cross sectional area of duct But I do not know the formula for velocity and density. Please explain the same. Secondly, please explain how an EP functions.

You need to study the Ideal Gas Laws to understand the relationships between gas volume, density and velocity. An EP works by inducing a strong electrical field between discharge and collection electrodes. Dust carried in the gas stream passing between these oppositely charged electrodes itself becomes charged and is collected on the collection electrode from where it is periodically knocked off into the collection hopper at the bottom of the EP by the rapping devices.

Please tell me, what are the standard norms of the gas velocity in kiln, at kiln inlet, riser pipes and cyclones at different stages of a preheater? Also, please give the formula or method to calculate the gas velocity in kiln, at kiln inlet and different stages of the preheater.