The gas velocity at the kiln inlet should not be greater than 10m/s and ideally significantly less than that. you can calculate the velocity by using the Ideal Gas Laws to convert the normal cubic metres of exhaust gas at the kiln inlet to the actual cubic metres at the inlet temperature. Division by the cross-sectional area of the kiln inside the refractory will then give you an estimate of the actual velocity.

Our preheater surging regularly. This is happening on a irregular basis. We suspect it is coming from cyclone No 2. We have investigated and have taken several actions. Unfortunately, we were unable to resolve it. Actions taken were as follows:
1. Damper adjustment
2. Check feeding system
3. Effects from other cyclones
4. Preheater riser duct buildup
5. Splash plate adjustment/buildup
We also include some technical data as an attachment.

Please ask the laboratory to check the LOI in C1A, C1B and C2 again. The reported LOI in C2 is higher than in the C1 cyclones. This is difficult to explain unless you have some water injection into C2 cyclone or other special process feature. In order to calculate the cyclone efficiencies the LOI should reduce in each successive cyclone down the preheater.I also suggest that the LOI at 600 degrees C be measured in addition to the LOI at 1000 degrees C. This will tell us whether there is any hydrate or organic carbon present in the kiln feed. Finally we must have the dust LOI to calculate the efficiency of the C1 cyclones.

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.

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.

We have received some suggestions regarding the possible effects of dam ring height from a major cement plant in North America as follows:
"I would suggest that the particle size distribution (PSD) be looked at for both instances. We have found that by changing internal settings in a VRM there are physical changes in the PSD which will impact the performance of the slag. By changing the PSD as little as 2 microns there is a significant change in the performance while not showing up in a simple test of Blaine." "If the dam ring height is increased the clinker and gypsum will stay on the grinding table longer and possibly be better ground when it exits the table and therefore the circulating load in the mill should be lower.
So the two things to look at are the amount of dehydration of the gypsum with lower dam ring height compared to the higher dam ring height and also the particle size distribution of the finished cement. With a lower dam ring there is the chance that there is more over grinding and a higher concentration of superfines."
Please let us know if you find there is a relationship between dam ring height and particle size distribution or gypsum dehydration as this would make an interesting case study for publication.

Our preheater surging. This is happening on a irregular basis. We suspect it is coming from cyclone No 2. We have investigated and have taken several actions. Unfortunately, we were unable to resolve it. Actions taken were as follows:
1. Damper adjustment
2. Check feeding system
3. Effects from other cyclones
4. Preheater riser duct build-up
5. Splash plate adjustment/build-up.

You need to take samples from each cyclone and measure the loss on ignition. If you send the results along with the raw mill product, kiln feed and dust loss on ignitions then the preheater cyclone efficiencies can be calculated. This will tell us if the problem is originating in cyclone 2.

I work at a plant 4500tpd, based on FLS design, with a five-stage preheater and precalciner, Our problem is repeated blockage in cyclone stage five (some four times at period of five months). We calculated the sulphate/alkali ratio before each blockage, we found it between 1.45 to 1.7. As we know the normal value should be less than 1.2. The LSF between 92 and 105, also the analysis result of a sample from the blockage material are: SiO₂=19.5, Al₂O₃ =4.76, Fe₂O₃ =3.63, CaO=62.1, SO₃=2.31, K₂O=1.37, Na₂O=0.93. Can you advise if the values of SO₃/AlK ratio to cause the blockage in Cyclone 5 or is it another reason?

From the information you have sent there seem to be two problems, (i) the SO₃/Alkali ratio between 1.45 and 1.7 is very high and would be expected to cause very hard dense coatings, (ii) the variability of the LSF from 92 to 105 is much too high and would be expected to cause major process and quality variability. However. the samples from the blockage do not show very high SO levels and have an SO₃/alkali ratio of 0.87 which should not cause any problems. The other cause could be premature calcination in the cyclone 5 due to variable LSF. This would happen with the change to low LSF, easy burning material.

I am working on a project for my university studying the different technologies used in the cement production process from different companies, and I would like to know if any corporation has already constructed its process with a fluidised bed cement kiln for commercial operation and could reach acceptable efficiency. Also, I am researching for the system with most number of steps at the preheater, and the performance of the process compared to other ones.

I am not aware of any commercial operations using fluidised bed for industrial cement clinker production. There are pilot and research installations but not of commercial capacity. There are number of kilns with six-stage preheaters. This brings the exhaust gas temperature down to less than 300 degrees Celcius. However, the most economic number of preheater stages is usually five as increased capital costs for six stages cannot be recovered by the energy savings. A company might choose a six-stage preheater if there is a shortage of water for exhaust gas cooling and conditioning. Therefore most of the existing six-stage preheater kilns are in desert environments.

What is function of preheater immersion pipe? What is the behaviour 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 to 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.