We are having Polysius design ILC six-stage kiln have dimension of 3.8m ID and 64m length. We are firing 100 petcoke in both main firing and calciner firing. We are facing problem of reduction in output and percentage of fines generation in clinker increased.The kiln feed and petcoke chemical analysis are as under: SiO₂ 13.80 - 14.10 Al2O₃ 3.6 - 3.75 Fe₂O₃ 3.4 -3.6 CaO 42.7 - 42.9 MgO 0.7 - 0.9 SO₃ 0.1 -0.16 K₂0 0.28 - 0.35 Na₂O 0.10 - 0.12 Cl 0.06- 0.09 Petcoke Analysis C 88.5 - 89.5 H₂ 3.8 - 4.2 S 6.0 - 6.5 Violatile Content 9.8 -10.4 Calorific Value 7960 - 8020 Kcal/Kg Coal Ash Content 0.30 - 0.70 Please suggest suitable counter measures to increase throughput rate and stable running of kiln.

Unfortunately these problems are regularly reported on kilns burning petroleum coke. The problem is caused by the sulphur content in the petroleum coke. This has the effect of reducing the viscosity of the flux and this leads to the increased fines generation in the clinker. You must ensure that you have good oxidising conditions in the burning zone to minimise the recirculation of sulphates. After that you need to change the chemistry to adjust the viscosity of the flux. Increasing the Al₂O₃ content may help, but perhaps the best solution would be to add some calcium fluoride to the kiln feed.

We have problem of hard clinker used in cement grinding. This clinker is produced by using 100 per cent pet coke in firing. Although chemical composition of clinker is correct. It has 50 per cent C₃S, 5.5 per cent C₃A, & liquid approx 28.5 per cent & SO₃ in clinker 1.6 per cent. But minerology observed under microscopy reveals following: Mineralogical composition and Granulometry of - 6 mm clinker: Phases present Quantity (per cent) Granulometry (size in micron) Min. Max. Average required size Alite (C₃S) 46.5 8 82.69 42.14 20 Belite (C₂S) 34.5 3.5 93.00 38.26 15 Liquid phase (C₃A+C₄AF) 18.6 Porosity Low porous 22 120 65 (more data attached) Photomicrographs are given in attachment. Kindly suggest How to reduce Alite grain size & increase porousity of clinker. Our kiln is already running in full RPM. Is it possible to make softer clinker by changing chemical composition.

I have looked at the photomicrographs and read your analysis with interest. In order to properly answer your questions I would have to ask Dr Chromy to examine and analyse the mineralogy of the clinker. I'm afraid that Dr Chromy would charge for that and therefore Aditya Birla would have to pay. I will contact Mr Modi and Mr Agrawal to see whether they want me to refer this to Dr Chromy. One we have his analysis then we might be in a position to suggest the means to reduce the alite grain size and make softer clinker by adjusting the chemical composition.

What are the current international standards of MTBF for kilns and mills?

There is a difference between mean time between failures and mean time between stops. Best practice for kiln MTBF in the cement industry is in excess of 750 hours, while MTBS is somewhat shorter. The problem with MTBF is that it is easier to massage the data and cheat because some stops are planned and therefore do not count. In that situation it is easy to bring forward a planned stop when you have an unexpected unplanned stop.

We regulate our raw material pile at 105-110 lsf. However the lsf of the raw mill's sample becomes 85-90. How can we have such a large difference?

There might be a problem in the sampling station. More likely you have a problem of segregation of the material. This is most likely when you are reclaiming the end-cones of the pile or in the intermediate feed bin between the pile and the raw mill. One solution is to add the end-cone to the next pile rather than sending it to the raw mill. The intermediate bin should be kept at a high level by setting the reclaimer start signal to a high bin level.

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.

Sometimes we need to produce special, low alkali clinker. In order to achieve good results we need to waste all dust from the kiln and to burn the kilnfeed harder than for the ordinary clinker. But in this case we are loosing almost all coating on the bricks. The questions: How and what could we change in our kilnfeed in order to protect the bricks even in case of low alkali clinker?

I think you are operating long wet kilns? If so you could add some chloride to the kiln feed to promote the volatility of the alkalis in the kiln. That will drive more off from the clinker and result in lower alkali content at lower temperatures. However, that may increase your impact on the environment. I would need to know more about your process and situation before recommending that.

We would like to use phospho-gypsum in place of mineral gypsum in our cement plant. Please advice us of its suitability. Phospho-gypsum has 36 per cent moisture and pH is 2.3. The cost of using this material is very low but what are the drawbacks?

I know of no reason why you should not use phosphogypsum. However, you will have to conduct trials to verify that no product quality problems are involved.

We have ESP at the kiln system. It is also used for raw mill system. System is sent ESP's feedback to kiln feeding silo. There are two homogeneous silos and two stockage silos. Material is sent from ESP to homogeneous silos. So, my question is that, I am thinking to feed the ESP's feedback directly to preheater system but this line will be entered to system after weighfeeder. We have got line to feed this material before weighfeeder but it causes to reduce of fresh feeding. In this way I want to increase clinker production with same feeding amount. What do you think?