232 posts
TimePosted 16/12/2009 06:01:05
xxxx says

fineness & production

how can we quantify the increase / decrease in tph if Raw Mill product fineness is changed for finer to coarser & vice versa? Please suggest me the formula?

how can we relate the kiln production with change in fineness of raw meal?what is the mathematical relation?

What is the impact of Granulometry of Raw meal on burnability? Is there any mathematical approach to Quantify burnability with granulametry?

please do reply




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138 posts
TimePosted 16/12/2009 20:46:16
lalbatros says

Re: fineness & production

Dear xxxx,

In principle, one should say that there is no general mathematical rule relating fineness and tph, for cement just as for raw meal.

The reason is simply because this relation would be determined at least by two elements: the characteristics of the mill and the characteristics of the separator, if a closed circuit is assumed.

That's the reason also why, in principle, a mathematical should should used, like the Austin model.

Even in open circuit, there is no such general rule, because it depend on the mill and its charge and all its internals, and even the grinding aids. A very simple model would assume a specific power consumption proportional to the finenes, for low finenesses, and a saturation when the fineness reaches a certain level.

Strange enough, I think that a closed circuit might well be even simpler than an open circuit. In this case the mill tph tends to be more or less constant, more or less independently of the fineness of the finish product. (at least up a certain limit) Practically, it is not such a bad hypothesis to assuming power consumption proportional to the fineness, together with a constant mill power. But this need to be checked in each case.

For burnability and fineness, FLS and many others has published many paper on this topic. You will find many good thing by googling "burnability fineness". Have a look also at "Innovations in Portland Cement Manufacturing" from the PCA, where I guess you may find good material on these topics.


2 posts
TimePosted 26/09/2010 22:26:56
Rodrigo says

Re: fineness & production

Mr Rajesh, how are you?

I´ve just logged in and created an account to try to discuss about the same problem your are dealing with..

I haven´t found any mathematic model or previous work regarding the subject...

 What about you? Since you posted you doubt, did you get any information?

 I´m thinking about to develop a DOE statistical aproach on it...


Ted Krapkat
536 posts
TimePosted 27/09/2010 04:28:09

Re: fineness & production

What is the impact of Granulometry of Raw meal on burnability? Is there any mathematical approach to Quantify burnability with granulametry?

Hello Rajesh,

Yes, raw meal burnability is mathematically related to raw meal fineness and chemistry. However the approach is essentially empirical and the data used to determine the formula needs to be accumulated by performing burnability tests on many raw meal samples having widely varied granulometry.

nThe amount of uncombined lime depends on the following drivers;-

  • Specific reaction area (the area of contact between the grains)
  • Local oversaturation (grain size of individual minerals)
  • Ambient conditions (pressure, temperature, and burning time)
  • Diffusion coefficient of CaO through the liquid phase (composition of the liquid phase)
  • Amount of liquid phase formed during burning
  • Supply and demand of CaO
If we assume that kiln conditions such as pressure, temperature and burning time can be kept relatively constant, the rest of these drivers can be condensed into just four main parameters;-
  1. Silica Ratio
  2. Lime Saturation Factor
  3. Amount of oversized quartz grains (>32um)
  4. Amount of oversized calcite grains. (>90um)

Having measured these parameters and performed burnability tests on many different raw meals, a mathematical relationship such as the one below can be obtained by regression analysis;-

Free Lime (burnability test) = w * Quartz(>32um) + x * Calcite(>90u) + y * LSF + z * SR - c

The coefficients w,x,y,z and c will be slightly different for each plant and the critical size criteria for oversized quartz and calcite often vary from researcher to researcher. Some papers I have read indicate that quartz >45um and calcite >125um are critical. ( I however prefer to err on the side of caution and choose the lower sizes I have given above.)


For further information, see my pervious post on this topic located here:-