Dear all, is there any case study or article, regarding to the effect of raw meal fineness on kiln output? Maybe DOE or regression analysis?
thanks
Ted Krapkat
Hello Rodrigo,
Raw meal fineness directly influences product quality rather than production rate. However if raw meal finess is excessively coarse, or excessively fine, it can indirectly effect production rate.
Very coarse raw meal, especially containing substantial amounts of coarse quartz (>40 microns) and coarse calcite (>100 microns) will invariably result in excessively high clinker free lime. This will force the kiln operator to reduce kiln feed in an attempt to burn out the high free lime, detrimentally effecting production rate.
At the other end of the scale, very fine raw meal can be detrimental in another way. Excessively fine raw meal has an increased surface area from which higher amounts of volatile components such as alkalis and sulphur can evaporate. This can increase buildups and falling slabs in the kiln inlet also reducing production rate, not to mention the extra cost of fine grinding.
The optimum raw meal fineness depends to a large extent on all of these factors plus product quality constraints and the raw materials available, so it is usually optimised experimentally at each plant. The rule of thumb is to just grind fine enough to prevent unacceptably high clinker free lime.
Ted.
ovancantfort
In addition, if the meal is really fine, the separation efficiency of the preheater cyclones will be less. Dust going up in the preheater tower will also reduce thermal exchange efficiency, resulting in higher top cyclone (raw gas temperature) and higher heat consumption. If the kiln is ID fan limited, production will also decrease.
We face this situation on some kilns where the raw material is soft and very fine chalk.
Best regards.
faslan
Mr. Ted,
You've written the fineness directly influences product quality rather than prod. rate. Also, you've mentioned about the coarse calcite (>100 mic) and coarse quartz (>40mic).
First question can you describe the quality effect of fineness deeply?
Second what can you tell about the allowable values of coarse particles (calcite quartz)
I'm trying to persuade the plant staff to increase the fineness from 7-8 to 11-12 and even more according to kiln. I'm relating the upper-transition zone unstable coating to somehow the very fine raw with the raw mix composition. Can you help me? or am i wrong?
Regards,
Firat.