1156 posts
Cement milling Question 41
I want to know what is Roslin Ramler slope and characteristic value for cements? Do they have any relationships and how do you understand the fineness by using them
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1156 posts
Re: Cement milling
The Rosin-Rammler-Sperling-Bennett particle size distribution for cement is found by measuring the residue on various sieves (25,32,45,63,90 microns etc.) Alternatively you can use laser granulometry or some other method of measuring the residues. You then plot the natural log of the sieve sizes on the x axis (ln(sieve)), against the double natural log of 100 divided by the residue on the y axis (ln(ln(100/Residue))). The reason for using these axes is that for fine powders such as cement the plot approximates to a straight line. The slope of the line gives a measure of the "tightness" of the particle size distribution and varies from 0.8 to 1.1 for cements, dependent on the type of equipment used for grinding. The characteristic grain size is the sieve size where 36.8 per cent of the cement would be retained. This can be calculated from the slope and intercept of the RRSB line and is typically between 20 and 30 microns for cement.
1156 posts
Cement milling Question 42
I have two questions: What is the effect of NOx and SOx in controlling the burning zone temp and what other parameters like kiln torque, kiln inlet oxygen or if anything else affects the kiln operation. Secondly: How to improve the ventilation in ball mills, as we observe the coating formation on the balls is on the high side.
1156 posts
Re: Cement milling
NOx and kiln torque are both good indicators of the temperature in the burning zone of the kiln. This is key to ensuring stable operation and good combination of the clinker. Kiln inlet oxygen is a good indicator of the combustion conditions in the kiln where a small excess of oxygen is necessary to ensure burning in oxidising conditions. SOx rises if there is reductive burning and CO present in the burning zone therefore this reinforces the kiln inlet oxygen measurement. To improve the ventilation in the ball mill you need to increase the speed of the induced draft fan. However if you are suffering coating of the media this is more likely related to temperature control in the mill. This is a function of the clinker temperature, ventilation and the cooling with water injection.