1156 posts
Raw milling Question 11
We are analysing particle size distribution of raw meal, coal mill product and cement mill product through CELAS PSA having facility to determine 0.7to 400 micron.
Q1. what is the best particle distribution (on various micron sizes) of raw mill in terms of best mill performance, burnability and kiln performance and which plant in the world is producing?
Q2. what is the best particle distribution( on various micron sizes) of coal mill in terms of best mill & kiln performance? Our coal ash is 28. Q3. what is the best particle distribution( on various micron sizes)of cement mill product to have optimum power consumption, best strength &good performance in concrete.
Know the answer to this question? Join the community and register for a free guest account to post a reply.
1156 posts
Re: Raw milling
There is no straight-forward answer to your questions. For raw mix the optimum particle size distribution depends on the mineral composition of your raw materials. If you have a high content of quartz then you must have a very tight fine particle size distribution with low content of oversize particles where the quartz will concentrate. On the other hand with a homogenous raw mix with no quartz it is not beneficial to have too small a particle size distribution as this will increase the dust losses from the top stage of the preheater. Similarly with coal there is no hard and fast rule. It is said that the 90 micron residue should not be more than 50 per cent of the volatile content of the coal. Increasing the fineness beyond that is counter-productive. For cement the optimum particle size distribution depends on the cement performance characteristics that your customers have come to expect. Ring formation is caused by the formation of liquids in the kiln at a particular position. These penetrate the refractory lining and cause a localised thickening of the coating. Fe2O3 can be a cause of these problems and I am not surprised that raising the alumina modulus has solved the problem. Many cement factories operate with higher alumina modulus than1.7 and I would recommend keeping the kiln feed mix design with the higher alumina modulus. A snowman is the formation of a large build-up on the first grate of the cooler where the clinker falls from the kiln rather than a build-up in the kiln.
1156 posts
Raw milling Question 12
I would like to know how to estimate the quantity of grinding media of each size required for a ball mill using the data; mill size, number of chambers and type of material to be ground. Kindly explain me what formula is to be used.
1156 posts
Re: Raw milling
The total quantity of media required for each chamber is determined by calculating the internal volume of the chambers. A rule of thumb is to change the first chamber to 30 per cent of this volume and the second chamber to 27 per cent. You can use 4.6t/m3 as the density of grinding media. As for the individual ball size gradings this has to be determined by conducting a series of axial tests in the mill while you are building up the media charge.