What is the significance of the cement mill residue measurement on 45 micron sieves

The significance of the residue on a 45 micron sieve is that it is an indication or control of how finely the clinker in the cement is ground. With multicomponents blended cements (e.g. clinker, gypsum and limestone) then the surface area can be high due to overgrinding of the softer components (gypsum and limestone in this example), but the clinker itself can still be relaively coarse. So monitoring and controlling the 45 micron residue allows trhe fineness of the clinker component of the blended cement to be controlled. 

There is no correlation between coal volatile matter and residue and burner pipe flame momentum.

This is covered in the CemNet Training Grinding and Milling course. The significance is that the slope and position parameter of the Rosin Rammler distribution defines the size distribution of a fine powder. It is calculated by plotting the double natural logarithmn of the residue retained on a sieve at a particular grain size against the natural logarithmn of the grain size.