Dry production of fine powders < 10 mu m is best carried out in ultra-
fine grinding and classifying processes. To draw up a balance for an e
ffective closed-circuit grinding system the grinding process can be de
scribed by grinding invariants (throughput characteristics), and the u
se of grading efficiency curves has proved successful for the classifi
cation system. Simulation calculations for closed-circuit grinding sys
tems for producing limestone meal are introduced on the basis of disco
ntinuous and continuous grinding trials and corresponding classifier g
rading efficiency curves, supported by CGC*) software solutions.