The throughput is dependent on material, graining, moisture content, roller diameter, roller length, circumferential speed, roller profile, grinding force and also on the type of feeding system, e.g. a plug screw or adjustable plates in the feeding funnel to throttle the material flow. Using the High Compression Roller Mill for the comminution of a given material it is especially interesting to know the dependence between throughput and roller speed. This dependence is shown as throughput characteristic M_t = M_t(u). Looking first of all at the cross section of the gap at a = 0 the equation for M_t is:

M_t = d_SrsLv_S           (1)

with M_t = throughput, d_S = solid volume portion at the narrowest gap, r = solid density, s = gap width, L = roller length, v_S = average material speed at a = 0.

In the narrowest gap there is a non-slip material transport as lon as the compaction is limited and values of d_S = 0,85 to 0,90 are not exceeded [13, 14]. Then v_S can be replaced by the circumferential roller speed u:

M_t = d_SrsLu            (2)

For the specific throughput n applies:

n = (M_t /rDLu) = d_S (s/D) = d_S s         (3)

As is generally known the throughput does not increase proportional with the circumferential speed. Therefore the gap width s respectively its relative value s as well as the solid volume portion d_S must be dependent on the roller speed u.

In the following pictures the throughput characteristics of quartz and limestone with smooth and corrugated rollers (profile B: 1-8-3/4) are presented. The all show the typical convex curved gradient. Significant throughput increases result from the moulded rollers. In addition material specific differences can be seen.

Comminution
grinding results for different materials

Exper. Setup
lab-scale mill, techn. data mill, intrumentation, feed materials, testing program, roller surface data, test execution

Throughput
literature, decoupling of throughput and comminution, energy absorption, characteristic of different rollers, phenomenons, throughput results, elasticity, friction angle, specific throughput

Pressure Distribution
pressure diagrams

Press Tests
tests with a molding press

Modelling
mathematic model of the process

Signs and Symbols
nomenclature