COMMINUTION ENERGY EFFICIENCY – UNDERSTANDING NEXT STEPS
Lawrence K. Nordell1, 3, Brandt Porter2, Alexander Potapor3
1)President, Conveyor Dynamics, Inc.,
2)Design Engineer, Conveyor Dynamics, Inc.,
3)Partner, Rocky-DEM, Inc.,
ABSTRACT
Improving comminution efficiencies with better machine geometries and motions, improved nip angles, rock movement control, and voids regulation between rocks are some of the next steps to better machine performance.
Recent gains (~30%) using High Pressure Grinding Rolls (HPGR) and Vertical Roller Mills (VRM), in theory and practice,are based on Prof. Klaus Schönert’s academic studies (1979-1996) on rock breakage physics. More recently, Prof. Bern Klein studies (2006-present) further validate theory with practice.
They demonstrated ideal compression breakage in the size range of HPGR and VRM. This is done using a piston-die apparatus with confined rock breakage behavior in the laboratory that translates to these machines. However, these studies do not extend to larger rocks (> 75 mm), do not demonstrate the influence of voids between rocks during comminution, and do not evaluate machine geometry nip angle efficiency for these machines and for machines that are fed with larger rock sizes such as gyratory, jaw, and cone crushers.
This paper illustrates a new machine CAHM (Conjugate Anvil-Hammer Millpresented at SAG 2011) that does encompass larger rock sizes, improves rock grip geometry, better improves voids, improves rock containment during compression, which significantly enhances rock breakage efficiency compared to all of these other devices based on modern Discrete Element Method (DEM) that incorporate rock breakage physics.
Specifically, we demonstrate the critical nip angle comminution device geometry necessary to capture rock by size, improve voids and agglomerations after breakage, influences that translates tomeasuring bettercomminution efficiency. Differences between machines are illustrated using advanced DEM techniques including key points of when/how does each machine: a) use geometry to advantage, b)initiatebifurcation breakage, c) provide a map of Particle Size Distribution (PSD) by location, and d) illustrates the importance of controlling voids to minimize agglomeration after breakage.
Key words: CAHM, comminution efficiency, comminution geometry, gyratory crusher, cone crusher, jaw crusher, HPGR, piston-die, nip angle, rock voids, vertical roller mill