It has been one and a half year since our last contribution to the newsletter. We are still aiming for a better understanding of the process of air classification and too further improvement of this process. In addition we are now looking to consolidate results from particle-movement simulations with Computational Fluid Dynamics (CFD) with results obtained during testing on the pilot plant.
Beckum, February 2012
In October 2010 it looked like the practical part of the investigations could start right away. As it turned out some minor issues had to be considered first. The material for our tests - which we had taken at the mill outlet from a nearby cement plant - was not suitable for the intended usage due to high variances and an altogether too coarse particle size distribution. After switching to a CEM I 32,5 cement with a particle size distribution close to mill feed for high-blaine cements the material feed arrangement of the pilot plant had to be adapted to ensure a better material flow into the separator. Using finished product as separator feed provided a particle size distribution which is sure to have a low enough variance over the duration of the conducted tests.
After these changes the first tests started in April 2011. The following evaluation of the test results helped to identify another problem. As the cut of the separator seems to be at quite a small particle size, the usage of a cyclone to separate the fines from the air turned out to be a less than desirable solution, a phenomenon which occurs mostly due to the widely varying operating points for the airflow aimed for in such a pilot plant. As a result the separation performance could not meet the expectations in the run-up.
The consequence of the fore mentioned results was to adapt the pilot plant to meet the requirements demanded by the intended test work. The adaption consisted of two main parts, the first of which being the installation of a Scheuch Impuls Bag Filter for the separation of the fines and the air. The second part was the installation of Schenck Mecha Tron Coni-Flex feeders to achieve a constant material flow to the separator. Combined with small changes in the plant and the needed modification of the programming at present the adaptions are nearing their completion and the next part of the test work should start very soon.
Considering the regions of top cut this pilot plant is capable of producing, it is an advance into new fields of product fineness for CPB.
Christian Streicher (University of Leoben)