Modelling of a mobile Gravitational-Inertial Air Classifier

Övrigt konferensbidrag, 2013

Due to environment reason the supply of natural sand has been limited in Sweden. The concrete industry in Sweden therefore has a rising demand for manufactured sand in the size range 0-2 mm. The quality demand on the manufactured sand is a good particle shape and a particle size distribution with low amount of fines (particles below 63 µm). These requirements might be in conflict as a good particle shape might require crushing by VSI crushers wish increases the amount of fines. Classification in that size range is not common in Swedish quarries; however air classification might be a possible solution to the problem but a wider understanding is necessary. A mobile air classifier with an external air cycle has been investigated using factorial design. The results show that the fines level can be reduced to acceptable levels. The cut point and efficiency of the cut will be affected by the valves controlling the air flow into the machine. The efficiency of the air classifier was shown to be mainly controlled by the internal recirculation of material towards the separation zone. The results from the factorial design were used to make a model of the air classifier. Modeling was done through the efficiency curve approach. Validation has been performed by comparing model simulations with actual test data from a crushing plant.