Dry attrition reclamation lowers new sand expenses. (Case history).

The cost of new sand, including storage and handling, makes the prospect of sand reclamation sound attractive. However, reclaiming green sand that has been mixed with chemically bonded core sand has been problematic. A rotary reclamation process that relies on dry attrition for sand processing installed at Western Steel Casting Co., Seattle, saved the foundry more than $70,000 in just under 6 months. The RSR 2000 Rotary Sand Reclaimer is produced by Roberts Sinto Corp., Lansing, Michigan, and Sand Molding Systems, Newaygo, Michigan.

The rotary reclaimer receives sand at a controlled rate, and the number of passes through the unit is determined in accordance with the required qualities of the reclaimed sand. Repetitive processing may be achieved on a batch type principal or through a series of units. The degree of friction and friction time can be preset by regulating the number of revolutions and throughput volume changes. The reclaimed sand particle surfaces show an improvement in shape and excellent removal of the live and dead clay, however, a high efficiency dust collection system is essential.

The grain size decreases with multiple passes through the reclamation unit as a result of the improvement in sand grain particle shape. After reclamation, the particles are more rounded and sometimes moved to a screen size below.

By means of scrubbing, new sands show a decrease in the level of thermal expansion, and dust produced by the scrubbing shows a high level of thermal expansion. The low levels of thermal expansion may be due to the effect of heat and impurities on the surfaces of sand particles or the effect of clean surfaces produced by scrubbing.

Green sand reclaimed in the system may be used to produce cores with furan, phenolic urethane, [CO.sub.2] and shell binder systems as well as used as a facing sand in molding.

As a result of the installation, from January to June 1999, the foundry needed no new facing sand, according to Western Steel President Robert M. Alexander. "Normally, I would have purchased six 100-ton cars at a cost of $4600/car," he said. "Add to this $16/ton for freight at a total delivered cost of $37,200 we saved on new sand purchases. Plus, we have not purchased any specialty facing sand for an additional savings of approximately $33,000."