Fata Aluminum, specialized in the design and construction of machinery for gravity casting of aluminum alloy castings and plant regeneration of the sand used in foundry, has recently received an order from Tupy, for the supply of a plant for the thermal - mechanical regeneration of green sand used by the foundry at its Mexican plant in Saltillo.
The plant regenerates the surplus of green sand molding lines resulting from the forming lines, together with a certain amount of waste cores.
It is a plant having a capacity of 12 tons / hour, which receives the products to be regenerated from the foundry, in both continuous, via a conveyor dedicated to the green ground of redundancy, both in a discontinuous manner, in containers coming from the core shop, for waste of cores.
The system integrates inside the preparation sand area, consisting of a zone of crushing of lumps and of elimination of the extraneous parts.
A first mechanical treatment, performed on machinery of attrition designed and manufactured by Fata Aluminum , removes from the sand a significant amount of bentonite.
This operation, carried out before the thermal treatment , allows to minimize the level of bentonite in the product that goes to the heat treatment furnace, and thus significantly reducing the percentage of oolitic present in the sand thermally treated.
The subsequent heat treatment is performed in an furnace which is also designed and manufactured by Fata Aluminum .
The furnace, fluidized bed type, is equipped with a heat exchanger embedded in the furnace itself, which cools the hot sand coming from the furnace by heating the fluidization air (which is also combustion air), in countercurrent, drastically reducing the consumption of gas needed to bring the sand at the right temperature to burn the resins and the coal contained in it.
The sand cooler is also a fluidized bed, where the sand is indirectly cooled with water circulating in a tube bundle immersed in the fluid bed itself.
The cooler is reduced compared to the usual standards, because the sand is pre-cooled before it goes out from the furnace.
The sand thus treated has a very low loss on ignition, but an oolitized layer of material is still on the surface of the grain. It is harmful for the subsequent manufacture of cores.
The regeneration cycle therefore provides, after the heat treatment, a second mechanical treatment, run on machines of attrition conceptually identical to those previously mentioned, which allow to remove the oolitized layer and give the foundry a product that can be used, without the addition of new sand, for the manufacture of cores.
The only conceptual difference of these machines, compared to the previous is that, since the latter provide the final product, ready for use, the mechanical treatment is followed by a dedusting and a thermal conditioning of the sand.
These two operations are performed in a fluid bed cooler, with dedicated tube bundle, where water coming from a refrigerating unit that allows to cool the sand at a controlled temperature circulates.
The reclaimed sand has a loss on ignition less than 0.05%; no active bentonite; maximum dead bentonite of 0.2%; maximum levels of residual oolitic of 2%.
The comparison of these parameters allows its use at 100% for the manufacture of cores.
The new sand is added to the circuit for the recovery of losses only (dust and various losses).
Fata Aluminum supply includes, in addition to the necessary machinery for the handling of the sand (such as bucket elevators, belts, vibrating machines , etc.) also accessory equipment, such as the installation of fumes and dust extraction system, and the system of closed circuit water cooling which circulates in the coolers, and of course the above mentioned cooling system for conditioning to the final temperature of the sand before use.