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Informe sobo los pretratamientos para adecuar los sub-productos de fundición

This information is a summary of Deliverable B.2 Report of the pre-treatments to adequate foundry by-products (DLB2.1)

The deliverable contains the evaluation of different pre-treatments for green and chemical moulding sands and dusts from foundry sector in order to adequate them as raw materials for the ceramic tile production. Energetic valorisation and consumption were evaluated for thermal pre-treatment.

Iron oxide and organic carbon contents are considered the most critical parameters for the foundry by-products reuse in the ceramic tile production. Introduction of foundry sands/dusts as raw materials has been fixed at maximum of 5%. In action B.1, it was determined that the by-products with Fe2O3 content higher than 1.5% are not adequate for white firing bodies, unless they are used in very low percentages (less than 0.5%). For red firing bodies, there is not an upper limit nor a lower limit in Fe2O3 content. Besides, the maximum limit for total organic carbon has been established at 2% for both white and red firing bodies to avoid the black core defect.

Physical separation, mechanical and thermal pre-treatments were applied in selected samples in terms of representativity (organic and iron oxide contents, industrial total amount landfilled and valorisation rate). Final organic carbon content obtained was higher than 2% when physical separation was applied, then this pre-treatment was discarded. Magnetic separation was demonstrated to be a valid pre-treatment as the final whiteness of ceramic tiles including in their composition pre-treated by-products is higher than for the ones including the original by-products. Introduction of 5% practically does not modify the firing temperatures of the porcelain tile composition. Organic carbon content was totally removed through thermal pre-treatments tested for chemical moulding dusts (T=600ºC, t=1h), nevertheless more time of exposure is needed for green moulding dusts to reach the final organic quantity of 2% (T=600ºC, t=4h). The selected dusts non-thermally and thermally treated at specific conditions above commented were subjected to magnetic separation as well. In addition to increase the whiteness, black core defect was not observed in the samples thermally treated. As it was expected, the organic matter reduction decreases the porosity created during firing, and therefore, bulk density increases. In Action B.3, bloating phenomena will be studied in more detail.

Samples presented low energetic valorisation potential due to high contents of silica in their composition and the energetic consumption of thermal pre-treatment for green moulding dusts was in the range of typical foundry by-products thermal treatments.

The results obtained from this action will be used in Action B.3 in order to define the pre-treatments to be performed at industrial scale, and thus to increase the by-products introduction percentage in ceramic tiles composition.