Elkeme coproduction development of rockwool and low nickel FeNi by feeding Aluflux
The R&D project “Coproduction development of special quality rockwool and low nickel FeNi through feeding of aluminium skimmings Aluflux” was successfully completed.
The project with the acronym Rock.FeNiAl was conducted by Elkeme and Fibran S.A., a Greek rockwool producing company in Serres and was co-funded by the Industrial Research & Technology Development Program (PAVET 2013), ESPA 2007-2013 (Project No 914-BET-2013), the partners being Elkeme S.A. (Coordinator) and Fibran S.A. Additionally, the National Academic Laboratory of Applied Mineralogy- Department of Geology-University of Patras and the EU R&D Institutes Fraunhofer Gesellschaft-ITEM (Institut für Toxikologie und Experimentelle Medizin) and Ricardo-AEA GBP were used as subcontractors for the performance of high quality, specialized testing required in the course of the research.
Rockwool is one of the most commonly used insulation materials. It is produced by melting a mixture of mineral raw materials such as basalt, amphibolite, limestone, dolomite and bauxite, in specialised furnaces and subsequent fiberisation of the melt, by the centrifugal process. After addition of adhesive resin, oil and special silica compounds, fibers enter the polymerization furnace. Compressing and cutting machines are used to shape the final products in sheets and rolls. The colour of the final product depends mainly on the iron oxide content (FeOx) of the raw materials mixture.
Aluflux is a byproduct generated during the secondary aluminum alloy production process in Elval (Viotia). Its main characteristics are: alumina (Al2O3) carrier, alumino-thermic reduction agent (Almet, AlN) and energy provider. This chemical composition renders it promising for use in rockwool production as a partial bauxite replacement additive. Furthermore, the aluminothermic reduction of NiO and FeOx contained in the raw materials mix, is expected during melting, to result, besides a lighter colored mineral wool, in the co-production of low nickel Ni-ferronickel metal.
Elkeme, in cooperation with Fibran, developed the theoretical model of the process, which includes fully parameterized mass balance, taking into account the thermodynamics of the heterogeneous metallurgical reactions, as well as calculation of the most important physicochemical properties of the slag (basicity, viscosity, density, surface tension and electrical conductivity). The theoretical process model was used for the design of the industrial trials, which were successfully performed in the EAF of Fibran in Serres, resulting in the production of 100 tons of rockwool by use of Aluflux in the raw materials mix.
According to the results, the lighter coloured rockwool products of the industrial trials exhibit high levels of mechanical and physicochemical properties, while meeting the biopersistence specifications prescribed for mineral wool products (No 1272/2008 Note Q Directive 67/548/EEC). The production of low nickel ferronickel alloy in the bottom of the EAF that was accomplished during the industrial campaigns validated the theoretical estimations. Furthermore, infrastructure requirements and fundamental technical adjustments, prerequisite for the industrial implementation of the studied process, have been determined.
Overall, the industrial adaptation of this innovative process, permits implementation of a circular economy concept, ensuring the use of secondary resources (Aluflux) in another industry/value chain for the production of high added value competitive materials (rock wool and low Ni-FeNi alloy) with significant environmental and economic benefits, not only for the involved parties but also for the national economy.
October, 2015