Thermodynamic and experimental study of the fluoride recovery from Spent Pot Lining recycling process by precipitation of calcium fluoride
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hdl:2117/344077
Correu electrònic de l'autorannamasherradorgmail.com
Realitzat a/ambChalmers tekniska högskola
Tipus de documentProjecte Final de Màster Oficial
Data2020-10-31
Condicions d'accésAccés obert
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Reconeixement-NoComercial 3.0 Espanya
Abstract
The material resulting from removing the electrolytic cell in primary aluminium production is
called Spent Pot Lining (SPL). SPL is considered to be toxic due to its high concentration of
fluorides and cyanides, corrosive and reactive with water. It is estimated that more than 50% of
the SPL generated annually is stored indefinitely or deposited in a landfill. Precipitation is
considered a simple and cost-efficient method of removing fluoride from aqueous streams
producing a valuable product such as fluorite. In fact, fluorite (CaF2) is one of 27 critical raw
materials for the EU because the risks of supply shortages and their impact on the economy are
high. Its high carbon and fluorine content, as well as CaF2 as the main raw material for almost
all fluorochemicals, have made SPL one of the most crucial wastes for recovery, reuse and
recycling in a circular economy.
This work is focused on the thermodynamic study to predict the behaviour of a stream coming
from an SPL recycling process by introducing calcium salts in order to obtain a precipitated
product of interest such as CaF2, within a circular economy approach. The thermodynamic of
the reaction chemistry was investigated by HSC Chemistry software and the subsequent
verification of these results in an experimental way.
As a result, the generation of a solid composed of CaF2 has been verified. Among the three
precipitation agents studied, it has been found that the one with higher purity values in
thermodynamic calculations is CaCl2 (45.1%). For the real sample, the presence of other
precipitates such as Na2CO3, CaO, Ca(OH)2, has been observed. A subsequent washing stage is
proposed to increase the degree of CaF2 purity.
Thus, the results present a reliable and environmentally friendly process that produces a product
with a high added value. The research indicates that the process could also be applied for the
treatment of wastewater with a high concentration of fluorine. The resulting product has a high
economic value and could be applied in the aluminium smelting industry.
MatèriesAluminum, Circular economy, Fluorspar, Thermodynamics, Sewage -- Purification, Alumini, Economia circular, Fluorita, Termodinàmica, Aigües residuals -- Depuració, Fluor
TitulacióMÀSTER UNIVERSITARI EN ENGINYERIA QUÍMICA (Pla 2012)
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