Industrial experience has revealed that when used to treat multi-component metal chloride waste liquors, existing fluidized bed acid regeneration facilities are not as efficient as when employed for the pyrohydrolysis of conventional iron chloride solutions (i.e. waste pickle liquor). As a result, experimental studies and thermochemical modelling were performed to characterize the transformation of a saturated Al-Fe-Mg-Cl solution at 105°C, after it is injected into a reactor at 850°C. Efforts were geared toward defining the sequence of reactions that take place as the liquor gradually transforms into oxides.C, after it is injected into a reactor at 850°C. Efforts were geared toward defining the sequence of reactions that take place as the liquor gradually transforms into oxides.C, after it is injected into a reactor at 850°C. Efforts were geared toward defining the sequence of reactions that take place as the liquor gradually transforms into oxides.C, after it is injected into a reactor at 850°C. Efforts were geared toward defining the sequence of reactions that take place as the liquor gradually transforms into oxides. / Upon completing a comprehensive literature review, testwork was initially performed with a simplified experimental set-up to study the physical behaviour of the chloride solution as it is exposed to a static bed of oxides at 850°C, and ultimately identify the various phases of the transformation process. Subsequently, controlled evaporative crystallization experiments were conducted under pseudo-equilibrium conditions to define the McClx·yH 2O precipitation path that takes place during the H2O evaporation phase and to determine whether the chlorides precipitate independently or as complex compounds. Further experiments were performed in a fully instrumented tube furnace to elaborate on the nature of the reactions (dehydration and/or pyrohydrolysis) that take place after all of the water in the starting solution has evaporated (i.e. T=300°C+). / In an effort to assist with the interpretation of the experimental results, thermochemical modelling was performed to predict the equilibrium phase assemblages that could occur during the transformation of the saturated Al-Fe-Mg-Cl solution, at reaction temperatures of 200°C+. / The research study at hand has shown that when the saturated Al-Fe-Mg-Cl solution at 105°C is exposed to fluidized bed pyrohydrolyzer operating conditions at 850°C, the following sequence of events take place: (1) rapid solvent H2O evaporation (i.e. vigorous boiling) and onset of solid metal chloride precipitation. (2) slurry densification due to a gradual increase in crystal content (i.e. AlCl·6H2O, FeCl2 ·xH2O, and MgCl2·xH2O, where x = 2 or 4). (3) hydrated crystal drying and onset of pyrohydrolysis (i.e. thermal decomposition of McClx·yH2O). The same holds true for the high temperature hydrolysis of typical waste pickle liquors (i.e. primarily FeCl2 solution). / The crystallization studies revealed that when the Al-Fe-Mg-Cl solution is allowed to gradually evaporate at 105°C,.AlCl3·6H 2O precipitates when 15% of the solvent water evolves from the liquor, followed by FeCl2·xH2O and MgCl2·xH 2O (where x = 2 or 4) at 26 and 41% evaporation, respectively. Ferric chloride remains in solution even after 54% of the water has been driven from the liquor. The latter result suggests that higher ferric concentrations in the reactor feed are more than likely to favour an increase in the quantity of liquor entrainment by the fluidizing gases and therefore lead to lower process efficiencies. Dedicated pyrohydrolysis experiments, with a simulated reactor atmosphere (gaseous, not dynamic), have shown that excluding kinetic effects, the transformation of the Al-Fe-Mg-Cl solution occurs primarily over the 300 to 600°C temperature range. / Thermochemical modelling revealed that with the exception of AlCl 3·6H2O hydrolysis, the majority of the reactions taking place as the saturated Al-Fe-Mg-Cl liquor is introduced into and eventually reaches 850°C are governed by either reaction kinetics or diffusion. Furthermore, the resulting phase assemblage at any given temperature was predicted to vary significantly with oxygen potential. A liquid chloride phase (including molten salt), other than the feed liquor, was not predicted to form at any temperature (i.e. 200°C or above) under the range of oxidizing or reducing conditions considered. / The findings of this research were quite useful in identifying the means for improving the performance of a commercial fluidized bed pyrohydrolyzer for a spent chloride liquor containing the said species.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.102490 |
| Date | January 2006 |
| Creators | Coscia, Carlo. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining, Metals, and Materials Engineering.) |
| Rights | © Carlo Coscia, 2006 |
| Relation | alephsysno: 002572406, proquestno: AAINR27766, Theses scanned by UMI/ProQuest. |
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