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Author:Tesfaye, Fiseha Firdu
Title:Kinetics of copper reduction from molten slags
Kuparin pelkistämisen kinetiikka sulakuonasta
Publication type:Master's thesis
Publication year:2009
Pages:84      Language:   eng
Department/School:Materiaalitekniikan laitos
Main subject:Materiaalitiede   (MT-45)
Supervisor:Gasik, Michael
Instructor:Kruskopf, Ari
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201410122802
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark V80     | Archive
Keywords:fayalitic slags
slag cleaning
carbothermic reaction
composition
reduction
Cu2O
FeOx
fajaliittinen kuona
kuonanpuhdistus
koostumus
korkealämpötila
hiilipelkistys-reaktio
pelkistyminen
Cu2O
FeOx
Abstract (eng): The objective of this thesis was to study the process of reduction of cuprous oxide by carbon from copper flash smelting slags.

The flash smelting and slag cleaning processes are described in the introductory part.
The studies are focused on the slag cleaning process in the three -electrode electric furnace (EF), where components of the slag reduce to matte and EF slag in a periodic batch process.

Parametric values of different variables (surface energy, density, viscosity, and equilibrium composition) and thermodynamics of reduction reactions of the slag cleaning process were also examined.
At higher oxygen potential additions of CaO and MgO were found to increase the activity coefficient of both CU2O and Fe2O3, thereby reducing the amount of CU2O and Fe+3/Fe+2 ratio in the slag.
Furthermore, reasonable additions of the basic oxides will break the (SiO4)4- chains and reduce viscosity of the slag.

Kinetics of reduction of CU2O and FeOx were reviewed based on data obtained from different publications.
Effects of various variables such as temperature, initial composition and reaction products on the reduction kinetics of CU2O were analysed in the temperature range of 1200 - 1650 °C, which was identified to be the most favourable in the slag cleaning process.

Results from both thermodynamic and kinetic analyses confirmed that increase in temperature increase the reduction rates of both CU2O and FeOx.
The reduction rates of the oxides were widely accepted to be the 1st order reaction with respect to their concentration and the rates limiting step was chemical reaction at the slag-coke interface.
In this analysis the reduction of Fe203 was confirmed to follow the 1st order reaction, but the reduction of CU2O was found to be autocatalytic.
Abstract (fin): Työn tarkoituksena oli tutkia kupari(l)oksidin (CU2O) hiilipelkistystä kupari liekkisulatusuunista tulevasta kuonasta.

Liekkisulatus- ja kuonan puhdistusprosessit on kuvailtu johdanto-osassa.
Tutkimukset ovat keskittyneet kuonanpuhdistuksen kemiaan kolme-elektrodisessa sähköuunissa, jossa kuonan komponentit jakautuvat jätekuonaksi ja kuparikiveksi panosprosessissa.
Erilaisten muuttujien (pintajännitys, tiheys, viskositeetti ja tasapainokoostumus) parametriset arvot ja pelkistymisreaktion termodynamiikka kuonanpuhdistus-prosessissa on myös tutkittu.

Korkeassa hapen osapaineessa CaO:n ja MgO:n lisäys suurentaa CU2O:n ja Fe2O3:n aktiivisuuskertoimia, joten CU2O:n konsentraatio ja Fe+3/Fe+2 suhde pienennevät.
Lisäksi emäksisten oksidien kohtuulliset lisäykset rikkovat (SiO4)4- ketjut pienentäen kuonan viskositeettia.

CU2O:n ja Fe2O3:n pelkistymiskinetiikka on tutkittu kirjallisuustyönä.
Erilaisten muuttujien (lämpötila, alkukonsentraatio ja reaktiotuotteet) vaikutusta CU2O:n pelkistymiskinetiikkaan on analysoitu lämpötilavälillä 1200 - 1650 °C, joka on havaittu parhaaksi lämpötila-alueeksi kuonanpuhdistusprosessissa.

Sekä termodynamiikan että kinetiikan analyysien tulokset vahvistivat lämpötilan nostamisen nopeuttavan CU2O:n ja FeOx:n pelkistymistä.
Pelkistymisnopeuksien aikaisemmin oletettiin olevan ensimmäisen kertaluvun reaktio konsentraation suhteen ja reaktionopeuden rajoittaja oli kemiallinen reaktio kuona-koksi-rajapinnalla.
Tässä analyysissä Fe2O3 pelkistymisen on todettu olevan ensimmäisen kertaluvun reaktio, mutta kupari(l)oksidin pelkistymisen havaittiin olevan autokatalyyttinen.
ED:2012-08-29
INSSI record number: 45153
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