Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Innovative process solutions towards recycling of salt cake from secondary aluminum smelting
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To offer better solutions for the recycling of salt cake from secondary aluminum melting, several innovative investigations were carried out based on hydrometallurgical and pyrometallurgical views.

Thermal diffusivity measurements as a function of temperature on salts-Al composites having various compositions (0, 2, 4, 6, 8, 10, 12wt pct metallic Al) were carried out. Its attempt to derive theoretical relationships between aluminium contents in the salt-Al composites and the thermal conductivities so that these would serve as calibration curves for industrial samples taken out from secondary aluminium re-melting at a later stage.

The AlN hydrolysis behavior in NaCl solution was investigated by immersing pure AlN powder in deionized water, 0.3mol/l NaCl aq, 0.6mol/l NaCl aq and NaCl solution respectively with CO2 bubbling at 291K. The results showed that AlN powder underwent enhanced hydrolysis in NaCl aq than that in deionized water, while, the introduction of CO2 was found to hinder the hydrolysis even in the presence of NaCl. The characterization of the products after hydrolysis was carried out using XRD, SEM and TEM analyses. It was shown that the hydrolysis process included a slow-reaction period involving the dissolution of aluminum hydroxide layer around raw AlN particle, followed by the precipitation of aluminum hydroxide gel and the crystallization of boehmite, bayerite and gibbsite. The effects of sodium chloride concentration on the hydrolysis behavior are presented.

The leaching process in CO2-saturated water showed that, at a solid to liquid ratio of 1:20 and 3h at 291K, the extraction of Na and K from the dross could be kept as high as 95.6% and 95.9%, respectively. At the same time, with continuous CO2 bubbling, the mass of generated NH3 during the leaching process decreased significantly, also the escaping NH3 gas decreased from 0.25mg in pure water down to <0.006mg. The above results showed that the introduction of CO2 causes hindrance to the hydrolysis of AlN, meanwhile, effective absorption of ammonia. The plausible mechanisms for the observed phenomena are discussed. The concept of the leaching of the salt cake by carbonated water and the consequent retention of AlN in the leach residue opens up a promising route towards an environment-friendly recycling process for the salt cake viz. recovery of the salts, utilization of CO2 and further processing of the dross residue, towards the synthesis of SiAlON from the leach residues.  

In alternative route to the processing of salt cake, the ammonia gas evolved by hydrolysis of AlN was collected by CO2-saturated water during water leaching at 373K. The products, i.e. ammonium carbonates which are free of chlorides, has application as a fertilizer, besides that, this method also has the advantage of fixing carbon from CO2, which is the subject of many investigations around the world.

The oxidation behavior of composites SiMgAlON phases (β-SiAlON, MgAlON and 15R) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples was investigated in air by thermogravimetric measurements. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO present in the salt cake residue. From the view of kinetics, the addition of Fe2O3 brings a lower activation energy and more aggressive oxidation. The additive of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673K, thus retard the oxidation rate. The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point. From the view of phase evolution, with the progress of oxidation, the composition of the material being oxidized moved towards the Al2O3-rich corner of MgO-Al2O3-SiO2 or CaO-MgO-Al2O3-SiO2 phase diagrams relevant to SiMgAlON composite. At lower temperatures, the addition of Fe2O3 and CaO facilitated the formation of cordierite and anorthite, respectively. With the increasing of temperature, islands of silicate melt were formed dissolving these oxides, with the liquidus temperature getting lowered as a consequence. The liquid phase formed engulfed the adjacent solid phases providing strong mobility for the cations and enabling the crystal growth. As a result, intermediate products, i.e. cordierite, anorthite, spinel, which formed earlier during oxidation are found to get dissolved in the liquid phase.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , vi, 94 p.
Keyword [en]
Thermal diffusivity, Model, Solubility, CO2, AlN, Crystals, Hydrolysis, Enhance, Hinder, Leaching, Absorption, Synthesis, SiMgAlON, Oxidation, Arctan, Activation energy, Mullite, Liquid, Crystallization.
National Category
Metallurgy and Metallic Materials
Research subject
SRA - Production
Identifiers
URN: urn:nbn:se:kth:diva-101074ISBN: 978-91-7501-440-1 (print)OAI: oai:DiVA.org:kth-101074DiVA: diva2:547241
Public defence
2012-10-08, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
XPRES - Initiative for excellence in production research
Note

QC 20120912

Available from: 2012-09-12 Created: 2012-08-22 Last updated: 2013-04-19Bibliographically approved
List of papers
1. Thermal conductivity of Al-Salt composites
Open this publication in new window or tab >>Thermal conductivity of Al-Salt composites
2012 (English)Report (Refereed)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 16 p.
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-102252 (URN)KTH/MSE--12/18--SE (ISRN)
Note

QC 20120912

Available from: 2012-09-12 Created: 2012-09-12 Last updated: 2012-09-12Bibliographically approved
2. Leaching process investigation of secondary aluminium dross: Investigation of AlN hydrolysis behaviour in NaCl solution
Open this publication in new window or tab >>Leaching process investigation of secondary aluminium dross: Investigation of AlN hydrolysis behaviour in NaCl solution
Show others...
2012 (English)In: Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, Vol. 121, 140-146 p.Article in journal (Refereed) Published
Abstract [en]

The AlN hydrolysis behaviour in NaCl solution was investigated by immersing AlN powder in deionised water, 0.3 mol L -1 NaCl aq and 0.6 mol L -1 NaCl aq at 291 K respectively. The pH value of the suspension was monitored continuously for the first 4 days, and the amount of NH 3 formed within 10 days period was measured by water quality-determination of ammonium- distillation and titration method. The characterisation of the products after hydrolysis was carried out using X-ray diffraction, SEM and TEM analyses. It was shown that the hydrolysis process included a slow reaction period involving the dissolution of aluminium hydroxide layer around raw AlN particle, followed by the precipitation of aluminium hydroxide gel and the crystallisation of boehmite, bayerite and gibbsite. The effects of sodium chloride concentration on the hydrolysis behaviour are presented.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-102250 (URN)10.1179/1743285512Y.0000000008 (DOI)2-s2.0-84864887718 (Scopus ID)
Note

QC 20120912

Available from: 2012-09-12 Created: 2012-09-12 Last updated: 2017-01-10Bibliographically approved
3. Leaching Process Investigation of Secondary Aluminum Dross: The Effect of CO 2 on Leaching Process of Salt Cake from Aluminum Remelting Process
Open this publication in new window or tab >>Leaching Process Investigation of Secondary Aluminum Dross: The Effect of CO 2 on Leaching Process of Salt Cake from Aluminum Remelting Process
Show others...
2012 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 5, 1220-1230 p.Article in journal (Refereed) Published
Abstract [en]

For the recycling/disposal of aluminum dross/salt cake from aluminum remelting, aqueous leaching offers an interesting economic process route. One major obstacle is the reaction between the AlN present in the dross and the aqueous phase, which can lead to the emission of NH 3 gas, posing a serious environmental problem. In the current work, a leaching process using CO 2-saturated water is attempted with a view to absorb the ammonia formed in situ. The current results show that at a solid-to-liquid ratio of 1:20 and 3 hours at 291 K (18 °C), the extraction of Na and K from the dross could be kept as high as 95.6 pct and 95.9 pct respectively. At the same time, with continuous CO 2 bubbling, the mass of escaping NH 3 gas decreased from 0.25 mg in pure water down to &lt;0.006 mg, indicating effective absorption of ammonia by carbonized water. Furthermore, the results in the case of the leaching experiments with synthetic AlN show that the introduction of CO 2 causes hindrance to the hydrolysis of AlN. The plausible mechanisms for the observed phenomena are discussed. The concept of the leaching of the salt cake by carbonated water and the consequent retention of AlN in the leach residue opens up a promising route toward an environment-friendly recycling process for the salt cake viz. recovery of the salts, utilization of CO 2, and further processing of the dross residue, toward the synthesis of AlON from the leach residues.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-102254 (URN)10.1007/s11663-012-9678-7 (DOI)000308822100023 ()2-s2.0-84869883595 (Scopus ID)
Note

QC 20121012

Available from: 2012-09-12 Created: 2012-09-12 Last updated: 2017-12-07Bibliographically approved
4. Recycling of Aluminum Salt Cake: Utilization of Evolved Ammonia
Open this publication in new window or tab >>Recycling of Aluminum Salt Cake: Utilization of Evolved Ammonia
2013 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, 16-19 p.Article in journal (Refereed) Published
Abstract [en]

The communication presents an extension of the leaching process of the salt cake earlier developed by the present authors. The process describes the investigations in capturing the ammonia gas evolved by hydrolysis of AlN during aqueous leaching at 373 K (100 A degrees C) by CO2-saturated water. The product, i.e., ammonium bicarbonate which is free of chlorides, is a value-added product and can find application in the fertilizer industry. The present method has the added advantage of fixing CO2 as well.

Keyword
leaching, hydrolysis, CO2, NH3, absorption
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-102256 (URN)10.1007/s11663-012-9779-3 (DOI)000314909000004 ()2-s2.0-84874000319 (Scopus ID)
Note

QC 20130320. Updated from submitted to published.

Available from: 2012-09-12 Created: 2012-09-12 Last updated: 2017-12-07Bibliographically approved
5. Oxidation Kinetics of AlN Under CO2 Atmosphere
Open this publication in new window or tab >>Oxidation Kinetics of AlN Under CO2 Atmosphere
Show others...
2012 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 2, 406-412 p.Article in journal (Refereed) Published
Abstract [en]

The oxidation kinetics of AlN powder in CO2 atmosphere was investigated using thermogravimetric analysis. The experiments were carried out in the isothermal mode at different flow rates of CO2, 20 mL/min, 40 mL/min, 150 mL/min, and 265 mL/min. The results showed that the oxidation rate was affected by temperature as well as the flow rate of CO2. Based on the experimental data, a kinetic model for predicting the oxidation behavior of AlN powder has been developed, which could simulate both the chemical reaction and diffusion -controlling periods as a function of temperature and carbon dioxide concentration.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-93645 (URN)10.1007/s11663-011-9611-5 (DOI)000301778200020 ()2-s2.0-84861828553 (Scopus ID)
Note
QC 20120424Available from: 2012-04-24 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
6. Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics
Open this publication in new window or tab >>Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics
2013 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, 210-219 p.Article in journal (Refereed) Published
Abstract [en]

The oxidation behaviors of composites SiAlON/MgAlON phases (beta-SiAlON, 15R-SiAlON and MgAlON) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples were investigated in air by thermogravimetric measurements. Combined kinetics, viz. linear law + arctan law + parabolic law, are used to describe the kinetics of oxidation in isothermal mode. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO, present in the salt cake residue. The addition of Fe2O3 results in a lower activation energy and more aggressive oxidation. The addition of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673 K (1400 A degrees C). The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point.

Keyword
impurities, arctan, activation energy, oxidation, SiMgAlON
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-102260 (URN)10.1007/s11663-012-9763-y (DOI)000314909000024 ()2-s2.0-84873993182 (Scopus ID)
Note

QC 20130320. Updated from submitted to published.

Available from: 2012-09-12 Created: 2012-09-12 Last updated: 2017-12-07Bibliographically approved
7. Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part II: Phase Evolution
Open this publication in new window or tab >>Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part II: Phase Evolution
2013 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, 220-232 p.Article in journal (Refereed) Published
Abstract [en]

The oxidation behavior of composite SiAlON/MgAlON phases, synthesized from the leaching residue after the aqueous treatment of salt cake from aluminum remelting, is compared with the oxidation of corresponding synthetic samples. The samples were subjected to oxidation under air as the oxidant atmosphere in the temperature range of 1373 K to 1773 K (1100 A degrees C to 1500 A degrees C). The phases present were analyzed by scanning electron microscopy (SEM)-electron-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) to arrive at the evolution of the various phases formed during oxidation. From the experimental results, especially by the characterization of the oxidation products, the mechanism of the oxidation reaction was deduced as follows: With the progress of oxidation, the composition of the material being oxidized moved toward the Al2O3-rich corner of MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2 phase diagrams relevant to the SiAlON/MgAlON composite. At lower temperatures, the addition of Fe2O3 and CaO facilitated the formation of cordierite and anorthite, respectively. With increasing temperature, islands of silicate melt were formed dissolving these oxides, with the liquidus temperature getting lowered as a consequence. The liquid phase formed engulfed the adjacent solid phases providing strong mobility for the cations and enabling the crystal growth. As a result, intermediate products, i.e., cordierite, anorthite, and spinel, which were formed earlier during oxidation, are found to get dissolved in the liquid phase.

Keyword
SiMgAlON, oxidation, mullite, liquid, crystallizationimpurities, arctan, activation energy, oxidation, SiMgAlON
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-102261 (URN)10.1007/s11663-012-9758-8 (DOI)000314909000025 ()2-s2.0-84873986908 (Scopus ID)
Note

QC 20130320. Updated from submitted to published.

Available from: 2012-09-12 Created: 2012-09-12 Last updated: 2017-12-07Bibliographically approved

Open Access in DiVA

thesis(5217 kB)2928 downloads
File information
File name FULLTEXT01.pdfFile size 5217 kBChecksum SHA-512
0bc24d5cf807b35b4ae723c0d1ebc7424bc5ce042ace50bb69aa7a319d6cc06297e54cb63cc3947e217ee94250c01e780d29ef92cdd50509c6bbdb76929bfbbb
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Li, Peng
By organisation
Materials Process Science
Metallurgy and Metallic Materials

Search outside of DiVA

GoogleGoogle Scholar
Total: 2928 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 442 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf