Studies on gas-liquid mass transfer in atmospheric leaching of sulphidic zinc concentrates

dc.contributorAalto-yliopistofi
dc.contributorAalto Universityen
dc.contributor.authorKaskiala, Toni
dc.contributor.departmentDepartment of Materials Science and Engineeringen
dc.contributor.departmentMateriaalitekniikan osastofi
dc.contributor.labLaboratory of Materials Processing and Powder Metallurgyen
dc.contributor.labMateriaalien valmistustekniikan ja jauhemetallurgian laboratoriofi
dc.date.accessioned2012-02-17T06:59:54Z
dc.date.available2012-02-17T06:59:54Z
dc.date.issued2005-05-12
dc.description.abstractIn this work, the mass transfer of oxygen in the atmospheric leaching process of zinc sulphide was investigated. Four new experimental apparatus items suitable for this purpose were designed and developed. The experiments conducted with the water model were focused on volumetric mass transfer, gas and liquid flow patterns, gas dispersion and bubble size. The effects of liquid properties and temperature on bubble size were examined with the bubble swarm system. Mass transfer coefficients, kL, between oxygen and different liquids were measured with mass transfer equipment. Modified high-temperature and pressure autoclave was used to determine the oxygen consumption rates in leaching conditions. The experimental set-ups and program carried out are discussed and the errors and problems associated with the techniques reviewed. The results revealed, amongst other occurrences, that the non-coalescence of bubbles occurs and the bubble size is controlled by the formation and breakage close to the impeller. According to the experiments, it seems to be possible to control the foaming and the surface aeration by adjusting the liquid volume and gas flow rate in the process. Too much liquid in the process increases the foaming, while too little increases the surface aeration. Furthermore, increasing the gas flow rate decreases foaming. Gas hold-up increased with mixing speed, while increasing the gas flow rate decreased the power consumption, as expected. Experimentally determined volumetric mass transfer values, kLa, varied between (2.17-12.00)×10−3 1/s and mass transfer values, kL, between (13.81-19.24)×10−5 m/s with oxygen and pure water. On the other hand, kL values between oxygen and process solutions varied between (1.5-11.32)×10−5 m/s. Increasing electrolyte content decreased the mass transfer values notably, sulphuric acid and zinc sulphate additions having a stronger effect than sodium chloride. Both the determined mass transfer parameters were also strongly dependent on the mixing intensity. The oxygen consumption rate in the process solution varied between 0.018-0.075 mmol/(m2s). Increasing the pressure and mixing intensity increased the oxygen consumption rate significantly, but temperature did not have a similar effect. Decreasing the dissolved zinc content in the solution increased the oxygen consumption rate significantly, whereas increasing the amount of concentrate only slightly increased the consumption rate. The experimental results of this work provide additional data for the improvement of existing leaching models, as well as the development of new ones.en
dc.description.versionrevieweden
dc.format.extent149
dc.format.mimetypeapplication/pdf
dc.identifier.isbn951-22-7665-8
dc.identifier.issn1795-0074
dc.identifier.urihttps://aaltodoc.aalto.fi/handle/123456789/2568
dc.identifier.urnurn:nbn:fi:tkk-005229
dc.language.isoenen
dc.publisherHelsinki University of Technologyen
dc.publisherTeknillinen korkeakoulufi
dc.relation.ispartofseriesHelsinki University of Technology doctoral theses in materials and earth sciencesen
dc.relation.ispartofseries3en
dc.subject.keywordleachingen
dc.subject.keywordatmosphericen
dc.subject.keywordzincen
dc.subject.keywordsulphidicen
dc.subject.keywordconcentrateen
dc.subject.keywordgasen
dc.subject.keywordbubbleen
dc.subject.keywordinterfaceen
dc.subject.keywordsolubilityen
dc.subject.keyworddissolutionen
dc.subject.keywordmass transferen
dc.subject.keywordcoefficienten
dc.subject.keyworddiffusionen
dc.subject.otherMaterials scienceen
dc.subject.otherGeoinformaticsen
dc.titleStudies on gas-liquid mass transfer in atmospheric leaching of sulphidic zinc concentratesen
dc.typeG4 Monografiaväitöskirjafi
dc.type.dcmitypetexten
dc.type.ontasotVäitöskirja (monografia)fi
dc.type.ontasotDoctoral dissertation (monograph)en
local.aalto.digiauthask
local.aalto.digifolderAalto_64093
Files
Original bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
isbn9512276658.pdf
Size:
2.94 MB
Format:
Adobe Portable Document Format