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

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en Kaskiala, Toni 2012-02-17T06:59:54Z 2012-02-17T06:59:54Z 2005-05-12
dc.identifier.isbn 951-22-7665-8
dc.identifier.issn 1795-0074
dc.description.abstract In 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.format.extent 149
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.ispartofseries Helsinki University of Technology doctoral theses in materials and earth sciences en
dc.relation.ispartofseries 3 en
dc.subject.other Materials science en
dc.subject.other Geoinformatics en
dc.title Studies on gas-liquid mass transfer in atmospheric leaching of sulphidic zinc concentrates en
dc.type G4 Monografiaväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Materials Science and Engineering en
dc.contributor.department Materiaalitekniikan osasto fi
dc.subject.keyword leaching en
dc.subject.keyword atmospheric en
dc.subject.keyword zinc en
dc.subject.keyword sulphidic en
dc.subject.keyword concentrate en
dc.subject.keyword gas en
dc.subject.keyword bubble en
dc.subject.keyword interface en
dc.subject.keyword solubility en
dc.subject.keyword dissolution en
dc.subject.keyword mass transfer en
dc.subject.keyword coefficient en
dc.subject.keyword diffusion en
dc.identifier.urn urn:nbn:fi:tkk-005229
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (monografia) fi
dc.type.ontasot Doctoral dissertation (monograph) en
dc.contributor.lab Laboratory of Materials Processing and Powder Metallurgy en
dc.contributor.lab Materiaalien valmistustekniikan ja jauhemetallurgian laboratorio fi

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