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Pyrometallurgical Extraction of Tin Metal from the Egyptian Cassiterite Concentrate

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Pyrometallurgical Extraction of Tin Metal from the Egyptian Cassiterite Concentrate International Journal of Scientific & Engineering Research, Volume 6, Issue 3, March-2015 54 ISSN 2229-5518 Pyrometallurgical Extraction of Tin Metal from the Egyptian Cassiterite Concentrate 1 2 1 1 1 A. B. El DeebP ,P I. M. MorsiP ,P A. A. AtlamP ,P A. A. OmarP ,P W. M. FathyP P (1) Al Azhar University, Faculty of Engineering, Mining and Petroleum Engineering Department. (2) Central Metallurgical Research and Development Institute (CMRDI), Egypt. Abstract— This study aims to investigate the Pyrometallurgical extraction of tin metal from the Egyptian cassiterite concentrate. The carbothermic reduction of cassiterite concentrate by char coal in the NaR2RCO R3R - NaNO R3R molten salt system was studied at the temperature • • range 850 -1000P CP . The results showed that more than 95% of tin was successfully extracted at smelting temperature 1000P CP and after 60 mint. smelting time. The kinetics of reaction was found to follow the chemical reaction model. The activation energy was calculated 106 KJ/mol. After purification process the tin produced had a purity of 99.6 %. Index Terms— Carbothermic reduction, Cassiterite, kinetics, alkaline molten salt. —————————— —————————— 1 INTRODUCTION in presently find extensive uses in industrial and domestic Tin is extracted from oxidic ores usually by reduction smelting • Tapplications. It has been used extensively for soldering, of the ore at high temperature (›1200 P CP ) in the presence of corrosion prevention and food packaging. Tin is found in suitable fluxing agent silica or lime depending on the type and Egypt as cassiterite mineral and the main tin bearing deposits quality of the gangue material present in the ore. [3] occur in the central part of the Eastern Desert of Egypt. [1] The principal difficulty in the Pyrometallurgical technique for There are many industrial techniques for tin extraction from gaining tin metal is the separation of tin from iron due to the its ores depending on the type of the ore itself, oxidic or sul- high temperature of smelting. The smelting conditions should fide. Each type of the ore should be treated by the suitable be such that the tin oxide is reduced to the metallic state while technique according to its chemical composition. [2,6] iron oxide is reduced to lower oxide (the ferrous oxide) and IJSERpasses into the slag. Besides that the reduction of some iron ———————————————— oxide is further facilitated if the formation of FeSn and FeSnR2R *A. B. El Deeb is currently pursuing masters degree program in Mining and Petroleum Engineering, Faculty of Engineering, Al Azhar University, Egypt. are formed. [7] Also it was found that the reduction of tin and He completed his under graduate degree in Faculty of Engineering, Al Azhar iron oxides depends on the acidity of the slags. In case of acid University, Egypt in the year 2010. His area of interest is Extractive Metallurgy slags the activity of tin and iron oxides are lower than that of and Materials Science Engineering. E-mail: [email protected] basic slags. An addition of lime to the slag enhances the reduc- *I. M. Morsi, is currently working as professor in Central Metallurgical Re- tion process. [8,10] The admixtures of KR2RCOR3R, SiOR2R, ALR2ROR3R, search and Development Institute (CMRDI), Egypt. He has published 60 jour- CaO and tin metal all accelerate the reduction of cassiterite by nals and 10 conferences.H is area of Interest is Extractive Metallurgy Engineer- ing. graphite. [10] Email: [email protected] *A. A. Atlam, is currently working as professor in Department of Mining and The Pyrometallurgical technique requires therefore the pres- Petroleum, Faculty of Engineering, Al Azhar University, Egypt. He has pub- ence of high temperature silicate fluxes working at high tem- lished 50 journals and 20 conferences. His area of interest is Extractive Metal- lurgy and Materials Science Engineering. perature and needs a long reaction times due to the sluggish Email: ahmed [email protected] reaction rate between solid tin oxide and carbon. Also in this *A. A. Omar, is currently working as professor in Department of Mining and process fairly large quantity of tin oxides fails to be reduced to Petroleum, Faculty of Engineering, Al Azhar University, Egypt. He has pub- lished 35 journals and 18 conferences. His area of interest is Extractive Metal- metallic form instead of this they combine with silica and goes lurgy and Materials science Engineering. into the slag. [4] To overcome the reduction of iron oxide to Email: [email protected] metallic state, smelting has to be conducted in moderately re- * P W.P M. Fathy, is currently working as Phd.lectur in Department of Mining and ducing atmosphere and at low temperature. [2] One very Petroleum, Faculty of Engineering, Al Azhar University, Egypt. He has pub- promising direction is using alkaline molten salts as media for lished 1 journals and 1 conference. His area of interest is Extractive Metallur- gy and Mineral Processing Engineering. the reduction of metallic oxides. Such melts fully correspond Email: [email protected] to the requirements of the medium in which the reactions of IJSER © 2015 http://www.ijser.org International Journal of Scientific & Engineering Research, Volume 6, Issue 3, March-2015 55 ISSN 2229-5518 reduction of tin oxides can proceed. Alkaline molten salt pos- was removed and tin metal was poured into steel mould and sess high dissolving ability with respect to starting substances. the slag was collected. The extracted tin metal and recovered Also they provide high rate of reduction reaction and can be slag were then weighed and analyzed. carried out at low temperature. [5, 6] 2.2.2. Methods of Analysis The carbothermic reduction of the cassiterite concentrate in The grade of the recovered tin was determined by chemical the presence of sodium carbonate and sodium nitrate analysis using volumetric titration method using standard ten salt system was investigated at various conditions. It was potassium iodate solution. The slag was analyzed chemically suggested that the intermediate sodium stannate compound using (XRF). Mineralogical analysis was conducted by (XRD) was formed during the interaction of cassiterite with this type and Scanning Electron Microscopy (SEM - EDX) to examine of melt. This compound is mainly reduced by gaseous CO in the resulting phases. The percent yield of tin was then calcu- the liquid melt with a high rate, thereby providing high recov- lated using the formula (R= Cc/Ff*100) where R is the percent ery of tin from the cassiterite concentrate into the crude alloy. yield of tin metal, C is the weight of tin metal produced, c is [11] the assay of tin metal produced, F is the weight of cassiterite In this paper, the kinetics of extraction process of Tin metal concentrate in the charge and f is the assay of tin in the cassit- from Egyptian cassiterite concentrate using the alkaline mol- erite concentrate. ten salts as fluxing agents as well as the mechanism of reduc- tion process were investigated. The parameters studied are 2.2.3 Purification of Crude Tin Metal Carbon stoichiometry, ratio of Sodium carbonate, Sodium ni- The crude tin metal was refined with boiling process followed trate added, temperature and time of reduction. by Liquation. In the boiling process, the tin was melted in the crucible at 300 •C then agitated with poles of green wood. The 2 MATERIALS AND METHOD green wood should be moistening to produce steam along 2.1 Raw Materials with the mechanical stirring of the poles. Most of the remain- ing impurities are floated on the surface to form scum, which The cassiterite concentrate sample weighing about 10 kg (- were then removed and tin metal was poured into the steel 2mm size) was obtained from Abo Dabbab mining site in the mould. Based on the difference in melting points and the dif- Eastern Desert of Egypt. This sample was mixed thoroughly ference in specific gravity of tin alloy components, the liqua- then ground in Bico mill to be passed through a sieve of - tion refining was carried out. In Liquation process the pro- 63µm size. Coning and quartering were done to take a repre- duced metal from boiling step was put on perforated funnel sentative sample weighing aboutIJSER 200 gm. This representative which was put on a crucible and then placed on the furnace sample was used for performing complete physicochemical adjusted at 231•C. The melted tin runs down and was collected analysis using X-Ray Fluorescence Spectrometry (XRF) and in the crucible, while the other materials remain above as sol- mineralogical analysis using X-Ray Diffraction analysis (XRD). ids. The high purity tin metal was then poured into the steel Other materials used were Char coal; sodium carbonate and mould. sodium nitrate are of chemically pure grade. 3 RESULTS AND DISCUSSION 2.2 Methods 3.1 Physicochemical Analysis of Cassiterite Concentrate 2.2.1 Smelting Process The mineralogical analysis of the concentrate sample using Each run of the smelting process was carried out on batches XRD in Fig. 1 revealed that the sample is composed mainly of containing 50 gm. of the concentrate in addition to char coal the following minerals as shown in Table 1. as reductant, sodium carbonate and sodium nitrate as fluxing TABLE 1 agents. The required weight of reactants to the desired propor- MINERALOGICAL ANALYSIS OF ABU DABBAB CASSITERITE CON- tions were weighed then mixed thoroughly in fireclay scorifi- CENTRATE SAMPLE. ers and finally the charge was transferred to a 30 cm3 volume fireclay crucible. A Muffle Furnace of maximum temperature Minor constituent 1200•C was preheated to the required temperature (850 - Major constituent 1000•C) then the crucible was inserted into the furnace. After Cassiterite Clinochlore completing the reduction reaction for each run, the crucible [SnO2] [(Mg, Fe, Al)6 (Si, Al)4 O10 (OH)8] IJSER © 2015 http://www.ijser.org International Journal of Scientific & Engineering Research, Volume 6, Issue 3, March-2015 56 ISSN 2229-5518 TABLE 2 CHEMICAL ANALYSIS OF ABU DABBAB CASSITERITE CON- CENTRATE.
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