Leaching is the most widely used process for extraction of nickel metal from lateritic ores. In this study, nickel extraction from Manisa-G&ouml / rdes region laterites by hydrochloric acid leaching is aimed. The mineralogical analysis of sample showed that hematite, goethite, dolomite, quartz and smectite are the main minerals in the ore. Attrition scrubbing, cycloning and magnetic separation with permroll were used as preconcentration processes but results were unsatisfactory. HCl leaching experiments were conducted both at room temperature and at elevated temperatures. The effects of various parameters such as leaching duration, particle size, concentration of HCl, pulp density, Cl- concentration and temperature on nickel recovery were examined. The results showed that under the optimised leaching conditions (particle size: 100 % -1 mm, HCl concentration: 3 N, leaching duration: 3 hours, leaching temperature: 100 oC, pulp density: 1/30 solid to liquid ratio by volume) it was possible to extract 87.26 % of nickel in the ore.

[pt] A redução por hidrogênio e a decomposição térmica de um minério laterítico saprolítico foram estudadas utilizando a técnica de termogravimetria (TGA). A identificação das fases minerais formadas após o processamento foi feita utilizando as técnicas de difração de raios X (DRX) e microscopia eletrônica de varredura acoplada a espectrômetro de energia dispersiva (MEV/EDS). O produto obtido manteve o níquel aprisionado na estrutura do material e forneceu um baixo índice de extração desse metal (em torno de 3 porcento) na etapa de lixiviação amoniacal. Desta forma, novos experimentos de redução foram conduzidos na presença de diferentes reagentes químicos (Na2CO3, S8 e NaCl) visando a aumentar a solubilidade do níquel. Observou-se que todos os reagentes químicos utilizados viabilizaram o aumento da extração de Ni, sendo o maior deles para os testes utilizando 10 porcento de NaCl. Então, experimentos de redução por hidrogênio e decomposição térmica, do mesmo minério, na presença de NaCl, foram feitos utilizando a técnica de termogravimetria, com as fases minerais e alguns produtos gasosos formados sendo identificados utilizando as técnicas de DRX e MEV/EDS. Tais experimentos e caracterizações sugerem que a presença do NaCl no sistema promove a segregação do níquel, e a sua consequente solubilização posterior, em função da ocorrência das seguintes reações: (1o) Redução do óxido de níquel pelo hidrogênio: NiO + H2(g) → Ni + H2O(g); (2o) Formação de HCl: Al2SiO5 + 2NaCl + SiO2 + H2O(g) à 2HCl(g) + 2NaAlSiO4; (3o) Cloração do níquel metálico pelo HCl: Ni + 2HCl(g) → NiCl2 + H2(g);(4o) Redução do cloreto de níquel pelo hidrogênio: NiCl2 + H2(g) → Ni + 2HCl(g). A influência da temperatura e da porcentagem de NaCl no forno de redução no rendimento da etapa de lixiviação amoniacal foram avaliadas e os resultados mostraram que a presença de apenas 1 porcento de NaCl aumentou os valores de extração para níveis próximos de 90 porcento, quando os experimentos de redução foram conduzidos à temperatura de 850°C. / [en] The reduction by hydrogen and the thermal decomposition of a lateritic saprolite nickel ore were studied using the thermogravimetric technique (TGA). The identification of the mineral phases generated after the processing was carried out using X-ray diffraction (XRD) and scanning electron microscopy coupled to a dispersive energy spectrometer (SEM/EDS) techniques. The reduced ore was leached in amoniacal solution and the low value of nickel extraction (≈3 percent) were attributed to the formation of forsterite and enstatite. Thus reduction test were carried out in the presence of chemicals (Na2CO3, NaCl and S8) and the highest extractions values were found for the tests using 10 percent NaCl. Finally, reduction tests on H2 atmosphere in rotary kiln were performed in the presence of NaCl and the product of the reaction was leached in ammoniacal solution. The presence of only 1 percent of NaCl in the furnace increased the nickel extraction values from ≈3 percent to ≈ 90 percent when the experiment was carried out at 850°C. According to the results of X ray diffractometry (XRD) and thermogravimetric analysis (TGA) the presence of NaCl in the system and the reducing atmosphere of H2 promote the segregation of nickel according to the following steps: 1).. Nickel oxide reduction by hydrogen: NiO + H2(g) → Ni + H2O(g). 2) Formation of HCl: Al2SiO5 + 2NaCl + SiO2 + H2O à 2HCl(g) + 2NaAlSiO4. 3). Chlorination of metallic nickel by HCl: Ni + 2HCl(g) → NiCl2 + H2(g). 4). Reduction of nickel chloride by hydrogen: NiCl2 + H2(g) → Ni + 2HCl(g).

Η επεξεργασία των νικελιούχων λατεριτικών μεταλλευμάτων της χώρας μας για την παραγωγή σιδηρονικέλιου στη Λάρυμνα συνοδεύεται με την εκπομπή 200000t/y λεπτομερούς σκόνης που συλλέγεται στα συστήματα αντιρρύπανσης των περιστροφικών κάμινων (Π/Κ), μέσης περιεκτικότητας 1.2-1.5% σε Ni και 4-5% σε C. Η διατριβή αυτή συνέβαλε στην ανάπτυξη μεθόδου ανακύκλωσης της σκόνης αυτής με απευθείας αναγωγική της τήξη σε ηλεκτρική κάμινο συννεχούς ρεύματος (DC-HEP) με εμφυσησή της μέσω του κεντρικού διάτρητου γραφιτικού ηλκετρόδιου. Την προκαταρκτική θεωρητική διερεύνηση και τις εργαστηριακές προδοκιμές ακολούθησαν βιομηχανικές δοκιμές στην κάμινο 125t DC-HEP στη χαλυβουργία Georgsmarienhutte της Γερμανίας, όπου έλαβε χώρα τήξη 70t σκόνης και 2.5t φιλομερούς μεταλλεύματος.Η ανάκτηση Ni ήταν πολύ υψηλή 93-99%. Παρήχθησαν χάλυβες χαμηλής κραμάτωσης σε σε Ni καθώς και ποικίλοι τύποι σκωρίας προς διερεύνηση της χρήσης τους στην παραγωγή σύνθετων τσιμέντων Portland και σκωριωτσιμέντων. Πραγματοποιήθηκε μεταλλουργική αξιολόγηση των δοκιμών και αναπτύχθηκε μοντέλο προσομοίωσης της αναγωγικής τήξης της σκόνης. / The tratment of the laterite nickel ferrous ores in Hellas for the production of ferronickel at Larymna is associated with the emission of 200000t/y of fine dust collected in the gas cleaning systems of the rotary kilns (R/Ks), with 1.2-1.5% and 4-5% . Average Ni and C contents respectively . This thesis contributed to the development of a method for the recycling of this dust by means of its direct reduction smelting in a DC-HEP furnace (Direct Current-Hollow Electrode Powder) by its injection through the central hollow graphite electrode. The preliminary theoretical study and the laboratory trials were followed by industrial heat campaigns in the 12st DC-HEP furnace at georgsmarienhutte steelwork in Germany, where around 70t of dust and 2.5t of ore fines were smelted. The Ni-recovery was very high 93-99.9%. Low Nickel alloyed steel grades were produced and various slag types for the investigation of their utilization for the production of composite-portland cements and slag cements. The metallurgical evaluation of the trials was performed and model for the dust reduction smelting process was developed.