Nıederschlag prosesi ile Emirli yöresi stibnit konsantrelerinden antimon üretimi
Antimony production from Emirli region stibnite concentrates via niederschlag process
Yazar: SEDEF PINAR BAŞAĞ
Danışman: PROF. DR. ONURALP YÜCEL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı / Üretim Metalurjisi ve Teknolojileri Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2016
Konu: Metalurji Mühendisliği = Metallurgical Engineering
Dizin: Antimon = Antimony ; Antimon sülfür = Antimony sulfur ; Metal sülfür = Metal sulfur ; Metalurji = Metallurgy ; Redüksiyon =   ; İndirgeme = Reduction ; İndirgenme reaksiyonu = Reduction reaction

Özet:
Kullanım tarihi 5000 yıl öncesine dayanan antimon parlak gri renkte olup doğada nabit halde bulunmamaktadır. Geçiş metali olan antimon 5A grubunda yer alır. Atom numarası 51, atom ağırlığı 121,75 g/mol, öz kütlesi 6,697 g/cm3'tür. Ortalama bir sertliğe sahip olan antimonun sertliği mohs sertlik skalasında 3'e denk gelmektedir.
Doğada sülfürlü ve oksitli olmak üzere yüzün üzerinde antimon minerali vardır. Bu mineraller arasında ekonomik açıdan en önemli mineral stibnittir (Sb2S3). Stibnit doğal bir trisülfür olup ağırlıkça % 71,4 Sb içermektedir. Karakteristik olarak siyah iğnemsi kristal yapısına sahiptir. Diğer mineraller ise antimon oksit ihtiva etmektedirler.
Ülkemizde mevcut en önemli antimon yatakları Kuzey-batı Anadolu, Tokat-Turhal ve Niğde-Gümüşler bölgelerinde yoğunlaşmaktadır. Günümüzdeki duruma bakıldığında rezerv açısından en büyük yataklarımız Kütahya-Simav-Dağardı, İzmir-Ödemiş-Emirli, Tokat-Turhal, Balıkesir-İvrindi ve Kütahya-Gediz'de bulunmaktadır.
Çalışma konusu kapsamında Etibakır A.Ş. tarafından işletilen Ödemiş-Emirli maden sahasından elde edilen stibnit flotasyon konsantresi kullanılarak Niederschlag Prosesi ile metalik antimon üretiminin koşullarının belirlenmesi amaçlanmıştır ve metalizasyon oranına etki eden parametreler irdelenmiştir.
Proses dahilinde redükleyici stokiyometrisi (demir miktarı) ve refrakter asidiklik oranının etkisi iki grup deney seti ile araştırılmıştır. Karakterizasyon çalışmaları kapsamında kimyasal analiz, atomik absorbsiyon spektrometrisi (AAS), X-ışınları difraksiyon spektrometrisi (XRD) ve X-ışınları flöresans spektrometrisi (XRF) teknikleri kullanılmıştır.
Her iki deney setinde de redükleyici stokiyometrisi ağırlıkça % 75 ile % 200 değerleri arasında değiştirilmiştir. Birinci deney setinde 1,4 refrakter asitlik derecesine sahip potalar, ikinci deney setinde ise 3,2 refrakter asitlik derecesine sahip potalar kullanılmıştır. Şarj olarak stibnit konsantresi ve redüktan olarak demir ile birlikte, sabit oranlarda silika (SiO2), sodyum boraks dekahidrat (Na2B4O7·10H2O) ve kalsiyum karbonattan (CaCO3) oluşan bir curuflaştırıcı karışımı da kullanılmıştır. Tüm deneysel çalışmalar 1100 ºC'de ve 60 dakika süre ile gerçekleştirilmiştir. 
Birinci deney setinden elde edilen fazlar üzerine yapılan karakterizasyon çalışmaları ışığında %150 Fe stokiyometrisine sahip deneyin %46,92 ile en yüksek metalizasyon değerini verdiği tespit edilmiştir.
İkinci deney setinde ise kullanılan potaların asitlik derecesinin metal verimine etkisini gözlemlemek amacı ile ilk deney setine paralel olarak 3,2 asitlik derecesine sahip potalar kullanılmış ve %100 Fe stokiyometrisinde elde edilen metal kazanım verimi %79,25 olarak ölçülmüştür.

Abstract:
Niederschlag process is commonly used to produce metallic antimony. The process is a metallothermic process which is conducted in one step for metallic antimony production. Using this method Sb2S3 is mixed with metallic iron and subjected to reduction. During heating, antimony sulfide is decomposed and sulphur combines with iron to form the matte phase and, metallic antimony is collected at the bottom of the crucible. In this study, evaluation of Sb2S3 concentrate, extracted and obtained from Emirli Region (West Anatolia) of Turkey was investigated by using Niederschlag process. Examined main parameters were reductant stoichiometry and crucible acidity ratio.
Antimony is a metalloid with an atomic number of 51. It is found in over 100 mineral species and found in nature mainly as a sulfide mineral stibnite (Sb2S3). Antimony is a lustrous grey metal that has a Mohs Scale Hardness of 3. This metalloid exists in two forms; metallic antimony is bright, silvery, hard and brittle, nonmetallic form is a grey powder. Antimony has poor electric and heat conduction. It is not attacked by dilute acid or by alkalis and stable in dry air.
Several production methods can be used for antimony production, such as; gasification and reduction method, electrolyte method and Niederschlag Process.
Stibnite is totally oxidized at 350-400°C in reverber type furnaces as for gasification and reduction method and it takes 10-12 hours approximately with carbon source. Gasificatioon method is a two step production method. The first step is oxidation and the second step is reduction. The main reactions of the process in question are given below.
Sb2S3 + 9O2 → 2Sb2O3 + 6SO2
Sb2S3 + 3C → 2Sb + 3CO
As electrolyte method; antimonite dissolves in hot sodium sulfide solution and then obtained sodium thio antimonite electrolyzed with steel anodes and cathodes to produce metallik antiomony.
With Niederschlag Process, stibnite can be directly reduced with metallic iron and a slight amount of carbon (to soften the bonds) in reverbetory type furnaces or blast furnaces in accordance with reaction below.
MeıX + Men = Meı + MenX
Niederschlag Process is candidate to be the most economic production method for antimony production if the process can be optimized to work with high metallization ratios. In this method antimony can reduced in one step. Sulphur is decomposed from stibnite and interacts with iron then a matte phase mainly consists of FeS would be obtained over the metallic antimony. The main reaction of Niederschlag Process is shown below.
Sb2S3 + 3Fe → 2Sb + 3FeS
Reduction reaction starts over 1100°C. Various flux materials can be used for the process, such as silica (SiO2), sodium borax decahydrate (Na2B4O7·10H2O), calcium carbonate (CaCO3), glauber salt or NaHCO3 to avoid metal losts. System has FeS-Na2S founded liquid matte phase and a metallic antimony phase is underneath the matte phase.
In this study the stibnite concentrate, which is mined in Ödemiş-Emirli and concentrated via flotation in Etibakir A.Ş. Halıkoy Plant be subjected to produce metallic antimony through Niederschlag Process. Dry concentrate was mixed with borax, soda and SiO2 as flux materials and iron as reductant. Experiments were conducted on various reductant ratios and refractory acidity ratios by using different amounts of iron.
In the Niederschlag experiments, stibnite concentrate having a Sb2S3 content of 69.00% and an average particle size of 60,76 µm was used. For different acidity ratios of refractory, two types of crucibles were used. First experimental set was completed with the crucible which has 1.4 acidity ratio and the second experimental set completed with the crucible which has 3.2 acidity ratio.
The initial mixtures were prepared from dried powders at various stoichiometric Fe ratios from 75% to 200%. The powder mixtures were charged into cylindrical fireclay pots. At the first experimental set 1.4 acidity ratio crucibles were used. These crucibles had 40 mm thickness, 58 mm inner diameter and 142 mm height. In the second experimental set 3.2 acidity ratio crucibles were used. These crucibles had 23 mm thickness, 42 mm inner diameter and 52 mm height.
The all experiments were conducted in a electrical resistant furnace at 1100 °C for a process duration of 60 minutes. Duration and temperature fixed for all experimental sets.
The obtained phases were characterized by using X-rays diffraction spectrometer (XRD, Rigaku Miniflex, Cu Kα X-ray tube - 30 kV; 15 mA), X-rays fluorescence spectrometer (XRF, ThermoScienthefic, w/ He tube), chemical analysis techniques and atomic absorption spectrometer (AAS, Perkin Elmer AAS 800).
For the first experimental, the ratio of required stoichiometric reductant amount was investigated. In this study, iron nails were used as reductant. Reductant amount was used from 75% stoichiometric Fe to 200% stoichiometric Fe. The highest metallization ratio was measured as 46.92% for the experiment conducted with 150% stoichiometric amount of Fe.79.25
In the second experimental set was conducted to understand the investigation of refractory acidity ratio on the metallization ratios of antimony by using differents types of the crucibles. For the second experimental set, we used the crucibles which have an acidity ratio of 3.2. As a result of the experiments, it was determined that increasing acidity ratio increased the metal recovery. The highest metallization ratio was obtained at the experiment conducted with 100% Fe stoichiometry as 79.25% metallization ratio. It was also the highest metallization ratio during the all experiments. 
For the last experimental set was conducted to understand the effect of acidic flux amount on the metalization ratios of antimony by using different amounts of flux materials. Flux amount was used from 10% to 30%. As a result of the experiments, it was determined that, increasing the acidic flux amount keeps stabile the metal recovery at proper level. The highest metallization ratio was measured as 78.32% with 25% weight amount of flux materials.
However, it is possible to collect the lost antimony amount (apart from the slight amount solved in the matte phase) in the form of antimony oxide in a dust collector of such a furnace system.