Gümüşköy atıklarının değerlendirilmesi ve tesis gümüş kazanma veriminin arttırılması
Beneficiation of gümüşköy silver plant tailings and increasing the plant recovery
Yazar: HAYRUNNİSA DİNÇER
Danışman: PROF. DR. GÜVEN ÖNAL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Cevher-Kömür Hazırlama ve Değerlendirme Ana Bilim Dalı
Derece: Doktora, 1997
Konu: Maden Mühendisliği ve Madencilik = Mining Engineering and Mining
Dizin: Atık değerlendirme = Waste evaluation ; Cevher hazırlama = Mineral processing ; Gümüş = Silver ; Maden yatakları = Ore deposits ; Yeniden kazanma = Recycling

Özet:
ÖZET Bu araştırma kapsamında; polimetalik refirakter gümüş cevherlerinin işlendiği Etibank 100. Yıl Gümüş İşletmesi Siyanür ile Çözündürme Tesisi'nde düşük gümüş kazanma veriminin nedenleri mineralojik yapı ve çözündürme koşullan açısından incelenmiştir. Ayrıca, 100 g/ton gümüş içeren artıklardan gümüşün kazanılma olanakları araştırılmıştır. Deneylerde kullanılan 100. Yıl Gümüş İşletmesi Artıkları ortalama 100 g/ton gümüş içermekte, gümüş mineralleri olarak; nabit gümüş, arjantit, pirarjirit, prustit ve frayberjit görülmektedir. Mineralojik incelemeler gümüşün 40 mikrondan daha küçük boyutlarda ve çoğunlukla diğer mineraller içinde kapanım halinde bulunduğunu göstermiştir. Artık numunesi ile yapılan siyanür ile çözündürme deneylerinde, sülfürlü minerallerin oksitlenmesi, gözenekliliği arttırarak kapanım halinde bulunan gümüş minerallerine siyanürün ulaşabilmesi için hidrojen peroksit kullanılmış ve hidrojen peroksitin cevher gözenekliliğini % 19.1 oranında arttırdığı saptanmıştır. Siyanür ile çözündürme deneylerinde optimum çözünme koşullan olarak; 2 g/l NaCN, 12 g/l H2O2, 0.4 g/l Ca(OH)2, 24 saat çözündürme süresi ve % 15 pülpte katı oram belirlenmiştir. Optimum koşullar altında yapılan çözündürme deneyleri sonunda artıktan % 45 verimle gümüş kazanılmıştır. Tuvenan cevher üzerinde yapılan siyanür ile çözündürme deneyleri sonunda; 1 00. Yıl Gümüş İşletmesi' hde % 60 verimle elde edilen gümüş % 80 verimle kazanılmıştır. Optimum çözünme koşullan olarak; 3 g/l NaCN, 12 g/l H202, 0.4 g/l Ca(OH)2, 24 saat çözündürme süresi, % 15 pülpte katı oranı, -53 mikron tane boyutu saptanmıştır. Bu araştırma kapsamında elde edilen bulgular sonucunda, 100 g/ton gümüş içeren ve yaklaşık 10 milyon ton birikmiş artığın değerlendirilmesi ile ekonomiye katkı sağlanırken, öte yandan mevcut koşullarda % 60 gümüş kazanma verimi ile çalışan tesisin % 80 gümüş kazanma verimine ulaşması ile de ülke ekonomisine yarar sağlanacaktır. Bu araştırma sonucunda, refrakter ve polimetalik sülfürlü Gümüşköy Cevherleri'nin siyanür ile çözündürülmesi sırasında hidrojen peroksit kullanımı ile minerallerin gözenekliliği arttırılarak kapanım halinde bulunan gümüşe siyanürün ulaşması sağlanmıştır. Hidrojen peroksit ile sülfürlü mineraller oksitlenerek sülfürlere bağlı gümüşün çözünmesi kolaylaşmış ve siyanür tüketimi azalmıştır. Bu çalışmada elde edilen sonuçlar, Gümüşköy gümüş cevherleri için optimum çözünme süresinin 48 saat yerine 24 saat, pülpte katı oranının ise; % 30 yerine % 15 olması gerektiğini göstermiştir. ıx

Abstract:
SUMMARY  Silver a dense metal has been known since ancient time, considered commercially to be a precious metal. Although silver occurs in the native form and as an alloy with gold (i.e. electrum), it is primarily cholcophile. The common silver sulfides include argentite (Ag2S), proustite (Ag3AsS3), pyrargyrite (Ag3SbS3), and argentiferous tetraedrite ((Cu,Fe,Zn,Ag)i2Sb4Si3). Silver also substitutes for metals, such as Zn in sphalerite, Pb in galena and Cu in chalcopyrite. The type of associations of the silver with the host mineral varies; galena-tetraedrite associations are characterized by intergrowths and totally enclosed particles. Associations with other host minerals are mostly dependent on the general textural features of the ore. For example, in a largely fractured pyrite or chalcopyrite, the silver minerals are distributed in fractures, in a compacts pyrite or chalcopyrite with very fine inclusions of minor minerals, the silver forms fine totally enclosed particles. According to Boyle (1968), the greatest silver concentration are in hypogene veins, lodes, stockwerks and mantos. Appreciable secondary silver enrichment may occur in near-surface parts of some of the veins because of supergene oxidation processes. Silver also commonly occurs in gold placers, veins and lodes. Silver is sometimes locally enriched in certain types of copper-bearing shales and in some copper and lead-bearing sand stones. In these occurrences, silver is mostly associated with the greatest concentrations of copper and lead, occasionally with uranium because of their similar solubilities. Silver may also occur in copper-nickel deposits associated with mafic rocks and in skarn-type deposits. Pegmatites have generally minor silver which, if present, is associated with the few scattered sulphide minerals in the bodies. About two-thirds of the world' s silver production are by-products or co-products of porphyry copper and base-metal sulfide ores. Among silver vein deposits, theepithermal silver-gold veins of Cenozoic age have dominated world production, followed by cordilleran veins, and silver, cobalt-nickel-arsenide deposits. The early metallurgy of precious metals was almost totally involved with gravity separation because of their conveniently high specific gravity. Even today the same form of gravity separation is used in the majority of the world's gold and silver recovery plants. Another early discovery was wetting of the gold by mercury and at about 1000 BC the amalgamation process was applied to gold and silver. Amalgamation evolved in to the Patio Process used in the Mexican Silver mines where the hooves of horses were used to mix the ore with mercury, copper sulfate and salt. Later, on the Comstock lode in Nevada, a variation of this method was called the Washoe Process. Today the use of amalgamation has virtually ceased, except for cleanup of the gravity concentrates, due to environmental reasons. During the long period of the 1800' s the chlorinating process became popular, being the first chemical method used for the dissolution of precious metals from ores. L.Eisner published the basic idea of leaching gold in cyanide solution and oxygen in the German Journal for Practical Chemistry in 1846. The reaction which Eisner, published in 1846 is given below; 2Au+4KCN+0+H20- >2AuK(CN)2+2KOH Although L.Eisner was the first to publish on the cyanide leaching of gold, Scotsmen, John S. Mac Arthur, a metallurgical chemist and two doctors who were brothers, Robert and William Forest of Glasgow, obtained the first British patent on the use of KCN for the dissolution of gold in 1887 and another in 1888 on the use of fine zinc particles as a precipitant for gold and silver from cyanide solutions. The first commercial use of cyanide for gold extraction was at the Crown Mine in 1889 and following that at Robinson Deep on the Witwatersrand in 1890 in New Zealand. In the United States it was first applied at Consolidated Mercur in Utah in 1891. The cyanide process was first applied to a silver sulfide ore at Sirena-Mexico in 1900. Almost hundred years after the invention of the cyanidation process for recovering gold and silver from its ores, this method being used successfully all over the world. During the this period equipment has changed in quality and size, and where difficult or refractory ores will not directly cyanide some ingenious soil has always come up with some methods of pretreatment such as flotation, roasting or chemical oxidation that permits adequate cyanidation. XIThe most common extraction processes used for treatment of precious metal ores include: -Gravity concentration (using jigs, tables, spirals, cones, etc.) -Amalgamation (with mercury) -Flotation (as free particles or adjoining to the base metal sulfide concentrates) -Pyrometallurgy (in the smelting and refining of base metal ores and concentrates) -Hydrometallurgy (direct cyanidation, cyanidation with carbon adsorption, heap leach, chlorination leach) -Combination methods (gravity or flotation concentration followed by cyanidation or roasting of flotation concentrates followed by cyanidation) The Kütahya 100th Year Silver Plant which is located in the Köprüören region of Kütahya Province, is designed to process one million tpy of silver ores having average 180 g/t Ag content in order to produce 122.4 tpy of pure silver. Five different types of deposits have been formed in the area and, depending on the formation silver contents vary between 70 and 460 g/ton Ag. Silver is produced with the following stages; crushing-screening, cyanide leaching, separation, fine filtration and smelting- electrolysis. In the Gümüşköy Silver Plant, ten millions tons of tailings have been disposed to the tailing pond with Ag content of 100 g/ton. Furthermore, the tailings also contain BaSCu with a content of 14.6 %; the low recovery in silver extraction is due to some problems related to the structure of ores, operating parameters in cyanidation and crushing processes. In this doctoral research; the recovery of silver from 100 th. Year Silver Plant tailings is investigated from the point of the mineralogical and cyanidation parameters and then a determination has been made of the possibilities of increasing the silver recovery of the plant. Beneficiation possibilities of barite is also studied in addition to silver recovery from the tailings. Chemical analysis of the sample, taken from the tailing pond showed that the plant tailings contain 100 g/ton Ag and 14.6 % BaS04. Additionally, tailings also contain; 4.93 % Fe203, 2.20 % Pb, 1.40 % Zn, 50.2 % Si02, 3.0 % S, 2.05 % As, 0.91 % Sb, 5.54 % A1203 and 1.34 % K20. The mineralogical investigation of tailings show that silver is mainly in the form of native silver, pyrargyrite, silveriferous tetraedrite, argentite and proustite. Also the size of the silver minerals were mostly, under 40 microns and the most of the silver minerals are coated by the other minerals. Besides, barite, galena, sphalerite, iron hydroxides, dolomite, cerrusite, antimonite, manganiferous rhinerals, quartz and some clay minerals constitute the ores. XIICyanidation tests were carried out in order to obtain the best Ag recovery from the tailings. The effect of cyanidation test parameters on the silver recovery, which are given below, have been investigated during the cyanidation tests. Cyanidation Test Parameters: -Leaching Time -Particle Size -NaCN Concentration -Pulp Density -Temperature -Oxidizing Agent Cyanidation test results which were carried out without using any oxidizing agent showed that it was necessary to use oxidizing agents in order to obtain higher silver recoveries. On the other hand mineralogical investigations have demonstrated that the most of the silver was coated by the other minerals. Therefore, hydrogen peroxide was used in order to oxidize sulfide minerals and to obtain porous structure necessary to permit the cyanide solutions to contact easily with Ag minerals. According to the porosity measurements of the sample under 74 microns, a 16 % increase of porosity was observed with the use of hydrogen peroxide. Porosity of the samples, with and without using of hyrogen peroxide under 74 microns was measured in TÜBİTAK, Seramic Section Laboratories, with the Micromeritics Autopore 9220 device. The following optimum conditions were found, after the cyanidation experiments on the tailing; Optimum Cyanidation Conditions for the Gümfisköv Silver Plant Tailings: - NaCN Concentration : 2 g/1 - H2O2 Concentration : 12 g/1 - Ca(OH)2 Concentration: 0.4 g/1 - Leaching Time : 24 Hours - Particle Size : -53 Microns -Pulp Density : 15 % A 45 % silver recovery was obtained after the experiments conducted depending on the optimum leaching conditions. Since it was possible to leach some silver from the plants tailings, it was decided to run similar cyanidation tests on the raw ores fed to the plant in order to see if there is same visible improvements on the total Ag recoveries. At the end of the cyanidation experiments on the feed to the Gümüşköy Silver Plant, the following optimum conditions were found: xixiOptimum Cvanidation Conditions for the Raw Ores Fed to the Plant ; - NaCN Concentration : 3 g/1 - H2O2 Concentration : 12 g/1 - Ca(OH)2 Concentration: 0.4 g/1 - Leaching Time : 24 Hours - Particle Size : -53 Microns -Pulp Density : 15 % 80 % of Ag recovery was obtained after the experiments which were carried out with the optimum leaching conditions. In conclusion, this research has demonsrated that the Etibank 100th Year Silver Plant recovery was increased from 60 % to 80 % by using H2O2 during the cyanidation and by grinding ores under 53 microns. From an economic aspect, this increase in the silver recovery rates and the evaluation og tailings will permit a six million USD gain in overall profits. xxv