Elektrik ark fırını baca tozlarının hidrometalurjik değerlendirilmesi
Hydrometallurgical treatment of electric arc furnace stellmaking flue-dusts
- Tez No: 14327
- Danışmanlar: DOÇ.DR. İSMAİL DUMAN
- Tez Türü: Yüksek Lisans
- Konular: Metalurji Mühendisliği, Metallurgical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1991
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 93
Özet
ÖZET Bu çalışmada Elektrik Ark Fırınlarıyla çelik üreten 3 ayrı tesisten temin edilen Baca Tozlarının NaOH ile çözümlendirilmesi ve böylece tozlar içinde mevcut Fe, Zn, Pb, Cd vb. gibi ağır metallerin kazanılma olanakları araş tırılmış ve bu doğrultuda proses tasarımında kritik ve önemli değerler olan çözümlendirme süresi ve sıcaklığı, kullanılan kostik (NaOH) miktarı, tane boyutu ve katı/sıvı oranının Zn, Pb ve Fe üç verimlerine etkisi incelenmiştir. Bu incelemelerin oluşturduğu genel çerçeve, prosesin bütünü içerisinde ön görülen kostik çözelti elektrolizine uygun konsantrasyonlarda elektrolitin elde edilmesidir. Bu nedenle parametrelerin değişim aralıkları, arıtıldığında elektrolit olarak kullanılacak olan liç çözeltisinin içermesi gereken serbest NaOH ve çinko konsantrasyonları, esas alınarak seçilmiştir. Ayrıca, bu metallerin insan ve çevre sağlığına etkisi, atık olarak depolanma ve çevreye atılma sorunları araştırılmış ve etkin öneriler sunulmuştur. Deneyler, 1- ve 2. Grup olmak üzere iki seri halinde yapılmıştır. 1. Grup Deneyler herhangi bir metalurjik ön işlem görmemiş tozlarla, 2. Grup Deneyler ise liç öncesi 700 C ' de 1 saat süreyle ön-redüklenmiş tozlarla yapılmıştır. NaOH çözümlendirmesi sonucu 1. Grup Deneylerde % 78 Zn, % BOPb, 2. Grup Deneylerde ise % 3h Zn, ve %3k Pb liç verimlerine ulaşılmıştır. Tez kapsamında yapılan deneyler sonunda; 95 C de, 400 g/l NaOH konsantrasyonunda, 1/5 K/S oranında, -200 mesh tane boyutlu numune 1 saat süreyle liç edildiğinde her iki deney serisinde de optimum verimler elde edilmiş tir. Liç artığında kalan demir, bazik sinter veya pelet üretiminde veya piroliz sonrasında gübre sanayiinde kos tik kalıntılarının giderilmesi suretiyle kullanılabilir. Liç çözeltisinden ise elektroliz yoluyla çinko tozu üretimi sözsonusudur.
Özet (Çeviri)
HYDROMETALLURGICAL TREATMENT DF ELECTRIC ARC FURNACE STELLMAKING FLUE-DU5TS SUMMARY Steelmaking dusts can be an important source of zinc and lead if these values can be recovered economi cally. The treatment or disposal of steel plant Electric Arc Furnace (EAF) dust has been given increasing attention in recent years for two main principal reason. Firstly, the dust is classed as a hazardous waste material under U.S. EPA Regulations which prohibit its disposal in dumps other than controlled landfill sites (Federal Register, Vol. *+5.l\lo:98, Section 261.32, page 3312U) because of the leachability of its toxic consti tuents (Zn, Pb, Cd and Cr). Its EPA assigned hazardous waste number is K061. Secondly, the dust contains certain metal values (like Zn and Pb) which may be economically recoverable. Other metallurgical dusts and waste materials, from both ferrous and non-ferrous operations, may require the same considerations as EAF Baghouse dust. Several studies have been carried out to examine various ideas dust treatment but few commercial plants are in operation. Technology employed uses pyrometal- lurgical techniques but a few hydrometallurgical plants are in operation in todays technology. The formation and characterization of EAF baghouse dust have been studied to determine if this dust is a suitable material for resource recovery. Arc Furnace VIdusts are considered to be composed primarily of a self- agglomerated collection of microfine physically and chemically complex particles consisting of complex oxides and ferrites. The composition of the dust is influenced directly by the type of scrap being melted. Carbon steel dusts tend to be richer in zinc and lead because of the greater use of galvanized and other coated products and post-consumer scrap in the melt. In the EAF, approximately 1,3 % to 1.8 % of each charge is converted to dust or fume. During melting and refining of stell, the gas leaving the furnace carries a substantial amount of fine dust particles. To protect the otmosphere, these particles are removed in cyclones, scrubbers and other similar devices. The dust particles are made up of two types of materials. Firstly, it consists of fine particles charged to the furnace such as those of iron oxides, calcium oxide and silica which are mechanically carried. away by the gas. Secondly, it consists of oxide particles of non-fer rous metals such as zinc ferrite, zinc oxide, lead oxide which evaporate at the high temperatures of steel bath and later condence and oxidize in the flue. Recent studies and literatures are referenced briefly as they pertain to the formation and characterization of dust, toxicity considerations and alternative dust treatment and disposal options. In this study, three different types of flue dusts which have been obtained from three different Electric Arc Furnace Steel-making Works, have examined. These dusts were equally mixed by weight and were screened un der -0.0775mm. (200 mesh). Table 1 showsthe size distri bution of the dusts, and Table 2 gives the VllTable: 1. Grain Size Distribution of EAF Baghouse Dust that were used in the all experiments. Weight Retained (So) 18 18 21 19 Chemical composition of the dust. Table: 2. Chemical Composition of the dust (Ldght.%) In the process desing, leaching duration and tem perature, caustic ratio, particle size and the effect of Solid/liquid ratio are critical and important parameters. In this study, the effect of these parameters, on the leaching efficiency of Zn, Pb and Fe are investigated. The general purpose of the leach experiments were pre- pearing a suitable electrolyte for the electrouiinning vmstep. In addition; the disposal of dusts in dumps and disposal regulations, the effect of these metals (Zn, Pb and Fe) to environment and human being life mere in vestigated and active suggestions uere represented. Experiments uere performed in two series. In the first group of experiments metallurgically non-treated dust uere leached uith IMaOH under the optimum experimental conditions uritten belou; Leaching temperature Leaching duration rJaOH concentration Feed (Particle)Size Solid/liquid Ratio Agitation 95°C 1 h. 400 g/1 -2DD mesh 1/5 6D0 min -1 From these group of experiments, 78% Zn and 80% Pb leaching efficiency uere obtained. 15.99% of the dust is zinc ferrite uhich hard to dissolve and thus a pre reduction step might be necessary tD upgrade the zinc and the lead efficiency. So, second group of experiments uere carried out. At 700 C, EAF dusts uere reduced in a mufl furnace for 1 hour in order to partly decompose the ferrite structure. Afteruards, pre- reduced dusts uere leached uith NaOH at the optimum experimental conditions uritten above, and 94% Pb and Zn efficiency uere obtained. The major chemical reactions can be expressed as follous: LEACHING 11 CEMENTATION: ZnO +2NaOH PbO +2NBÖH Si02+2NaQH Na“Pb02+Zn Na2Zn02 Na2Si03 + H20 Na2Pb02 + H20 + H20 Pb + l\la2Zn02 IXELECTROLYSIS: Cathode Anode Global ZnÛ”+ 2H“0 + 2e 20Hf ZnO~ + H2D Zn + 4DH HO + 1/20 +ee Zn + 20H”+ 1/2 0, After both experimental series, solid/liquid sepe- ration were done. Caustic leach residue uere washed with T IM.of l\laOH. Caustic leach residue, consisting mainly of zinc ferrites and iron oxides is thickened, filtered, dried and pelletized with possible addition of a reductant such as coke breeze, before used in industry. Caustic leachate is purified by zinc cementa tion to remove substances that have a detrimental effect on zinc electrodeposition. Lead-containing purification residue may be a suitable feed to a lead smelter. After words, electrowinning step comes and zinc can be produced as zinc powder. to b and toxi leve fore zinc make viab trea attr The e a lead city İs m seea pro dus le. t ot acti cau tech fro in ay n ble duct t tr A 1 her ve a stic nica m ca the ot b circ s or eatm arge meta nd m leach lly fea rbon st leach r e entir umstanc dispos ent at r, cent llurgic erits d -elec sible eel E esidu ely e es, s al er an on raliz al usa etail trowi meth AF ba es in limin ubsid edits -site ed fa stes ed st nning p od of r ghouse terms ated. ies, pr may be facili cility could b udy. rocess ecover dust a of Pb Houeve emium requi ty eco that c e comm appears ing zinc lthough and Cd r, under prices on red to nomically an also ercially
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