Atık Fe-mo-co Ferro Alaşımının Liç Kinetiği Ve Ürün Kazanımı

Abstract

Ferromolibden alaşımları günümüzde çelik üretimi için çok önemlidir. Çelik üretimi sırasında ferromolibden alaşımı ilavesiyle molibden çelik yapısına katılabilmektedir. Hatta saf molibden ilavesine göre çelik içerisine ferromolibden katılması, çok daha kolay çözünme sağladığından çoğu tesiste tercih edilmektedir. Kobalt da aynı molibden gibi alaşımlamada sıklıkla kullanılmaktadır. Kobaltı da yapısında bulunduran ferromolibden alaşımlarının üretimi sırasında önemli miktarlarda atık alaşımlar oluşabilmektedir. Bu atık alaşımların tekrar değerlendirilmesi ve içeriğinde bulunan metallerin ticari ürünler halinde kazanılması günümüz metal sektörü için önemli bir konudur. Bu tez çalışmasının amacı da atık haldeki demir, kobalt, molibden içeren ferro alaşımın hidrometalurjik yöntemle çözeltiye alınmasının ve bu metallerin her birinin ticari ürünlere dönüştürme deneylerinin incelenmesidir. Çevreci bir metalurjik üretim yöntemi olan hidrometalurjik üretim yöntemi deneyler boyunca kullanılmıştır. Deneyler, 100 ml’lik balonjojeler içerisinde, su ile ısıtmalı bir sistemle gerçekleştirilmiştir. Deneylerde çözeltiye almak için H2SO4 ve HNO3 asitleri kullanılarak, oksitleyici etkisi, sülfürik asit konsantrasyonu, karıştırma hızı, katı-sıvı oranı, çözümlendirme süresi ve sıcaklığı parametreleri incelenmiştir. Sıcaklık ve zaman bazlı deneyler sonucu liç kinetiği ortaya çıkarılmıştır. Bileşimde bulunan üç ana metalin de çözeltiye alınması için gerekli tepkimelerdeki aktivasyon enerjileri hesaplanmıştır. Yapılan hesaplamalarda, 33,36 kJ, 19,51 kJ ve 25,62 kJ aktivasyon enerjileri bulunmuştur. Çözünme mekanizmasının difüzyon kontrollü olduğu ortaya konulmuştur. Jander Üç Boyutlu Model’i tek tek üç metale de uygulanmış, bulunan değerlerden yapılan yorumla modelin difüzyon kontrollü mekanizmaya uyduğu kanıtlanmıştır. Çözünme gerçekleştirildikten sonra elde edilen, çözünen üç ana metali barındıran çözeltilerden uygun proses şartlarında, ticari safiyette MoS3, Fe2O3, Co(OH)2 kimyasalları elde edilmiştir.

In our day, ferromolybdenum alloys are quite important for steel production. By ferromolybdenum addition during the steel production, molybdenum can join in steel structure. So that it's preferred by many facilities to add ferromolybdenum into the steel instead of pure molybdenum due to the fact that it ensures much more easy dissolution. Also cobalt can join in structures as an alloy element. The waste alloys can be formed, after produce ferro alloys which contain cobalt. Assesment of waste alloys and recycling metals as commercially pure compound is an important issue for metal industry. The aim of this project is to investigate dissolution of waste ferromolybdenum alloy which contain cobalt by hydrometallurgical process and recovery of each three metals as commercially pure compounds. The hydrometallurgical production method used throughout the experiments which is known to be an environmentalist way. Experiments were carried out in volumetric flasks within a water heated system. In the experiments, H2SO4 and HNO3 were used for solution treat, and oxidizing effect, sulphuric acid concentration, stirring speed, solid-liquid ratio, dissolution time and temperature parameters were investigated. Leaching kinetics were undisclosed in consequence of temperature and time based experiments. Activation energies for all three metals in compound to be treated into solution were found. By calculations, activation energies were found as 33,36 kJ/mol, 19,51 kJ/mol and 25,62 kJ/mol. It's stated that dissolution mechanism is diffusion controlled. Jander 3 Dimensional Diffusion Model was applied to all three metals, based on found values, it's proved that the process is diffusion controlled. After the dissolution, all of these three main metals were obtained commercially pure as MoS3, Fe2O3 and Co(OH)2 under the appropriate process conditions. There are three methods applied in metal production: pyrometallurgy, hydrometallurgy and electrometallurgy. Hydrometallurgy is the most preferred metal production method due to its affordability, ability to utilize low-tenor ores, quality to help the high-purity recycling of seperate metals in a synchronous way, homogenious nature of its reactions in aqueous medium and controllability. Hydrometallurgic production begins with making the leching in an acidic or alkaline iye. The iye which includes metal, is seperated from leaching remnant. Lastly, with the use of various methods the metal compound is obtained. After the metals are solubilized they are recovered by being selective. First, the leaching solution is needed to be purified and enriched. Metal recovery, precipitation or electrolytic methods are realized. The advantages of this method are its frequent use to obtain metal from complex ores and its feasibilty to process residue, waste byproducts from oxidised and oxysulphide combined ores. And the disadvantages are the remaining of valuable materials in a waste solution after leaching process and the insufficient amount of leach on a mass per unit basis in especially large scale solutions. Leahing process is a total of heterogeneous reactions. While this heterogeneousity is between the different states of matter, generally the reactions take place in solid and liquid states. To understand a chemical reaction, the reaction must beanalysed from both termodynamic and kinetic perspective. From a general point of view, termodynamics analyses whether a rection will take place or not. On the other hand, kinetics looks at the speed of the reaction and the factors affecting it. Kinetics is interested in the mass change inthe unit of time. To understand the reaction speed in especially solid-liquid reactions, resolution systematics must be analysed during heterogeneous reactions. In solid-liquid reactions, the surrounding of the solid is wrapped with stagnant liquid film. The materialisation of the reaction depends on the reactant’s reaching to interface layer, diffused from film surface. This film layer is formed because the liquid sticks to the layer, holds on there and has viscosity. If the reactant can be diffused from film layer, it will reach to interface surface. This interface surface is known as Nerst Boundary Surface. The processing of the reaction is controlled by a certain phenomenon. Speed control can be a diffused or chemical reaction based on different parameters and features. While the reaction takes place in the interface, either chemical reaction or diffusion materialises faster. Based on how fast this takes place the mechanism which will control the reaction. If the chemical reaction taking place in the interface gets faster than the reactant which is diffused to the interface, the materialised process is named as diffusion controlled. If vice versa happens and the diffusion takes place faster, process is named as chemical controlled. The mechanism which will control the reaction shows change according to different factors. The basic determining parameters are fluid speed, temprature, reactant concentration. Through estimating activation energy, looking at the change of the reaction based on certain parameters, diffusion controlled reactions can be interpreted. However, there are many models in the literature putting forward the mechanism of the reaction. One of them is designed by Jander in 1927. It is a three dimensional model, based on core model. If reaction is diffusion controlled during solid state reactions, this model is often used for putting forward the reaction mechanism. This model is set forth with the help of parabolic speed evenness. Precipitation process is the last step of metallurgic process. Metals can be precipitated through many different ways. The ionic precipitation method is done through adding a non-ionic factor to the solution and producing metal composites in a selective way. The resolution of the solutions made through this method is low but the creation speed is high. Materialised reactions may include hydrolysis rections. The precipitation of metal composites is possible through electron transaction. Thim method is known as degraded precipitation. The metal which will be precipitated is degraded by a degrader to a lower load. At the same time, it is surely oxidised. In electrochemical precipitation method, yönteminde ise, a more noble metal is used for precipitating a more noble metal. To compare nobility, electrochemical potentials are used. With the help of electrochemical potentials, precipitating a metal in another metal solution becomes a possibility. Taking advantage of hydrogen’s asility to act sometimes as metal, sometimes as non-metal, it is often used in substitution reactions. Thanks to that, it plays a huge rol in producing metals through precipitation. By substituting hydrogen with copper, hydrogen with nickels, this metals can be produced. Aqueous solution can produce its own metal, if only an outer electromotor force is passed from the right source of current. This method is called electrolytic precipitation. The time and temprature experiments to determine leaching kinetics are executed with 100 milliliter volumetric flasks. In this volumetric flasks nitric acid and sulpuric acid concentrations are practiced together and in order to make heating homogeneous the glass with water in it is heated and volumteric flasks have reached certain temprature. During the experiment oxidising effect, sulphuric acid concentration effect, mixing speed effect, solid-aquatic ratio, mixing speed, resolving time and tempreature are analysed. The experiments to determine leaching’s optimum conditions were practiced with 50 mililiter solutions. Settling test are performed to realise the commercial recovery of the metals which are taken into the solution in optimum conditions. By using previous experiment outputs, 500 mililiters of solution in optimum conditions are prepared. For this experiments, a total 100 grams of ferromolibden powder was seperated into 10 grams and leached for 10 times. Through this, metals in ferromolibden powder were degraded. First, to recover the molibden in prepared solution, H2S gas was produced and this gas was passed from the solution. For this, powder FeS, including %29 of S, and 1/1 H2SO4 were reacted together with kipps apparatus. At the end, H2S gas was produced and this gas was passed from the solution. After all this process, MoS3, which has a commercal value in its ph volüme one. To equalise pH in the experiments, 5 M NaOH was used. Second, to produce a resoluted iron and transform the Fe+2 ions in the solution to Fe+3, %35 oxidised H2O2 was used. Until it has become pH 3, 5 M NaOH addition was the case. With this, alongside the increasing time, iron ions were precipitated. The sediments which were filtered with filtter paper, were processed in the oven at 700°C and it is deprived of H2O in its structure while leaving the way to the production of Fe2O3 having commercial value. Lastly, cobalt, which is a basic element, was brought to pH 9 with NaOH addtion at 60°C and was precipitated as Co(OH)2.