Chapter 11 - Physiochemical separation of iron ore

11 - Developments in the physiochemical separation of iron ore

With the depleting reserves of high-grade iron ore in the world, froth flotation has become increasingly important to process intermediate- and low-grade iron ore in an attempt to meet the rapidly growing demand on the international market. In over half a century's practice in the iron ore industry, froth flotation has been established as an efficient method to remove impurities fro m iron ore. In this chapter, the industrial practice and fundamental research activities of iron ore flotation are reviewed. The latest innovations in iron ore flotation at major iron ore operations around the world are introduced. The development of flotation routes fro m direct an ionic flotation to reverse cationic flotation, and the rising of reverse anionic flotation in China in recent years is discussed. Although direct anionic flotation was the first flotation route employed in the iron ore industry, it was later largely replaced by the more efficient reverse cationic flotation route. The application of reverse anionic flotation in Ch ina in recent years effectively overcomes some flaws of reverse cationic flotation such as high reagent cost and high metal loss in desliming. The reagents used in iron ore flotation, including starch, amines and fatty acids, and the mechanisms of their interactions with the minerals in iron ore are examined. The p resence of some specific impurities other than quartz in iron ore, such as alu mina containing minerals, i.e. kaolinite and gibbsite, and phosphorous, is detrimental and attracts penalties. The removal of these specific impurit ies has received increasing attention in the iron ore industry. The industrial pract ice and latest research activities in this area are closely reviewed.

Froth flotation has been widely used in upgrading iron ores. Iron ore flotation can be performed in two technical routes: direct flotation of iron oxides and reverse flotation of gangue minerals with depression of iron oxides. Nowadays, reverse flotation is the most commonly used route in iron ore flotation. This review is focused on the reverse flotation of iron ores, consisting of reverse cationic flotation and reverse anionic flotation. It covers different types of collecting agents used in reverse iron ore flotation, the surface characteristics of minerals commonly present in iron ores (e.g., iron oxides, quartz, alumina-bearing minerals, phosphorus-bearing minerals, iron-bearing carbonates, and iron-bearing silicates), and the adsorption mechanisms of the collecting agents at the mineral surface. The implications of collecting agent–mineral interactions for improving iron ore flotation are discussed.

One of the main challenges in processing fresh ferruginous quartzites is to obtain high-quality iron ore concentrates containing more than 70% total iron and less than 1.8% silica to produce DR pellets and hot Briquetted Iron (HBI). Currently, it is widely recognized that the most effective methods to achieve high-quality iron ore concentrates is through reverse flotation using cationic amine collectors in an alkaline medium. However, due to the very fine impregnation of magnetite in quartz, the insufficiently complete release of magnetite even with fine grinding, and the proximity of the flotation (surface) behavior of the separated minerals, high-quality concentrates are not always achievable in the flotation process. Consequently, exploring methods to enhance the efficiency of flotation separation of minerals and improve concentrate quality remains a pertinent issue. Historical studies have shown that electrochemical treatment can adjust the properties of reagents, enhance their effect on specific minerals, and thus control the flotation process. The efficiency of quartz and other silicates flotation by amines significantly depends on the ratio of ionic and molecular forms of the reagent in aqueous solutions of the collector and in the flotation pulp. Altering this ratio can impact the outcomes of reverse cationic flotation of iron ores. It is feasible to change the ratio of the amine forms through electrochemical oxidation or reduction of the reagent solution. Moreover, the electrochemical treatment facilitates the dispersion of the amine in the aqueous medium and its physical adsorption on minerals. Therefore, electrochemical pretreatment of amines can be considered a promising method for intensifying the reverse flotation of iron ore. This paper presents research results aimed at improving the quality of the oversize of the fine screening of ordinary magnetite concentrate from Mikhailovsky GOK, named after A.V. Varichev, through the use of electrochemically treated solutions of cationic amine class collectors in the process of reverse cationic flotation. The research findings confirmed the feasibility of using preliminary diaphragmless electrochemical treatment of reagents Tomamine RA-14 and Lilaflot 811M (esters of monoamine of different composition) for the targeted modification of their properties and for increasing the efficiency of reverse flotation. Consequently, the silica content in the flotation cell product decreased from 1.66–1.7% to 1.51–1.56, with the grade of total iron exceeding 70%.

The paper is about the froth flotation process and its application. It is a metallurgical process for the extraction of metals in a pure state from their ores: especially for sulfide ores. Froth flotation is one of the steps which is generally performed before roasting and it deals with the surface chemistry of liquids and of the minerals to be separated. This process requires a particular setup to be performed which contains different components. Surfactants play the most important role here. Different types of surfactants are used in different ways and each of them plays a crucial role like, collectors, frothers, froth stabilizers, depressants and activators, pH regulators etc. The sulfide ore flotation process can be studied by both chemical and electrochemical phenomena considering the interfacial energies. A broad application of this process in industrial field is the flotation of iron ores which is of two types: direct and reverse flotation. The later one is again based on two different types as cationic and anionic reverse flotation. In all these processes different types of flotation reagents are used. Another application is separation of malachite and azurite ore using sulfidization flotation.

Effect of a low-molecular-weight polyacrylic acid on the coagulation of kaolinite particles

Interactive effect of minerals on complex ore flotation: A brief review

Flotation is one of the main concentration processes being employed for many classes of minerals (sulfides, oxides, silicates, phosphates, for example) at different particle sizes. In the iron ore industry, reverse quartz flotation has been successfully employed for particle sizes below ISOfim after the desliming process. The high demand for iron ore products has made flotation the main process for concentration in this industry, thus a better understanding of its mechanisms and the effect of the particle sizes in the process has become imperative. Flotation tests were carried out with three different size fractions of an itabirite iron ore, obtained using cyclone classification after desliming. The results showed distinct behaviors of the different size ranges. Higher etheramine dosages are required when coarse and fine fractions are floated separately and also this procedure is more sensitive to variations in etheramine dosages and pH values. The differences in particle size distributions and the specific surface area may explain the different flotation behavior of the distinct size fractions. The split flotation circuits for coarse and fine particles indicated an increase of 3% points in the metallurgical recovery with reduction of SiO2 content in final concentrate, increase of etheramine dosage and reduction of corn starch dosage. Economic feasibility analysis indicated a positive net present value of 50 million of dollars with split circuits for coarse and fine particles, considering a production of 10 million tons per year of pellet feed.

Role of silica and alumina content in the flotation of iron ores

Investigation of Adsorption Mechanism of Reagents (Surfactants) System and its Applicability in Iron Ore Flotation – An Overview

The depletion of high-grade iron ores has necessitated the beneficiation of low-grade iron ores. Flotation is considered the most efficient operation to upgrade the iron content of fine-grained ores that do not respond to gravity or size classification units. Out of several reagents used in iron ore reverse flotation, depressants play a crucial role in selectively making the iron oxides hydrophilic and prohibiting them from reporting to the gangue-rich froth phase. Starch is widely used as the depressant in iron ore flotation. The present paper attempts to highlight different facets of starch as an iron ore depressant. It reviews the important research papers that discuss the origin and chemistry of starch, starch-iron oxide interaction mechanism, and the application of different types of starches and their alternatives in iron ore flotation.

The iron ore deposits are sedimentary in nature. In 2021, approximately 1.95 billion metric tons of crude steel were produced globally, compared to 2.6 billion metric tons of usable iron ore. Iron ore is the primary source of the iron and steel industries, which in turn are essential to maintaining a strong industrial and economic base. Globally, 86% of the total iron produced is used in steelmaking. The most important iron ore minerals include hematite, magnetite, and taconite. The other iron ore minerals include goethite, laterite, etc. Hematite and magnetite are most commonly exploited for their iron values. Considering the non-renewable nature of iron ore, there is a paradigm shift towards the upgrading and beneficiation of low-grade iron ore. The widely accepted techniques for beneficiation include jigging, magnetic separation, enhanced gravity separation, froth flotation, etc. Owing to density contrast, iron can be separated from the gangue in simple jigging cycles. The electromagnetic laboratory-scale Wet High Intensity Magnetic Separator (WHIMS) removes fine magnetics and para-magnetics from mineral slurries. The physical and chemical properties of the ore mineral, as well as their mutual relationship, have a large impact on the beneficiation efficiency. In most of the processing units, the small, dense particles report to the tailing fraction, causing a significant loss in ore values. In such challenging cases, the enhanced gravity technique is useful. It is a combination of centrifugal force and gravitational force that facilitates the separation of low-density ore minerals and gangue. The paper focuses on the importance of a characterization study for the success of beneficiation.

Investigation of complex multiphase flows by advanced optical methods at the example of the flotation process of fluorite

Currently, a small range of commercial collectors is available for the use in reverse iron ore flotation at Vale. This input represents a considerable unit cost, being essential for the concentration of low content itabiritic iron ores. The present work evaluated the reverse cationic flotation of an itabiritic ore with low iron content (39.6 % Fe) from the Iron Quadrangle (BR) in bench scale tests, focusing on the use of new collectors to remove coarse quartz. The sample presents 19% of its particles as oversize in the 0.150 mm sieve. The poor flotation of coarse quartz particles (>0.150 mm) causes significant problems in various iron ore flotation circuits by contaminating the concentrate. The study evaluated the performance of 10 new collectors from the etheramine family with different degrees of neutralization and at different collector dosages. The flotation process variables were set as industrially practiced at the Cauê iron ore plant (BR). In tests varying the specific collector dosage, the non-neutralized etheramines showed improved performance compared to the current 50% neutralized etheramine used in the plant, achieving industrial targets: concentrate SiO2 content rate lower than 4.5% (1.4%), tailings iron content lower than 23% (18.94%), metallurgical recovery greater than 66% (74,8%), and Gaudin Selectivity Index greater than 6.6 (10.5). The 0.150 mm oversize in the concentrate, mostly coarse quartz particles, was reduced from 5.7% down to 1.2%, indicating the potential for the industrial application of non-neutralized etheramines in the recovery of coarse quartz.

Froth flotation of Arufu ore was carried out at varying particle sizes after characterization. Fifty (50) kilogram crude sample of the ore was sourced from Arufu zinc mine in Arufu town of Nassarawa state, Nigeria. The whole sample was crushed out of which five (5) kilogram was sampled out using random sampling method. One kilogram each of the resulting sample was then ground and sieved to three particle sizes viz; 63 µm, 90 µm and 125 µm. Chemical analysis of the representative sample of the sourced ore was carried out using Energy Dispersive X-Ray Fluorescence Spectrometer (ED –XRF). 250 grams of the 63 µm sample was charged into Froth flotation cell mixed with water at a ratio of 1:4 to form slurry. The Slurry formed was condition to a pH of 9, while other froth flotation reagents were added one after the other. This resulted in froth and depressed samples, which were dewatered after 24 hours and samples picked for compositional analysis. The procedure was repeated for 90 µm and 125 µm. The characterization of head sample revealed that the ore contains predominantly 36.80%ZnO (26.29% Zn), 31.1 % SiO2 alongside other trace mineral as gangue in the ore. However, Froth flotation studies of the ore at varying particle size revealed that, appreciable amount of mineral of interest (ZnO) was lost to the tailing at sieve sizes 63 µm and 90 µm. This was attributed to over-grinding above the ore’s liberation size phenomenon which has been proven to have adverse effect on the mineral’s quality and overall separation efficiency. It was concluded that the froth flotation is best carried out at a particle size of 125 µm, pH of 9, using potassium ethyl xanthate (PEX) as frother to yield concentrate grade of 50.21 % ZnO (35.93 % Zn) at a recovery of 46.3%. This was re – cleaned to yield high grade of 82.36%ZnO (66.42%Zn). The re – cleaned concentrate produced falls within the standard requirement of 65 % Zn needed as a charge into the blast furnace for Zinc metal production.