Magnetic Separation and Iron Ore Beneficiation Oct04

Magnetic Separation and Iron Ore Beneficiation...

Magnetic Separation and Iron Ore Beneficiation Magnetic separation is an old technique for the concentration of iron ores and for the removal of tramp iron. Since 1849, a number of patents on magnetic separation have been issued in USA, and texts of some of the patents before 1910 describe a variety of magnetic separators for mineral processing. Magnetic separation methods are used to take the advantage of the difference in the magnetic properties for separating iron ore from the non-magnetic associated gangue materials. Magnetic separation can be conducted either in a dry or in a wet environment, although wet systems are more in use. Magnetic separation is a physical separation of discrete particles based on the three way competition between tractive (i) magnetic forces, (ii) gravitational, hydro-dynamic drag, frictional, or inertial forces, and (iii) attractive or repulsive inter-particle forces. These forces combine to act differentially on particles of differing magnetic properties in the feed material. Fig 1 shows the principle of the magnetic separation. Fig 1 Principle of magnetic separation The forces in the magnetic separators which compete with the magnetic forces and act on all of the particles which travel through the separator are those of gravity, hydrodynamic drag, friction, and inertia. Depending on the type of magnetic separator, certain of these forces can have higher or lesser importance. The gravitational force is significant for large particles while the hydrodynamic drag force is significant for the small particles. Thus in the magnetic separator which treats large particles in dry form, the feed material passes through the force of gravity. The magnetic forces need to be sufficient to hold the magnetic particle against the competing force of gravity. In a wet separator for small particles, the magnetic force need to be larger than the...

Metallurgical Coal

Metallurgical Coal Metallurgical coal is also called ‘met coal’ or ‘coking coal. It is a bituminous coal which allows the production of a coke suitable to support a blast furnace (BF) charge. It is distinguished by the strong low-density coke produced when the coal is heated in a low oxygen (O2) environment or in absence of air to reduce mineral impurities (e.g. less sulphur, phosphorus). On heating, the coal softens, and volatile components evaporate and escape through pores in the mass. On cooling, the resultant coke has swollen, becoming a larger volume. The strength and density of coke is particularly important when it is used in a BF, as the coke supports part of the ore and flux burden inside the BF. Metallurgical coal possesses the ability to soften and re-solidify into a coherent, porous mass, when heated from 300 deg C to 550 deg C in the absence of air in a confined space. The conversion from coal to coke occurs in chambers called coke ovens where the volatiles from the coal escape, leaving behind what is referred to as metallurgical coke, which reaches a temperature of around 1,000 deg C to 1200 deg C before being removed from the ovens. The coking cycle is normally dependent on several parameters. Coke is used primarily as a fuel and a reducing agent in a BF. The gross calorific value (CV) of the metallurgical coal is greater than 5700 kcal/kg on an ash?free but moist basis. It presents unique plastic properties during carbonization which in turn produces a porous solid, high in carbon (C) coke. Metallurgical coals, when heated at a moderate rate in the absence of air, undergo complex and continuous changes in chemical composition and physical character. During carbonization, most bituminous coals, except those bordering...

Role of Concentration and Priorities in Effectiveness...

Role of Concentration and Priorities in Effectiveness Both the concentration and setting of priorities play a major role in an executive’s effectiveness. In fact, an effective executive does first things first and he does one thing at a time. The need of concentration is embedded both in the nature of the executive job as well as in him as a person. There are many apparent reasons for this. There are always more important contributions to be made than there is time available to make them. If someone analyses the richness of the important tasks to which the executive contributes and the time available with the executive for the tasks, then he comes up with an embarrassing situation which reveals a scarcity of time available for the work that really contributes. It is a fact that no matter how well the executive manages his time, the greater part of it is still not his own and hence, there is always a time deficit. The more an executive focuses on upward contribution, the more he needs fairly big continuous shares of his time. The more he switches from being busy for the achievement of the results, the more he has to make sustained efforts and these efforts require a fairly large quantity of time to bear fruit. And to ensure that this time which is really productive is available, the executive needs self-discipline and a very strong determination to say ‘No’. Similarly, the more the executive makes efforts at making strengths productive, the more he becomes conscious of the necessity to concentrate on the human strengths available to him on major opportunities. This is the only way to get results. But concentration is dictated also by the fact that most of the persons find it hard...

Low grade Iron Ore Beneficiation and the Process of Jigging Sep25

Low grade Iron Ore Beneficiation and the Process of Jigging...

Low grade Iron Ore Beneficiation and the Process of Jigging Iron ore resources are getting consumed at an accelerated rate because of the growth in the production of iron and steel. Due to this reason the availability of high grade iron ore is reducing and the supply of high grade iron ore to iron and steel plants is declining sharply. Hence, the scenario is steadily shifting towards the use of low grade iron ores and slimes which are stock piled in the mine’s sites for years. These dumped slimes also, in fact, falls in the category of low grade iron ore.  Also, some of the ores of iron have a complex mineralogical composition and do not respond to conventional beneficiation techniques. Modern beneficiation processes allow for effective and low cost upgrading of lump, fines and ultra-fines of such ores. Since the iron ores consist of several compositions, mineralogies, shapes, and sizes, so there is no ‘one size fits all’ approach to the beneficiation of iron ore. Most of the ‘run-of-mine’ (ROM) iron ore contain a large percentage of other materials which need to be removed through the process of beneficiation before the ore attains the specifications needed for its use. The extent of the beneficiation techniques employed depends on the level and nature of diluents and the form of distribution of the gangue and impurities in the ore structure. Liberation of ore is an essential step for making it responsive to the beneficiation techniques. For selection of appropriate techniques, it is necessary to carry out first the mineralogical assessment of the ore so as to get the insight into the ore and to know the gangue association, and grain size etc. There are several issues relating to categorization and beneficiation of low grade iron...

Bituminous coal

Bituminous coal Bituminous coal is an organic sedimentary rock formed by diagenetic and sub metamorphic compression of peat bog material. It is also called as black coal. It is often referred to as soft coal. However, this designation is a layman’s term and has little to do with the hardness of the rock. Bituminous coal is by far the largest group and is characterized as having lower fixed carbon (C) and higher volatile matter than anthracite coals. It is the type of coal which is most widely used in the world today. Bituminous coal is the second highest quality of coal (below anthracite) and the most abundant type. Usually, bituminous coal comes from fairly old coal deposits (around 300 million years old).The energy density of this coal is relatively high, therefore, releases a significant amount of energy when burned. Bituminous coal is defined as a medium?rank coal with either a gross calorific value (CV) on a moist, ash?free basis of not less than 24 mega joules per kilogram (MJ/kg) and with a Vitrinite mean Random Reflectance less than 2.0 %, or with a gross CV on a moist, ash?free basis of less than 24 MJ/kg provided that the Vitrinite mean random reflectance is equal to, or greater than 0.6 %. Bituminous coals are agglomerating and have a higher volatile matter (VM) and lower C content than anthracite coal. This coal is originated by coalification of plant matter deposited in sequences dominated by clastic sediments under diagenetic conditions (thermal and pressure mode) of a given coal basin. Coalification proceeded under geologic time scale. In various coal basins (coal seams) coal matter differs in regard of different primary composition of plant matter and sedimentary environment. Composition of coal (e.g. elemental composition, VM etc.) and mean reflectance of vitrinite reflect final stage of coal metamorphism of a given sedimentary basin. Bituminous...