Coal based Direct Reduction Rotary Kiln Process Feb14

Coal based Direct Reduction Rotary Kiln Process...

Coal based Direct Reduction Rotary Kiln Process The coal based direct reduction rotary kiln process was developed for converting iron ore directly into metallic iron without the melting of the materials. The process has the advantage of low capital expenditure and no requirement of coking coal. The metallic iron in this process is produced by the reduction of iron oxide below the fusion temperature of iron ore (1535 deg C) by utilizing carbonaceous material present in the non-coking coal. As the iron ore is in direct contact with the reducing agent throughout the reduction process, it is often termed as direct reduced iron (DRI). The reduced product having high degree of metallization shows a ‘honeycomb structure’, due to which it is often called sponge iron. Coal based DRI plants are flexible with respect to plant location since non-coking coal is widely distributed in large deposits and is easy to transport. Most plants employ reduction process which is carried out in rotary kilns. These plants use wide variety of raw materials and non-coking coal. The quality of these materials has direct bearing on the process as well as the product. Some plants do not use iron ore directly. These plants use iron ore pellets in the rotary kiln. Raw material mix consisting of iron ore, dolomite and non-coking coal is fed at the one end of the rotary kiln and is heated by coal burners to produce DRI. The product DRI along with char (sometimes called dolo char) is taken out from the other end of the kiln. Apart from this, primary air and secondary air are supplied to the kiln to initiate the combustion and sustain the reaction process in the kiln. Raw materials The main raw materials for the production of DRI by...

Geology, Prospecting and Exploration for Iron Ore Deposits Apr09

Geology, Prospecting and Exploration for Iron Ore Deposits...

Geology, Prospecting and Exploration for Iron Ore Deposits Iron has been known since antiquity. Iron is ubiquitous in the lithosphere as either a major constituent or in trace amounts. In abundance it ranks fourth behind oxygen, silicon and aluminum. Iron ores have a wide range of formation in geologic time as well as a wide geographic distribution. These ores are found in the oldest known rocks in the crust of the earth, with an age in excess of 2.5 billion years, as well as in rocks formed in various subsequent ages. In fact, iron ores are even forming today in the areas where iron oxides are being precipitated. Several thousands of iron occurrences are known throughout the world. They range in size from a few tons to several hundreds of millions of tons. Iron ore deposits are distributed in different regions of the world under varied geological conditions and in different geological formations. The largest ore concentration is found in banded sedimentary iron formations of Precambrian age. These formations constitute the bulk of iron ore resources of the world. Iron ores occur in a wide variety of geological environments in igneous, metamorphic or sedimentary rocks, or as weathering products of various primary iron bearing materials. Iron ores can be grouped into types of similar geological occurrence, composition and structure. The following is a simplified classification which is based on genesis of the deposits and geological environment. It shows the main modes of occurrence of iron ores as well as it illustrates the varied geology of iron ore deposits. Igneous ores -These iron ore deposits are formed by crystallization from liquid rock materials, either as layered type deposits that possibly are the result of crystals of heavy iron bearing minerals settling as they crystallize to...

Understanding Iron Ores and Mining of Iron Ore Apr03

Understanding Iron Ores and Mining of Iron Ore...

Understanding Iron Ores and Mining of Iron Ore Iron (Fe) is an abundant and a widely distributed element in the in the crust of the earth, constituting on an  average ranging from 2 % to 3 % in sedimentary rocks to 8.5 % in basalt and gabbro. Its supply is essentially limitless in almost all regions of the world. However, most of this iron is not in a form which can be used in current iron making practices. Hence only that part of the total iron in the crust of the earth which is available to the steel industry both economically and spatially, may correctly be termed iron ore. However, what constitutes iron ore varies widely from place to place and time to time. There are many factors which determine whether iron bearing mineral can be classified as an iron ore, but basically it is a question of economics. Keeping this concept in mind, a logical definition of iron ore for commercial purposes is ‘iron bearing material that can be economically used at a particular place and time under then current cost and market price conditions.’ Because iron is present in many areas, it is of relatively of low value and thus a deposit must have a high percentage of Fe to be considered ore grade. With the advent of improved methods of beneficiation, concentration and agglomeration, the variety of iron bearing materials that can now be used has been broadened and many low grade material types which were once considered uneconomic, are now being considered as iron ore. Typically, a deposit must contain at least 25 % Fe to be considered economically recoverable. Over 300 minerals contain iron but five minerals are the primary sources of iron ore. They are (i) magnetite (Fe3O4),...

Processes for Beneficiation of Iron Ores Mar28

Processes for Beneficiation of Iron Ores...

Processes for Beneficiation of Iron Ores  Iron is an abundant element in the earth’s crust averaging from 2 % to 3 % in sedimentary rocks to 8.5 % in basalt and gabbro. Because iron is present in many areas, it is of relatively low value and thus a deposit must have a high percentage of metal to be considered ore grade. Typically, a deposit must contain at least 25 % iron to be considered economically recoverable. Over 300 minerals contain iron but five minerals are the primary sources of iron ore. They are (i) magnetite (Fe3O4), (ii) hematite (Fe2O3), (iii) goethite (Fe2O3.H2O),  (iv) siderite (FeCO3), and (v) pyrite (FeS2). Mining of iron ores requires drilling, blasting, crushing, screening, and blending of the ores. Crushing and screening are an integral part of ore producing facilities. Crushing usually involves a primary crusher and secondary crushers operating in closed circuit with vibrating screens. Equipment selection is determined largely by the friability of the ore. Most of the screening operations on high grade ores are dry except when the fines fraction can be effectively upgraded by desliming. Iron ores normally fall within one of the three categories namely (i) direct shipping, or high grade ores, which contain enough iron to be charged to the iron making furnace directly and may only require crushing, screening, and blending, (ii) associated low grade merchant ores which occur around the high grade ores that can be mined concurrently and which require minor upgrading by washing to increase their iron content, (iii) low grade ores that requires extensive crushing, grinding and concentration to produce an acceptable concentrate. The iron ores that fall within these three categories have quite different processing requirements. To obtain a uniform product, ores of different grades, compositions, and sizes...

Use of Iron Ore Pellets in Blast Furnace Burden Jun13

Use of Iron Ore Pellets in Blast Furnace Burden...

Use of Iron Ore Pellets in Blast Furnace Burden  Pelletizing is a process that involves mixing very finely ground particles of iron ore fines of size less than 200 mesh with additives like bentonite and then shaping them into oval/spherical lumps of 8-20 mm in diameter by a pelletizer and hardening the balls by firing with a fuel. It is the process of converting iron ore fines into ‘uniformed sized iron ore pellets’ that can be charged directly into a blast furnace. Fig 1 shows iron ore pellets. Fig 1 Iron ore pellets  There are several iron ore pelletizing processes/technologies available. However, currently, straight traveling grate (STG) process and grate kiln (GK) process are more popular processes. The physical properties of iron ore pellets are given below. •     Size – 8-20 mm •     pH (40 gm/L, 20 deg C; slurry in water) – 5.0 – 8.0 •     Melting point – 1500-1600 deg C •     Bulk density –  2.0 -2.2 t/Cum •     Tumbler index (+6.3 mm) – 93-94 % •     Abrasion index (-0.5 mm) – 5-6 % •     Compression strength (daN/p) – Around 250 •     Porosity – > 18 % The chemical analysis of iron ore pellets is given below. BF grade                     DRI grade Fe                                            %         63 – 65.5                       65 -67.8 SiO2 + Al2O3                         %              < 5                                 <5 CaO + MgO                            %           Up to 3                      Up to 0.10 P, max                                     %              0.05                              0.05 S, max                                     %              0.01                              0.01 Basicity, min                           %              0.5 Disintegration (-3.15 mm)   %                                                     2 Swelling Index                        %            13-18 Reducibility                             %                65 Different ISO standard tests for pellets are given in Tab 1 Tab 1 ISO standard tests used for BF pellets ISO standard test Measurement values Purpose ISO 4700 /Crushing strength  daN Pellet cold strength ISO 3271 /Tumble strength Fractions +6.3 mm...