Sintering Technology for Iron ores and Optimization of Sinter Machine Design Oct19

Sintering Technology for Iron ores and Optimization of Sinter Machine Design...

Sintering Technology for Iron ores and Optimization of Sinter Machine Design  The technology of sintering in its most basic form is very simple and has been in use since early twentieth century. However, while the basic technology is simple, control of the process relies on a number of extremely complex interdependent process parameters and requires a thorough understanding of the effect of these parameters on production capacity and sinter quality. Basic sintering technology The sintering technology is basically an agglomeration process for the iron ore fines which is dependent on heat to melt the surface of the smaller particles together to form larger agglomerates. A typical sinter plant consists of a number of sequential operating units with the sinter machine at the heart of the plant. The simplified process sequence is as follows. Raw materials consisting of iron ore fines, coke breeze, slag modifiers such as lime stone, dolomite, manganese ore, lime, quartzite, and sand etc., and waste materials such as mill scale, screenings, dusts, sludges, and converter slags etc. are batched and conveyed to a blending system. The raw materials are blended in a rotating mixing drum after addition of sinter return fines and water to achieve a green feed for the a process. The mixing process is normally referred to as ‘nodulizing’. The nodulized green feed is charged to the strand of the sinter machine on top of a sized hearth layer to form the ‘sinter bed’. This bed passes through the ignition furnace (hood) to initiate the reaction. Burners in the hood ignite the carbon in the green feed charged in the form of coke breeze. The reaction is propagated by chemical reaction between the carbon and the air sucked through the sinter bed by the exhaust fans. The sinter burns...

Understanding Sinter and Sinter Plant Operations Mar15

Understanding Sinter and Sinter Plant Operations...

Understanding Sinter and Sinter Plant Operations               Sintering is a process of agglomeration of fine mineral particles into a porous and lumpy mass by incipient fusion caused by heat produced by combustion of solid fuel within the mass itself. The sintering process is a pre-treatment step in the production of iron, where fine particles of iron ores and also secondary iron oxide wastes (collected dusts, mill scale etc.) along with fluxes (lime, limestone and dolomite) are agglomerated by combustion.  Agglomeration of the fines is necessary to enable the passage of hot gases during the blast furnace operation. Sintering has been referred to as the art of burning a fuel mixed with ore under controlled conditions. It involves the heating of fine iron ore with flux and coke fines or coal to produce a semi-molten mass that solidifies into porous pieces of sinter with the size and strength characteristics necessary for feeding into the blast furnace. Although simple in principle, sintering plant requires that a number of important factors in its design and operation be observed to attain optimum performance. A simplified schematic flow diagram of sintering process is at Fig 1.  Fig 1 Simplified flow diagram of a sintering process  There are basically the following three types of sinters. Non flux or acid sinters – In these sinters no flux is added to the iron ore in preparing the sinter mix. Non flux sinters are very rarely being produced these days. Self fluxing or basic sinters – These are the sinters where sufficient flux is added in the sinter mix for producing slags of desired basicity (CaO/SiO2) in blast furnace taking into account the acidic oxides in the blast furnace burden. Super flux sinters – These are the sinters where sufficient flux is added in...

Sinter Quality and Process of Sintering Iron Ores Nov21

Sinter Quality and Process of Sintering Iron Ores...

Sinter Quality and Process of Sintering Iron Ores Sinter is normally the major component of the blast furnace (BF) charge burden. Sinter consists of many mineral phases produced during process of sintering of iron ores. The quality and properties of sinter are dependent on the mineral structure of sinter. However, since the sintering conditions are usually not uniform throughout the sinter bed, the phase composition, and therefore the sinter quality, varies in the sinter bed. The structure of sinter is not uniform. It consists of pores (of varying sizes) and a complex aggregate of mineral phases, each with different properties. It is the combination of these pores and mineral phases, and the interaction between them that determines the sinter quality, but also makes the prediction of sinter properties very difficult. Though a large number of investigations have been carried out on sinter, still the correlation between the chemical composition and mineralogy of sinter with its properties and behaviour is still not clearly understood. Schematics of sinter mix and the product sinter are at Fig 1. Fig 1 Schematics of sinter mix and product sinter  Sintering process is a generic term that is used to describe the process of agglomeration of a green mix of iron ores, fluxes and coke and plant solid wastes having a particle size of -10 mm so as to produce sinter  which can withstand operating pressure and temperature conditions existing in a BF. Solid wastes such as dusts, sludges, slags and mill scales etc. are used for their utilization in sinter mix because of the complex chemical structure and mineral components of these materials. The process of sintering is described in detail in a separate article which is available under the link http://ispatguru.com/the-sintering-process-of-iron-ore-fines-2/ During the process of sintering, as the...

Iron Ore Sinter

Iron Ore Sinter  Iron ore sinter or simply called sinter is usually the major component of a blast furnace iron bearing burden material. Sinter normally consists of various mineral phases produced by sintering of iron ore fines with fluxes, metallurgical wastes and a solid fuel. Coke breeze is normally used as fuel in the sinter mix since it supplies necessary heat energy for sintering of sinter mix. Fig 1 shows a piece of sinter. Fig 1 A piece of sinter  In sintering, a shallow bed of fine particles is agglomerated by heat exchange and partial fusion of the still mass. Heat is generated by combustion of coke breeze admixed with the bed of iron ore fines, fluxes, and metallurgical wastes (sinter mix) being agglomerated. The combustion is initiated by igniting the fuel exposed at the surface of the bed, after which a narrow, high temperature zone is caused to move through the bed by an induced draft applied at the bottom of the bed. Within this narrow zone, the surfaces of adjacent particles reach fusion temperature, and gangue constituents form a semi liquid slag. The bonding is affected by a combination of fusion, grain growth and slag liquidation. The generation of volatiles from the fuel and flux materials creates a frothy condition and the incoming air quenches and solidifies the rear edge of the advancing fusion zone. The product sinter consists of a cellular mass of sinter mix materials bonded in a slag matrix. Important factors that affect the granulation efficiency and permeability of the sinter mix are water addition, particle size distribution, ore porosity, surface properties of the iron ore and the wettability of the iron ore. During sintering process, coke breeze increases the temperature of the sinter mix within the sinter bed...

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...