.SUMMER INDUSTRIAL TRAINING REPORT on STEEL PRODUCTION PROCESS at BOKARO STEEL PLANT - SAIL Ankit Gourav (5912161) USN – 1SI12EE007 IV Semester Electrical and Electronics Engineering Siddaganga Institute of Technology, Tumkur 1 . CERTIFICATE This is to certify that the project entitled “STEEL PRODUCTION PROCESS” at SAIL- BOKARO STEEL PLANT has been carried out by Mr. Ankit Gourav from 30th June 2014 to 9th August 2014, under my supervision in partial fulfilment of his BE, Electrical and Electronics Engineering course at Siddaganga Institute of Technology, Tumkur I am satisfied with his sincere performance and study conducted by him in SAIL-BOKARO STEEL PLANT. The project is hereby approved as a bonafied work carried out and presented in a manner satisfactory to its acceptance area to the Electrical and Electronics Enginnering for which it has been submitted. I recommend submitting the project report. I wish him all success in life. This is also certified that the project work is original and has not been submitted to any other place. Project Guide Mr. Rajendra Kumar Jr. Manager - HRD Bokaro Steel Plant Date: 8th August 2014 SAIL 2 . ACKNOWLEDGMENT I am highly obliged to Mr. Rajendra Kumar -Junior Manager, HRD SAIL-BSL, my prime internal guide for his invaluable support, guidance and knowledge that he shared with me thereby aiding me in making this project a success along with different guides of each sections who provided their utmost working knowledge, which has broaden my area of interest and benefited mostly in completing the project. Their guidance and suggestions was always there without which it was a difficult step to complete the project alone. This training provided me some experience not only in practical aspects of industry but also in human relation, group work , individual work and provided great insights into the actual working of an industry. I hereby also declare that the contents in the report are true to the best of my knowledge. Lastly I thank faculty and staff members of Siddaganga Institute of Technology, Tumkur and Bokaro Steel Plant –SAIL which gave me an opportunity regarding training purpose and helped me in building some experience in my career. 3 . DECLARATION I hereby declare that the following documented project report titled “STEEL PRODUCTION PROCESS" is an authentic work done by me as a part of my industrial training in Bokaro Steel Plant, SAIL. I also further state that the project has been prepared by my own with the secondary data provided in the reports of the company, which were essential for the completion of the project. The project was undertaken as a part of the course curriculum of BE, Electrical and Electronics Engineering . Ankit Gourav (5912161) 1SI12EE007 SIT, Tumkur 4 ........................................................5 Cast House...................................................2 Types & Sources of Coking Coal...........................3 BOKARO STEEL PLANT.....................................................25 4...............................................................................................................................................................................................20 3............14 2....2 Blast Furnace and Accessories......................14 2............12 2 RAW MATERIAL HANDLING PLANT...............................................................................................................27 4..................................................................................................................................................................................................................................3 Zones in Blast Furnace....... Table of Contents 1 COMPANY PROFILE..............................................................................................................................................................................9 1......................2 SAIL Today..........8 1.......................................16 2.................................................................21 3.................3 Coal Handling Plant.....................................................................28 5 STEEL MAKING................................................................31 5 ................................................................................4 Hot Blast Section.1 BACKGROUND & HISTORY...................................................................................................................24 4...3 Material Handling Equipments..............................21 4 BLAST FURNACE.............................................1 Introduction............................................................................................................................................................................................................................................2 Different Raw Materials...........................26 4..1 Introduction.19 3 COKE OVEN & COAL CHEMICALS.................26 4........................................................16 2...6 1.....................20 3...............................5 Benefits of RMHP/OHP/OB&BP............4 Customers of RMHP.............................................................................................................................................................18 2..........1 Introduction.......................... ........32 5.............................31 5......................................................................................................................................................................1 Introduction...............................................................................2 Continuous Casting Shop...................................................................6 BOKARO STEEL PLANT ...................................................................42 7..................................................38 7 OTHER FACILITIES.................................................................................43 6 ..PRODUCT BASKET....................................................................2 Hot Metal Desulphurisation..............40 7.................42 7......37 6..........................................................................................41 7..............................................................................................36 6..............................3 Open /Twin Hearth Furnaces.............3 Slabbing Mill..............33 6 CASTING................4 Basic Oxygen Furnace (BOF)........................5 Cold Rolling Mill...................1 Steel Melting Shops.....................................................................1 Introduction....36 6.......................................................................................40 7.LD Converter...........................................................................2 Casting Preparation..........................3 Casting Process............................................................33 5..............................................................................................................................4 Hot Strip Mill..........................41 7............................. 5....................................................................... . 1 COMPANY PROFILE 7 . STEEL Authority OF INDIA LIMITED Satisfaction Customer Aspiration Unlimited Improvement Continual Leadership Market 8 .. Steel Authority of India Limited (SAIL) is the leading steel-making company in India. the builders of modern India worked with a vision . The steel sector was one amongst which to propel the economic growth. From April 1957. It is a fully integrated iron and steel maker.. Bokaro Steel Limited.1 BACKGROUND & HISTORY After independence in the formative years of an emerging nation – India. railway. It has triggered the secondary and tertiary waves of economic growth by continuously providing the inputs for the consuming industry. Since its inception. automotive and defence industries and for sale in export markets. SAIL is India's largest steel producing company with a turnover of Rs. Besides. SAIL manufactures and sells a broad range of steel products that are used for different purposes like domestic construction. the preliminary work was done by the Iron and Steel Ministry. Hindustan Steel Private Limited was set up on January 19. 9 .042 crore. it has immensely contributed to the development of technical and managerial expertise. engineering. SAIL is among the five Maharatnas of the country's Central Public Sector Enterprises. the supervision and control of these two steel plants were also transferred to Hindustan Steel. was incorporated in January 1964 to construct and operate the steel plant at Bokaro. SAIL has been instrumental in laying a sound infrastructure for the industrial development of the country. The President of India held the shares of the company on behalf of the people of India. 1954.to lay the infrastructure for rapid industrialization of the country. A new steel company. 1. Hindustan Steel (HSL) was initially designed to manage only one plant that was coming up at Rourkela. 47. power. For Bhilai and Durgapur Steel Plants. Durgapur. 1973 with an authorized capital of Rs. the Alloy Steel Plant and the Salem Steel Plant.. The company also owns iron ore. located principally in the eastern and central regions of India. Rourkela and Burnpur.2 SAIL Today SAIL today is one of the largest industrial entities in India. limestone and dolomite mines: domestic sources of raw materials. incorporated on January 24. as well as the export markets and a large pool of technical and professional expertise. MAJOR UNITS Major units of SAIL consist of integrated Steel plant. was made responsible for managing five integrated steel plants at Bhilai. These mines are situated close to the eastern and central regions of India giving company competitive advantages. 1. In 1978 SAIL was restructured as an operating company. The company. special steel plant & subsidiary units. The policy statement was presented to the Parliament on December 2. The Ministry of Steel and Mines drafted a policy statement to evolve a new model for managing industry. SAIL produces iron and steel at five integrated plants and three special steel plants. 1972. 2000 crore. This led to the formation of Steel Authority of India Ltd. The company has the distinction of being India’s second largest producer of iron ore and of having the country’s second largest mines network. Its strength has been the diversified range of quality steel products catering to the domestic. Bokaro. Integrated Steel Plants Bhilai Steel Plant (BSP) in Chhattisgarh Durgapur Steel Plant (DSP) in West Bengal Rourkela Steel Plant (RSP) in Orissa Bokaro Steel Plant (BSL) in Jharkhand IISCO Steel Plant (ISP) in West Bengal Special Steel Plants Alloy Steels Plants (ASP) in West Bengal Salem Steel Plant (SSP) in Tamil Nadu 10 . On this basis the concept of creating a holding company to manage inputs and outputs under one umbrella was mooted. raw material resources and other facilities to maintain its dominant position in the Indian steel market..) Limited S & T Mining Company Pvt. Limited Today. The objective is to achieve a production capacity of 26. Limited International Coal Ventures Private Limited SAIL SCI Shipping Pvt. SAIL Future Into the Modernization & Expansion SAIL. both within and outside India. Limited SAIL RITES Bengal Wagon Industry Pvt. Limited (BPSCL) Mjunction Services Limited SAIL SCL Limited SAIL-Bansal Service Centre Limited Bhilai JP Cement Limited Bokaro JP Cement Limited SAIL & MOIL Ferro Alloys (Pvt. Visvesvaraya Iron and Steel Plant (VISL) in Karnataka Subsidiary Maharashtra Elektrosmelt Limited (MEL) in Maharashtra Joint Ventures NTPC SAIL Power Company Pvt. the accent in SAIL is to continuously adapt to the competitive business environment and excel as a business organization. is in the process of modernizing and expanding its production units.2 MTPA of Hot Metal from the 11 A new unit coming up at ISP . Limited (NSPCL) Bokaro Power Supply Company Pvt. The production target of hot metal.91 2.2) Plant-wise Capacity Envisaged After Expansion (Mtpa) Plant Hot Metal Crude Steel Saleable Steel BSP 7.8 BSL 7.2 (23.5 7.33 0.6 MTPA (2006-07 – Actual).6 (21.23 0..18 24.59 23. 12 .37 SSP - 0.6 After Expansio n 26.48 0.4) 23.53 ISP 2.5 4.6 13.83 RSP 4.54. base level production of 14.18 0. RSP & DSP Expansion have been placed and these packages are in various stages of implementation.5 12.44 7. Orders for all major packages of ISP & SSP and part packages of BSL.0 6. BSP.43 VISL 0.13 The investment for modernization and expansion programme of SAIL is estimated at about Rs. crude steel and saleable steel after Expansion is indicated below: (Million tonne per annum) Item Hot Metal Crude Steel Saleable Steel Base Case (2006-07) Actual 14.5 3.22 Total 26.333 crores.00 6.2 3.53 DSP 3.5) 24. Objective of Expansion Plan is to expand the production.0 2.1 (20.34 ASP - 0.5 2. Bokaro has provided a strong raw material base for a variety of modern engineering industries including automobile. The Plant is hailed as the country’s first Swadeshi steel plant. Bokaro is designed to produce flat products like Hot Rolled Coils. LPG cylinder. Hot Rolled Sheets.. Its first Blast Furnace started on 2nd October 1972 and the first phase of 1.started taking shape in 1965 in collaboration with the Soviet Union.the fourth integrated plant in the Public Sector . material and know-how.7 MT ingots steel was completed on 26th February 1978 with the commissioning of the third Blast Furnace.3 BOKARO STEEL PLANT Bokaro Steel Plant . barrel and drum producing industries. Bokaro is producing top quality hot rolled products that are well accepted in the global market. Cold Rolled Coils. built with maximum indigenous content in terms of equipment. pipe and tube. Tin Mill Black Plates (TMBP) and Galvanized Plain and Corrugated (GP/GC) Sheets. It was originally incorporated as a limited company on 29th January 1964. Cold Rolled Sheets. With the completion of Hot Strip Mill modernization. Hot Rolled Plates. 13 . The construction work started on 6th April 1968. All units of 4 MT stage have already been commissioned and the 90s' modernization has further upgraded this to 4.5 MT of liquid steel. 1. and was later merged with SAIL. through the Public Sector Iron & Steel Companies (Restructuring & Miscellaneous Provisions) Act 1978. first as a subsidiary and then as a unit. 2 RAW MATERIAL HANDLING PLANT 2..1 INTRODUCTION 14 . Raw Material Handling Plant or Ore Handling Plant or Ore Bedding and Blending Plant play a very important role in an Integrated Steel Plant. stacking. It is the starting point of an integrated steel plant. Different types of major raw materials used in an integrated steel plant are Iron Ore Lime stone Dolomite Manganese Ore Ferro and Silica manganese Quartzite and Coal For Blast Furnace route Iron Making the main raw materials required are Iron ore lump Blast furnace grade lime stone Blast furnace grade dolomite Coke Sinter Scrap LD Slag Mn Ore Quartzite The main objective of raw material handling plant/ore handling plant/ore bedding and Blending plant is to: Homogenize materials from different sources by means of blending Supply consistent quality raw materials un-interruptedly to different customers Maintain buffer stock Unloading of wagons/rakes within specified time norm Raw material preparation (like crushing .). e. unloading. bedding. where all kinds of raw materials required for iron making/steel making are handled in a systematic manner. screening.g. blending. 15 . reclamation. crushing.. screening etc.. etc. Crushing of coke/flux and base mix preparation. Iron Ore Fines 3. Quality of raw materials (incoming) and processed material (outgoing) is monitored by checking the incremental samples collected from the whole consignment samples are collected at Auto Sampling Unit or Sampling Unit. Dispatch of processed inputs to customer units 2. The main functions of RMP/OHP/OB&BP are – Unloading& stackingof raw materials. Iron Ore Lumps 2. 2.. BF grade Dolomite 5. Manganese Ore 8. BF grade Lime 4. LD Slag Generated inside the plant Right quality raw material is basic requirement to achieve maximum output at lowest operating cost. Flue dust Generated inside the plant 11. Major Equipments Main Function 1 Wagon Tippler For mechanized unloading of wagons 16 . SMS grade Limestone 6. Mill Scale Generated inside the plant 10. SMS grade Dolomite 7. The samples prepared after quarter and coning method are sent for further analysis. Quality of raw materials plays a very important and vital role in entire steel plant operation. Screening of iron ore lump & fluxes.3 Material Handling Equipments Sl No.2 Different Raw Materials 1. Mixed Breeze Coke generated inside the plant (Blast Furnace & Coke Ovens) 9. Therefore. Bed formation takes place by means of to and fro movement of stacker. More is the number of layers. more is the bed homogeneity and lower the standard deviation.).. which adversely affects the blast furnace operation. from which this screened ore is supplied to blast furnace. Iron Ore Lump Screening : Screening of IOL is necessary because IOL coming from mines contains lot of undersize fraction (-10 mm. unloaded in wagon tippler or track hopper is being conveyed through the series of belt conveyors to the designated bed and stacked there with the help of stackers. IOF.this means that blending is a process of homogenization of single/different raw materials over a full length of pile/bed. Dolomite. etc. Number of optimum layers in a bed is controlled by stacker speed. 17 . Number of layers in a bed determines the homogeneity of the bed and is reflected in standard deviation of final bed quality. this undersize fraction (fines) is screened out at IOL screening section and then stacked in the designated IOL beds. For pushing the rakes inside the wagon tippler 2 Car Pusher 3 Track Hopper For manual unloading of wagons 4 Stackers For stacking material and bed formation 5 Barrel / Bucket wheel For reclaiming material also called blenders 6 Transfer Car For shifting equipments from one bed to another 7 Screens For screening to acquire desired quality material 8 Crushers For crushing to acquire desired quality material 9 Belt Conveyors For conveying different materials to the destination The material such as IOL.Homogenization increases rapidly as the no of layers exceeds 400 & the effect goes on decreasing after 580 layers. Blending is the mechanized process of stacking & reclaiming to get optimum result in physical & chemical charecteristics of raw material. Lime Stone. etc.) 85 %.e. Flux: Flux is a mixture of Lime Stone and Dolomite in certain proportion required in sintermaking.) is screened out and sent along with sinter to blast furnace as a nut coke. Flux acts as a binder in sinter making to increase the sinter strength..5 mm. mixed at certain proportion. Fraction of (-3mm. The under size material is crushed in the two stage roll crusher i. LD slag fines. Base Mix Preparation : In some plants. ( Minimum) Coke for base mix preparation is received from coke ovens and blast furnace.4 Customers of RMHP Sl. 2.) 85%. The main function of flux is to take care of gangue in blast furnace and also to increases the rate of reaction to form the good quality slag. mill scale. The size fraction ( + 12. called mixed breeze coke. (-3mm.e. No. crushed coke. primary and secondary roll crusher to achieve requisite size fraction of (-3mm. Base mix is a near homogeneous mixture of IOF. Rod mill or hammer crusher are used for crushing Limestone & Dolomite Lumps to required size i. Coke Breeze: Another important ingredient in base mix is crushed coke of size fraction (-3mm. flue dust. Customer Product/ Material 18 .) in crushed flux is 90% and more. crushed flux.. base mix or sinter mix or ready mix for sinter is being prepared at RMHP/OHP/OBBP for better and consistent quality sinter and also for increasing sinter plant productivity.) > 90%. dolomite fines & crushed coke. 1 Blast Furnace 2 Sinter Plant 3 Calcining/ Refractory Plant Size Ore or Screen Iron Ore Lump Mix or iron ore fines.5 Benefits of RMHP/OHP/OB&BP Provides consistent quality raw materials to its customer and also controlling the cost by: Minimizing undersize in iron ore lump & flux by means of screening Consistency in chemical & physical analysis by means of bedding & blending Input quality over a time period is known Metallurgical waste utilization 19 . nut coke SMS grade Limestone & Dolomite 2.. crushed Flux. into metallurgical coke.1 Introduction Coke making is the process to convert coking coal.. The process starts from unloading of the coal at the wagon tipplers & ends at sizing & transportation of coke to Blast furnace. 20 . 3 COKE OVEN & COAL CHEMICALS 3. through a series of operations. Coking coals are classified as: Prime Coking Coal (PCC) Medium Coking Coal (MCC) These are generally known as Indigenous coal. In addition to the above coking coal the following types of coal are also used for coke making in all SAIL plants. Formation of Coal: The plant & vegetations buried under swamp bottom during earthquakes or due to other environmental changes were subjected to heat & pressure. i. 21 .e.. all types of coal can’t be used for coke making. Over a long period of time water is forced out due to tremendous pressure of the overburden & due to heat generation. available in India. Imported Coking Coal (ICC) – Hard Soft Coking Coal (SCC) Coal is extracted from coal mines & processed in the coal washeries to lower down the ash content to make it fit for coke making. converting the mass to LIGNITE. During the initial period plants & vegetations decay to form peat. i.3 Coal Handling Plant Coke is one of the most important raw materials used to extract iron from the iron ore.e. 3. Continuous compaction & ageing converts the Lignite to Bituminous coal.2 Types & Sources of Coking Coal All coals are not coking coals. This process takes million of years. 3. From the coal yard. It is very important to stack different types of coal separately so as to avoid mix up of two types of coal. 22 . Mix up of coal is highly detrimental for coke making. It has been observed that the same coal blend. Pre-carbonisation technique is controlled by Coal handling Plant. Importance of Crushing: Fine crushing of coal is essential to homogenize the different inherent constituents of coal otherwise the coke produced will have different coking behaviour depending on its original coal structure. Here the wagons are mechanically clamped & turned through 180° to 360° to discharge the coal onto down below conveyors. Then through a series of conveyors the coal is stacked in coal yard through a Stacker. The system of crushing the coal & then blending is followed is RSP where as blending is done before crushing in BSP. Bulk density can also be increased by addition of briquettes. carbonization & post-carbonisation techniques used in Coke ovens. Bulk density is the compactness or close packing of the coal charge in the oven. These wagons get unloaded in wagon tipplers. The quality of coke depends upon the pre carbonisation technique. called a rake. are brought to the plant at one time. which is used in Blast Furnace. Crushing of coal is done by hammer crusher. The success of Blast Furnace operation depends upon the consistent quality of coke. Crushing also adds to improve the bulk density of coal charge in the ovens. Unloading & lifting of coal: Washed coals from washeries are received at the Coal Handling Plant by Railways wagons.. The coal yard is divided into separate segments where different types of coal can be stacked in respective earmarked areas. Crushing & Blending: The sequence of crushing & blending is different in different SAIL plants. Generally 58 wagons. coal is reclaimed through Reclaimer & by a series of conveyors gets transported to either crushers or silos as per prevailing system in different SAIL plants. Higher the bulk density better is the coke strength. This facility exists in RSP & BSP only. after crushed to a fineness of 70% against the normal requirement of 82%. 0%.e.2mm size coal after crushing. which causes problem in battery operation. This is known as crushing Index. by 1. during discharge from one conveyor to another conveyor through a chute. blending is to be done in a very accurate manner so that required coke property does not get adversely affected. denoted as M-10. Blending is generally done by adjusting the discharge of different types of coal from bunkers or silos to a common belt. Hence a proper mixing.. in a predetermined ratio to reduce the ash percentage of the blend coal. In case where blending is done after crushing proper mixing takes place at several transfer points. will result in deterioration in strength. The different type of coals gets thoroughly mixed during crushing where blending is done before crushing.e. Blending is a process of mixing the different types of coal. However over crushing is not desirable as this reduces the bulk density & increases micro fines. It is desirable to have 80% to 82% of .5% to 2. Importance of Blending: Blending plays a vital role in producing good metallurgical coke. PCC. during transportation to coal towers or service bunkers.3. blending of both types of coal is necessary. i. However. Soft & Hard. 23 . keeping the other coking properties intact.e. As evidenced from the table under properties of coal the Indigenous coals contain a relatively higher percentage of ash & Imported coals contain a relatively lower percentage of ash. i. MCC. i. .1 Introduction 24 . 4 BLAST FURNACE 4. The high alumina content makes the slag highly viscous and creates problems for stable furnace operation. reduces coke consumption in the BF 25 . The lumpy porous mass thus available / obtained is known as “sinter” Coal dust: Acts as an auxiliary fuel. The counter current nature of the reactions makes the overall process an extremely efficient one in reducing atmosphere. sinter and coke are the major raw materials for blast furnace smelting. It is the principal mineral in blast furnace for extraction of pig iron. generally rich in iron content varying from 60% to 66%. Iron ore: Iron bearing materials. The real growth of blast furnace technology came with the production of high strength coke which enabled the construction of large size blast furnaces. is sent through the bottom via tuyeres. Helps in reducing the melting point of gangue present in the iron bearing material and combines effectively with acidic impurities to form slag in iron making. Sintering is the process of agglomeration of fines (steel plant waste) by incipient fusion caused by heat available from the fuel contained in the charge. The heat is transferred from the gas to the burden and oxygen from the burden to the gas. Manganese ore: Acts as additive for the supply of Mn in the hot metal. The following raw materials used for the production of pig iron: (i)Iron ore (ii) Limestone (iii) Dolomite (iv) Quartzite (v) Manganese ore (vi) Sinter.32% for steel plant use Coke: Acts as a reductant and fuel supports the burden and helps in maintaining permeable bed Sinter: It is iron bearing material.route. The raw materials and their quality: In India steel is being produced largely through the blast furnace/ B. Gas ascends up the furnace while burden and coke descend down through the furnace. in which solid raw materials are charged from the top of the furnace and hot blast. Iron ore. provides iron to the hot metal. Mn ore is available in the form of combined oxides of Mn and Fe and content of Mn is about 31.F. Quartzite: Acts as an additive quartzite is a mineral of sio2 (silica) and under normal circumstances contains about 96-97% of sio2 rest being impurities. Limestone: Acts as flux. BF is a counter current heat and mass exchanger.O.. where the molten material is collected and is cast via the tap hole. The hearth. The sections from top down are Throat.. composed of two truncated cones placed base to base. Zn etc. Coal tar: Acts as an auxiliary fuel.Gas Shift Reaction Carbon Deposition Decomposition of Carbonates MIDDLE STACK ZONE Direct/Indirect Reduction Gas utilization LOWER STACK ZONE Calcinations of Limestone Reduction of Various elements Reduction of unreduced Iron Reduction of Silicon Reduction of Mn.3 Zones in Blast Furnace UPPER STACK ZONE Reduction of Oxides Decomposition of Hydrates Water . 26 . P.2 Blast Furnace and Accessories Blast furnace is basically a counter current apparatus. The shaft or stack. 4. The bosh parallel or belly and The bosh. Formation / melting of slag. where the burden surface is. where the reduction is completed and the ores are melted down. where the ores are heated and reduction starts. reduces coke consumption in the BF 4. thereby transforming the cold blast to hot blast. retains the heat from the hot flue gases thereby cooling the flue gases in one cycle. On blast: stove in the blast mode 27 . while it gives the retained heat to the cold blast in the next cycle. called gas cycle.. Air preheated to temperatures between 1. Each stove consists of a combustion chamber and refractory checker brickwork. There are 3 or 4 stoves for each furnace. called checker works. Mn.250°c is produced in the hot blast stoves and is delivered to the furnace via a hot blast main. Si and Sulphur Reaction impurities reach their final concentrations Falling/drop of Metal and Slag bring heat down into the Hearth.000 and 1. There are two cycles in the stove operation.250°c in the hot blast stoves. Air is preheated to temperatures between 1.4 Hot Blast Section Stoves are refractory heat exchangers.000 and 1. The hot blast reacts with coke and injectants. The refractory mass. through which hot products of combustion of BFG (blast furnace gas) and blast air flow alternately for specified periods. Final reduction of FeO and melting of Fe COMBUSTION ZONE Burning and combustion of Coke Complete reduction of Iron Oxide RACEWAY Coke and Hydrocarbons are oxidized Large evolution of heat HEARTH Saturation of Carbon with Iron Final Reduction of P. bustle pipe and finally through the tuyeres. 1. The function of Hot blast stove is to preheat the air before admission into the furnace through tuyere. forming the so-called raceway in front of the tuyeres. called blast cycle. On gas: stove in the heating mode 2. 4. The flue gases will be carried out through the chimney. The tapping time will be around 90 – 120 minutes. Process and parts of cast house: In the BF of single tap hole. The monkey is equipped with pneumatic or manual cinder stopper. Generally 8 -9 tapings will be done in a day. called raceway in front of the tuyeres. Cast house consist of tap hole. compensator. 4. iron and slag runners and their spouts and various equipments. This is called ‘on gases. as ready for on blast cycle The hot blast is delivered to the furnace via a hot blast main. there is a provision to flush the slag through the slag notch (called monkey) situated at a height of 1400 mm . Thus at any point of time two stoves are ‘on gas’ and one or two stoves are ‘on blast’ and the cycle is repeated continuously. In the first cycle the stoves are getting heated by using bf gas and/or coke oven gas for 2 hrs.5 CAST HOUSE Function The function of cast house is to tap the liquid metal and slag via the tap hole from hearth on scheduled time and separate the metal and slag in trough which is made up of refractory mass by skimmer block and direct metal to metal ladles and slag to the slag ladles or CHSGP. Thus hot blast is produced and this blast is sent into the blast furnace via hot blast main. The hot metal is tapped out at an interval of 1-2 hrs depending upon the furnace condition. The usual way of opening the tap hole is to drill the tap hole until the skull is 28 . forming a cavity.. ‘On blast’ will continue for one hour and will be followed by “on gas’ cycle. Oxygen enrichment is also done whenever necessary through the blast itself. The steam is injected for the humidification of the blast before pre-heating in the stove. Increasing the number of toppings can reduce flushing operation. bustle pipe.1600 mm from the axis of the tap hole. trough. In this cycle called ‘on blast’ the sensible heat that is stored the checker brickwork is carried away by the cold blast and is getting heated. tuyeres stock and tuyeres. A snort valve on the cold blast main regulates the volume of blast. bustle pipe and finally through the tuyeres. A mixer valve regulates hot blast temperature. Heated stove kept isolated. The hot blast reacts with coke and injectants. When the dome temperature reaches to the desired level the gas is stopped and cold blast that is coming from the power and blowing station is sent thorough the cold blast valve. Moulds are filled with the hot metal from the ladle at the spout. which is electrically or hydraulically operated The hot metal is collected in a refractory lined vessel called hot metal ladle and for safety reasons it is filled up to 85-90%. Similarly slag is collected in slag ladles and is dumped in the dump post or sends to slag granulation plants (SGPs) in which slag is granulated. After opening the tapping hot metal will comes out first.Hydro-pneumatic or electric drilling machines are used for opening the tapping 2.used for local placement of the metal ladle Auxiliary sections: The auxiliary section of blast furnace consists of following sections: 1. Cast house crane . The equipments available at the cast house are: 1. Pig casting machine Ladle repair shop: ladle repair shops provided for relining. At the end of the tapping the tap hole is closed with the mud gun. repairing and cleaning of the iron ladles. of moulds in one belt with lime coating arrangement underneath the machine. Generally the tap hole is located in such a way that after tapping minimum amount of metal should remain in the hearth. Sometimes oxygen lancing is carried out to melt the skull. After some time the liquid level in the hearth decreases and the slag that will be floating on the metal comes out of the tap hole. The control of this operation is accomplished by cutters located in the runners or with the help of rocking runner and pusher car. and this granulated slag is sold to cement manufacturers. Rocking runner . cooled by water sprays on the 29 . Drill machine .to divert the metal into a different metal ladle (tilting runner) 5. Ladle repair shop 2. Mud gun . Pig casting machine: there is double strand pig casting machines. PCM and foundry.Hydraulic or electric drilling machines are used for closing the tapping with anhydrous or water bonded tap hole mass 3.for material handling during cast house preparation 4. The skimmer plate separates the slag from the metal and diverts the slag into the slag ladles/SGP through slag runners.. Pusher car . reached. cranes for speeding up the job. So it is almost at the bottom most part of the hearth. Using these ladles hot metal is transported from blast furnace to mixers in SMS. The hot metal continues to flow down the bend runner from which it is diverted into individual metal ladles. Each machine contains no. Shop contains E O T. with the paws attached in both the sides of the ladle..(frames) to hold the ladle firmly. there is a lot of pressure on bf operators to lower the operating costs and maximize productivity. TWO STANDS. The fuels used for this purpose are pulverized coal. productivity or bf availability. without losing hot metal quality.g.to make a thick coating of lime on the moulds to avoid sticking of cold metal with the moulds. RUNNER. Auxiliary fuel injection In the present competitive environment.to lift the loaded liquid metal ladle. 30 . refractory mass required for blast furnace department is made and stored e. The challenge now is to achieve high PCI rates with cheaper. Tap hole mass shop: here. Equipments of PCM WINCH. LIME SPRAY UNITS. tap hole frame mass and runner mass etc.. and coal tar. mud gun clay. lower quality raw materials. bed while on movement and the pigs are separated from mould chain by knockout arrangement.to receive the liquid metal and to pour into the moulds through spouts.. One way to achieve this is by injecting auxiliary fuel into the blast furnace. 5 STEEL MAKING 31 .. nickel. The various processes involved in steel making are as follows. Main impurity present is Carbon and other impurities like phosphorus.010%. the sulphur content can be reduced to levels below 0. which is produced by Blast Furnaces. consists of various impurities. injection lance is lowered deep into the metal. silicon. 5.1 Introduction The Hot Metal.1% as per the requirement. phosphorus are removed and alloying elements such as manganese. and calcium carbide may be used in proper proportion. which is reduced below 0. Then start injection of the said material through the lance and is continued for 5 to 10 minutes 32 . In desulphurization methods alone lime. nonmetallic inclusions etc are also present. the hot metal must be de-sulphurised in another way. As the steel quality often requires a sulphur content of 0. chromium and vanadium are added to produce the exact steel required. Hot Metal contains around 4% of Carbon. In this way.2 HOT METAL DESULPHURISATION Sulphur is mainly present in the iron ore and in the coal. After proper positioning of the ladle. Steel such produced is the pure form of metal. HMDS—HOT METAL DESULPHURISATION BOF—BASIC OXYGEN FURNACE OH/TH—OPEN HEARTH/TWIN HEARTH ARS—ARGON RINSING STATION LF—LADLE FURNACE RH DEGASSER—RUHR –STAHL HERAUS (Process is named on a German town and a German scientist) VAD—VACCUM ARC DEGASSER VOD—VACCUM OXYGEN DECARBURISATION CCS/CCP—CONTINUOUS CASTING SHOP/ PLANT 5. or magnesium reagent.020% in the blast furnace is difficult from an economical standpoint. sulphur. Other impurities like sulphur. They are injected into the metal with special designed lances under a gaseous stream. Reducing the sulphur content to less than 0. Hot metal in a ladle brings to Desulphurization unit by EOT cranes or rail.005 %. Steel making is the process of purification of this Hot Metal.. 33 . iron ore etc. most open hearth furnaces were closed by early 1990’s. The tap-to-tap time of THF is cut by half since the furnace is tapped from both the hearth alternatively at an interval of one half of the heat duration in one hearth. the other will be in liquid period. energy efficient and simple. there by both the hearths are engaged in different operations. In SAIL modified form of Open hearth furnace is still in operation called Twin Hearth Furnace. While one is in solid period. Twin hearth furnace works on synchronization between the two hearths. in one hearth when melting starts the other hearth must be tapped.4 BASIC OXYGEN FURNACE (BOF). The fundamental principle of Twin Hearth Furnace is physical and chemical heat generated during blowing in one hearth is utilized in the adjoining hearth for preheating the charge. Basic oxygen steel making (BOF) or LD process replaced open hearth furnaces. Hot metal is then sent to converter. Ladle is then taken to slag racking machine to remove the slag formed during the injection process. dolomite.. O means oxygen as it is blown in converter and F means furnace.3 OPEN /TWIN HEARTH FURNACES One of the oldest established process of steel making. Twin hearth furnace consists of two hearths separated by a bridge wall with a common roof. making the process faster. Operational efficiency of the furnace is based on the equal duration of the both cold and hot period i. As compared to open / twin hearth process is fast. depending upon sulphur content in hot metal . Scrap is also used as a coolant and is also used in the process. Fluxes: Fluxes such as lime. 5.LD CONVERTER Basic Oxygen Furnace is commonly known as BOF process or LD process. low productivity and cumbersome operation. because of their fuel inefficiency. Tap to tap time in BOF is around 45-50 minutes.e. 5. Inputs: The major input materials in BOF or LD converter are: Metallic: Hot metal containing around 4% carbon is the main input in the BOF. The name BOF Stands B mean basic because basic refractory is used. When desired composition and temperature is achieved the steel is tapped. Impurities like Si. Oxygen Purity should be more than 99. As soon as the steel finishes the converter is lifted and tapping is complete. Charging sequence followed in BOF is first scrap and then metal. Main impurities carbon reacts with oxygen and is removed in the gaseous form. The slag is basic in nature. ferro manganese (Fe-Mn) etc are being added to make the desired grade of steel. P. Sample and temperature is also taken manually. In addition to metal.0%. Refractories 34 . Ferro-Alloys: while tapping the steel Ferro-alloy such as ferro silicon (Fe. Main advantage of nitrogen splashing is to increase the lining life of the converter. dolomite. After charging converter is kept vertical and lance is lowered in the converter through which oxygen is blown at a pressure of around 14 kg/cm2.. It is charged into converter with the help of EOT cranes. Converter is kept vertical and lance is lowered. iron ore etc are added to make slag. Converter blowing: The process of blowing means reaction of Oxygen with hot metal and fluxes in LD converter. When the blowing is complete converter is tilted to take out the slag in a slag pot. Nitrogen Slashing: After tapping. Process: Charging: The process start with mixer in steel melting shop. Oxygen: one of the important inputs comes mainly from captive Oxygen plants in addition to the Purchased liquid oxygen. the residual slag in the converter issplashed with the help of nitrogen. Metal is stored in Mixers and it is taken out as and when needed. Through the same lance nitrogen is blown which splashes the basic residual slag in the converter and gives a coating on the refractory bricks. The blowing process usually takes 17 mins. S and other non metallic impurities are removed in the form of slag. scrap is also charged.Si). Nitrogen: Nitrogen is used for purging and ceiling purpose. As per the grade of steel the Ferro-alloys are also added into ladle during tapping. During the blowing process fluxes such lime. silico manganese (Si-Mn). Tapping: tapping means discharging the liquid steel into ladle through the tap hole present in the converter by tilting it. It is also used for slag splashing. fire retarding jackets.. 35 . Refractory plays a very important role in BOF shop. Blowing should not be done if there is any water leakage in the lance. Number of heats made in a converter from one new lining to next lining is known as the lining life of the converter. Before charging. It should be dried by adding lime. Its tip is made of copper. blue glass. Primarily water is sprayed over the gases to separate the solid particles. We should strictly follow the safety norms. ladles etc are lined with refractory bricks. Lance: It is made of three concentric steel tubes to circulate water around the centre tube and pass oxygen through the innermost tube. Always a stand by lance is provided in a converter. Dolomite bricks or magnesia carbon bricks are commonly used in converter. Safety Aspects As we deal with liquid metal in the Shop personal as well as equipment safety is of large concern. Now a day’s all plants are trying to achieve higher lining life. Persons working in the steel melting shop should use personal protective equipment i. Cleaned gases are either collected in a gas holder or burnt in the atmosphere to control air pollution. In recent times magnesia carbon bricks have replaced dolomite bricks. converter. It can be rotated through 3600. As liquid metal is handled in BOF so all vessels like mixer. Charging and deslagging is done through mouth where as tapping of steel is done through a hole called tap hole. There should not be any water in the slag pot in which the slag is dumped. it should be ensured that no liquid slag is left in the converter.e. Equipments Major equipments in BOF shop are: Converter: A converter is an open pear shaped vessel made of steel and lined from inside with basic refractory bricks. gloves. Gas Cleaning Plant: A huge quantity of waste gases containing dust particles generated during the process is passed through the GCP. It protects the shell of vessel and retains the metal temperature. Different types of refractory as per their usage are given below: Converter Vessel: The bricks used here are basic in nature. 6 CASTING 6..1 Introduction 36 . accumulates liquid steel from the ladle and feeds to two or more moulds through SEN depending on the m/c and process. The basic design of the caster is to solidify liquid steel to its solid products uninterruptedly/continuously. Steel that is to be cast should not have high ppm of O2 otherwise casting cannot be done because O2 of steel will form unwanted oxides viz CaO. There are two types of casting practices are in use namely cold tundish and hot tundish practices.2 Casting Preparation 1. Tundish is a device through which continuity of the casting is maintained. 2. Continuous casting not only meets the higher production within same time frame but the quality of such products is quite lucrative and hence demanding. Steel that is to be cast is treated well at SRU for smooth casting. Tundish through which casting will be done is to be prepared. continuous casting products are the best compared to teeming of the steel to make ingots and then to roll the ingots to produce slabs or billets or blooms. Tundish is a device where it collects. After that tundish boards are fixed over the refractory lined. Liquid steel comes from the ladle into the tundish and in turn the tundish feeds the liquid steel into the mould through different outlet at the bottom of the tundish. Liquid steel comes from the ladle into the tundish. 3. For that the steel to be cast must be killed. For rolling to very thinner products.. SiO2. Tundish is made of steel and inside of which is lined with refractory bricks or castable. Preparing of the mould: 37 . Steel from which oxygen (dissolved in steel during steel making in BOF) is removed at SRU using highly deoxygenating elements like Al (Aluminum) Si (silicon) etc is called KILLED STEEL. Oxygen in steel is measured using Celox Temp and expressed in ppm. MgO and will be deposited over the entry nozzle and thus will restrict the flow of steel into the mould. In modern steel plants everywhere there is a demand for more and more quality finished products. Submerged entry nozzle (SEN) are fixed by clamping device in each of the tundish outlet. 6. Length of the slab/billet is maintained by using cutting torch/ shearing blades. In some cases temperature at which liquid steel gets solidified may be reached during casting. All sides of this mould is made up of Cu plate and heat from liquid steel immediately discharges trough the copper plates by mould cooling system Copper plates are cooled by circulating soft water through designed tubes in the form of coils. Mould is the most important equipment in the caster m/c. This phenomenon is called Chocking. which gets deposited over the steel into the mould and interrupts the steel flow. This DUMMY BAR head is packed. Immediate actions are to be taken and if necessary casting should be stopped without waiting for any other decision to be asked from anyone. Mould is made purely of copper as copper has the most heat discharge capacity than any other metal economically available. which is fed into the mould with a fixed rod or flexible chain. Abnormalities: During casting and form some unwanted hard oxides. Then one shroud is fixed at the bottom of the ladle collector nozzle so that no stream of liquid steel comes in contact with the atmosphere and no spillage occurs. This liquid steel gradually fills the tundish and from there liquid steel leaves tundish nozzle/TSG through SEN into the mould. An alarm is provided as soon as the difference of temperature raises more. primarily mould is prepared according to the shape and size of the product. So during fixing of the SEN proper care should be taken.3 Casting Process Liquid steel taken into ladle is refined at SRU is placed over the turret arm and ladle SG is fixed. It is very much hazardous part in caster m/c during casting. This is called Freezing. which caused solidification at SEN and restricts the steel flow. 6. For solidification of the initial liquid steel that enters into the mould one DUMMY BAR head is used. Here the difference of MOULD COOLING WATER Outlet Temperature & Inlet Temperature is monitored continuously. Sometimes casting is to be aborted due to this flow restriction. Initially steel rests on the DUMMY BAR head on which some chillers are placed to get the liquid steel freeze/solidifies quickly then the m/c starts with MOM & casting powder is to be sprayed continuously at a certain mould level. and then also casting continuity gets disturbed and casting stops.. 38 . The process continues after the DUMMY BAR head is disconnected as it reaches at its particular position. Some Casting Defects: Types of defects: • Surface cracks • Internal cracks • Blow holes. Pin holes etc Remedial measures: • Control of superheat of liquid steel (appropriate temperature) • Steel chemistry • Casting speed 39 .. Another major problem that hinders the casting process is Break Out. .1 Steel Melting Shops 40 . 7 OTHER FACILITIES 7. Bokaro has two Steel Melting Shops . SMS-I has 5 LD converters of 130T capacity each. The 41 . PLCs and technological control systems. Extra Deep Drawing. Suitable alloying elements are added to produce different grades of steel. CCS produces steel of Drawing.363 million tonnes has a wide range of products . with suppressed combustion system and Continuous Casting facility. The mill is equipped with state-of-the-art automation and controls.thickness varying from 1. unique in the country.SMS-I and SMS-II. Boiler and Tin Plate quality. 7. producing high quality slabs of width ranging from 950 mm to 1850 mm. It is capable of producing Rimming steel through the ingot route. SMS-II has 2 LD converters.2 Continuous Casting Shop The Continuous Casting Shop has two double-strand slab casting machines. Controlled heating in Soaking Pits. The Ladle Furnace is used for homogenizing the chemistry and temperature.2 mm to 20 mm and width from 750 mm to 1850 mm. WTCR. Deep Drawing. The shop has Hot and Cold Scarfing Machines and 2800 T Shearing Machine. close dimensional accuracy during rolling and hot and cold scarfing help produce defect-free slabs. The rolling capacity of the Mill is 4 MT per annum.3 Slabbing Mill Slabbing Mill transforms ingots into slabs by rolling them in its 1250 mm Universal FourHigh Mill. The fully automatic Hot Strip Mill with an annual capacity of 3. to produce internally clean slabs. The material is supplied as per Indian specifications and many international/ foreign specifications. The concast machines have straight moulds.5% pure Oxygen through it in the LD converter. 7. 7.. It produces various Killed and Semi-Killed steels. It also produces low alloy steels like LPG. each of 300 T capacities. CCS has a Ladle Furnace and a Ladle Rinsing Station for secondary refining of the steel.4 Hot Strip Mill Slabs from CCS and Slabbing Mill are processed in the state-of-the-art Hot Strip Mill. SAILCOR and API Grade. HR Coils rolled against direct shipment orders are sheared and finished to customer-required sizes and dispatched to customers. Hot Metal from the Blast Furnaces is converted into steel by blowing 99. using advanced systems for process optimization with on-line real time computer control. Hot Rolled Coil Finishing All the Hot Rolled coils from the Hot Strip Mill are received in HRCF for further distribution or dispatch. Cold rolling is done to produce thinner gauge strips of very smooth and dense finish. This complex made certain innovations for higher productivity to help re-build earthquake ravaged Gujarat. 75.000 Tonnes/ year respectively. 7.5 Cold Rolling Mill The Cold Rolling Mill at Bokaro uses state-of-the-art technology to produce high quality sheet gauge material. Hot Dip Complex Galvanizing The Hot Dip Galvanizing Complex integrated with the CRM produces zinc-coated Cold Rolled strips resistant to atmospheric. 45. 42 . with better mechanical properties than hot rolling strips. Tin Mill Black Plate and Galvanized Products.000 Tonnes/ year and 4. shop has two shearing lines with capacities of 6. this complex has maintained a high-standard of coating quality and its SAILJYOTI branded products enjoy a loyal market.. liquid and soil corrosion The first shop of Bokaro Steel to get the ISO 9001certification way back in 1994. 000 (mm) (mm) HSM HR Coils/ Sheets/ Continuous Tones) 3955 HRC Plates HR Sheets/ Plates Mill Shearing Line- - HR Sheets/ Plates I Shearing Line- HR Coil II Slitting Line CR Coils/ Sheets CRM-I CR Coils/ Sheets complex CRM-II CR Coils/ Sheets.6-4 1500 1.6 1850 650- 0.5 0.PRODUCT BASKET Mill Capabilities Shop Products Facility Annual Thickness Width Length Capacit range range (meter) y (.6 BOKARO STEEL PLANT .5 700- 0.8 1250 650- 0.3-1.63-2. complex DCR Mill F CRM 1. 7.22-0.6 -16 900- 5-10 1850 1800 2.6 1040 650- 1660 TMBP GP Coils & Sheets HDGL 100 170 GC Sheets 1250 By Products Nitration-grade Benzene Anthracene Oil Pitch Creosote Nitration-grade Toluene Extra-hard Pitch Light Solvent Naphtha Hard-medium Pitch (solid/ Still Bottom Oil liquid) Liquid Nitrogen Hot Pressed Naphthalene Ammonium Sulphate Phenol Fraction Mixture BF Granulated Slag 43 ..63-1.5-4.5-12 1.