Iron Making - 2 PDF

# **Iron Making** ## **Introduction** - In the history of human civilization, the intentional heating of iron mineral with charcoal was the beginning of iron making. - It was first developed at Egypt in the year of 6000 BC. - Now-a-days most advance iron making processes are developed. - Generally...

# **Iron Making** ## **Introduction** - In the history of human civilization, the intentional heating of iron mineral with charcoal was the beginning of iron making. - It was first developed at Egypt in the year of 6000 BC. - Now-a-days most advance iron making processes are developed. - Generally 2 types of iron making processes are used: - Blast furnace process - Sponge iron making process ## **Blast Furnace Process** ### **Raw Material used for Iron Making:** - Generally 4 types of raw materials are used for iron making: - Iron bearing material (iron ore, sinter, pellet) - Metallurgical coke (made by carbonisation process) - Flux (acid, basic both fluxes are needed) - Air (hot air) ### **Approximate quantity of raw material for producing 1 tonne of pig iron from the blast furnace:** | Material | Quantity | |---|---| | Iron bearing material | 1.5 - 2.5 tonnes | | Coke | 0.4 - 0.5 tonnes | | Flux | 0.3 - 0.4 tonnes | | Air | 4 - 5 tonnes | | **Total** | **6.2 - 8.4 tonnes of material** | - The total charge is about 6-8 tonnes for producing 1 tonne of pig iron. ## **Iron Ore** - It is the most abundant (mostly available) material available in the earth crust. - There are different types of iron ore available in the earth crust. Such as: - **Oxide:** - Haematite (sp.g. 4.5-5.3) - Magnetite (sp.g. 4.9-5.2) - **Hydroxides:** - Limoniti (sp.g. 4.0-4.4) - Goethith (sp.g. 4.0-4.4) - **Carbonate (Most Kiderites)** - Siderite (sp.g. 3.8-4.1) - Sparthose - **Sulphide:** - Pyrites - Pyrrhotile - **Complex one:** - Silicate - Ilmenite (FeO-15.002) (sp.g. 4.5-5.0) ### **Classification of Iron Ore According to their Appearance:** - **Red ore:** - Haematite (HCP) - Magnetite (BCC) (volume, metalic) - **Reddish brown ore:** - Lemoniti - **Black ore:** - Sideriti - **Brown one:** - Lemoniti (ball, dustom) - **Grey or white one:** - Sideriti (maand natterirodees ud shan) ### **Classification According to their Gangue Association:** | Nature | Gangue Contented | |---|---| | Siliceous | Silica & Aluminavarf mani gid | | Aluminous | Clay | | Angilaceous | Clay | | Calcareous | Limestone | | Bituminous | Coal matter | | Titaneferious | Titanium | ## **Evaluation of Iron Ore** - The value of an iron ore deposit depends on the several factors: - Richness - Location - Composition of the gangue - Treatment and preparation needed before smelting - End use ### **Richness** - Richness means percentage of metallic iron in the ore. - The richer the ore the lesser will be the amount required to produce a unit weight of pig iron - The iron ore contain higher amount of metallic value then very less amount of ore require to produce 1 tonne of pig iron. - Richer ore required less amount of coke & flux for iron production. ### **Location** - The location of an ore both geographical and geological is very important. - **Geological location:** related to wheather open cast mine or is deep mine. - **Under ground mining:** required expensive excarston but open cast mine is easier to operate or mining of the ore - **In geographical location:** it is related to the transpotation ## **Gangue Material** - The gangue material also affect to the DRI process (direct reduce iron): otherwise blast furnace is used - The gangue found then it is name to the DRI process. ## **Evaluation of Flux** ### **Definition of Flux:** - Flux is a substance which when used durning the smeting process, lowers the softening point of the slag and reduces the viscosity of slag. ### **The available bare value depends on the baricity of the slag under operating condition.** - **In blast furnace the baricity is calculated by this ratio:** - 1/ % of basic oxide present in the slag / % of all acid oxide - (CaO + MgO)/ (SiO2 + P2O5). - Usually the ratio is about 1.2-1.3. So, for evaluating the flux there is an another formula is used: - % of (CaO + MgO) / % of SiO2. B = baricity of the Blf - **It also required heavy cost because of installation of railway harbour (CRIH).** - **It also affect the manufacturing cost because of the metal.** ## **Composition of Gangue** - The composition of gangue associated with one or more other oxides. - The effect of associated gangue is very important because, the associated gangue may be entirely stay with the slag, partially stay with the slag on remain with the metal. - The initial condition is the best condition for associated gangue material. - If the oxides remain with metal during smelting process, that type of ore is not use for the extraction of metal. ## **Treatment & preparation needed before smelting:** - The treatment & preparation needed before, it is charged into the blast furnace. - If very high amount of preparation needed, then, it is not use for the extraction process otherwise the manufacturing cost increases. - Sometimes fines are also charged after at aglomonation process because fines are enrich metallic value as compare to lump ore. ## **End use:** - End use means the deciding the value of ore. - There are two ways of wring iron one for iron production. ## **The flux should contain minimum of phosphorus, Sulphur, silica & alumina.** - The Lower earthy impurities; the heigher is its value as a fluxing. - In general calcium carbonate contain should not be less than 40% - 95% in the flux and the other impurities should be less than 3%. - The size of flux +10-40 mm is taken as a charging size of the flux ## **Blast Furnace Fuel** ### **Metallurgical Coal:** - Generally blast furnace uses coke as a fuel. But it is the carbonised product of bituminous coal. - Those coals are used for coke making are called metallurgical coal. - __Function of coke:__ - Coke fulfils the 3 major rules in the blast furnace: - It is a fuel providing heat for melting the metal and slag and for all blast furnace reactions. - It generate reducing gas for the reduction of iron oxide. - It support the total burden of the blast furnace with out fragmentation. - Coke provides permeable bed through which slag and metal parsed down to hearth, no n. - It carbonikes the iron and lowering the melting point of iron. ## **Properties requirement of coke which is used in BIF:** - The efficiency of BIF, directly depends on the quality of coke. - Three qualities are: - Chemical composition - Reactivity - Size range - Thermal stability at high temp. - Strength and abrasion resistance ### **Chemical composition:** - The useful component of the coke is fined carbon, which is the fuel as well as reducing agent in the blast furnace. - Except carbon, coke contain ash, moisture, volatile matter and other impurities. - Other matters are increase, reduces the available carbon, and also the ash go which contain silica, alumina, calcium oxide to increases the gangue material content in the blast furnace. - An increases ash contains content of coke by 1% resulting decrease is production by 3-6% and increases the coke consumption by 4-5%. - It also increases then fein requirement in the blast furnace hence chemical comporition reeverly affect the production of blast furnace. ### **Reactivity:** - It may be defined as the rate at which carbon atom at tt of coke react with oxidiling gares like oxygen, CO₂, t 1 - A heigher reactive coke may react with carbon dioxide, from the asen ascending gases in the blast furnace and get consumed in the stack and losses it strength. - If the reactivity is less then, it will not easily react at the tuyere for zone to form reducing gases and heat. - Rea A Reactivity is mealice by; - CRI (Coke reactive Index) - CSR (Coke strength after reaction) ### **Thermal Stability:** - The most important parameter of the coke is size range and strength. - Size range and strength are mutually interdependent. There is narrow size range is ured for the coke otherwile it may affect the distribution and ascending flow of gas. - The coke size always chooser longer than the ferron ore rize to get better permeability. - The average coke to bunden rize ratio 4:1. - The general size of cake is +40-80mm. ### **Thermal Stability:** - Durning the desend of coke from stack to tuyere the temp. ofcoke gradually increases up to 11500-1600 cm. - When the coke gets heated it begins to contract in larger size begins to differential expansion, contraction takes place causes degradation. - Lange coke has less thermal stability as compare to smaller cdce. ### **Strength Abracion Resistance:** - Coke should be of high strength and abrasion resistance because form the coke cake oven to blast furnace tuyere, it involves with large amount of drop and flows at several places. - It has to be seobstain subitend 20-25m and alco border. - For getting the value of strength and abrasion resistance, tumbler, shatter & micum teet are carried out. ## **Preparation of Blast Furnace Fuel is India:** - Blast furnace required coke as a fuel which is produced from metallurgical coke. - Coke is made by carbonication process and it is produced in coke oven. - Now-a-days recovery type coke ovens are used where bob products are collected to obtained different ureful gares and material. - The ones are usually 400-600mm wide and 1300-140 mm long and it's height does varry for 4-7 metre. - Several such champber about 15-80 numbers are put together to forem coke oven battery. - The gap between two adjscent chamber are the heating chambers where fuels are burn to heat up the chamber. - The chambers are lined with silica brick wherce below 3mm coke coal fines are charged. - General carbonisation perioded is 16-20 house. - After carboniration coke is pushed out and quenchel immediately either by water or nitrogen where crushing rection where vizelng carried out and finally send to the blast furnace. - Generally Indian coals are not use because it has a high ash contain so, ver coal is imported form other countres. - **Alternate fuel:- Auxiliary fuel:-** - Coke is a non renewable source of fuel. So, nowadays every attempt is made decrease consumption by substituting other alternative fuels. - It is also very expensive and takes major expence for the production of pig iron. - So, different types of alternative fuels are used to reeduce the production cost of pig iron. - The alternative fuels are: - Natural gas, oil, coal tar, powderized coal, formed coke, charcoal and ferero coke. - For getting the heat inside the blast furnace, we can substituti the coke by natural gas, oil, coal tar, pulverried coal, those are injected from the tuyere. ### **Formed Coke:** - Formed coke: (non coking coalt iron bearing) This substitute of conventional coke is recently developed i-e formed coke. - It is also called moulded solid fuel, where non coking coal is mixed with the iron bearing. - Both arce mixed by bindern & moulded by pretting. ### **Advantages:** - Cheaper non coking coal are used to make the formed coke. - Choose of coal according to their gangue material. ### **Ferro Coke:** - Ferro coke: (iron bearing fines + non-metallurgical coalt) When iron bearing fines and non-metallurgical coke mixed together and carbonired then the product is obtained is called ferro coke. - The propertion of iron making bearing fines in ferro coke is about 15-20%. ### **Advantages:** - Non metallurgical coal is weed directly as a fuel in the blast furnace. - Total fuel requirement inside the furnace is reduced since certain propertion of iron is charged as pre reduced iron. - Coke consumption is the blast furnace decreases. - Blast furnace productivity increases / it improved. - Production cost is low. - Alternative fuel: formed coke, coal fare, pulverried coal, natural gas, oil, charcoal & fern's coke. ### **Mining:** - India: Odisha, Chhattisgarh, Joda, Goa, Madhya Pradesh, Keenjhar, Nemeendi, Karnataka, cinghkhun, jajpure, Barisu, odlika, Goa, Maharashtra, Mayurbhayirin, Kialburu, Andra Pradesh, Gunkhin, Kialburu, Kenalk, Rajsthan, Tamil Nadu. # **Burden Preparation:** ## **Burden Quality:** - To achieve smooth operation in the blast furnace, the burden should have following qualities: ### **Physical Qualities:** - Close rize range of the change material with minm fines. - Ability to with stand the physical stress develop durning transpotation, changing and inside the furnace. - Non- decripitating nature / high thermal stability. - Ability to with stand mildly reducing condition at a temperature without breaking and Jourg. - It should have bulk reducibility. - Low swelling tendency durning reduction. - High softening temperature with narrow range of fusion. ### **Chemical Qualities:** - Burden should have high percentage of iron & Low percentage of gangue in containg: - 1) Iron - 2) Silica, Aluminum - 3) Other gangue materials. - Proper overall chemistry of the burden to ensure de-sulphurisation of metal & absorption of coke ash in slag. - Proper overall chemistry to ensure clean slag and metal at minimum temperature & free flour of metal and slag from the furnace opening. ## **Agglomeration:** - Agglomercation is a process where value of fires matexld are made lumpy mass which is sultable for charging into the blast furnace. - The different process of agglomeration process are: - Sintering - Pelletising - Briquettisting - Nodecliving - Vaccum Extrusion ### **Sintering:** - Sintering may be defined as a process of agglomeration where are fines are heated its incipient fusion tenip to form bulky porous mais structure. ### **Principle of Sintering:** - Sintering is carried out by using a mixture of iron fines, coke fires, flux fines, all are mixed together with required properction and heated about 1200 to 13000 by a burner with the down draught or up draught condition. - At this temp. the different zone are form is the sinter and finally the sinter are obtain which is usefe for the blast furnace. - It is the batch of sinter machine where cold charge is filled on the grate & it ignited at the top. - The process u-room ren with down drought condition where alx is suction at the bottom. - When heating is takes place at the top differrent zones are form: i.e cold charge, drying zone, hot sinter, cold sinter. - All the zones are formed gradually from top to bottom, finally sintering takes place. - The agglomeration takes place in the combustion zone where temp. ratres upto 1200- 1300℃. - At this temp. different types of bond are formed between the particles, due to this bond fines particles are attached together to forem lumpy mars. - There are crushed in to required rize & charged into blast furnace. ### **Dwight- Lloyed Sintering machine:** - It is also called continous intering machine where are fines are filled aref of endless bond of pallets moving over static wind box. - **Over Static wind box. ** It's depend developed by diight- Noyed is mexico. - It is a machine acher where pallets are moving endles trade over the rail & it's is attached with 2 huge pulley out of which one pulley is driven by motor. - The raw materials are loaded at one end of machine & top layeret His ignited immediately when it comes under ignition head. - As the pallets moves the ruction of air takes place by the wind box and "Sintering" is completed when the pallet trip Reached to anotheres ends. - **5. At the other end rinter coke drops, when the pallet moves upside down, the coke is breakage.** - **6. The required size sinter is send to the blast frennas. The fines are again send to the sintering machine.** - **7. Sintering machine, conset of different parts.** - Storage bbins, mixer (S), feeder (S) eto, - Charge leveller, - Ignition hood, - Pellets, - Drive mechanium, - Sinter breaker, screen, cooler etc, - Wind box, dust extractor, exhaust fan, chimney. - **Depth of bed:** - Cold sinter. - Hot sinter & preheating of air. - Combustion zone. - Preheating zone. - Drying zone. - Cold charge. - Grate (erijusd fo ### **Mechantum of Sintering** - Treld ignition att of bres - Triable Sinter. - Strong - Sinter - Dry heating - Time, extend - Durning sintering on a static bed, the zones are formed in the order of cold charge, drying, pre heating, combustion, hot sintern, cold sinter. - The same order of changes trikes, moving bed allo. Due to the moving bed, the zones are formed are in the inclined nature i.e each-zone is extended diagonally over the length. - At the end of the bed, the combustion is at bottom which indicates that the completion of sintering, two types of bounds are formed during sintering. ### **Diffusion / Recrystaliration / Solid state -** - It is formed as a result of recrystallization of the parrent phare at the point of contact of two particular in the solid state. ### **Slag / Glass bond:** - It is formed as a result of formation of low melting slag or glass at the point of contect of two particles when gangue of particles & flux are added. ### **Types of Sinten:** - There are three different types of sintes are produced depending upon the addition of flux in the sintering. - There are: - Acid Sinter - Flux sinter - Super flux sinter ### **Acid Sinter:** - If the flux is not added in the sinter, then it is called acid sinter. - When it is charged in the furnace, then, the flux is added separately. ### **Flux Sinter:** - If the amount of flux added in the mix is sufficient for the slag produced by the sintex only, then it is called flux sinter. - There is no separate addition of flux for the sinter, but flux is added for other raw materials which is charged in the furnace. ### **Supper flux Sinter:** - If the amount of flux added which is sufficient for the sinter slag as well as for other raw materials, which is charged in the furnace then, it is called Supper flux sintex. - There is no addition of "extra flux" in the furnace. ### **Pelletisation** - The process of rolling of moist material into the balls, to walp us pole pritison. - It is developed in 1913. - For the 1st time. it is adopted by USA - It is mainly wed due to utilisation of iron ore fins which are form during mining. ### **Pelletiring Process:** - It is essentially conellt of small green balls by rolling iron bearing fines material with critical amount of water and external binder may be added if required. - These green balls are 5-20mm in size. - The green balls are pre-heated & firred, under oxidiring condition at a temperature of 1250-1350; bellas. - At this temperature bonds are developed between the particle with good strength. - The pelletiration process consist of the following steps: - Feed preparation & sizing - Green ball production - Green ball industion - Drying - Preheating - Faringragis - Cooling of hardened pallets ### **Theory of Bandings:** - Bonding of pallets takes place by 3 water particle system, there are: - Pendalar - Funnicular state - Capillary state ### **Pendular State:** - When water is present just at the contact point of the particle, due to surface tension particles are hold together. ### **Furnicular State:** - When some pores are fully occupied by water in an aggregate system then funnicular states is appear. ### **Capillary State:** - When all the porces are filled with water, but there is no coherent film convering the entire surface then capillary state is form. - Bonds are not only strengthen by the water and particle but also mechanical inter Locking plays and significant role for developing the base strength. ### **Mechanism of Ball formation:** - The formation of balls on the pelletisation depends on the moisture content. - If the moisture content is less than the critical amount, then material is relatively dry and seed formation does not takes place. - If the amount of moisture is more than the critical amount growth is more & deformation strength is less, because of this plasticity. - Seeds are form only when moisture level is maintained: - Nuclei formation - Transition formation period. - Ball growth region - **Ball growth region:** - Ball growth takes place by two modes: - Growth by assimilation - Growth by layering. ### **Growth by Assimilation:** - If no fresh feed material is added for Balling due to the rolling action weaker nuclei are breaker is to fines and joins with the expence of weak nuclei. ### **Growth by Layering:** - If the feed is given from outride and the small balls pick up the feed while rolling on the top layer or expose surface and made itself a larger ball, this is called growth by layering. - Growth by layering is more predominant in dick fellittres and growth by arsimilation is more predominant in drum pellitiser. ### **Disk Pellitiser:** - It is essentially a disc with an outwarding sloping which is rotated around its, centre & has the inclination with the horizontal about +45°. - Disc has the diameter 3.6-5.6m. The materials to be pelleticed is generally feed direct by directly into the disc & moisture level is controlled by water spray is provided to prevent buid up of molst material on the disc with required rpm due to centirfuga force the feed materials are move out and form a nucleation zone for the balls. - The balls are of pellet tend to rise on the inclined surface of the pelletiser in the direction of rotation and fall down to the toe rection of the disk. - The balls are deflected downward by the scrapper. - Durning this moment balls meet with the fresh feed material & growth takes place by "layering". - **Islam prania atin aniaj han sanif water at constant head pellet min Vibratory Vibratory goes to Dibo feeder.** - **Under size with a bittren of 8 to 10% and recycle is bruare betoten.** - **It is a continous process when the balls are in required size it in discharged to the screen to differentiate the required size and under cire.** ### **Drum Pelletiser:** - Drum pelletirer is a simple steel drum open at both end with a length to diameter ratio 2.5 to 3.5 rotating around it's own aris in a slightly inclined parition to the horizontal. - Drums are 2 to 3m. in diametere 12/6 to 19ms in length and rotate at 10-15 rpm depending upon the diametere. - The angle of inclination in working porition is about 2-10°. - The change is feed at the heighers end where required water spray is given. - The materials are rolled over the surface of ivide the drum and cascading is takes place inside the drum due to the inclination and the in working porition is about 2-10. . - **The change is feed at the heigher end, where nequined water spray is given. The matterials are rolled over the surface of ivide the drum and cascading is takes place incide the drum due to the inclination of the drum. And aftere nucleation growth takes by the assimilation. After ball formation it is discharged at the other end where screen is fixed to get required size & under cire.** ### **Drying:** - The green ball from drum pelletirer and disc pelletizer are der dried by powing hot air through the bed of ball is on the grate. - The temp. of the hot blast is abt about 300℃. - Drying is carried out by down drought & updrought condition. ### **Preheating & Diring:** - Preheating & firing is carried out to leliminate te decrepitation & its strength of the bond to maintain its size & shape inside the furnace. - In the preheating stages partial oxidation takes place and if sulphur is prierent it is removed by the oxidation. - If carbonates are present then cabination is takes place durning preheating. - After, preheating firing is carried out by shaft klin. - The firing is carried out at a temp of 1250-1350c. - At this temp. pallet get sufficient temp and the T.A.H pd besubang of beilggo i elgiasing. ### **Nodulising:** - In the nodulisation process flue durt, fines are genet ate concentrate with some carbonaceous material like tar are mixed together and parsed through a rotary klin. - They are heated by gas on oll. - The feed material travel counter current to the garse. - The temp. inside the kiln is just to soften the ore not to fure them. - The kiln is usually inclined to the the blast horizontal and rotate about 1 to 2 repm. - The diameter of the klin is 2m and its to length 32-60m. - The travelling time of feed material is 1.5 - 2. Size of the nodules mainly depend upon tax and temp content. - The nodules which are produced too dence & less porous. - It is reeduction is very difficult hence it has hotlared int good furnace. ### **Briquetting:** - Briquetting concert of pressing of ore fines with on without a binder to a block or other suitable size or shape then it subjected to hardening processions. - The binder which are used are tar, pitch, rodzumsilicate, magnezium chloride, Limestone, Borstite, Benor bentonite. - In the carly version of the process fire orce mixed with water and pressed into blocks and hardened in the tunnel kiin at a temp about 1350°c. - Iron one breigquents are not commonly used bed it's principle is applied to produced by H.B.I (hot brriquettet iron) in which sponge inon fines are used. ### **Vaccum Extrusion** - It is mainly wed in the ceramic industry where moist ore with on without bentonite as a binder is feed in the chamber and extruded into a cylindrical product which is cut into desired small sizes then it subjected to drying and firing before ured it in the blast furnace. ## **Blast Furnace Accessories.** ### **Blast furnace Refractories:** - In the earlier days blast furnace were lered with high duty fire brick throughout the cross rection. - The life of lining decreases by the condition of funnar operation. - The compaign life failure are due to following reason: - Carbon monoxide attack - Action of alkali vapor - Action of lime & alkaline slags - Action of other volatile matters - Abbrassion by rolids, Liquids and gases. - Temperature - Action of molten metal - Conditions of operation and design - Blowing procedure. - All there factors are not seen in the single place. All the factors are distributed through the blast furnace from top to bottom. ### **Stack Lining:** - The linery should have good abrasion resistance and should have resistance to carbon monoxide attack. - Refractoriness is relatively less important. . - It is a common pa practire to use armour plate ni at the treat to withstand the impact & action of the burden. - Below this, over a length of nearly 2-3m, high fund rupere duty fire bricks are ured. - There bricks are made up machine moulding under high pressure. The At the top of the stack 35-40% alumine fire brick is ured but at the louver part of the stack 60% alumina brie is ured. ### **Hearth Lining:** - The lining should primarily prevent breakths in hearth. - Neither uses of brick of high alumina to silica ratio, lower perniability & porrority with well lald joint can minimize breakout. - Still than hearth suffered from frequent breakout. - The breakout is due to penetration of the metal & slag into the refractory joints. - So in the latere stage carbon refractories is used which have high refractoriness, high thermals conductivity, high porority and non a wetable in nature and its joints are very less so penetration of liquid metal & slag list avoidedarand, ducts to better property breakouts is completly elimiriateds.) - Now-a-days carbon blocks are used to facing the metal and slag & high duty firebrick arce ured as a backing Refractory. - The size of the block is about feit square meter in size. - **All the blocks are anchored with the furnace the hearth wall:-** - As like as hearth lining, carbon blocks are used as facing refractory and hugh duty fire bricks are used as backing refractory. - In the backing layer a graphite layere is pronided for effective cooling of the refractory. ### **Bosh Lining:** - For reverity of temperature and chemical attack is absut this region the lining should porcess good refractor- iers, refractoriners. under Load recistance to action of molten Ume & alkali slags. - Those boch lining generally of high duty ore or super duty fire brilck which content 45-65%. alumina. - Now-a-days carbon blocks are adopted similarly to the hearth lining. - Due to the high thermal conductivity efficiency, cooling can be carried out in the refractory of the bosh. ### **Blast furnace Cooling arrangement:** - Good quality of refractory can't give the guarant for longer life & normal function of the blast furnace. - This cooling effect keep the refractory temp. with in limit. - Due to this cooling arrangement thickness of refractory can also be reduced so cooling effec . - **The type of cooler are wed is the furnace are very advantageous.**** - Boz cooler - Spray cooler - Water jacket cooler - cooling pipe - **Different types of cooler are currently is wed: ** - Cantilevere type - L- type - Platen type - **There are made by cart iron boxes with steel tube . Now a days tubes are also ured for the cooling arrangement. ** - **The box contain an finlet and siet let through while cooling water is flows and cool the refractory. ** - **The box are incated into the roof refractary from outride of the furnace, and it is assemble wit with the refractory which is in contact for better heat transfere. ** ### **Shaft Coolers & Stack cooler:** - For smaller furnaces cantilever type of coolers are wed where as larger furnaces L-type coolers or plate type cooler are ured. - **Now-a-days the upper part of the stack is cooled by L-type cooler and the lower type of stack is cooled by platy & coolest.** - **To mesteltt treneproces pritsar sitt & of th pritsos os brouber, ed s'ante nas.** ### **Hearth & Boch cooler:** - Plate Type flat cooler are used to cool the lining of the both and hearth wall of the furnace. - Because this plate coveres the maximum area of the refractory which increases the cooling efficiency. - On the both zone the number of cooler is less than the hearth zone because in the hearth zone there is simutaneous effect of slag & metals. - Now-a-days spray cooler and water jacket cooler are used because carbon block has the thermal conductuity 18 times more than the other refractory, so spray and water jacket cooler are suffiecient att to cool the refractory. - Water used for the cooling has the temp. is 20-40°c which able to extract heat efficiently from refractory. - **Durning cooling most of the water evaporates.** - **Cooling of Hearth Bottom:** - When the hearth diameter is small the thermal conductuity of carbon block is adequets to remove sufficient heat from the centre of the hearth by the hearth cooler, but when the size of the furnace increases, the thermal load also increases, so plates are provided at the bottom of the furnace in which pipes are harnanged through which watte and air are circulated to ensure cooling of bottom refractory. - **It is estimated that thickness of furnace bottom can be reduced to (600-800 mm) by using cooling arrangement. Saving att fo Jood Hro bad ett fo. ** ### **Tap hole:** - Molten iron va accumulate in the hearth andelslag also. Ot should be removed from the furnace, periodically through a hole Located at the bottom of the furnace. - This hole is called taphole. - Tap hole is a closed & open by a clay gum & drilling machine respectively. - The hole is closed after every tapping and it is open by the drilling machine. - **The thole where slag is escape, out, from the furnaces is called monkey notch, Chinder notch, låg notch and the tap holest used for the metal is called metal tap hole.** - **The tap holes are cooled by copper and water, arrangement which maintain the temp of tap holes as well as control wearing at tap hole** ### **Cart House:** - The area around the blast furnace with a concrete platform where channels are provided for flowing of metal and slag is known as cart housing. - A huge masiluet platform resting on the columns is used for the moving of equipment. - Platform consists of claygren, electronic drill, machine, electric operated crains which issued for the moving of equipment. - **In the early days, cart houses contain sand bis through which channels are made but now a days refractory materials are manufactured for metal& slags. ** - **At the end of cart house , spouts are provided to flow the metal & slag from cart house to the laddle. ** ### **Tuyere Assembly:** - **Tuyere is the most important part of the furnace from which hot blast is supplied to the frerenace.** - **This is concert of elbow, nock, pipe hole and nozzle. ** - **Nozzle is made in coppere and the othere parts is made inirstavio steet and the refractory lining is given ins the tuyere. The complete tuyer has water cooling arrangement at elbow. The connecting point between expansion joints are given for reduceing the effect of expansion & contration. ** ### **Raw material Section:** - **Blast furnaces are generally located is now is a steel plantavery ett of leinaton. ** - **In the bucket charging system buckets are arranged in a regular fashion in the endless chais. So, that it can contincsurly provide the storage material to the furnacest tak spol.** ### **Conveyer Belt:** - A endless flat rubber belt are move by the help of two pullies out of