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Glossary of Terms used for a Blast Furnace

• satyendra
• October 11, 2013
• 10 Comments
• blast furnace, Hot metal, slag, top equipment,

Glossary of Terms used for a Blast Furnace

Various terms used in the blast furnace (BF) ironmaking process which describe the BF, its equipment, its raw materials, and the process are given below.

Access tower – It is the tower made of steel with platforms at various levels so that easy access can be made to various levels of the BF. The tower is normally free standing.

Active zone – The active coke zone is bounded by the cohesive zone, raceway, and deadman. It consists of loosely packed coke feeding the raceway or moves towards the deadman zone.

Additives – Additives are miscellaneous materials like manganese ore, quartzite, and titani-ferrous iron ore etc. which are charged in BF for the adjustment of the chemical analyses of hot metal and slag.

Adjustable armour – It is adjustable throat armour system, used in connection with the bell type top charging equipment to control and vary the burden distribution so that optimum permeability in the BF stack can be achieved.

Air cooled slag – Air cooled slag is that slag which is produced when the liquid slag is poured into beds and slowly cooled under ambient conditions. Air cooling produces a hard, lump slag, which is subsequently crushed and screened. Air cooled slag has a crystalline structure.

Alkalis – Alkalis are the compounds of the metals potassium and sodium. Alkalis have negative influences on the BF process.

Alumina refractories – These refractories are used for lining of the BF. Alumina content of refractories varies depending on in which zone of the BF they are used for lining.

Annular space – It is the difference between the stock line radius and the large bell radius.

Armour – These are the steel castings used for lining of the throat of the BF.

Auxiliary fuels – Auxiliary fuels are those fuels which are injected in the BF through the tuyeres. Examples are pulverized coal, natural gas, heavy oil, tar, and coke oven gas etc.

Banking –In case of banking of the BF, the blast is taken off, the blow pipes are dropped, and the tuyere openings are plugged with clay to prevent air from drafting through. Thus, the heat of the hearth is preserved and the BF can be returned to operation with a minimum effort. Banking of the BF is adapted for short outages. The banking is also resorted to as an emergency measure when some unforeseen event needs a shutdown of the BF. Banking operation is carried out as a planned event. Preparations are made depending upon the length of the banking time anticipated

Bell – In BFs with two bell charging system, two numbers of bells (small and big) are used to control the entry of charge materials in the BF as well as to prevent escape of BF gas in the environment. These bells are of conical shape.

Bell less top equipment – It is the furnace charging equipment which does not use the two bells but uses a rotating chute for furnace charging.

Bell overhang – It is the vertical distance between the bottom of the large bell closed and the inner bell seat.

Belly – It is the cylindrical portion of the BF below the stack. It connects the upper bosh diameter with the largest diameter of the lower stack.

Bellows – These are part of tuyere stock. It accommodates relative movement of blow pipe with respect to bustle pipe. Bellows can normally adjust movements upto 3.5 degrees.

Bend line – It is the horizontal line at the upper termination of the in-wall batter.

Blast furnace – Blast furnace is essentially a counter-current moving bed vertical shaft metallurgical furnace with solids (iron bearing burden, coke and flux), and later molten liquids, travelling down the shaft. It is used for smelting iron ore to produce liquid iron. The cross section of a BF showing nomenclature of different portion of the BF is shown in Fig 1.

Fig 1 Cross section of a blast furnace

Blast furnace coke – It is the fraction of coke in the size range of 30 mm to 80 mm.

Blast furnace gas – Blast furnace gas is the name given to the by-product which is continuously produced from the upward gaseous rise of blast air through the burden in the BF during its operation.

It is almost colourless (mild whitish), and an odourless gas. Having the main characteristics of (i) very low calorific value normally in the range of around 700 kilo-calories per cubic meter (kcal/cum) to 850 kcal/cum, and (ii) relatively a high density normally in the range of around 1.25 kilograms per cubic meter.

Blast furnace slag – Blast furnace slag is the non-metallic product consisting essentially of silicates and alumino-silicates of calcium and other bases which is produced in a molten condition simultaneously with liquid iron in the BF.

Blast pressure – It is the pressure of the hot blast air Injected in BF through the tuyeres.

Bleeder valves – Bleeder valves are pressure relief valves or explosion prevention valves installed in bleeder pipe of furnace top pressure control systems. These valves are needed for controlling high top pressure at the BF top and to protect the top of the furnace from sudden gas pressure surges.

Blow down – .Blowing down of a BF means running the BF without charging until the burden level in the BF is reduced to around the tuyere level.

Blow out – The blowing out is also called sometimes raking out. BF is normally blown out when the production from the BF is no longer needed. The blow out is done after the installation of blow out equipment and following the blow out procedure.

Blow in – Blow in is the process of starting a BF after its construction or after its relining. The blow in process is carried out in several steps which consist of (i) drying out the lining, (ii) filling of the BF with a specially arranged high coke blow in furnace charge, (iii) igniting of the coke or lighting of the BF, and (iv) gradually increasing the hot blast with frequent castings to ensure the raising of temperature of the BF hearth. During the period of blow-in, the burden ratio (ratio of the ore to coke) is adjusted according to a pre-determined schedule until the normal operation of the BF is achieved.

Blow pipe – The blowpipe is an inte­gral component of the hot blast system of the BF. Positioned between the bustle pipe down-leg and tuyere, the blowpipe is normally a two-piece component, consisting of an elbow and a cone section, and is typically constructed with an outer steel shell lined with a two-component refractory system.

Bosh angle – It is the acute angle formed by a horizontal line and the slope of the bosh.

Bosh diameter – It is the diameter of the inside of the lining at the bosh line. It is also the diameter of the straight section or belly above the bosh.

Bosh line – It is the horizontal line at the intersection of the slope of the bosh and the belly. In case there is no belly in a blast furnace then the bosh line is at the intersection of the slope of the bosh and the batter of the in-wall.

Bottom in-wall line – It is the horizontal line through the intersection of the vertical line of the belly and the in-wall batter. In furnaces with no belly portion the bottom in-wall line coincides with the bosh line.

Break out – A ‘breakout’ is the term used to denote the conditions and results of the escape of gas and coke, or slag, or iron, from the bosh, tuyere breast, or hearth of a BF. Breakout can occur at any point below the fusion zone in the furnace, but the most of the severe breakouts are of liquid slag and of liquid iron. Liquid iron breakout takes place at a level below the surface of iron lying in the hearth, and are either through the hearth walls and jacket or into the hearth bottom and out under the hearth jacket.

Breast cooler – It is the circular cooler fixed on the furnace shell on which normally intermediate cooler and tuyere is mounted. Breast cooler is water cooled.

Burden – Burden is the furnace charge, of iron-bearing materials (e.g. iron ore pellets, and sinter), coke, and flux (e.g. limestone) descends through the shaft, where it is preheated and reacts with ascending reducing gases to produce liquid iron and slag.

Burden distribution – It indicates the distribution of the burden materials across the BF cross-section during their charging in the BF. Control of the burden distribution is important for improving the gas utilization and lowering of the fuel rate. Control of the burden distribution is also necessary to control the shape of the cohesive zone of the BF.

Burden materials – Burden materials are (i) fuels and reductants like BF coke, and nut coke, (ii) iron bearing raw materials like sinter, pellet, and calibrated lump ore also known as sized iron ore, (iii) fluxing materials like lime stone, dolomite, and quartzite, and (iv) additives like manganese ore, quartzite, and titani-ferrous iron ore etc.

Bustle pipe – It is also known as bustle main and is a large diameter refractory lined pipe encircling the BF shell above the tuyere level. Through the bustle main hot blast air is supplied to the BF through the tuyere stock.

Calibrated iron ore – It is the sized iron ore normally in the size range of 10 mm to 30 mm.

Capital repairs – Capital repairs of are those repairs which are taken up after the end of a campaign of the BF. During the capital repairs, the main jobs which are normally taken up are (i) relining of the furnace, (iii) repairs of the damaged portion of the shell, (iii) major revisioning of all the equipment with replacement of the worn out components, (iv) replacement of those equipments, instruments, and automation items which have become obsolete or completed their useful life, and (v) modification work the need of which was felt during the running of the BF in the campaign which has just ended.

Carbon blocks – These are refractories made of carbon and are used for lining of hearth bottom and hearth walls.

Cast house – This is the area around the BF at the tap hole level. It contains equipment for opening and closing of tap-hole and trough and runners for flow of hot metal and liquid slag.

Charge conveyor – It is the conveyor with steel cord rubber belt for taking charge materials to the furnace top from the stock house. Conveyor charging is alternate to skip charging.

Charging equipment – It is the equipment used for charging of materials at the top of BF without allowing escape of BF gas to the atmosphere.

Channeling – The phenomenon of channeling happens when the ascending gases in the furnace does not properly get uniformly distributed both radially and circumferentially in the furnace and find a passage of least resistance.

Chilling – The chilling of a BF hearth occurs when the temperature of the hot metal which is tapped from the furnace is very low. The chilling of a BF is a very serious phenomenon which happens due to the abnormal operation of the BF. The revival of a chilled BF is a big and herculean task and it takes a very long time and needs a lot of patience to bring back a chilled BF to normal working condition.

Chute – It is part of the bell less charging equipment for charging charge material in the furnace. The chute is normally rotated while charging and its angle to the vertical can be changed.

Cohesive zone – Cohesive zone is the region lower down the BF. Here, slag starts to form at around 1,100 deg C. Initially it is relatively viscous, and surrounds the iron oxide particles, preventing further reduction. As the temperature increases to level of around 1,400 deg C to 1,450 deg C, it melts and reduction continues. This region is critical in terms of burden permeability.

Cinder notch – It is also known as slag notch. All the BFs do not have this notch. The cinder notch is used for tapping slag from the furnace.

Coke – It is a hard carbon material produced in the process of the ‘destructive distillation’ of various blends of bituminous coal. It has a multiple role. It is a reducing agent, source of reducing CO (carbon mono-oxide) gas, a source of heat, a filter of dust and soot, and a carburizer of hot metal, besides supporting the burden and providing gas permeability.

Coke rate – Coke rate is the parameter for the consumption of BF coke. It is measured in kilograms of BF coke consumed per ton of hot metal produced.

Cold blast valve – Cold blast valve is intended for the complete separation of the BF stove from the cold blast main. It is installed on the horizontal cold blast main near the stove.

Cooling staves – They are also called cooling plates. A stave is a cooling device having one or more water channel, and is installed in numbers on the inner surface of the BF to protect its steel shell and maintain the inner profile. The staves are conventionally made of cast iron but in high heat flux zones of the BF now copper staves are also being used.

CRI – CRI is the coke reactivity index. It measures the ability of coke to withstand breakage at room temperature and reflects coke behaviour outside the BF and in the upper part of the BF

CSR – CSR is the coke strength after reaction. It gives indication of the strength of coke after being exposed to the reducing atmosphere of the BF.

Deadman zone – It is the stagnant flow region (dead-man) which is a discontinuous mass of partially reacted coke particles in the centre part of the hearth. Fig 2 shows schematics of BF showing different zones.

Fig 2 Schematics of blast furnace showing different zones

Dolomite – Dolomite is a complex mineral with a composition of CaCO3.MgCO3. It is used as fluxing material as well as adjusting the MgO content of the slag.

Down comer – It is the pipe which carries BF gas from uptake to the dust catcher.

Drilling machine – It is one of the cast house equipment used for drilling the tap hole during its opening.

Dripping zone– Dripping zone plays a crucial role in modern high productivity BFs. It affects production rate, hot metal quality, and process efficiency. Dripping zone is a four phase region, where gas, solid, liquid, and powder coexist with each other. In this zone, solid and liquid flow downward driven by gravity, while gas and powder suspended in the gas flow upward due to the pressure force. The flow of four phases in this zone is considerably different from that in the upper shaft region due to the geometry and the presence of deadman zone at the centre and discrete raceways at the periphery.

Dry slag pit – It is a pit where liquid slag is diverted for solidifying in case of some problem in the slag granulation plant.

Dust catcher – It is situated by the side of cast house and used for preliminary cleaning of BF gas. It works on the principle of reversing the direction of flow of BF gas for separating coarse dust particles from BF gas.

Elbow – It is part of tuyere stock. At the elbow, hot air blast takes 90 degree turn. Elbows have peep sight for watching inside the furnace.

Flux – Flux is the material which combines with the gangue material of the ore and ash to form slag.

Furnace pad or foundation – It is the civil foundation on which the steel and supporting structure of the BF is erected. This foundation carries the load of the running BF.

Furnace shell – Furnace shell is made from crack resistant steel and is normally free standing. It is normally designed after comprehensive stress distribution analysis.

Gas cleaning plant – The primary function of the BF gas cleaning plant is to remove particulate matter from this gas. The raw BF gas is cleaned in gas cleaning plant in two stages namely primary gas cleaning stage and secondary gas cleaning stage. The gas cleaning plant can be a wet type plant or a dry type plant.

Gimbal system of charging – Gimbal system of charging facilitates controlled distribution of charge material into the BF through a Gimbal type oscillating chute.

Granulated slag – Granulated BF slag is produced by quenching the liquid slag to a glassy state resulting into little or no crystallization to occurs This process results in the formation of sand size (or frit-like) fragments, normally with some friable clinker like material. The physical structure and gradation of granulated slag depends on the chemical composition of the slag, its temperature at the time of water quenching, and the method of production.

Hanging – Hanging of the burden material in the BF stack occurs when the material below the hang continues to move downward, forming a space which is void of materials but filled with gas at very high pressure.

Hearth – It is crucible shaped bottom of the BF where produced hot metal accumulates before it is tapped. It is normally lined with carbon blocks.

Hearth diameter – it is the diameter of the inside face of the refractory lining of the BF hearth, excluding any increases in wall thickness at the tap holes.

Hearth line – It is the horizontal line at the intersection of a vertical line through the nose of the tuyere cooler and sloping line of the bosh. With ceramic lined boshes, the line through the noses of the bosh plates determines the slope of the bosh.

Height between bottom of large bell and top of hopper – It is the vertical distance between bottom of the large bell closed and the intersection of the hopper or the hopper extension with the gas seal.

Height of bosh – It is the vertical distance between the hearth and bosh line.

Height of hearth – It is the vertical distance between the hearth line and the centre-line of the tap hole. The latter is determined by the centre of the tap hole opening in the hearth jacket.

Height of in-wall – It is the vertical distance between the bottom in-wall line and the bend line.

Height of large bell hopper – It is the vertical distance between the inner large bell seat and the intersection of the hopper or hopper extension with the gas seal.

Hot blast air – It is the air which is heated in the hot blast stoves and fed to the BF through the tuyeres for the combustion of the fuel.

Hot blast main – It is the refractory lined pipe which connects the hot blast stoves with the bustle pipe.

Hot blast stove – Hot blast stove is used to preheat blast air used in the BF for the combustion of fuel. It works as a counter-current regenerative heat exchanger.

Hot blast valve – Hot blast valve is intended for complete separation of a hot blast stove from a hot blast main under ‘on-gas’ operation of the stove. It is installed in the horizontal hot blast main and consists of a water cooled disc resting on a water cooled seat, and moving vertically within a water cooled valve body and bonnet, and other supporting members and mechanisms.

Hot metal – Hot metal is the output of the BF. It is liquid iron which is produced by the reduction of descending ore burden by the ascending reducing gases.

Hot metal ladle – It is bucket shaped refractory lined vessel in which hot metal is tapped for its transportation. Hot metal ladle can be open top or torpedo shaped known as open top ladle or torpedo ladle respectively.

Hot metal trough – Hot metal trough is a deep trench through which the hot metal and slag flow down once the tap hole is drilled open.

Inner volume – It is the total inner volume of the BF between the hearth bottom and the level of the top ring.

Injection lances – These lances are used for injecting either oxygen or auxiliary fuels into the BF through tuyeres. These lances are normally inserted in blowpipes.

Intermediate cooler – Intermediate cooler functions as a tuyere cooler. It is situated between the breast cooler and the tuyere. It is the water cooled copper device in which the tuyeres become fixed in the furnace housing. It helps to make the heat exchange of the tuyere, taking away heat and preventing its passage into the surroundings of the BF.

In-wall batter – It is the negative slope of in-wall expressed numerically as the base of a right triangle whose altitude is 300 mm and whose hypotenuse is the slope of the in-wall.

Iron notch – It is also known as tap hole. It is the opening in the furnace hearth for draining the hot metal as well as slag from the furnace. The iron notch is opened by drilling for tapping and after tapping closed with taphole mass by the mud gun.

Iron ore – Iron ore is a type of mineral rock from which metallic iron is extracted economically. This ore is normally rich in iron oxides and vary in colour from dark grey, bright yellow and deep purple to rusty red. The mineral in the iron ore can vary depending on the deposit. The minerals which are important for iron smelting are magnetite, and hematite.

Lance – It is a small diameter pipe fitted at an angle in the blow pipe through which auxiliary fuel / oxygen is injected in the BF.

Lime stone – Limestone is an odourless white, grayish-white or tan material which ranges from sized stone to a granular powder. It consists mostly of calcium carbonate (CaCO3) and used as a fluxing material.

Liquid iron – It is the hot metal which is the output of the BF.

Lumpy zone – The lumpy zone is also known as stack zone. In this zone, coke and ore particles make a stratified descent down the furnace.

Mini blast furnace – Mini blast furnace is normally viewed as miniature version of the conventional large BF with the internal volumes ranging from 35 cum to 600 cum.

Mud gun – It is equipment installed near taphole in the cast house for pushing taphole mass under pressure in the taphole for the purpose of closing it. Mud gun performs one of the most important and critical operations of the tap hole. Closing a blast furnace tap hole under any condition is a key safety requirement.

Mushy zone – It is the soft structure of the ferrous burden which is formed at temperatures of around 1,100 deg C.

Nut coke – It is fraction of the coke in the size range of +10 mm to -30 mm. It is charged with the ore burden in the BF.

Off-takes – These are two in numbers and connect uptakes with the down comer.

Oxygen enrichment – It consists of injection of oxygen gas in the hot blast air for increasing its oxygen content to a level which is more than what exists in the normal air.

Pellets –Pellets refers to the thermally agglomerated substance formed by heating a variable mixture of iron ore, limestone, olivine, bentonite, dolomite and miscellaneous iron bearing materials. It is used as a substitute of lump ore for the production of hot metal.

Permeability – It is the characteristic of the burden in the BF which determines the smooth upward movement of the gases in the BF.

Pulverized coal – It is normally low volatile non coking coal which is ground to very fine coal particles for its injection in the raceway of a BF.

Pulverized coal injection – Pulverized coal injection is a process which involves injecting large volumes of fine coal particles into the raceway of the BF.

Quartzite – It is the ore which is very rich in silica and is added in BF as additive.

Raceway – It consists of combustion zone in front of the tuyeres. In this zone burning of the fuel takes place.

RAFT – RAFT is the ‘raceway adiabatic flame temperature’. The flame temperature is an important parameter as it affects the slag and metal chemistry, evaporation and recirculation of the alkali elements present, and the flow of metal in the hearth. It is difficult to measure the flame temperature and so it is normally calculated from an energy balance of the raceway zone. The calculated value is known as RAFT.

Reducing agent – Reducing agents in the BF are carbon of coke, and CO gas generated in the furnace by the combustion of coke and injected pulverized coal.

Runner – It is the channel in the cast house for directing of liquid products. Hot metal runner is refractory lined and directs hot metal from trough to the hot metal ladle while slag runner directs liquid slag to slag granulation plant, or to slag pot, or to slag pit.

Runner mass – It is the refractory material used for preparing of runner before the cast is opened. It is normally water based.

Salamander tapping – Salamander tapping of the BF is the final taping for draining out the last liquid iron from the BF hearth. It is done after the blow down, especially when the BF is to be completely emptied for relining during the capital repairs.

Scaffold – The term scaffold is used when there is accretion or scab formation on the BF wall which causes a decrease in the cross sectional area of the shaft of the BF. Scaffold can occur relatively at the higher level of the BF shaft or relatively low in the BF shaft (near the top of the bosh).

Sealing valve – Sealing valves are the part of the bell-less top charging system. They play an important role during the charging of the raw materials in the BF. These valves are meant for sealing the bin from the BF gas leakage. They are mainly used for equalizing pressure and releasing gas of the BF charging system.

Shaft – BF stack is frequently being called as shaft.

Shell – BF is covered with a shell of steel plate which is internally lined with refractories and has stave coolers for its cooling.

Silicon carbide refractories – These refractories are normally used in belly and bosh areas in modern BFs.

Sinter – Sinter is normally the major component of the iron bearing burden of the BF. It normally consists of various mineral phases produced by sintering of iron ore fines with fluxes, metallurgical wastes, and a solid fuel. The chemical composition of the sinter needed for BF depends upon the other components constituting the furnace burden. Normally the sinter ranges from fluxed (CaO/SiO2 around 1.2) to super-fluxed (CaO/SiO2 around 1.7 to 2.2) sinter.

Skimmer – It is a block of refractory which is set across and into the trough. The skimmer has a small opening underneath it. The hot metal flows through this skimmer opening, over the ‘iron dam, and down the ‘iron runners’. Since the slag is less dense than iron, it floats on top of the iron, down the trough, hits the skimmer and is diverted into the slag runners.

Skip – It is a special shape bucket for carrying the charge material to furnace top from the stock house. Usually there are two skips in each furnace. One skip goes up while the other comes down.

Skip hoist – It is the hoisting mechanism for taking the skip from the stock house to the furnace top.

Slag – Slag is the non-metallic product consisting essentially of silicates and alumino-silicates of calcium and other bases which is produced in a molten condition simultaneously with liquid iron in the BF.

Slag granulation plant – In slag granulation plant, liquid slag is granulated by quenching it with high pressure water jet.  It is normally situated by the side of the cast house.

Slag notch – It is also known as cinder notch. All the BFs do not have this notch. The slag notch is used for tapping slag from the furnace.

Slipping – The collapsing of the BF hanging is a phenomenon called ‘slipping’ during which the charged materials fall uncontrollably toward the hearth of the furnace in a thermally unprepared state which leads to the furnace getting cold. It also forces the hot gases upward with the force of an explosion.

Snort valve – Snort valve is a butterfly valve which installed in the cold blast line main before the stove. It is normally located near the BF and is used for reducing or completely stopping the air blast to the BF without stopping the operation of the blower.

Specific productivity – Specific productivity is the means for determining the BF performance. It measures the efficiency which is normally expressed in tons per day per cubic meter (t/d /cum) of working volume. In some countries, in place of working volume, useful volume is considered.

Stack – It is the furnace volume between belly and the throat.

Stave cooler – Stave coolers with water circulating in them are installed between the shell of the BF and the refractory lining in the upper part of the furnace to protect these components from heat radiation.

Stock bins – Stock bins are storage bins in the stock house in which the furnace charge materials are stored.

Stock house – It is the place where furnace charge materials are stored, screened, and weighed before sending to the furnace top for charging.

Stockline diameter – It is the diameter of the furnace at the stockline measured from face to face of the brickwork, embedded armour, or inner face of movable armour.

Stockline level – For BF with the two bell top, it is the horizontal line at the bottom of the large bell when closed. For example, a 2 m stockline means the horizontal line located 2 m below the large bell when closed. For BF with bell less top, it is the horizontal line located 1 m below the tip of the rotating chute in the vertical (90 degree) position.

Stoves – These are used for heating the air blast for the BF. They are constructed with checkers bricks. Normally three or four stoves are there for a BF. They works as a counter-current regenerative heat exchangers.

Tapping – Tapping a BF is necessary not only to deliver the BF products, but also essential to the safety of the furnace and the operators in the cast house. The tapping is a process which removes hot metal and liquid slag from the BF hearth. A tapping cycle begins as the tap hole is drilled open and is terminated by plugging the tap hole with the tap hole mass when the furnace gas bursts out.

Tap hole – The tap hole also known as iron notch, is used for tapping the hot metal from the furnace. It is located slightly above the floor of the hearth. Tap hole is an essential part of The BF. Large furnaces normally have 2 to 4 tap holes. Tap hole is normally exposed to an extremely dynamic environment with high temperature and pressure, frequent drilling and plugging, substantial chemical attack, and flow induced shear.

Tap hole drill – Tap hole drill is a high capacity drill hammers to ensure effective drilling of the tap hole for the opening of the BF tapping. The tap hole drills can have electro-mechanical, pneumatic, hydro-pneumatic, or hydraulic drive.

Tap hole mass – Tap hole mass is a prepared ready to use refractory product, made of a bond of aggregates, additives, and plasticizers. It is used to close the tap hole of a BF after tapping so that no material can leak out, and to keep it plugged until the tap hole is opened for next tapping. It is applied to ensure periodical and stable tapping and also to protect the inner surface of tap hole bricks.

Throat – It is the portion of the BF above the stack. The furnace throat is exposed to descending burden as well as ascending gases. It is also exposed to water when the top sprays are required for top temperature control. The operating condition in this area subjects throat to a range of wear mechanism which includes abrasion, impact erosion, temperature fluctuations, and high temperatures.

Tilting runner – Tilting runner is essential equipment for the cast house for the reliable and safe teeming of hot metal. It is normally positioned between two hot metal tracks. The runner is first tilted to fill the hot metal ladle on one track and then tilted back to fill the ladle on the other track.

Top gas – It is the gas which comes out at the top of a BF. The gas is cleaned in the dust catcher and the gas cleaning plant to remove dust from the gas.

Top pressure – It is the pressure which is maintained at the top of the furnace.

Top pressure recovery turbine – Top pressure recovery turbine is a mechanism which utilizes the BF gas heat and pressure energy to drive a turbine for the generation of electric power.

Torpedo ladle – Torpedo ladle is used for the transport of hot metal. It is normally mounted on a rail car for its movement. The torpedo ladle is having a shape of a torpedo. The closed shape of the torpedo ladle helps in the preservation of heat during the transport of the hot metal

Total bell height – It is the vertical distance between the upper termination of the throat section and the bottom of the large bell when closed.

Total height of furnace – It is the vertical distance between the centre-line of the tap hole and the intersection of the large bell hopper or hopper extension with the gas seal.

Total volume of the furnace – It is the furnace volume between a horizontal plane at the centre-line of the tap hole and the bottom of the closed large bell.

Tuyeres – Tuyeres are special shaped nozzles through which hot air blast is injected into the BF. They are made of copper and are normally water cooled since they are directly exposed to the furnace temperature.

Tuyere coolers – Tuyere coolers are the water cooled copper devices in which the tuyeres become fixed in the furnace housing. They help to make the heat exchange of the tuyere, taking away heat and preventing their passage into the surroundings of the BF. They play a significant role in the tuyeres resilience, helping to achieve the functional stability of the BF.

Tuyere platform – It is the maintenance platform at the tuyere level to facilitate changing of tuyeres and blow pipes.

Tuyere stock – It is assembly of gooseneck, expansion bellow, connecting pipe, elbow, peep hole, blow pipe, fixing arrangement and tensioning device. Tuyere stocks connect bustle pipe to the tuyeres. The purpose of tuyere stocks is to supply hot blast air into the BF.

Uptakes – They are four in numbers and collect hot dirty BF gas from the furnace.

Useful volume – It is the inner volume of the BF between a plane through the centre-line of the tap hole and the stockline level.

Volume below tuyeres – It is the inner volume of the BF between the horizontal planes through the centre-line of the tap hole and the centre-line of the tuyere.

Working height of the furnace – It is the vertical distance between the centre-line of the tuyeres and the stockline.

Working volume – It is the inner volume of the BF between a plane through the centre-line of the tuyeres and the stockline level.