Glossary of Terms used for a Blast Furnace


Glossary of Terms used for a Blast Furnace

A cross section of a blast furnace showing nomenclature of different portion is shown in Fig 1

BF cross section

Fig 1 Cross section of a blast furnace

Various term used to describe a blast furnace and its equipment are described below.

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

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

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

Armor – These are the steel castings used for lining of the throat of the blast furnace.

Bell – In blast furnaces with two bell charging system, two numbers of bells (small and big) are used to control the entry of charge materials in the blast furnace 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 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 blast furnace 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 usually adjust movements up to 3.5 degrees.

Bend line – It is the horizontal line at the upper termination of the inwall batter.

Bleeder valves – They are located at the extreme top of the uptakes and releases gas and protect the top of the furnace from sudden gas pressure surges.

Blow pipe – Blow pipe is part of tuyere stock for delivery of hot blast to the blast furnace. The blow pipe is refractory lined.

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 inwall.

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

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

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

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 blast furnace at the taphole level. It contains equipment for opening and closing of tap-hole 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 blast furnace without allowing escape of BF gas to the atmosphere.

Chute – It is part of 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.

Cinder notch – It is also known as slag notch. All blast furnaces donot have this notch. The slag notch is used for tapping slag from the furnace.

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 a blast furnace 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 blast furnace now copper staves are also being used.

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.

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 deg turn. Elbows have Peep sight for watching inside the furnace.

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

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

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

Hearth diameter – it is the diameter of the inside face of the refractory lining of the blast furnace 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 centerline of the taphole. The latter is determined by the center of the tap hole opening in the hearth jacket.

Height of inwall – It is the vertical distance between the bottom inwall 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 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.

Injection lances – These lances are used for injecting either oxygen or auxiliary fuels (PCI, natural gas, oil, coal tar etc.) into the blast furnace through tuyeres. These lances are usually inserted in blowpipes.

Inwall batter – It is the negative slope of inwall expressed numerically as the base of a right triangle whose altitude is 300 mm and whose hypotenuse is the slope of the inwall.

 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.

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 between the tapping.

Offtakes – They are two in numbers and connect uptakes with the down comer.

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 taphole to the hot metal ladle while slag runner directs liquid slag to slag granulation plant or slag pot or slag pit.

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

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

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 granulation plant – In slag granulation plant liquid slag is granulated by quenching it with high pressure water jet.  It is usually situated by the side of the casthouse .

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

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, imbedded armor, or inner face of movable armor.

Stockline level – For blast furnace with bell top, it is the horizontal line at the bottom of the large bell when closed. For example, a 1.83 m (6 feet) stockline means the horizontal line located 1.83 m below the large bell when closed. For blast furnace with bell less top, it is the horizontal line located 0.91 m (3 feet) below the tip of the rotating chute in the vertical (90 degree) position.

Stoves – These are used for heating the air blast for the blast furnace. They are constructed with checkers bricks. Usually three or four stoves are there for a blast furnace,

Tap hole mass – It is the refractory material used for closing of the tap hole. Taphole mass is normally oil based.

Throat – It is the portion of the blast furnace 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.

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 centerline of the taphole 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 centerline of the taphole and the bottom of the closed large bell.

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

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.

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

Useful volume – It is the inner volume of the blast furnace between a plane through the centerline of the taphole and the stockline level.

Volume below tuyeres – It is the inner volume of the blast furnace between the horizontal planes through the centerline of the taphole and the centerline of the tuyere.

Working height of the furnace – It is the vertical distance between the centerline of the tuyeres and the stockline.

Working volume – It is the inner volume of the blast furnace between a plane through the centerline of the tuyeres and the stockline level.