Factors affecting Fuel Rate

1.Gas Utilization   

2.Hot Blast Temperature 

3.Sinter %  

4.Steam Enrichment  

5.Heat loss 

6.Flux Rate  

7.Coke ash  

8.Coal ash

9.Coal RR

10.Slag Rate

11.Fines carryover

12.Metalloids Mn, Ti, P, Si

Fe in Burden

What happens to Fuel carbon in BF?

•Input fuel

–Coke + Nut  420 kg/thm (from top)

–Coal  120 kg/thm (through tuyeres)

»102 kg/thm coke equivalent

–Total coke equivalent 522 kg/thm

•Out put

–In HM as carburization 4.5% say  52 kg/thm coke equivalent

•Remaining 470 kg/thm will be used in direct reduction and will burn in front of tuyeres.

•Now assume 30% DR

–The coke used in DR = 141 kg/thm

–Remaining 329 kg/thm will be burnt in front of tuyeres

–Out of which coal 120 kg/thm = 102 kg coke equivalent

–And the coke burnt in front of tuyeres = 227 kg/thm

Gas Cleaning Systems in Ironmaking Blast Furnaces

In a blast furnace, iron ore and coke are charged into the top of the furnace. The molten iron is removed near the bottom of the
furnace. Combustion air is supplied through tuyeres at a level just above the iron tap hole. The combustion air is called wind. Wind is
air that has been preheated, compressed and may contain added oxygen, natural gas, pulverized coal or other additives. One of the
limiting factors of increasing production of an ironmaking blast furnace is the velocity of the wind in the furnace. If the wind
velocities become too high, the normal downward flow of the charge materials is inhibited.1 One technique used to increase the
amount of wind available for combustion is to increase the pressure at the top of the furnace. This increase in top pressure increases
the pressure of the incoming wind, which increases the gas density, and lowers the wind velocity. Because of the resulting
improvement in blast furnace performance, top pressures above 15 psig are becoming more common and some furnaces are operating
at top pressures as high as 30 psig. 2,3
Blast furnace gas has a modest heating value from the carbon monoxide and hydrogen that it contains. The gas is burned to recover
this heat and to reduce the carbon dioxide emissions from the process. Some of the gas is used to preheat the blast furnace wind in
stoves that are normally located adjacent to the furnace. For efficient operation and longevity of the stoves, the blast furnace gas must
be clean and dry.

Gas Cleaning Systems in Ironmaking Blast Furnaces

1.Venturi.Gas cleaning,
2.Scrubber, 
3.Cyclone, 
4.Dust catcher, 
5.Recovery turbine

Reasons for Frequent tuyreburning

1] Enlargement of Dead Man Zone

2] Poor hearth Annulus

3] prolonged operation in low blast

4] Insufficient cooling water pressure at tuyre

5] Coke value CRI CSR

6] Manufaturing Defect in tuyre.

7] Viscosity of the slag

8] High Pressure drop in furnace

Why the Blast Furnace can be used to extract iron from Fe2O3 but not Aluminium from Al2O3.?

Iron is liberated from it's oxide in a blast furnace by carbon monoxide, the carbon monoxide simply removes oxygen from the iron oxide to become carbon dioxideleaving elemental iron. The same process will not work with aluminum oxide because aluminum has a much higher electropositive potential than iron. What this means in simple language is that aluminum gives up more energy than iron when it forms it's oxide and it takes more energy to remove oxygen from aluminum oxides than it does from iron oxides.

Effect of high Al2O3 slag on the blast furnace operations

Increasing the Al₂O₃ content in the blast furnace slag, the blast furnace operations tend to make troubles such as excess accumulation of molten slag in the blast furnace hearth and increasing pressure drop at the lower part of the blast furnace. So, it will be important to keep good slag fluidity at the blast furnace operations such as, drainage of tapping and keeping good permeability. In order to clarify the effect of high Al₂O₃ slag fluidity on the blast furnace, high Al₂O₃ slag (20%) test operations of experimental blast furnace have been carried out. Investigation results of the test operation are as follows; 1) Slag MgO improves the hearth drainage rate at high Al₂O₃ slag operation. 2) Permeability of the dripping zone is improved by decreasing slag CaO/SiO₂, at high Al₂O₃ slag operation of the blast furnace. 3) It was verified that the slag drainage phenomena were able to described by the fluid model. 4) The optimum composition of high Al₂O₃ slag of the blast furnace is high MgO and low CaO/SiO₂.