BLAST FURNACE GAS

Presented BY

M.Abdullah Irshad DDP-SP13-BEC-032

Shahzaib chuhdary DDP-SP13-BEC-085

Zagham Nadeem DDP-SP13-BEC-097

M.Ajmal DDP-SP13-BEC-107

Blast Furnace Gas

It is the by-product of blast furnaces that is

generated when the iron ore is reduced

with coke to produce molten iron.

Blast Furnace It is a tall cylindrical furnace

made of steel.

It is narrow at the top and has

an arrangement for the

introduction of ore and outlet for

gases.

Heated with help of Hot Gases.

The function of a blast

furnace is to reduce and

convert iron oxides into

liquid iron

The blast furnace is a huge,

steel stack lined with

refractory brick.

Purpose Of B.F.G

Oxygen in the air reacts with coke to give carbon dioxide:

C(s) + O 2(g) CO2(g)

The limestone breaks down to form carbon dioxide:

CaCO3(s) CO2 (g) + CaO(s)

Carbon dioxide produced in 1 + 2 react with more coke to

produce carbon monoxide:

CO2(g) + C(s) 2CO(g)

Step Involved In Blast Furnace

The carbon monoxide reduces the iron in the ore to give

molten iron:

3CO(g) + Fe2O3(s) 2Fe(l) + 3CO2(g)

The limestone from 2, reacts with the sand to form slag

(calcium silicate):

CaO(s) + SiO(s) CaSiO3(l)

The excess limestone from the second reaction reacts

with the sand (coming from minerals in iron ore) and

forms calcium silicate (slag)

CaO(s)+SiO(s) --> CaSiO3(l).

Slag and molten iron are drained from the bottom of the

furnace and gas produced exits through holes in the top

of the furnace

Composition Of Blast Furnace Gas

C0 (22-25)%

H2 (4-5)%

CO2 (16-20)%

N2 (51-55)%

O2 (0.2-0.5)%

Little amount of NH3, H2S Almost Nill

Yield Of B.F.G

• About 3 tons of blast furnace gas is

generated for 1 ton of pig iron produced,

the coke rate of furnace being 600-900

kg\ton pig iron

• Volumetric yield of B.F.G is about 2000-

2200 Nm3\ton pig iron

Properties of blast furnace

Ignition Temperature

• It’s ignition temperature value range b/w 670 to 690

almost.

• Higher than many other fuel gases.

Calorific value

• Its calorific value is about 800-900

• Contain more co, less H2 and has a much lower calorific

value than coke oven gas and other fuel.

Flame temperature

• The value of flame temperature is about 1450°C.

• Lower as compare to other

fuel gases.

Fuel Flame Temperature

acetylene 3,100 °C

candle 1,000 °C (1,800 °F)

carbon monoxide 2,121 °C

cigarette 400-700 °C (750-1,300 °F )

ethane 1,960 °C

hydrogen 2,660 °C

natural gas 2,770 °C

oxyhydrogen 2,000 °C

propane 2,820 °C

Density

• Its density is about 1.3 to1.4 (kg/Nm3)

• Slightly heavier than air (1.28 (kg/Nm3)

Other properties

• colourless, odourless and tasteless in nature

B.F.gas Processing nd cleaning

• B.F.gass leave the furnace at 125-350°C

• With pressure is about 0.5-1.5 kg/cm2

• 10-25gms of dust/Nm3

• Diameter of dust particles 0.1 micron to 5mm.

• It is very poisonous gas. Due presence of carbon

monoxide. Carbon monoxide is harmful when breathed

because it displaces oxygen in the blood and deprives the

heart, brain, and other vital organs of oxygen. Large

amounts of CO can overcome you in minutes without

warning causing you to lose consciousness and suffocate.

Poison Gas

Process

Characteristics Of Blast Furnace Gas•It has a very low calorific value of 800 to 900 kcal/Nm,

depending upon blast furnace coke rate

•It has got a low theoretical flame temperature

•It has a low rate of flame propagation

•It has a high specific gravity

•It burns with non-luminous flame

Poisonous effect of B.F Gas

• Man inhales B.F gas

• React with hemoglobin form Carboxyhaemoglobin

• Effect Dizziness, headache and shivering

• Prolonged exposure in excess of the gas will kill the man exposed.

Determination of Low C0 concentration In atmosphere

Palladosulphite tubes

• A small tubes is packed with short length of plain white silica gel

followed by a length of gel impregnated with yellow

potassiumpalladosulphite each end of the glass tube is drawn to a

fine point and sealed

• Gas is drawn through the tube at stated rate for two minutes

• Carbon monoxide causes the colour of the yellow to dark brown to

blue

• Dark blue means concentration of about 1000 ppm of

carbon monoxide in atmosphere

Uses of B.F Gas

• Low calorific value but large quantity of the gas produced

it is one of the most important fuels in an integrating iron

and steel plant.

Uses of B.F Gas

Blast Furnace stoves

Soaking pits

Reheating Furnace

Billet heating

• Foundrary ovens

• Annealing furnaces

• Boilers

• Coke oven underfiring