Gas Based Sponge iron

Gas-Based Process:

·         This process utilizes natural gas the reducing agent.

·         Natural gas is reformed to enrich with H2 and Co mixture and this enriched and reformed gas mixture is preheated in gas-based process.

·         A vertical retort is used for the reduction of iron ore as against a rotary kiln in coal based sponge iron process.When the gases are traveling upwards the charge moves downward by gravity.

·         Gas-based sponge iron is not subjected for magnetic separation, as no contamination with non–magnetic is possible either it can be cooled indirectly or briquetted in hot condition to get hot briquetted iron (HBI).

The basic reactions are as follows: 

There are only two well established processes
1. Midrex 
2. Hyl 
In gas-based process more preferable feed is pellets but lump ore is also used for with proper size distribution to have required permeability.

 Chemical and Physical Composition of Iron Ore

Constituent

%

Chemical Composition

 

Total iron

65 - 67 %

Sio2 + al2 o3

2 - 3 %

Cao + mgo

0.5 - 1 %

Sulphur

0.02 % max.

Phosphorous

0.04 % max.

Physical Composition

 

Size

5 - 20 mm

Shatter Index

+ 95 %

Tumbler Index

+ 88 %

Abrasion Index

+ 5 % max

Reducibility Index

+ 94 %

Thermal Degradation Index

5 %


»  Typical Chemical Analysis of Coal

Constituent

%

Moisture

8 % max

Total Iron

27 - 30 %

Ash

23 -25 %

Fixed Carbon

+ 40 %

Size

0 - 20 %

Ash Softening Point

1250 deg cent

Calorific Value

5200 k . Cals / mole

Reactivity

2.2 co / gm . Deg c


»  Typical Chemical Analysis

Cao

40 - 45 %

L.O.I

40 - 45 %

Insolubles

5 - 7 %

Size

0.5 - 4 mm


» Typical Analysis of Sponge Iron Produced in Coal Based Process

Total Iron

91 - 93 %

Metallic Iron

80 - 84 %

Metallisation

90 - 92 %

Gangue

3 - 4 %

Carbon

0.25 %

Sulphur

0.02 - 0.03 %

Phosphorous

0.035 - 0.05 %