Needle coke is the special grade of petroleum
coke produced in Delayed coking operation. The good quality
of needle coke is hard and dense mass formed with a structure
of carbon threads or needles oriented in a single direction.
 |
 What
is the use of Needle Coke? |
 |
Needle coke is mainly used in the manufacturing
of graphite electrodes used in electric arc furnaces in steel
industry.
|
What
are the important properties of Needle Coke? |
|
The important properties of good Needle
cokes are as follows:
| » |
Higher real density (more
than 2.13 gm/cc) |
| » |
Lower sulfur (less than
0.5wt%) & ash content (less than 0.5wt%) |
| » |
Lower co-efficient of thermal
expansion (CTE) (less than 1.0x10-6 cm/cm/ C for premium
grade), etc. |
|
Why
it is important to reduce the sulfur content of Needle
Coke? |
|
Sulfur in Needle coke causes problems
with "puffing" or the swelling or bloating in the
green electrodes during graphitization. This adversely affects
the density and mechanical strength of the electrode.
|
Why
it is important to have lower CTE of Needle coke? |
|
When an electrode arcs with steel in
an electric arc-furnace, the thermal gradient is over 2000°
C per centimeter. Low CTE allows the electrode to operate with
high temperature gradient without spalling the hot tip.
|
How
Needle coke can be produced? |
|
Needle coke can be produced in Delayed
coking operation using selected feedstocks having specific properties
under optimum operating conditions like temperature, pressure
and recycle ratio.
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