1. Plasma Processing in
Extractive Metallurgy
DEPARTMENT OF METALLURGUCAL AND
MATERIALS ENGINEERING
INDIAN INSTITUTE OF TECHNOLOGY
KHARAGPUR
2. PLASMA
• Plasma is considered to be the 4th state of matter next to
solid, liquid and gas.
• “A gas in which an appreciable number of atoms or
molecules are ionized is called Plasma”.
3. PROPERTIES OF PLASMA
• Exists at temperatures over 10,000 K
• It is electrically neutral
• Electrons in it have highest energy and molecules the
least
• Electrically conductive
• Responds to Electric and Magnetic Fields
4. UTILIZATION OF PLASMA
1. As a heat source and
2. As a carrier medium.
In material processing plasma is used both as a heat source
and a carrier medium.
5. Plasma Furnace Design
Plasma Torch
• Heat source in the plasma furnace.
• Used for generating a direct flow of plasma.
Types of Plasma Torches
Electrode No Electrode
AC Radio
Frequency (RF)
DC Used in Lab furnaces
Industrially used
• Transferred
• Non transferred
6. Plasma furnace design
DC Plasma Torch
• Electric arc is formed between electrodes
made up of Cu, W, Mo, graphite etc.
• Carrier gas used is Oxygen, Hydrogen, Helium,
Nitrogen etc along with Ar or He.
• The electrodes are continuously cooled.
16. Mechanism of Shaft Furnace
Step 1: Shaft Furnace is filled with coke
Step 2 : 3 plasma torches of 6 MW each are
installed
Step 3 : The powdered initial raw material is
reduced by fluidized bath of plasma gas, i.e.
Carbon dioxide.
USES
reduce for Pig Iron , Non-Ferrous metals, Fe-Cr
processing
17. Falling Film Plasma Furnace
Step1 : Fine raw material
with reducing agent is
tangentially introduced .
Step 2 : The intensely
whirled gas dispersed
flow forms a metal film
on the wall of the reactor
anode.
Step 3 : The film falls on the
bottom part of the
furnace and gets reduced
on the way.
18. Falling Film Plasma Furnace
Reduction of 0.07%Cu
Hemetite+H2+Natural Gas
hematite:
0.06%C
• Very pure Fe was
obtained.
• Electrical energy 0.06%Si
consumption was
3.9KW/kg Fe. S & P=0.01%
Remaining was Fe
Mass Balance
20. Plasma Arc Melting
Plasma Arc Melting (PAM): Utilises an arc in
a non-reactive gas, as a heat source and is
applied to the melting of reactive and
refractory metals.
21. Plasma Arc Melting
Advantages :
• Improves quality of the produced metal
• Decreases the specific electric energy consumption
under increased output
• Enables production of low carbon alloys
Disadvantages :
• Working life of plasma electrodes is short under high
power density and in case of high capacity steel
formation.
23. Plasma Induction Melting
Mostly used in foundries for the preparation of molten alloys
in quantities up to 3 tons.
COMPONENTS
• plasma torch of power capacity 100 KW up to 400 KW
• plasma gas argon
24. Applications
• Scrap Recycling
• Production of Special alloys
• Ultra low Carbon Stainless Steels
• Production of alloys used in High Temperature or Cryogenic
Conditions
25. Plasma Arc Remelting
Plasma remelting furnaces are multi—duty systems.
Utilized for :
Simple and complex castings
Near—net shapes
Finished shapes.
26. Applications
•
•
Production of high temperature alloys
Processing of high melting and reactive metal alloys.
• Melting ceramic materials and glass.
28. Fundamental studies of plasma heat generation
and application
(a) Investigation of physical problems of plasma arc in the power range 1 MW to 10
MW;
(b) Pilot scale investigations of kinetics, thermodynamics of gas exchange processes,
evaporation processes, deoxidation , decarburization, during plasma heating;
(c) Investigations of electrode erosion, process and methods of extending electrode
life or improving its thermal stability in industrial scale systems;
(d) Reduction of cooling requirements of the bottom electrode in transferred arc
plasma melting systems for overall improvement of electrical efficiency and
maintenance requirements;
(e) Development of methods for the intensification of energy—mass exchange
between the plasma arc and the heated body;
(f) Design, development of high response plasma power sources for plasma torch
operations in a wider voltage range,different gas atmospheres and pressure
conditions within the melting chambers.
29. Advantages
• The atmosphere can be controlled to meet any process
requirement.
• No need for pelletization or agglomeration as fine ore
particles can be used.
• More efficient than other processes at Higher
Temperatures
• Processing rate is very high.
• Total enclosure: avoids contamination.
• High value metals can be recovered from waste.
• Can process low grade complex minerals.
30. Disadvantages and Scope for
Improvement
•Heat recovery: Products have a high latent
heat.
•Electrode life: Electrodes have to be
regularly replaced thus inhibiting continuous
operation.
•High cost of maintenance.
