Vedanta Aluminium Limited implemented slotted anodes across its smelter operations to reduce energy consumption and costs. During trials over 3 cycles, slotted anodes reduced pot voltage by 16 mV, anode effect frequency by 0.28 events/pot/day, and noise by 1.01 mV, saving 51.2 kWh/MT. A full line implementation over 3 cycles reduced pot voltage by 21 mV, saving 67.3 kWh/MT and 36.44 million kWh/year, increasing current efficiency by 1.32% and production by 20.89 kg/day. Slotted anodes also reduced anode effect frequency by 0.15 events/pot/day and PFC emissions by

1. Engineering Excellence Awards 2013
Reduction in Energy Consumption
by
Implementation of
Slotted Anodes
Presented By –
Vedanta Aluminium Limited
|

2. Corporate Overview – Vedanta Aluminium Limited, Jharsuguda
 Vedanta Aluminium Ltd is an associate company of the London Stock Exchange listed, FTSE 100
diversified resources group Vedanta Resources Plc. originally incorporated in 2001.
 The firm operates a 0.5 MTPA Greenfield Aluminium smelter plant 1 and 1215 MW Captive Power Plant
(CPP) supported by highly modern infrastructure at Jharsuguda, Odisha.

In addition to this, construction of 1.2 MTPA Aluminium smelter expansion project at Jharsuguda is
going to be commissioned soon.
 Rewards and Recognitions –







IMS Certified Plant (QMS-ISO-9001, EMS-ISO:14001 and OHSAS: 18001)
Frost & Sullivan’s Green Manufacturing Excellence Awards 2013 "Aspirants Award -Large Business"
Received certification for ISO: 50001, Energy Management System.
Best HR strategy in line with Business by World HRD congress.
Received certification for ISO: 27001 in information Security,
Recognized as “Excellent Energy Efficient Unit” at 14th National Award for “Excellence in Energy Management
2013” organized by CII.
Third prize in “All Odisha EHS Award 2013” by CII.
| 2

3. Vedanta Aluminium Limited, Jharsuguda
VISION
“We will be the world’s most admired
company that consistently defines the
leading standards in our businesses,
making our stakeholders proud to be
associated with us.”
MISSION
“Our mission is to be a world-class
metals and mining group and generate
superior financial returns.”
| 3

4. Fundamentals Of Hall Heroult Process
1.
The amount of substances
deposited or dissolved during an
electrolytic process is proportional
to the quantity of electricity passed
through the electrolytic cell.
96485 Coulombs deposit – 1 gm Equivalent of Aluminium
1.
One gram equivalent weight of
matter is deposited or dissolved on
each electrode for 96485 Coulomb
(Faraday Constant ) of electricity
charge passed through the
electrolyte
1 KA in 24 Hrs produces – 8.052 Kg of Aluminium
|

5. Raw material Consumption – Production of Aluminium
To produce 1 T of aluminium the following
amounts of raw materials are needed:
4 T bauxite
2T
Alumina
Cryolite
+
415 Kg
Carbon
+
20 Kg
Aluminium fluoride +
2 Kg
+ CO2
+
+ CO + HF + CF4 + Coke +
Other gases
=
13000 - 15000 kWh
Electrical energy
1T
Aluminium
|

6. Process Flow – Aluminium Production
| 6

7. Cost Sensitivity
2980.6
| 7

8. Constituents of Pot Voltage
External Voltage
Drop
269 mV
Clamp Drop
0.2%
8 mV
Rod Drop
0.40%
15 mV
Transition Joint Drop
0.10%
6 mV
Steel Yoke Drop
1.6%
65 mV
Stub to Carbon Drop
1.8%
75 mV
Anode block Drop
Anode
Voltage
Drop
6.42%
3.80%
161 mV
Bath Drop
37.5%
1569 mV
Decomposition Drop
40.6%
1700 mV
Cathode block drop
7.5%
313 mV
Bolt drop
0.2%
8 mV
Anode
Bath
Electrolyte
Drop
Metal
Cathode
Cathode
Voltage Drop
| 8

9. Introduction to Bath Voltage & its components

The bath voltage contains a resistance & an electrochemical
part.
Components of Bath Voltage
•E0 – Reversible Electromotive
Force
•U Ω – Ohmic Bath Voltage
•UBub – Bubble Voltage
Bubbles
•Anodic concentration
Overvoltage
•Anodic Reaction Overvoltage
Bath
•Cathodic Concentration
Overvoltage
|

10. Reasons for High Voltage drop across the Electrolyte

Anode

During Aluminium smelting, CO2 gases are
evolved.
CO2 bubbles get accumulated under the
anode – forms a high resistance partially
insulating film.
Increases Energy
Consumption
Gas accumulation under the anode
| 10

11. How to reduce the bubble Drop???
 Minimizing bubble drop - most economical way to reduce
energy consumption.
 Modification of anode surface by Introducing slots can
reduce both the bubble drop and anode overvoltage.
 Scope of reduction – 50-100 mV
CO2
Slotted Anode
Slots reduce
the bubble
resistance by
16-18%
CO2 Gas
Bubbles
| 11

12. Conceptualization & Design Engineering
 Anode surface slots were not present in
the initial design.
 In house design engineering done
for appropriate slot height and
slope
 Straight slots may be a problem in gas
evacuation.
 Design of experiment and data
analysis performed on Slanted
slots
 Design modifications have been made in
the anode forming equipment (Vibrocompactor).
 Ensure proper removal of packing coke.
Clogging of the slots will lead to excess
coke dusting in pots.
 In situ Design & Installation of Slot
cleaning machine in bake oven.
| 12

13. Slotted Anode Trial (Line 1-Section 7)
 Trial
period – 27th July to 25th Oct
 Sample Population – 6.3% of the total operating pots.
 Total no. of anodes made for Trial – 5000 nos.
Benefit realized
• Reduction in Pot Voltage - reduction of 16 mV
• Reduction in AEF - Reduction of 0.28 no./pot day.
• Reduction in Noise - Reduction of 1.01 mV.
• Net saving in Power Consumption of 51.2 kWh/MT.
Before
Parameters
Cycle-1
Cycle-2
24-Aug to 2028-jun to 26-Jul 27-jul to 23-Aug
Sep
Cycle-3
21-sep to 18Oct
Benefit
Avg V
V
4.257
4.254
4.243
4.241
0.016
AEF
No./pot/Day
0.51
0.57
0.46
0.23
0.28
Noise
mV
14.79
11.76
12.33
13.78
1.01
|

14. Pot room Parameter Analysis for Slotted Anodes on Full line
Implementation
Implementation period – 23rd Oct’12 to 13th Jan’13
Benefits observed
•
Reduction in Pot Voltage - a net reduction of 21 mV.
•Net saving in Power Consumption of 67.3 kWh/MT. (36.44 MU/Year)
•
Increase in productivity –
•Current efficiency increase by 1.32%. Volume increase by 20.89 Kg/Day
•Amperage Ramp – Net increase of 1.89 KA. Production Volume Increase by 8.6 Kg/Day
•
Reduction in AEF - 0.15 no./pot day. Total reduction by 46%
•Reduction in PFC & CO2 Emissions – Net reduction by 57% in whole pot line.
Parameters
UOM
Before
1st Cycle
2nd Cycle
3rd Cycle
Benefit
Amperage
KA
324
324.2
324.55
325.66
1.66
Avg V
V
4.279
4.273
4.268
4.258
0.021
AE Frequency
No./Pot/Day
0.32
0.26
0.24
0.18
0.22
Noise
mV
17.7
15.8
15.4
13.8
3.9
|

15. Trial & Full Implementation - Impact on Energy consumption
Full Implementation of Slotted Anodes
Stabilization Period
Decrease
by 2.23%
Impact on
Power
Consumption
(Kwh/MT)
Impact on
Current ramp
Up
(KA)
Increase
by 0.58%
| 15

16. Impact on CE
 In practice, an electrolytic pot always produces less Aluminium than is as per theoretical (Faraday’s
Law) calculation.
 Actual CE % = (Actual Production/Theoretical Production)*100
Increase by
1.43%
Full Implementation
Stabilization
| 16

17. Slotted Anodes and Environment – Impact on AEF and PFC Emissions
Full Implementation of Slotted Anodes
Stabilization Period
Reduction
by 47%
Impact on AE
Frequency
(No./Pot/Day)
Reduction
by 57%
Impact on PFC
Emissions –
CF4* and C2F6*
(MT/MT of Al)
*CF4 (MT/MT) – AEF*AED*0.14, C2F6 (MT/MT) - AEF*AED*0.14/10 (As per universally accepted calculation)
| 17

18. Intangible Gains through Slotted Anodes
Impact of Slotted anodes
 Conservation of non renewable
resources of energy.(Coal & Oil)
 Total Power Savings by 36.44
MU/Year.
 Reduction of CO2 emissions by –
15.26 KT/Yr.
 Emissions of green house gases (PFC) reduced by 57%.
 Manpower productivity has improved.
 Anode effect frequency has been
decreased to a large extent productivity has increased.
 Elimination of Safety and health hazard
 reduced anode effect frequency
and immediate auto quenching
methods.
| 18

19. Way forward -
20 cm
deep slot
28 cm
deep slot
VAL
(Press Forming)
207.5,200 mm
575
13.8 days
VAL
(Slot Cutting)
300,280 mm
575
Reduction of energy by additional
60 Kwh/MT of Al
20 Days
| 19

20. | 20

21. Present Performance (Jan’13 – Aug’13)
| 21

22. Calculations for CO2 Emissions
Savings by Slotted anodes = 67.3
Kwh/T
Volume
541593
MT
Considering 93.6% CE, 6
3 pots, 326.5 KA.
Savings in a yr. =
36449203
Kwh/Yr
.
36449.2
Mwh/Yr
.
Now, 1Mwh = 1000 Units
36449.203
Mwh/Yr. 36449203
= 36.4492
Units
MU
Now, 1 MU = 1 Gwh
As of world standards, The level of the performance standard will be fixed at 420 tonnes
of carbon dioxide per gigawatt hour (CO2/GWh).
therefore, by implementing Slotted anodes, savings in CO2 Emissions /Yr. will be
= 15308.67
T/Yr.
= 15.30
KT/Yr.
| 22