Vedanta aluminium ltd

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Reduction in Energy Consumption by

Implementation of Slotted Anodes

Engineering Excellence Awards - 2013

Presented By – Vedanta Aluminium Limited

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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.

Corporate Overview – Vedanta Aluminium Limited, Jharsuguda

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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.”

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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.

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

96485 Coulombs deposit – 1 gm Equivalent of Aluminium

1 KA in 24 Hrs produces – 8.052 Kg of Aluminium

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To produce 1 T of aluminium the following amounts of raw materials are needed:

2 T 415 Kg 20 Kg 2 KgAlumina Carbon Aluminium fluoride

Cryolite

+ =

13000 - 15000 kWh 1 TElectrical energy Aluminium

+ + +

4 T bauxite

+ CO2 + CO + HF + CF4 + Coke + Other gases

Raw material Consumption – Production of Aluminium

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Process Flow – Aluminium Production

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Cost Sensitivity

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2980.6

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Constituents of Pot Voltage

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Metal

Bath

Anode

Cathode

Anode Voltage

Drop

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 3.80% 161 mV

Electrolyte Drop

Bath Drop 37.5% 1569 mV

Decomposition Drop 40.6% 1700 mV

Cathode Voltage Drop

Cathode block drop 7.5% 313 mV

Bolt drop 0.2% 8 mV

External Voltage Drop

6.42% 269 mV

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The bath voltage contains a resistance & an electrochemical part.

Introduction to Bath Voltage & its components

Components of Bath Voltage

•E0 – Reversible Electromotive Force

•U Ω – Ohmic Bath Voltage

•UBub – Bubble Voltage

•Anodic concentration Overvoltage

•Anodic Reaction Overvoltage

•Cathodic Concentration Overvoltage

Bubbles

Bath

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Reasons for High Voltage drop across the Electrolyte

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During Aluminium smelting, CO2 gases are evolved.

CO2 bubbles get accumulated under the anode – forms a high resistance partially insulating film.

Gas accumulation under the anode

Increases Energy Consumption

Anode

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How to reduce the bubble Drop???

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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

Slotted Anode

CO2

CO2 Gas Bubbles

Slots reduce the bubble

resistance by 16-18%

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Conceptualization & Design Engineering

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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 (Vibro-compactor).

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.

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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.

ParametersBefore Cycle-1 Cycle-2 Cycle-3

Benefit28-jun to 26-Jul 27-jul to 23-Aug

24-Aug to 20-Sep

21-sep to 18-Oct

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

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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

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Trial & Full Implementation - Impact on Energy consumption

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Full Implementation of Slotted Anodes Stabilization Period

Impact on Power

Consumption(Kwh/MT)

Impact on Current ramp

Up(KA)

Decrease by 2.23%

Increase by 0.58%

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Impact on CE

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Full Implementation Stabilization

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%

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Slotted Anodes and Environment – Impact on AEF and PFC Emissions

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Impact on AE Frequency

(No./Pot/Day)

Impact on PFC Emissions –

CF4* and C2F6*(MT/MT of Al)

Full Implementation of Slotted Anodes Stabilization Period

*CF4 (MT/MT) – AEF*AED*0.14, C2F6 (MT/MT) - AEF*AED*0.14/10 (As per universally accepted calculation)

Reduction by 47%

Reduction by 57%

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Intangible Gains through Slotted Anodes

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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.

Impact of Slotted anodes

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Way forward -

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Reduction of energy by additional 60 Kwh/MT of Al

VAL (Press Forming)

207.5,200 mm 575 13.8 days

VAL (Slot Cutting)

300,280 mm 575 20 Days

20 cm deep slot

28 cm deep slot

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Present Performance (Jan’13 – Aug’13)

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Calculations for CO2 Emissions

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Savings by Slotted anodes = 67.3 Kwh/T

Volume 541593 MTConsidering 93.6% CE, 63 pots, 326.5 KA.

Savings in a yr. = 36449203 Kwh/Yr .

36449.2 Mwh/Yr .

Now, 1Mwh = 1000 Units

36449.203 Mwh/Yr. 36449203 Units

= 36.4492 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.