WQD2011 - Breakthrough Process Improvement - EMAL - Alumina Silo Rotary feeder Cyclic Stopping Interval

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2 2

Introduction

Emirates Aluminium Company (EMAL) is a strategic joint venture between

aluminium producer Dubai Aluminium Company (DUBAL) and Mubadala

Development Company (MUBADALA).

The company’s facility at Al Taweelah, halfway between Abu Dhabi and Dubai,

EMAL’s present work force is 2500 employees on rolls.

EMAL will be largest single site Aluminium smelter complex at the end of phase-

2 with a capacity of 1.3 Million Ton of aluminium per year

EMAL produces a wide range of high grade semi finished aluminium products,

like low profile sow , high profile sow, standard ingots, billets, sheet ingots etc.

Supplying to worldwide customers.

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Aluminium Smelting

Process

Power

Plant

Port

DC Power

Alumina

Molten Aluminium

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Project Charter

Anode effect frequency was increasing drastically during and after breakdown in Gas treatment center/ Pot feed system. Which was creating disturbances in Reduction pots.

Huge number of people were involved in quenching the anode effects and stabilizing the pots.

Heavy PFC generation during anode effects, not safe for

employees and environment.

Problem

faced by

EMAL

A

B

C

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Project Charter

1.The Goal Statement.

To reduce the impact of Pot feed system and Gas treatment center stoppage

during breakdown and power outage on Reduction Pot performance by

improving Alumina quality supplied to pots

2.The teams involved:

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Teams Roles

Process Control Controlling and monitoring

Operation ( Pot feed system & Pot line) Operating the system

Maintenance Maintaining the system

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Project Charter

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• Maintaining the equipment's in good working condition

• Controlling and monitoring the process and equipment's

• Manufacturing Aluminium from Alumina

• Supplying Alumina to Pot lines

Pot feed system

operations

Pot lines Operations

Maintenance Process Control

3.Stakeholders model:

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Project Charter

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Problem Identificatio

n

Selection of solution

Trials Plant wide

implementation

Controls and

monitoring

Oct - 2010 April-June 2011 Jan-March 2011 Dec - 2011 June-July 2011

4.The Project Timelines

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Measure

8

2B039

0.0

10.0

20.0

30.0

40.0

50.0

60.0

10/13/2010

4:48

10/13/2010

9:36

10/13/2010

14:24

10/13/2010

19:12

10/14/2010

0:00

10/14/2010

4:48

10/14/2010

9:36

10/14/2010

14:24

Time

-32

5 %

Feeder 2 Feeder 4

2A144

0.0

10.0

20.0

30.0

40.0

50.0

60.0

10/13/201

0 4:48

10/13/201

0 9:36

10/13/201

0 14:24

10/13/201

0 19:12

10/14/201

0 0:00

10/14/201

0 4:48

10/14/201

0 9:36

10/14/201

0 14:24

Time

-325

%

Feeder 2 Feeder 4

2B045

0.0

10.0

20.0

30.0

40.0

50.0

60.0

10/13/2010

4:48

10/13/2010

9:36

10/13/2010

14:24

10/13/2010

19:12

10/14/2010

0:00

10/14/2010

4:48

10/14/2010

9:36

10/14/2010

14:24

Time

-32

5 %

Feeder 1 Feeder 3

Line-2 Sec -4 Line-2 Sec -8

During pot feed system stoppage Fines content increases in Alumina

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Measure

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Line-2 Sec -4 Line-2 Sec -8

• During and after Pot feed system stoppage anode effect frequency increases

drastically .

• This indicates whenever Fine contents increases in alumina it creates

anode effects and disturbs the pot performance.

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Analyze

A.Problem Statement

• Avoid disturbance in reduction pots by reducing the

Anode effects frequency in reduction pots from 0.4

AE/Day to less than 0.15 AE/Day during and after

breakdown or stoppage of pot feed system and GTC.

• Reduce the fines content in Secondary alumina from 40

% to less than 20% by avoiding segregation of alumina

inside Secondary alumina silo, transport air slides, and

reduction pots.

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Analyze

B. Validation of the Root cause

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Alumina entering

to Pot hopper/ Silo

Finest particles

settles out and

accumulates here

Alumina entering

to Pot hopper/ Silo

Finest particles

settles out and

accumulates here

•During silo and pot hopper filling fine

alumina gets segregated and

accumulates along the wall of pot

hopper and alumina silo. This is due to

the static, near to full level operation of

the silo and hopper. These areas may

have become inactive by the cohesive

nature of reacted alumina when left

static over long periods of time.

•During any breakdown in GTC or Pot

feed system these fine material starts

entering in to the pot and causes anode

effects which affects pot performance.

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Improve

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A. Solution Criteria: The solution should allow the alumina silo to vary between 40-

80% level

The solution should allow the pot to vary 75-100% level

B. Solution evaluation: Trial conducted for one pot for evaluating purpose by stopping

alumina filling manually after every 6Hrs duration .During trial no

change in quality of alumina observed.

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Improve

C. Solution Selection Process

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Reacted Alumina Silo

Rotary Feeder Cyclic

Stopping Interval

Through PLC Logic

Modification

Automatic Pot

Hopper Exercising

and Alumina Silo

Feed Modifications

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Improve

C. Solution Selection Process

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Sr.No Criteria

Ranking

Engineering

Solution In-House

Solution

1 Easy implementation 1 5

2 Cost involved 1 5

3 Time to implement 2 4

4 Maintenance and control 1 4

5 The results 5 4

Silo Level Trend

85%

83%

Implementation

Reacted Alumina Silo Level Trend

X

Y

85%

35%

Implementation

Reacted Alumina Silo Level Trend

X

Y

85%

35%

Implementation

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Implementation

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Reacted alumina rotary feeder is being operated with a continuous 6-hour

cyclic stopping interval.

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Plan

Do Check

Action Results of Trial

2A105 9.9 2A142 39.1

2A094 11.8 2A144 53.4

2A117 10.9 2A146 49.5

2A128 11.4 2A189 18.6

2A136 12.8 2B01 53.4

2A146 13.9 2B039 49.3

2A152 13.4 2B045 38.5

2A164 12 2A142 40.7

2A172 12 2A144 44.1

2A189 12.2 2A146 39

Average 12 2A189 20.2

2B01 35.1

2B039 49.2

2B045 48.6

Average 41.3

Pot No % Fines

Comparison of % fines in the hopper after stoppage of pot feeding system

Pot No % Fines

After Potfeed system stopage for 6 Hrs

(During Trial )

After Potfeed system stopage for 6 Hrs

(During normal operations)

Stoppage of GTC or Pot feed system in normal situation % fines in pot alumina

increases, where as % fines in pot alumina remains unchanged where reacted

alumina rotary feeder cyclic stopping interval has been implemented.

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Plan

Do Check

Action Results of Project

On 23rd April during GTC

breakdown Sec-3, & Sec-4

are not affected as much as

normal sections

AE-frequency in normal sections was 0.365 AE/Pd whereas in Sec-3 & Sec-4 AE-

frequency was 0.167 AE/Pd where reacted alumina rotary feeder cyclic stopping interval

has been implemented. This indicates the change in the quality of alumina.

Plan

Do Check

Action Results of Project

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The underfeed duration went down in the normal sections where as it was normal in

Sec-3 & Sec-4 where reacted alumina rotary feeder cyclic stopping interval has been

implemented. This indicates the change in the quality of alumina.

On 23rd April during GTC breakdown

Sec-3, & Sec-4 are not affected as

much as normal sections

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Control Plan

Do Check

Action

Alumina Silo level

Rotary

Feeders

Operation

System is controlled by SCADA, and continuously monitored by

operations and Process control

Plan

Do Check

Action Benefits of Projects

• Engineering Solution

• For Automatic Pot hopper Exercise

= $27,810 x 8 sections x 2 Lines

= $444,960

• For Reacted Alumina 700t Silo

Modifications

= $800,618.47

• Total Proposed Project Cost

= $444,960 + $800,618.47

=$1,245,578.47 or

= AED 4,575,321.07

• In-House Control Modification

• Project covered both engineering

proposal to a single cost-effective and

cost avoidance solution.

• Regular man-hours was used in

developing the PLC logic modification

and monitoring the system.

• Control flexibility was incorporated to

enhance mass-balance of the

upstream and downstream process.

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Total Cost Avoidance: AED 4,575,321.07

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Plan

Do Check

Action Results achieved

Improved work environment in the

Pot lines as emissions reduced

(Environment Protection)

Supply of good quality Alumina to

Potlines will improve Pot performance

AE frequency

reduced during

GTC/Pot feed

stoppage

Eliminated / Avoided

costly engineering

solutions for the

Alumina segregation

problem.

Problem of

Segregation of

Alumina is

eliminated.

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Project Closure Plan

Do Check

Action

Team Recognition: Team was recognized by EMAL management by selecting best

improvement project in June-2011, and team is nominated for

2011 Annual FALAH award.

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Plan

Do Check

Action