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Increase Current Efficiency of Potline 3 (P/L-3)
2
Dubai Aluminium Company Limited (DUBAL)
• Annual Production of > 1 million tonnes of aluminium
• >4000 Employees
• Based in Jebel Ali, Dubai
• 8 Potlines consisting of 1573 aluminium cells
• One of the few smelters in world to produce primary high purity metal for use in electronics and aerospace industries.
Introduction
3
• Smelting converts alumina (ore) into aluminum metal
through electrolysis process
―By using Direct Current (DC)
―Current Efficiency (CE) is the ratio of electrical direct
current that results in actual metal production
• Therefore, improvement in Current Efficiency remains
one of the strategic objectives of any Aluminium
smelter
Project Background
4
Problem Statement:• Potline 3 Current Efficiency is at 92.9% for H1 2009 which is below target
since increase of current amperage to 200 kA,
• resulting in decreased plant hot metal output.
Project Target: Increase average Potline 3 current efficiency to
target of 93.1% for 2010.
1. Define 2. Measure 3. Analyze 4. Improve 5. ControlDefine Phase
5
In Scope:
Potline 3 Process Parametersand Procedures
Out of Scope:
All other Potlines
Unit of measurement: Potline 3 Current Efficiency
Operational Definition: Monthly Average CE from iRPMS (Smelting Database System)
1. Define 2. Measure 3. Analyze 4. Improve 5. Control
Project Scope:
6
Team Charter:
Data collection and implementation of solutions.Act, Manager, Line 3, 7 & 9Devadiga H.R. 7
Data collection and implementation of solutions.Snr. Manager - PC PR &
CLMaryam Al-Jallaf8
Data collection and implementation of solutions.Supt Potroom OperationsTariq Majeed 6
Team Leader.Manager – Projects D18Daniel Whitfield1
Data collection and implementation of solutions.Snr Process Control Engineer – PotroomsAdam Sherrif 9
5
4
3
2
S.No
Data collection and implementation of solutions.Snr ManagerNajeeba Al-Jabri
Data analysis and report making.Snr. Planner – ProdnServicesSaif Mohamed
Data analysis and report making.H.O.D: PC-CLMohamed Tawfik Boraie
Data analysis and report making.Snr Process Control Engineer – PotroomsAndries Louw
Project ResponsibilitiesFunctional RoleName
Data collection and implementation of solutions.Act, Manager, Line 3, 7 & 9Devadiga H.R. 7
Data collection and implementation of solutions.Snr. Manager - PC PR &
CLMaryam Al-Jallaf8
Data collection and implementation of solutions.Supt Potroom OperationsTariq Majeed 6
Team Leader.Manager – Projects D18Daniel Whitfield1
Data collection and implementation of solutions.Snr Process Control Engineer – PotroomsAdam Sherrif 9
5
4
3
2
S.No
Data collection and implementation of solutions.Snr ManagerNajeeba Al-Jabri
Data analysis and report making.Snr. Planner – ProdnServicesSaif Mohamed
Data analysis and report making.H.O.D: PC-CLMohamed Tawfik Boraie
Data analysis and report making.Snr Process Control Engineer – PotroomsAndries Louw
Project ResponsibilitiesFunctional RoleName
1. Define 2. Measure 3. Analyze 4. Improve 5. Control
7
Stake Holder Model : ARMI Chart
Adam Sheriff
Maryam Al-Jallaf
Devadiga H.R.
Tariq MajeedP/L-3 Process Technician
VP-Power & Desal.Najeeba Al JabriP/L-3 Operators
VP-FinanceSaif MohamedP/L-3 Technicians
VP-MarketingMohamed Tawfik BoraieP/L-3 Superintendent
VP-CasthouseAndries LouwManager D-18VP-Smelter Ops.
Interested PartyMemberResourceApprover
1. Define 2. Measure 3. Analyze 4. Improve 5. Control
8
Project Schedule
1. Define 2. Measure 3. Analyze 4. Improve 5. Control
9
2. Measure1. Define 3. Analyze 4. Improve 5. ControlMeasure Phase
• Current efficiency is key measure of process performance, and is regularly reported and monitored
• It is difficult to be measured directly; therefore, inferred from actual metal production as below:
Actual Hot Metal ProductionCurrent Efficiency = --------------------------------------
Theoretical Hot Metal Production
• Three months average taken to ensure reasonable accuracy of the data
10
Measurement System Analysis
• Review of existing plant system for measuring and reporting current efficiency showed no significant concerns over accuracy or precision
2. Measure1. Define 3. Analyze 4. Improve 5. Control
• Actual Metal Production =Total Weight of Metal delivered to Casthouse
Casthouse scales regularly calibrated and checked – Verified Calibration Records and is OK
• Theoretical Metal Production = f (Amperage supplied by Power Plant)
Power Plant amperage supply tested on monthly basis – Found Ok
Measurement System – Found Satisfactory
11
Carbon Dusting
Anode Spike
High Bath Temp /
Low AlF3
Excessive Sludge
Cell Underfeeds
Excessive Anode Effects
Bath Height Too Low
Cell Overfeeds
Low Bath Temp /
High AlF3
Excessive Anode Airburn
BRSP Set too low
Cell ACD Reduced
Al solubility in bath
increases
Al mixes back into
electrolyte
Oxidation of Al to Al2O3
Low Current
Efficiency
Cell Becomes Unstable
Excess heat
generation
Current bypasses electrolyte
Current Efficiency – Back Reaction Flow Chart
Possible causes for low Current Efficiency Bath temperature/AlF3 Age Anode Effects Alumina Feeding Metal and Bath height Base Resistance Set Point (BRSP) Noise/stability Operational problems Anode Problems
3. Analyze1. Define 2. Measure 4. Improve 5. ControlAnalyze Phase
Tool (s) Applied:- Process Flow
Diagram
12
Tool (s) Applied: Multi-Variable Linear Regression
• In multi-variable linear regression, there are several independent variables up to N.
Yi = βo + β1xi + β2xi + … where i = 1, …. N.
Variable P-valueBath Temperature 0.000
AlF3 0.034Age 0.038AEF 0.066
TRSP 0.094UF Duration 0.275
Time Unstable 0.305Dumps 0.451BRSP 0.537
Metal Height 0.554Bath Height 0.583
Average Resistance 0.608Volts 0.736Noise 0.746
• Age refers to life of reduction cell, and hence it is an unassignable cause
3. Analyze1. Define 2. Measure 4. Improve 5. Control
• P-value shows the significance of the correlation (p-value of 0.05 = 95% statistical significance or confidence). As much P-value closer to 0.0 as much as the parameter is statistically significant
• Strongest correlation between bath temperature and AlF3 (interrelated variables)
Needs more investigation
13
• Based on accumulative experience, it is proven that increase of 5oC in bath temperature can lead to 1% drop in current efficiency
960
962
964
966
968
970
972
974
976
84 86 88 90 92 94 96 98 100
Current Efficiency (%)
Bath
Tem
pera
ture
(C)
3. Analyze1. Define 2. Measure 4. Improve 5. Control
Bath Temperature
Linear regression covers the relationship:
CE = (-0.2259 x bath temperature) + 309.13
(R2= 0.9543)
14
• Relationship between BRSP/ACD and CE well established
84
86
88
90
92
94
96
98
100
13.5 14.0 14.5 15.0 15.5 16.0 16.5
BRSP (micro-ohms)C
urre
nt E
ffici
ency
(%)
• Initial analysis looked BRSP and CE. No big correlation above ~14.75 µ
• Some correlation < 14.75 µ
Base Resistance Set Point (BRSP)
3. Analyze1. Define 2. Measure 4. Improve 5. Control
15
Tool (s) Applied: Cumulative chart
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Number of Cell (%)
Loss
of C
urre
nt E
ffici
ency
(%)
3. Analyze1. Define 2. Measure 4. Improve 5. Control
~20% of cells represent 47% of total CE loss (Actual CE – Target CE).
Poor Performing Cells
16
Root Cause 1: High Bath Temperature
Root Cause 2: Low Base Resistance Set Point (BRSP)
3. Analyze1. Define 2. Measure 4. Improve 5. Control
Validated Root Causes/ Parameters
× Age – Life of Cell: Difficult to address this cause
17
Improve Phase
Current Efficiency Vs Bath Temp
y = 0.052x + 92R2 = 0.6879
91.0
91.5
92.0
92.5
93.0
93.5
94.0
94.5
95.0
22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 1 3
Week No. (2009 - 2010)
Cur
rent
Effi
cien
cy (%
)
954
956
958
960
962
964
966
968
Bat
h Te
mp
(°C
)
Bath TemperatureCurrent EfficiencyLinear (Current Efficiency)
Root Cause 1: Action plan for high bath temp and low CE pots
4. Improve1. Define 2. Measure 3. Analyze 5. Control
Dec. 2009Daniel Whitfield
Adjust Bath Chemistry to improve Current Efficiency
1
Completion Date
Responsibility
Action PointS. No.
18
• Established Control Limits so that BRSP not to be lowered below 14.5 µ without careful monitoring of the current efficiency
• Critical BRSP Limit of 14.75 µ.
• Increased the BRSP in low CE/BRSP cells
• Example of “action plan for implementation” as a result of weekly meetings is given below
Cell CE - 4wks CE - 16wks CE - 52wks Action Person Target Date146 89.3 90.6 92.9 Increase BRSP by 0.1µcheck dumpweight AS/MSW 07/01/2010198 90.3 91 92 Check BFT, Cu tab and dumpweight MSW 10/01/2010271 92.5 91 91.9 Improving in last 28 days, no action 20/01/2010149 89.3 91.1 93 Increase BRSP by 0.05µcheck Cu tab MSW 07/01/2010117 92 91.2 90 Under Fe attack FM NA102 93 91.3 91.5 Increase BRSP by 0.1µ AS 07/01/2010
4. Improve1. Define 2. Measure 3. Analyze 5. Control
• Average increase of 0.34 µ in 25 cells, average increase of 1.5% CE
Root Cause 2: Action plan for low Base Resistance Set Point (BRSP)
19
Current efficiency after improvement actions
91.5
92.0
92.5
93.0
93.5
94.0
94.5
95.0
95.5
Nov-07
Jun-0
8
Dec-08
Jul-0
9
Jan-1
0
Aug-10
Feb-11
Sep-11
Curr
ent E
ffici
ency
(%)
193
194
195
196
197
198
199
200
201
Ampe
rage
(kA
)
Monthly CE3-month Running AverageTarget CEAmperage
Project Start
4. Improve1. Define 2. Measure 3. Analyze 5. Control
20
• List of poor performing cells in Potline 3 developed, updated and released on weekly basis for setting up proper action plans.
• Work Instruction was developed to diagnose and action poor performing cells
System established for identifying and improving poor CE cells
9693908784
Summary for L3 CE, June 2009
98969492908886
Summary for L3 CE, Feb 2010
+1.3%
-0.76%
+1.38%
Difference
91.4 %
2.47 %
92.32 %
227
92.7 %1st Quartile
1.71 %STD. Dev.
93.70 %Mean
227Sample size
Distribution of L3 CE, Feb 2010Distribution of L3 CE, June 2009
After the ProjectBefore the project
5. Control1. Define 2. Measure 3. Analyze 4. ImproveControl Phase
21
• Potline 3 monitoring on daily basis by Potline Engineers and Technicians through potroom monitoring and reporting system (Smelter Analytics)
• Fine-tuning and changes to pots operating targets
5. Control1. Define 2. Measure 3. Analyze 4. Improve
22
Increased average Potline 3 current efficiency
92.292.492.692.8
9393.293.493.693.8
9494.2
2009, 2nd Half 2010, 1st Half 2010, Full year 2011, YTD
Cur
rent
Eff
icie
ncy
(%) Actual CE%
Target CE%
Project yielded re-occurring financial benefits of AED 1.47 millions per annum
Project Success & Benefits
Improved overall Potline performance
23
Recognitions:
• All team members received gift and cash award
• Project selected for Share Best Practice Session – to 200+ employees
• Nominated for CII Symposium
Learnings and Roll-over:
• Documentation of the project report
• Use of statistical tools and gained better understanding w.r.t. Smelting Process
• Roll-over of the successful initiatives from projects – to sister Potline 1– Achieved similar increase in current efficiency
Project Closure
24
• Achieved one of the best current efficiencies in D-18 type of cell design (at higher Amperage of 200kA)
• Combination of technical as well as statistical methods by using DMAIC approach
• Project experiences rolled-over to Potline of similar cell design and resulted in improvements
• Quantum contribution to company’s process performance
• Environmentally beneficial
Why this Project is an Excellent Improvement Example?
25
Thank you
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