análisis del proceso papelero
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Análisis del Proceso Papelero
IPE Curso Auditoria Parte Húmeda
Madrid 21 Octubre 2004
Esteban Soto
Metso Automation
Pulp and Paper Automation Solutions
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Contents
• Customer benefit
• Tools
• Typical Process
• Analysis Procedure
• Typical analysis results
• Main disturbance sources
• Examples
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Customer’s Benefit of Process Analysis
• Problems restricting process performance and runnability,
such as:- Tuning of the basic controls
- Control strategies
- Instrumentation equipment (mainly valves)
- Process equipment
- Process design
More tons (with less raw material ) by reducing
process variability.
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Tools to Detect Variability
• Processes have always variability - detect the cause andstabilize the process to get the best performance
Process Control Process Design Fibre Flocculation
V a r i a b i l i t y ,
%
Process analysis
Machine analysis
Sensodec 6S
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Typical Process
• All companies
• Paper grade produced;
- WFC / WFU, LWC, SC, or other high ash containing grades,news and colors paper
• Annual production more than 100 000 ton/y
• High speed machine (>1000 m/min)
• Multi grade production line
• Sophisticated wet end process
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Process Analysis Procedure
• Familiarizing with customer’s process
- flow sheets and discussion with customer
• tag numbers, signals, piping, …
• Setting up the data collection
- MA own or customers PC, with needed specification
- 700 - 1400 signals with 5 s update time
- interesting cycles 20 s ---> hours
- Data collection with QMM (OPC if not metsoDNA system)
• Data collection phase
- ~ 2-4 weeks
• Data analysis & Reporting
- analysis in Matlab environment
- written report
- presentation of the results to the customer
• Typical time span of an analysis is about 3 months
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Another Analysis
• High frequency analyses (T < 1 sec)
- Vibration analyses
- Pulsation measurements- Quality variable fixed point measurements are included
• Tuning services
• Analysis from paper samples
- Tapio analysis can be done externally
• Setpoint optimization (Cost function needed...)
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Summary of Typical Improvement Proposalsin the Analysis Reports
• Re-tuning of the basic controls
• Calibrations of the transmitters
• New control strategies
- e.g. IQWetendMD, IQCharge, OptiFeed controls
• Valve upgrades
- Maintenance
- New positioners
• Process operating policies
• Machinery maintenance
• Process improvements- Changes in piping
- Changes in chemical / filler dosing points
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Typical Disturbance Sources in the Process
• Based on studies on several SC and fine paper machines
- High ash content of produced papers
- Complex process layout of the wet end
• Main sources
1) Disc filter process2) Broke dosing
3) Level controllers
4) Dosing of additives
5) Consistency control strategies
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Exemple 1- Level Control
Chests in Series Can Amplify Cycles
LICFIC FICLICFIC
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Example - 2Consistency Control Strategies
Simple solution Advanced solution
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Simple Control Solution
( )⎟⎟ ⎠
⎞⎜⎜⎝
⎛ −=−=
−==
tot
d
tot
d
tot
d tot
tot Q
QCs
Q
QCsCs
Q
QQCs
Q
QCsCs 11
11
1112
tot d Q
Cs
Q
Cs 12
−=∂
∂
Total flow rate affectsthe process gain!!
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Simple Control configuration
• Non-linear process gain
- High gain when flow is low
• Needs an equal percentage valve- High gain with big valve opening (high flow)
- Compensates process gain change
- What is true installed characteristic curve?• Disturbances caused by flow rate changes are compensated
through error in the consistency
• Feeding pressure of the dilution water causes consistencydisturbances
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Advanced Control strategy
( )K Cs
Q
KQCs
Q
QCsCs
tot
tot
tot
d −=⎟⎟
⎠
⎞⎜⎜
⎝
⎛ −=⎟⎟
⎠
⎞⎜⎜
⎝
⎛ −= 111 1112
12 CsK
Cs
−=∂
∂
Total flow rateis de coupled
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Advanced Control Configuration
• Process gain does not depend on total flow rate
- Same process gain in all flow rates
• Needs a linear dilution water valve- Cascade flow controller controls flow accurately
- Valve can be linearized for accurate flow control
• Flow rate changes are compensated without consistencyerror
• Changes in the dilution water feeding pressure arecompensated with fast flow controller
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Simple Consistency Control StrategySudden Flow Change
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Advanced Consistency Control StrategySudden Flow Change
E l 3
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Example - 3Long Term Performance Following
• Fast variability level changes easy to observe (for examplemalfunction of a process device)
• Problems were variability develops slowly more difficult
- No reference level of the variability
-People get used to problems as time goes on
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Long Term Performance Following
• Ways to observe- Some index (ex. standard deviation) from certain time period
• One number, data to be cleaned carefully before calculation
- remove break time and some data after the break
- remove some data after set point changes
• Distribution of a variable from specific time period calculatedwithin sliding window
• No time resolution, you can’t see when the problem started
- Sliding standard deviation calculated within a time window ofa day
• As a result surface which shows performance distribution fromday to another
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day 1 day 2 day 3 day 4 day 5
One hours windowSlides over the time
period (e.g. one day)
Produces a sliding COVtrend of variable
Cumulative trend of
COV
% of operation time
COV %
COV %
time
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day 1 day 2 day 3 day 4 day 5
% of operation time
COV %
COV %
time
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On top view
Colors added
Significance Information Needed
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