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



© Metso Automation Inc. 2003

Contents

• Customer benefit

• Tools

• Typical Process

• Analysis Procedure

• Typical analysis results

• Main disturbance sources

• Examples




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.




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




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




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




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...)




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




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




Exemple 1- Level Control

Chests in Series Can Amplify Cycles

LICFIC FICLICFIC




Example - 2Consistency Control Strategies

Simple solution Advanced solution




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!!




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




Advanced Control strategy

( )K Cs

Q

KQCs

Q

QCsCs

tot

tot

tot

d −=⎟⎟

⎠

⎞⎜⎜

⎝

⎛ −=⎟⎟

⎠

⎞⎜⎜

⎝

⎛ −= 111 1112

12 CsK

Cs

−=∂

∂

Total flow rateis de coupled




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




Simple Consistency Control StrategySudden Flow Change




Advanced Consistency Control StrategySudden Flow Change

E l 3




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




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




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




day 1 day 2 day 3 day 4 day 5

% of operation time

COV %

COV %

time




On top view

Colors added

Significance Information Needed




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análisis del proceso papelero

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