process control department of chemical engineering ntu september 2008

Process Control

Department of Chemical EngineeringNTU

September 2008

Class InstructorHsiao-Ping Huang (Room 213)

Professor Department of Chemical EngineeringNational Taiwan University

Work with NTU since 1970

Teaching Assistant (401)PhD. Candidate

Class ContentsLectures: every Monday: 09:10~10:00every Wednesday: 10:20~12:00Examinations: Mid term Exam. Final Exam.Home works: will be assigned after lectures

Backgrounds

Chart5

16.9

15.2

12.9

9.2

7.9

5.8

5.3

4.9

4.1

3.7

14.1

Industry

Percent

Employment of US Chemical Engineers 2005

Sheet1

Graphs for Chemeca 2006 Plenary Lecture8/5/06 draft

Fig. 1

RegionSales

Europe38.00%

Asia Pacific28.00%

North America25.00%

Latin America5.00%

MEAF4.00%

100.00%

Figure 2: New large Chem plants

YearAsia PacificMid EastEuropeUSALatin AmCanadaAfricaTotalChemical Plant Projects

1995150301056565634242005 vs Avg '00-02

1996120309048451810361

1997120309048451810361Middle East148.6%

1998120309049451810362Asia Pacific71.4%

1999120309049451810362USA22.7%

200090357525282515293Latin America-8.0%

200170805550301818321Africa-8.2%

2002506011535301616322Europe-14.3%

20034570922015816266Canada-18.6%

2004120488550251630374

20051201457045271615438

Avg 00-01-0270588237292016312

Change 05 vs Avg71.4%148.6%-14.3%22.7%-8.0%-18.6%-8.2%40.4%

Figure 4: Starting Salaries

$

MajorAnnual Salary

Liberal Arts30,800

Marketing36,300

Business39,900

Civil Eng.45,000

Accounting45,700

Computer Sci.50,000

Mechanical Eng.50,700

Electrial Eng.52,900

Chemical Eng.55,900

table 1: Top Employment Industries

Total respondants=1614IndustryPercent

IndustryCoreMedicalPetroChemOil ProdNat. GasMetalsPlasticEvironmentalCommodityCatalystsFibers/FilmsSoap,DetergControlsPaint, CoatingsUtilitiesSafety,HealthNuclearSemiconductSoftwareTotal%Chemicals16.9

Engineering D&C170597924515.2%Engineering Services15.2

Chemicals162902027216.9%Oil & Gas12.9

Pharmaceuticals1271277.9%Materials9.2

Bio & Live Sci.718794.9%Pharmaceuticals7.9

Petroleum12655131520912.9%Education5.8

Materials2621748191489.2%Consumer Products5.3

Education94945.8%Bio, Medical, Life Science4.9

Government60603.7%Energy Production4.1

Consumer Products7312855.3%Government3.7

Energy103026664.1%Others14.1

Auto & Aero32322.0%Total100

Industrial Gases30301.9%

Electronics23914462.9%

Others7.5%

100.0%

Sheet1

ACC, 2004

Global Sales of Chemical Products

Sheet2

Source [2]

Mid East

Asia Pacific

Europe

USA

Asia Pacific

Mid East

Europe

USA

Latin Am

Canada

Africa

Year

No. of Projects

New Chemical Plant Projects

Sheet3

Source [5]

Profession

Starting Annual Salary ($)

Salaries by ProfessionUSA 2006 Graduates

Industry

Percent


Chart2

30800

36300

39900

45000

45700

50000

50700

52900

55900

Source [5]

Profession



Sheet1


Fig. 1

RegionSales

Europe38.00%

Asia Pacific28.00%

North America25.00%

Latin America5.00%

MEAF4.00%

100.00%

Figure 2: New large Chem plants


1995150301056565634242005 vs Avg '00-02

1996120309048451810361

1997120309048451810361Middle East148.6%

1998120309049451810362Asia Pacific71.4%

1999120309049451810362USA22.7%

200090357525282515293Latin America-8.0%

200170805550301818321Africa-8.2%

2002506011535301616322Europe-14.3%

20034570922015816266Canada-18.6%

2004120488550251630374

20051201457045271615438

Avg 00-01-0270588237292016312

Change 05 vs Avg71.4%148.6%-14.3%22.7%-8.0%-18.6%-8.2%40.4%

Figure 4: Starting Salaries

$

MajorAnnual Salary

Liberal Arts30,800

Marketing36,300

Business39,900

Civil Eng.45,000

Accounting45,700

Computer Sci.50,000



Chemical Eng.55,900

table 1: Top Employment Industries
















Others7.5%

100.0%

Sheet1

0

0

0

0

0

ACC, 2004


Sheet2

Source [2]

Mid East

Asia Pacific

Europe

USA

Asia Pacific

Mid East

Europe

USA

Latin Am

Canada

Africa

Year

No. of Projects


Sheet3

Source [5]

Profession



Industry

Percent


Chart2

580006100080500

745007350094000

835508500097350

8952092000108000

100500110000125000

102500113200113850

100000115500135000

110000118050120000

83000119000142170

PhD

MS

BS

[Source 4]

BS

MS

PhD

Years of Work Experience

Median Salary ($/Yr)

ChE Salaries by Education LevelsUSA 2005

Sheet1


Fig. 1[Meyers talk, Beijing, 06]

RegionSales

Europe38.00%

Asia Pacific28.00%

North America25.00%

Latin America5.00%

MEAF4.00%

100.00%

Figure 2: New large Chem plants[Hydrocarbon Processing, March '06]


1995150301056565634242005 vs Avg '00-02

1996120309048451810361

1997120309048451810361Middle East148.6%

1998120309049451810362Asia Pacific71.4%

1999120309049451810362USA22.7%

200090357525282515293Latin America-8.0%

200170805550301818321Africa-8.2%

2002506011535301616322Europe-14.3%

20034570922015816266Canada-18.6%

2004120488550251630374

20051201457045271615438

Avg 00-01-0270588237292016312

Change 05 vs Avg71.4%148.6%-14.3%22.7%-8.0%-18.6%-8.2%40.4%

Figure 4: Starting Salaries[CEP, Aug '05]

$

MajorAnnual Salary

Liberal Arts30,800

Marketing36,300

Business39,900

Civil Eng.45,000

Accounting45,700

Computer Sci.50,000



Chemical Eng.55,900

table 1: Top Employment Industries[CEP, Aug '05]
















Others7.5%

100.0%

Median ChE Salaries by Ed. Level[CEP, Aug '05]

Yrs Work ExperienceBSMSPhD

558,00061,00080,500

1074,50073,50094,000

1583,55085,00097,350

2089,52092,000108,000

25100,500110,000125,000

30102,500113,200113,850

35100,000115,500135,000

40110,000118,050120,000

4583,000119,000142,170

Sheet1

0.38

0.28

0.25

0.05

0.04

ACC, 2004


Sheet2

15030105656563

120309048451810

120309048451810

120309049451810

120309049451810

90357525282515

70805550301818

506011535301616

4570922015816

120488550251630

1201457045271615

Source [2]

Mid East

Asia Pacific

Europe

USA

Asia Pacific

Mid East

Europe

USA

Latin Am

Canada

Africa

Year

No. of Projects


Sheet3

Source [5]

Profession



Industry

Percent


PhD

MS

BS

[Source 4]

BS

MS

PhD

Years of Work Experience

Median Salary ($/Yr)

ChE Salaries by Education LevelsUSA 2005

Where the control application is ?

Float Level ControlBall cock level control started by EgyptiansWater clocksStill used in many domestic and industrial applications

Biological Control SystemsBlood pressure controlAdjust stroke rate of heartdilation of arteries

Governor Speed ControlJames Watt invented in 1769Used on both stationary and railway steam enginesJ.C Maxwell analyzed in 1868

Washing Machine Fuzzy Logic ControlConcept of Fuzzy Logic introduced by Lofti ZadehFuzzy sets defined by membership functionsConcepts of dirty measured by water turbidity

CD ControlPosition control of laser headSpeed control of drive

Modern Car Control Adaptive Cruise Control

Pick and Place RobotVision feedback systems now common

The Sojourner Mars ExplorerLanded Mars, July 4 199711 kg, 2km/hr top speed, 10 m rangeSolar poweredUHF Radio Modem CommsFirst attempt at remote control on another planet

Copolymerization ProcessRXHPSLPSLPSProductPurgeFresh Monomer feedChain Transfer AgentCo-Monomer feedInitiator6-30 secs~ 1 min~ 10 minsLong Recycle LoopVery High Pressure; High TemperatureMedium PressureLow PressureMeasurement System

Chemical Process Control

Chemical Plant

Industrial Backgrounds

Source of Benefits

Industrial EnvironmentCommodity marketsReduce costs by 3% p.a. just to stand stillEnvironmental issuesResponsive to customer demandsQuality product differentiationTiming just in time manufacturingVolume multi-purpose plants

Industry TargetsOn-line equipment efficiency > 95%

Maximum 100%, world class > 85%Operators in regular contact with customersNo alarmsNo health, safety, environmental concerns

Incident Reporting SystemAccidentsIncidentsNear MissesErrors & Recoveries

_964790552.doc

1

10

30

600

Critical Incident

Major Incident

Serious Incident

Incident

Potential Major Incident

Potential Serious Incident

_1035701038.doc

1

10

30

600

Critical Incident

Major Incident

Serious Incident

Incident



_963314271.doc

1

10

30

600

Critical Incident

Major Incident

Serious Incident

Incident



Managing Abnormal Situations - Anatomy of a Disaster From Operations Perspective

Various cost elements

Efficiency

Operating Target

Current Limit

Theoretical Limit

Plant Performance

Comfort Margin

Theoretically possible; currently unsustainable

Lost opportunity(Cost of comfort)

Future upgrades (e.g., Advanced Control)

Lost Profit

Additional unplanned costs

Break-even

Loss

Fixed Costs(Idle Plant)

Equipment damage, etc.

Accident

Lost Revenue

Profit

Shut down

Incident

Lost Opportunity = 3-8% of Capacity!

Economics of Better Operation

Sumary on the backgroundsThe performance requirements becomes increasingly difficult to satisfy.---Tougher environmental and safty regulations, repid changing economic conditions tighten product qualify specifications.

Modern plants featured by complexity and highly integrated process become more difficult to operate without process control.

Increased emphasis placed on safety, efficient plant operation make process control increasingly important than ever.

Now, the course of Chemical Process Control

What to learn?Exposure to control instrumentation and hardware as practiced in industryUnderstand dynamic behaviors of processesBecome proficient in Analysis of dynamics systems---Use Laplace transformationLearn the effects of feedback system and PID controllersTuning PID controllersAdvanced control strategies

Process: The conversion of feed materials to products using chemical and physical operations taking place in some unit or equipment Process dynamics refers to unsteady state process behavior. Transient operation occurs during important situations such as start-up and shut downs, and unusual disturbances or planned transitions from one product to another.Process control refers to maintain a process at the desired operating conditions, safely and efficiently while plant environment or product changes by manipulating some flow of material or energy.Key words:

Process Control Symbols for easy communicationFor functional identification For easy communicationFor P&ID diagram

Scientific Apparatus Manufacturers Association (SAMA)

Example continuous processes

Blending Process

Control questions: when x1 varies with time , how can we ensure the outlet conc. X remains at or near its desired value, xsp?

ProfitableRequired for operations inalmost all manufacturingplantsEconomic considerationsTraditional approach?Model-Based approach?Mathematical programming

Classification of variablesControlled variables : The variables that must be maintained, or controlled.Manipulation Variables: the variables used to maintain the controlled variable at constant levels (Set-points)Disturbance variables: Variables that cause the controlled variables to deviate from their set-points.

ControlledVariableManipulation variableSteam flow rateDisturbance VariablesSteam pressure

Classification of Control StrategiesFeedback control --- Control action occurs only if deviation from set-point is detected.Feedforward control --- Control action occurs at the same time when disturbance enters the processInferential control --- Control actions based on indirect measurement

Advantages DisadvantagesSimple Can compensate for any disturbance that enters the processControl action takes place only after error occursThe error correction is essentially a trial-and-error operation

Advantages DisadvantagesControl action takes place before error occursPerfect control is theoretically possibleMay result in permanent errorsDisturbance must be measurableUsually encounters Implementation difficulties

Feedback & Feedforward Control

Feedforward control takes care of major and measurable disturbancesFeedback control takes care of all other unmeasurable disturbances and the imperfect compensations left behind from feedforward control

Incentives for Process ControlFor safetyTo meet operational ConstraintsTo meet product qualityTo meet environmental regulationsTo save energyTo improve operability

Safty valvePressure ControlSafty

Product QualityConcentration Control

Smooth Operation---Improve operabilityLevel Control

Improve operability

Save energy costMake use of cheap cooling water as much as we can to lower the column pressure so as to save steam consumption

Save energy costUse cheap CW as much as we can during the normal operations.Switch to the use of more expensive refrigerant in case of abnormal situations

Why is feedback important?To correct errorTo stabilize inherently open-loop unstable processesTo reduce sensitivity of a system to the external inputsTo reduce sensitivity of a system due to modeling error

Positive FeedbackMicrophone loud speaker arrangements

Basic components of a control systemProcess ---- ObjectSensor/transmitter ---- Measurement and feedback Controller --- Decision makingFinal Control Element --- Action

Types of Control --- based on signal feedbackOpen loop-control --- manipulation variables changes according to a pre-determined scenarioClosed-loop control --- manipulation variables changes according to the feedback measurements

Control Objectives Servo-control --- To make controlled variable follow changes of set-point

Regulatory Control --- To correct the deviations caused by the disturbances

ProfitableRequired for operations inalmost all manufacturingplantsEconomic considerationsTraditional approach?Model-Based approach?Mathematical programming

What Are We Trying to Achieve?

Constraints on OperationMinimise quality give-awayMaximise productionConstraint

Control Performance

_1043662381.doc

, 2006(3rd ed).

***This slide looks at production-- for example, capacity realized--and does not factor in costs required to attain that capacity nor costs of accidents. The typical 125kbbd refinery or average chemical plant has an area under the curve worth on the order of $1 Billion U.S.

Investments in advanced control are intended to move the distribution of production rates to the right. @sset.MAX plant solutions are designed to slice off the tail on the left. *

process control department of chemical engineering ntu september 2008

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