1

Overview of Plant Operation

by Dr. AA

Objectives of Plant Operation

Ensuring that the plant has the capacity and flexibility to achieve a range of operating conditions safely, reliably, profitably and with good dynamic performance

2

We need to establish good operability

• Follow work system & procedure

• troubleshoot problems

• Making decision & taking effective action

Consider a Distillation System Methane as main product at the Top

3

E9

FI1

TI1 TI5

AI10

FI9

Feed

Methane Ethane (LK) Propane Butane Pentane

P 1000 kPa T 298 K

TI3

TI4

TI2

TI7

TI6

TI10

FI10

AI9

FI8 TI9

LI9

PI9

E2 E1

T1

M9

M10

E10

Process fluid

Steam

People & Environmental Protection

Equipment Protection • Product Specification • Economy

Workshop Out of Control !

Handouts will be given in classroom

4

Challenges in Modern Plant

More stringent product specifications

Tighter Constraints due to low over-design margin

More interactions due after removing intermediate storage

More complex plant structure due to process integration

5

More Stringent Quality Requirement

-1s 2s m -3s

0.135 % 0.135 %

+1s +2s +3s

99.73 %

m ± 3 s

Traditionally three-

sigma is acceptable,

now, the industry is on

six-sigma

-1s 2s m -3s +1s +2s +3s

99.9999998%

m ± 6 s

-6s +6s

6

Reduced Variability Product

7

Goal: Maximize conversion of feed ethane but do not exceed 864 oC

Which operation, A or B, is better?

Explain why.

864 C Temp.

Co

nve

rsio

n

0

0.1

0.2

0.3

0.4

0.5

0.6

842 846 850 854 858 862

Temperature

freq

uen

cy

0

0.05

0.1

0.15

0.2

0.25

842 846 850 854 858 862

Temperature (C)

freq

uen

cy

B

A

FC

TC

Fuel

Ethane

Feed

Flue gas

AC

Air

8

Improving Efficiency by Operating Near Constraints

Which operation, A or B, is better?

Explain why.

B A

0

0.1

0.2

0.3

0.4

0.5

0.25 1.25 2.25 3.25 4.25 5.25

O2 mole %

fre

quency

80

82

84

86

88

Effic

iency %

Frequency

Efficiency

0

0.05

0.1

0.15

0.2

0.25

0.25 1.25 2.25 3.25 4.25 5.25

O2 mole %

frequency

80

82

84

86

88

Effic

iency %

Frequency

Efficiency

FC

TC

Fuel

Ethane

Feed

Flue gas

AC

Air

9

Reduced Variability in Performance

10

Process Interaction

E9

FI1

TI1 TI5

AI10

FI9

Feed

Methane Ethane (LK) Propane Butane Pentane

P 1000 kPa T 298 K

TI3

TI4

TI2

TI7

TI6

TI10

FI10

AI9

FI8 TI9

LI9

PI9

E2 E1

T1

M9

M10

E10

Process fluid

Steam

Discuss Process Interactions issues in this plant

• Set goals and design specifications

• Select process technology

• Define process structure (sequence)

• Simulate the flowsheet

• Design equipment

Construct and start up

Often performed for

one operating point

Operate the plant over a range

of conditions, many operating

points and transitions between

them

Inconsistency!

Between Design & Operation

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The design procedure should ensure that the plant

is operable, that it functions “well”. This requires a

specification that addresses a range of conditions,

for example:

• Feed compositions and rates

• Product qualities

• Equipment capacities and availabilities

• Environment (summer, winter)

• Major disturbances

Process Design With Operability

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What do the following words have in common?

Music Love

Operability Happiness

Class Workshop

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I need to regulate the flow,

but how complex should the

equipment be?

Does the need for operability

affect this decision?

From the simplest to

most complex process,

we must think about

operability!

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Conclusion I’ll think about it !!