1. Process Operability Class Materials Copyright © Thomas Marlin 2013
Process Efficiency
Basic flowsheet
Design with Operability FC 1 LC
Copyright © Thomas Marlin 2013
The copyright holder provides a royalty-free license for use of this material at non-profit educational institutions

2. PROCESS OPERABILITY: EFFICIENCY
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
PROCESS OPERABILITY: EFFICIENCY
In this Lesson, we will learn
The objective and degrees of freedom
Improvement through equipment selection
- Pump/fluid flow
Improvement through equipment utilization
- Pump/driver, boiler
Improvement through process structure
- Ethylene plant, packed bed chemical reactor
Improvement through operating conditions
- Fired heater/reactor, Flash, CSTR

3. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Degrees of freedom
EFFICIENCY
Efficiency: We will use this term to imply good economic performance, which can result from improved product quality, increased product rate, lower raw material, effluent and energy consumption, or other improvements.
Others might say “optimization”.
Increase: profit = sales – feed – fuel – electricity - …
Reduce effluents (e.g., total SO2, particulates, etc.)
Reduce greenhouse gases
Reduce use of feed (natural resources)

4. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Degrees of freedom
EFFICIENCY
1. Safety
2. Environmental
Protection
3. Equipment
protection
4. Smooth operation
production rate
5. Product quality
6. High profit
7. Monitoring &
diagnosis
Let’s recall that these objectives have higher priority. They must be achieved; then, we seek to increase profit.
Additional flexibility is required for increased efficiency & optimization
Objectives 1-5 
Profit/
Efficiency 

5. I can complete and check with answers in Operating Window topic.
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Approach 1: Design with the appropriate equipment capacities.
Recall the general tradeoffs in sizing process equipment.
Small equipment
Large equipment
I can complete and check with answers in Operating Window topic.
Advantages
Not too big
Not too small
Just right!
Disadvantages

6. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Efficiency through equipment capacity: Equipment with excessive capacity can operate at lower efficiencies.
Constant speed centrifugal pump
Let’s purchase a really large centrifugal pump for this application. What do you recommend?

7. EFFICIENCY Efficiency through equipment capacity:
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Efficiency through equipment capacity:
Constant speed centrifugal pump
Pump head curve
Steady-state flow rate at given conditions
head
“system” curve, pressure drop vs flow rate
Flow rate

8. EFFICIENCY Efficiency through equipment capacity:
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Efficiency through equipment capacity:
Constant speed centrifugal pump
To achieve the desired flow, we compensate for the larger pump by causing a large pressure drop across a valve .
Too large a pump wastes energy.
Do not
oversize
pumps!
head
Flow rate

9. EFFICIENCY Efficiency through equipment capacity:
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Efficiency through equipment capacity:
Most likely flow rate
The constant speed centrifugal pump (red curve) is selected to
Provide sufficient flow for the maximum demand
Operate near its maximum efficiency at the most likely (design) flow rate
head
Flow rate
The control valve affects the system (blue) curve
Usually about 70% open at design (but, must provide maximum flow rate)

10. Do we always install a control
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Follow-up Point #1 - Efficiency through equipment capacity:
Constant speed centrifugal pump
Do we always install a control
valve? If not, why?

11. EFFICIENCY Follow-up Point #1 - Efficiency through equipment capacity:
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Follow-up Point #1 - Efficiency through equipment capacity:
No control valve resistance
The constant speed centrifugal pump (red curve)
The flow is the maximum for the system, pump and piping design.
head
Flow rate
When the optimum flow rate is always the maximum flow, we do not use a control valve.
Example, cooling water utility in a chemical plant.

12. Do we always install a constant speed pump? If not, why?
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Follow-up Point #2 - Efficiency through equipment capacity:
Constant speed centrifugal pump
Do we always install a constant speed pump? If not, why?

13. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Follow-up Point #2 - Efficiency through equipment capacity: More flexible equipment can save energy at the expense of higher capital costs.
An alternate design uses a variable speed source of power (motor or turbine). (The control valve is not needed.)
This design is more energy efficient and may be the best economically (e.g., lowest NPV).

14. EFFICIENCY Follow-up Point #3 - Efficiency through equipment capacity:
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Follow-up Point #3 - Efficiency through equipment capacity:
Constant speed centrifugal pump
What is the best pipe diameter?
(Best = trade-off of capital and operating costs)

15. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment capacities
EFFICIENCY
Follow-up Point #3 - Efficiency through equipment capacity: A larger pipe diameter reduces pump work but increases piping costs.
Pipe diameter “rules of thumb” (guidelines, Woods, 1995)
Pumped liquid - velocity of
Vapor - velocity of
1 m/s
20-30 m/s
See Woods (1995) for correlations for many systems and fluids

16. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment utilization
EFFICIENCY
Approach 2: Use existing equipment in most efficient manner.
We provide extra equipment to
Increase reliability
Expand the operating window
Increase flexibility
To capitalize on optimization opportunities

17. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment utilization
EFFICIENCY
Efficiency through equipment utilization: We can use the lowest cost from parallel equipment.
Decision is usually made and implemented by a plant operator
electricity
motor
steam
Pumps with different power sources
turbine
Depending on the time of day and the steam usage elsewhere in the plant, the lowest cost source of work can change! We have the flexibility to respond.

18. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment utilization
EFFICIENCY
Efficiency through equipment utilization: The total demand of steam must be satisfied. The steam can be produced in boilers with different efficiencies. We can optimize. PC PY x
We adjust the ratios to lower fuel cost; fast pressure control not affected.

19. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment utilization
EFFICIENCY
Efficiency through equipment utilization: Several boilers provide increased reliability. Also, they allow boilers to be operated near their maximum efficiencies, compared with one large boiler, as the total steam demand changes.

20. EFFICIENCY Efficiency through equipment utilization
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment utilization
EFFICIENCY
Efficiency through equipment utilization
We must satisfy the plant demand. How much steam from each boiler (i = 1,4)?
Minimize total fuel = (fuel)i
when
(Steam)i = Demand
(fuel)i = (Steami*Hvap)/(Hcombust * i)
i = f(Steami)
We will learn how to formulate and solve this type of problem in 4G03.

21. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment synthesis
EFFICIENCY
Approach 3: We can increase efficiency by designing the best process structure (synthesis).
We provide extra equipment to
Recover & recycle unconverted feed
Recover & recycle solvent
Recover & reuse effluents (e.g., water)
Use heating (cooling) far from ambient
Thorough economic analysis is required to find the best investment of capital and operating costs

22. Equipment synthesis
EFFICIENCY
Propose a process structure change to increase efficiency/profit
COMP
RXN
Hydrogen,
methane
Naphtha feed
ethylene
DIST
naphtha
REFRIG
Products: Hydrogen to gasoline
ethane
Ethane feed
FRACT
propylene
butadiene
……..

23. Equipment synthesis
EFFICIENCY
Propose a process structure change to increase efficiency/profit
Recycle unconverted ethane to reactors
COMP
RXN
Hydrogen,
methane
Naphtha feed
ethylene
DIST
naphtha
REFRIG
Products: Hydrogen to gasoline
ethane
Ethane feed
FRACT
propylene
butadiene
……..

24. EFFICIENCY Efficiency through process structure:.
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment synthesis
EFFICIENCY
Efficiency through process structure:.
Discuss this packed bed reactor with an exothermic reaction.
Is this the best design? What alternative(s) would you evaluate?
heat
cool

25. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment synthesis
EFFICIENCY
Efficiency through process structure: We want to use raw materials and “energy” (material significantly hotter or colder than ambient). One typical structure involves recycle.
Cold product
Discuss this packed bed reactor with an exothermic reaction.
Advantages
Disadvantages
The reactor effluent is hot.
Cold feed
Hot effluent

26. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment synthesis
EFFICIENCY
Efficiency through process structure: One typical structure involves recycle.
Advantages
Disadvantages?

27. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Equipment synthesis
EFFICIENCY
Efficiency through process structure: One typical structure involves recycle.
Advantages
Good energy efficiency
(exhaust to environment closer to ambient)
Cannot startup the process (need heating)
No flexibility for changing operation
Poor dynamics (see section of dynamic performance)
I suspect that
we are not
through with
this exercise!
Disadvantages?

28. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Operating Conditions
EFFICIENCY
Approach 4: We can increase efficiency by selecting the best values of operating conditions.
Many conditions can be changed in the process that do not affect safety …. product quality, but they affect profit, e.g.,
Recycle compositions
Conversion in a chemical reactor
Intermediate separation
The best values can change from day to day
Thorough economic analysis is required to find
the best (optimum) conditions

29. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Operating Conditions
EFFICIENCY
Goal: Maximize conversion of feed ethane but do not exceed 864C
What is the best value of the reactor temperature?

30. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Operating Conditions
EFFICIENCY
“Constraint Control” to push against the constraint: Operate as close to 864 as is possible, given typical variability
Goal: Maximize conversion of feed ethane but do not exceed 864C

31. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Operating Conditions
EFFICIENCY
Efficiency through operating conditions: In many conditions, product can be made efficiently or inefficiently by changing process variable values within the operating window.
How do I
decrease
energy
cost?

32. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Operating Conditions
EFFICIENCY
Efficiency through operating conditions: In many conditions, product can be made efficiently or inefficiently by changes process variable values within the operating window.
Use the least
costly heating

33. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Operating Conditions
EFFICIENCY
Efficiency through operating conditions: In many conditions, product can be made efficiently or inefficiently by changing process variable values within the operating window.
Blend these components
To meet product specifications

34. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Operating Conditions
EFFICIENCY
Efficiency through operating conditions: In many conditions, product can be made efficiently or inefficiently by changing process variable values within the operating window.
Best Feed flow rate
How much H2 recycle?
Best reactor T

35. Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
Operating Conditions
EFFICIENCY
Efficiency calculations can be automated when conditions change frequently.
This is basically HYSIS run many times to obtain the optimum answer*
Model
Model Updating
Optimizer
Model parameters
Results analysis
Data Evaluation
Model predictive control
Advanced control
measurements
plant operations
* Solution approaches covered in 4G03
PLANT, SENSORS, REGULATORY CONTROL

36. Smithsonian Award-winning application in Sarnia by SUNCOR
Operating Conditions
SUNOCO OPTIMIZER RELIABLY SOLVES LARGE SYSTEMS AND EARNS SUBSTANTIAL BENEFITS
Smithsonian Award-winning application in Sarnia by SUNCOR

37. EFFICIENCY INDUSTRIAL PRACTICE
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
EFFICIENCY
INDUSTRIAL PRACTICE
Since we have an operating window, flexibility exists to optimize efficiency
Sometimes we use mathematical models for optimization (see 4G03 next semester)
Sometimes we use plant experiments to optimize (see 4C03 next semester)
Optimization can interact with other goals, such as consistent product quality. Therefore, we optimize slowly to prevent disturbing the processes.

38. EFFICIENCY In this Lesson, we will learn
Key Operability issues
1. Operating window
2. Flexibility/
controllability
3. Reliability
4. Safety & equipment protection
5. Efficiency & profitability
6. Operation during transitions
7. Dynamic Performance
8. Monitoring & diagnosis
EFFICIENCY
In this Lesson, we will learn
The objective and degrees of freedom
Improvement through equipment selection
- Pump/fluid flow
Improvement through equipment utilization
- Pump/driver, boiler
Improvement through process structure
- Ethylene plant, packed bed chemical reactor
Improvement through operating conditions
- Fired heater/reactor, Flash, CSTR