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

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

Key Operability issues Degrees of freedom EFFICIENCY 1. Operating window 2. Flexibility/ controllability 3. Key Operability issues Degrees of freedom EFFICIENCY 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: 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 SO 2, particulates, etc. ) • Reduce greenhouse gases • Reduce use of feed (natural resources)

Key Operability issues Degrees of freedom EFFICIENCY 1. Operating window 1. Safety 2. Flexibility/ Key Operability issues Degrees of freedom EFFICIENCY 1. Operating window 1. Safety 2. Flexibility/ controllability 2. Environmental Protection 3. Reliability 3. Equipment protection 4. Safety & equipment protection 5. Efficiency & profitability 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 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis Objectives 1 -5 Profit/ Efficiency

Key Operability issues Equipment capacities EFFICIENCY 1. Operating window 2. Flexibility/ controllability 3. Reliability Key Operability issues Equipment capacities EFFICIENCY 1. Operating window 2. Flexibility/ controllability 3. Reliability Approach 1: Design with the appropriate equipment capacities. Recall the general tradeoffs in sizing process equipment. 4. Safety & equipment protection Small equipment 5. Efficiency & profitability 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis Large equipment Advantages Disadvantages big too ll t ma No os t to t! No igh st r Ju I can complete and check with answers in Operating Window topic.

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

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

Key Operability issues 1. Operating window Equipment capacities EFFICIENCY Efficiency through equipment capacity: 2. Key Operability issues 1. Operating window Equipment capacities EFFICIENCY Efficiency through equipment capacity: 2. Flexibility/ controllability Constant speed centrifugal pump 3. Reliability 4. Safety & equipment protection 5. Efficiency & profitability Do not oversize pumps! head 6. Operation during transitions 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. 7. Dynamic Performance 8. Monitoring & diagnosis Flow rate

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

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

Key Operability issues 1. Operating window 2. Flexibility/ controllability Equipment capacities EFFICIENCY Follow-up Point Key Operability issues 1. Operating window 2. Flexibility/ controllability Equipment capacities EFFICIENCY Follow-up Point #1 - Efficiency through equipment capacity: No control valve resistance 3. Reliability head 4. Safety & equipment protection The constant speed centrifugal pump (red curve) The flow is the maximum for the system, pump and piping design. 5. Efficiency & profitability 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis 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.

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

Key Operability issues 1. Operating window 2. Flexibility/ controllability Equipment capacities EFFICIENCY Follow-up Point Key Operability issues 1. Operating window 2. Flexibility/ controllability Equipment capacities EFFICIENCY Follow-up Point #2 - Efficiency through equipment capacity: More flexible equipment can save energy at the expense of higher capital costs. 3. Reliability 4. Safety & equipment protection 5. Efficiency & profitability 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis 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).

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

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

Key Operability issues Equipment utilization EFFICIENCY 1. Operating window 2. Flexibility/ controllability 3. Reliability Key Operability issues Equipment utilization EFFICIENCY 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 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

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & 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 turbine Pumps with different power sources 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.

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability Equipment utilization EFFICIENCY Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 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 4. Safety & equipment protection 5. Efficiency & profitability 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis PY x We adjust the ratios to lower fuel cost; fast pressure control not affected.

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & 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.

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & equipment protection 5. Efficiency & profitability 6. Operation during transitions 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) 7. Dynamic Performance 8. Monitoring & diagnosis We will learn how to formulate and solve this type of problem in 4 G 03.

Key Operability issues Equipment synthesis EFFICIENCY 1. Operating window 2. Flexibility/ controllability Approach 3: Key Operability issues Equipment synthesis EFFICIENCY 1. Operating window 2. Flexibility/ controllability Approach 3: We can increase efficiency by designing the best process structure (synthesis). 3. Reliability We provide extra equipment to 4. Safety & equipment protection 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis Recover & recycle unconverted feed • Recover & recycle solvent • 5. Efficiency & profitability • 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

Equipment synthesis EFFICIENCY Propose a process structure change to increase efficiency/profit RXN COMP Hydrogen, Equipment synthesis EFFICIENCY Propose a process structure change to increase efficiency/profit RXN COMP Hydrogen, ethylene Naphtha feed DIST naphtha 0 REFRIG 0 0 Ethane feed ethane FRACT propylene butadiene ……. . Products: Hydrogen to gasoline methane

Equipment synthesis EFFICIENCY Propose a process structure change to increase efficiency/profit Recycle unconverted ethane Equipment synthesis EFFICIENCY Propose a process structure change to increase efficiency/profit Recycle unconverted ethane to reactors RXN COMP Hydrogen, ethylene Naphtha feed DIST naphtha 0 REFRIG 0 0 Ethane feed ethane FRACT propylene butadiene ……. . Products: Hydrogen to gasoline methane

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

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability Equipment synthesis Efficiency Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability Equipment synthesis 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 4. Safety & equipment protection 5. Efficiency & profitability EFFICIENCY Cold feed Discuss this packed bed reactor with an exothermic reaction. 6. Operation during transitions • Advantages 7. Dynamic Performance The reactor effluent is hot. 8. Monitoring & diagnosis • Disadvantages Hot effluent

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

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

Key Operability issues Operating Conditions EFFICIENCY 1. Operating window 2. Flexibility/ controllability 3. Reliability Key Operability issues Operating Conditions EFFICIENCY 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 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

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

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & 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

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & 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?

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & 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

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability Operating Conditions EFFICIENCY Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 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. 4. Safety & equipment protection 5. Efficiency & profitability 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis Blend these components To meet product specifications

Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & Key Operability issues 1. Operating window 2. Flexibility/ controllability 3. Reliability 4. Safety & equipment protection 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 H 2 recycle? 5. Efficiency & profitability 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis Best reactor T

Key Operability issues 1. Operating window 2. Flexibility/ controllability Operating Conditions EFFICIENCY Efficiency calculations Key Operability issues 1. Operating window 2. Flexibility/ controllability Operating Conditions EFFICIENCY Efficiency calculations can be automated when conditions change frequently. 3. Reliability Model Updating 4. Safety & equipment protection Model Optimizer Model parameters Results analysis 5. Efficiency & profitability 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis Data Evaluation This is basically HYSIS run many times to obtain the optimum answer* Advanced control measurements Model predictive control plant operations PLANT, SENSORS, REGULATORY CONTROL * Solution approaches covered in 4 G 03

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

Key Operability issues EFFICIENCY 1. Operating window 2. Flexibility/ controllability 3. Reliability INDUSTRIAL PRACTICE Key Operability issues EFFICIENCY 1. Operating window 2. Flexibility/ controllability 3. Reliability INDUSTRIAL PRACTICE • Since we have an operating window, flexibility exists to optimize efficiency 4. Safety & equipment protection • Sometimes we use mathematical models for optimization (see 4 G 03 next semester) 5. Efficiency & profitability • Sometimes we use plant experiments to optimize (see 4 C 03 next semester) 6. Operation during transitions 7. Dynamic Performance 8. Monitoring & diagnosis • Optimization can interact with other goals, such as consistent product quality. Therefore, we optimize slowly to prevent disturbing the processes.

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