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Chemical Engineering 3P04 Process Control Tutorial # 7 Learning goals Experience with a single-loop controller Answerin

Chemical Engineering 3P04 Process Control Tutorial # 7 Learning goals Experience with a single-loop controller Answering some questions from PC-Education. Vapor product. PAH. TC-6. PC-1. T5. T1. T2. Feed Methane Ethane (LK) Propane Butane Pentane. LAL LAH. FC-1. T3. LC-1.

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Chemical Engineering 3P04 Process Control Tutorial # 7 Learning goals Experience with a single-loop controller Answerin

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  1. Chemical Engineering 3P04 • Process Control • Tutorial # 7 • Learning goals • Experience with a single-loop controller • Answering some questions from PC-Education

  2. Vapor product PAH TC-6 PC-1 T5 T1 T2 Feed Methane Ethane (LK) Propane Butane Pentane LAL LAH FC-1 T3 LC-1 F2 F3 Liquid product AC-1 L. Key Process fluid Steam An Introductory Experience with Feedback Control • We use many feedback controllers for a typical process • Each controller has one measurement and one manipulated variable

  3. An Introductory Experience with Feedback Control Let’s look at one example feedback loop v1 T 4-20 mA A Product composition 4-20 mA 3-15 psi v2 control display and computer Heating medium

  4. An Introductory Experience with Feedback Control Our first task is to learn about the dynamics. We can apply the process reaction curve experiment. v1 T A Product composition 3-15 psi v2 Heating medium

  5. An Introductory Experience with Feedback Control Mole fraction minute % open

  6. An Introductory Experience with Feedback Control • Observations from the experiment. • An increase in valve opening increases the concentration. The process gain is positive. • Time to steady-state is about 25 minutes. • Dead time is about 6 minutes and time constant is about 6 minutes. • The process is stable and overdamped. • The measurement has noise

  7. An Introductory Experience with Feedback Control • The computer has a defined algorithm using the feedback measurement to determine the next value of the manipulated variable • Calculations are done every 1/3 second • The engineer enters the appropriate parameters v1 T A Product composition 3-15 psi v2 Heating medium

  8. An Introductory Experience with Feedback Control Parameter sets the “aggressiveness” of the controller. Mole fraction KC = 0 (Controller off) minute % open

  9. An Introductory Experience with Feedback Control Parameter sets the “aggressiveness” of the controller. Mole fraction KC = 0.3 minute % open

  10. An Introductory Experience with Feedback Control Parameter sets the “aggressiveness “ of the controller. Mole fraction KC = 0.8 minute % open

  11. An Introductory Experience with Feedback Control Parameter sets the “aggressiveness“ of the controller. Mole fraction KC = 1.2 minute % open

  12. An Introductory Experience with Feedback Control Parameter sets the “aggressiveness” of the controller. Mole fraction KC = 1.8 minute % open

  13. An Introductory Experience with Feedback Control • Observations from the samples of feedback performance. • Feedback that is “too weak” takes a long time to compensate a disturbance • Feedback that is “too strong” gives poor behavior and can result in instability • Feedback can result in underdamped behavior for a process that is overdamped. • The process dynamics have the dominant effect on control performance.

  14. An Introductory Experience with Feedback Control • Observations from the samples of feedback performance. • Even the best behavior is “not perfect”. The process must be upset before feedback takes action. • The valve must be moved to a different steady-state to compensate for a disturbance. We move the disturbance from the important controlled variable to the less important manipulated variable.

  15. S_LOOP parameters for this example

  16. S_LOOP parameters for this example

  17. S_LOOP parameters for this example

  18. S_LOOP parameters for this example

  19. Reinforcing PID Controller Concepts Let’s Perform the following exercises from PC-Education Interactive Learning Modules 8.5 – 8.9 and 8.13 Tutorial 8.5 (Problems with solutions – it doesn’t get any better than this!)

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