Simulacion

CHAPTER 1 : INTRODUCTION TO PROCESS CONTROL
When I complete this chapter, I want to be able to do the following.

• Explain the feedback concept applied to control • Explain and identify the three elements in a feedback loop • Be able to apply feedback manually to many chemical process examples

CHAPTER 1 : INTRODUCTION TO PROCESS CONTROL
Outline of the lesson.

• Why Process Control andWhy Now? • Basic Questions about Control
- What does a feedback system do? - Why is control necessary? - Why is control possible? - Where is control done? - How is control documented?

• Workshop • Self-Study Guides

WHY HAVE A PROCESS CONTROL COURSE?
• When I run a kinetics experiment, how do I maintain the temperature and level at desired values? How do I manufacture products withconsistently high quality when raw material properties change? How much time do I have to respond to a dangerous situation?
Every engineer needs basic knowledge about control. Many exciting career opportunities exist for a technical specialist.

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WHY NOW FOR THE CONTROL COURSE?
• • We started with steady-state analysis because it is easier and important. We are building expertise infundamentals (fluids, heat transfer, thermo, etc.) and process units (distillation, CSTR, etc.). Now we have examples that need control! We need to master control before integrating our knowledge in process design?
It’s a perfect time to learn how to “drive” the chemical process. With this insight, we will be able to design plants that can be controlled safely and produce high quality products.

•WHAT DOES A FEEDBACK SYSTEM DO?
Let’s look at a few examples first. Then, we will develop a general concept.
• Describe your method for driving a car. • Could you drive a car without looking out the windshield? • What must be provided by the car designer? • Can a “good design” eliminate the need to steer?

WHAT DOES A FEEDBACK SYSTEM DO?
Let’s look at a few examples first. Then, we willdevelop a general concept.
• Describe how home heating works. • Describe the dynamic behavior of T. • What must be provided by the house designer? • Can a “good design” eliminate the need to change the heating?

WHAT DOES A FEEDBACK SYSTEM DO?
Why does the temperature cycle?

Is this good enough for all variables in a chemical process? Hint: if “yes”, the course is over!

WHAT DOES AFEEDBACK SYSTEM DO?
The control systems appear to have three basic elements.
Desired value

CONTROLLER FINAL ELEMENT PROCESS Inputs Outputs

SENSOR

WHAT DOES A FEEDBACK SYSTEM DO?
What is a typical “final element” for chemical processes?

Desired value

CONTROLLER FINAL ELEMENT PROCESS Inputs Outputs

SENSOR

What is the meaning of the arrows?

How do we select the sensor location?WHAT DOES A FEEDBACK SYSTEM DO?
Desired value

CONTROLLER FINAL ELEMENT PROCESS Inputs Outputs

SENSOR

CONTROL (verb): To maintain desired conditions in a physical system by adjusting selected variables in the system. FEEDBACK CONTROL makes use of an output of a system to influence an input to the same system. input = cause output = effect

WHAT DOES A FEEDBACK SYSTEM DO?
Caution:Common misunderstanding in terminology!

WHAT DOES A FEEDBACK SYSTEM DO?
Caution: Common misunderstanding in terminology! Common vernacular

Negative feedback: “You are an idiot!

Positive feedback: That was a good idea. Thank you!

WHAT DOES A FEEDBACK SYSTEM DO?
Caution: Common misunderstanding in terminology! Common vernacular Engineering & Science

Negative feedback: “You are anidiot!

Negative feedback: Action to reduce the error from desired. Positive feedback: Action to increase the error from desired.

Positive feedback: That was a good idea. Thank you!

WHAT DOES A FEEDBACK SYSTEM DO?
Caution: Common misunderstanding in terminology! Common vernacular Engineering & Science

Negative feedback: “You are an idiot!

Good!
Positive feedback: That was a...