ECHM 451
Chemical Engineering
Process Dynamics and Control
Spring, 2014
REID 104
What is Process Control?
• Techniques and technology to control a
process.
• Example: light switch
• Example: coffee maker
• This class will focus on automated control
About me…
•
•
•
•
Office: COBL 310
Phone: 406-994-7902
Email: jeff.heys@gmail.com
Office hours:
– Tuesday 11:00am – 12:00pm
– Thursday 1:00pm – 2:30pm
– Open office policy, but focus on TTh
About this class
• Meet twice per week on Tuesday and
Thursday.
• Scheduled time 9:25-10:40 (typically less)
• http://www.coe.montana.edu/jeffrey.heys/web451
• “Typical class”…. Lectures, homework, 2
exams including the final, and a project
• Lecture capture?
History
• 1995: Ron Larsen took a sabbatical with Dow
focused on process control
• 1996: I took the course from Dr. Larsen the
first time he taught it
• 1996 – 2011: Dr. Larsen refined and improved
the course and wrote a textbook along the
way.
• 2011-12: Dr. Larsen promoted to associate
provost
2013
• I’m teaching this course for the third time
(some experience at Stone Container).
• We will use Dr. Larsen’s book (pick up in main
office…$14.50)
• Read the syllabus and schedule
• Homework policy (boxes, staple, 1 or 2 per
page, etc…)
• Check your MSU email account frequently
Chapter 1
• Example #1: Thermostat (On/Off control with
set points (SP))
• Example #2: Cruise control (proportional
control)
𝑚𝑔𝑎𝑠 = 𝑘 ⋅ 𝑣𝑆𝑃 − 𝑣𝑎𝑐𝑡𝑢𝑎𝑙 + 𝑚𝑠𝑒𝑡
• Determining 𝑘 is difficult
Why?
1. Convenience (and lower labor costs)
2. Safety (many industrial accidents could have
been prevented with better process controls)
3. Consistent quality (computers are just better
at mundane details)
Why?
• Most chemical and biological engineers are not
process control experts, but they need to
understand the basics!
• Production engineering: responsible for day-today operations. Need to understand process
controls to deal with daily issues.
• Process engineer: longer term view toward
continuous process improvement…these
improvements often involve new or modified
process controls.
Specialists
• Some chemical and biological engineers
become process control engineers – focus on
improving process control systems and
implementing standard systems
• Even fewer become process control specialists
– implement solutions for specialized,
nonstandard, control situations.
Types of Process Controls
1.
2.
3.
4.
Manual control (open loop)
On/Off control (closed feedback loop)
PID control (chapters 2-9) (closed feedback loop)
Dynamic model-based control (closed
feedforward loop)
1. Empirical models (e.g., cold shower)
2. Phenomenological models
This book…
• Focus is on information needed by process
and production engineers (i.e., not specialists)
• Other books focus on process modeling and
Laplace transforms first, and then they discuss
PID controls for those processes (and the
result are engineers that cannot tune a
controller without a model).
Larsen vs. Luyben, Riggs, etc.
Traditional
• Process Modeling
• Convert model to Laplace
space
• Learn about
hardware/software (briefly)
• Analysis of
hardware/software in
Laplace space
Larsen
• Learn about
hardware/software (briefly)
• Learn basics for analysis of
hardware/software
• Process Modeling
• Convert model to Laplace
space
• Analysis of
hardware/software in
Laplace space
Basic Control System
• Oil heater that uses steam
Basic Control System
• #1 – we need a sensor (and we cannot
measure everything, like entropy or fugacity)
Basic Control System
• #2 – we need a controller (e.g., PID controller)
Basic Control System
• #3 – we need something to control (and we
cannot control everything like steam T and P)