CBE 430 Week 01 01 - Introduction and definitions

Summary

This lecture delves into the complexities of chemical and biological process dynamics, emphasizing the importance of understanding coupled systems of differential equations. The focus is on process control, where engineers design systems to maintain desired conditions through controlled variables and manipulated variables. The lecture introduces three key control laws, emphasizing simplicity, process understanding, and liquid level control. It distinguishes between continuous and batch processes and introduces critical process variables such as controlled, manipulated, and disturbance variables. The ultimate goal is to enhance process design, control, and efficiency, ensuring safety and regulatory compliance.

Takeaways

• 😀 Chemical and biological processes often involve complex dynamics described by systems of coupled non-linear ordinary differential equations and differential algebraic equations.
• 😀 Both chemical processes (like pumps and pipelines) and biological systems (from organelles to tissues) can be modeled using similar mathematical tools.
• 😀 The class will focus on understanding these mathematical tools to better control the dynamics of chemical and biological processes.
• 😀 Engineers must understand process dynamics to design and maintain systems that operate efficiently and within desired conditions.
• 😀 Process control systems must consider product specifications, process safety, and compliance with environmental regulations.
• 😀 Process design typically focuses on steady-state operation, but real-world processes rarely operate at steady state.
• 😀 The best process control system is the simplest one that can accomplish the task, adhering to Occam's Razor.
• 😀 Understanding the process is essential before designing a control system, which will be the focus of several weeks of the course.
• 😀 Liquid levels should always be controlled in most continuous processes, with few exceptions like surge drums on recycle lines.
• 😀 A process is defined as the conversion of a feed stream to products using chemical, biological, or physical operations, and can include both the operations and equipment used.
• 😀 There are different types of process variables: controlled variables, manipulated variables (usually flow rates), and disturbance variables, with each playing a specific role in process control.

Q & A

What is the main focus of the course described in the script?

The main focus of the course is to develop mathematical tools to understand how coupled systems of differential equations and differential algebraic equations behave, specifically for controlling chemical and biological processes.

What types of processes are the course's mathematical tools applicable to?

The mathematical tools are applicable to both chemical processes, involving unit operations, pipelines, and pumps, as well as biological processes, ranging from organelles to cells to organs and tissues.

What are the three process control laws from Leuben and Loyben's 'Essentials of Process Control' introduced in the script?

The three process control laws are: 1) The best process control system is the simplest one that will do the job, 2) You must understand the process before you can control it, and 3) Liquid levels must always be controlled.

How do the first and second process control laws relate to design and operation?

The first law emphasizes simplicity in design, suggesting that overly complex control systems may not be necessary and could introduce reliability issues. The second law stresses the importance of deeply understanding process dynamics before attempting to design control systems.

What is the significance of liquid level control in process systems?

Liquid levels are critical to control in most process systems to ensure stable operations. The script notes that, with rare exceptions like surge drums on recycle lines, liquid levels must be regulated to avoid process instability.

What distinction is made between continuous and batch processes in the script?

Continuous processes involve material moving continuously from one unit operation to another, with all operations occurring simultaneously. Batch processes, on the other hand, involve operations performed sequentially in distinct allotments of feed.

What are the key types of process variables mentioned in the script?

The key process variables include controlled variables, which have a set point to maintain; manipulated variables, which are adjusted to control the system; and disturbance variables, which affect controlled variables but are not directly manipulated.

How are manipulated variables typically controlled in process systems?

Manipulated variables, which often include flow rates such as feed, effluent, or utility stream flow rates (e.g., heating steam or cooling water), are adjusted by the control system to maintain the set point of controlled variables.

What is the importance of understanding disturbance variables in process control?

Understanding disturbance variables is crucial because they influence controlled variables but cannot be directly manipulated. Identifying these variables helps in designing effective control systems and preventing disruptions in process stability.

What will be covered in the next video based on the script?

In the next video, the definitions of controlled, manipulated, and disturbance variables will be applied to a blending tank operation to illustrate key concepts of process control.