RMP Lecture Notes

Material and Energy Balances: Introduction

The primary focus of this class is on understanding and solving problems based on balance equations. These concepts and solution techniques are used to determine the distribution of material and energy flows in a chemical process.

Balance computations are based on the principles of conservation of mass and energy. They are probably the most common computation performed by chemical engineers -- almost all chemical engineering problems, no matter how simple or complex, start out by closing the material and energy balances. By "closing", we mean applying the balance equations to determine the flows, compositions, and temperatures of all streams in a flowsheet; starting from what we know or are able to measure.

You have seen energy balances in Thermo I and will use balance equations again in Thermo II, kinetics, mass transfer, and heat transfer. Each new topic will consider special cases or applications of the balance relationships; however, the core ideas and approaches -- which you can learn in this class -- will stay the same.

The course will also address issues of stoichiometry: the analysis of how chemical compounds combine. You've already encountered the basics of this topic when you balanced equations in your chemistry courses.

Clearly, much of what we do in this class is not entirely new. We will use concepts and tools from chemistry, physics, thermo, and the ChE intro course as building blocks for what we do. We will also build within the course itself. We will start with "bare bones" problems and gradually add layers of complexity as we move through the semester. This means it is very important to keep up! Come see me when you first start having problems. Maybe I can help. If you wait too long, I may not be able to do much.

Success in this course will depend on your ability to solve problems. For most of you, this means that you must "buy in" to a systematic approach to problem solving (see p. xii of the text). In Thermo I, I tried to convince you of the value of such an approach. We'll do the same thing here (although the template will change somewhat to reflect different classes of problems).

References:

Himmelblau, D.H., Basic Principles and Calculations in Chemical Engineering, 6th Edition, Prentice-Hall, 1996, pp. 141- 2.
Reklaitis, G.V., Introduction to Material and Energy Balances, John Wiley, 1983, pp. 7-8.

R.M. Price
Original: 6/17/94
Modified: 8/20/97, 12/14/2004