Page 55 - Separation process engineering

9. Take a break. Don’t quit, but do something else for a while. Coming back to the problem may help you
see a solution path.
10. Ask someone for a little help. Then complete the problem on your own.

Ten heuristics is probably too many to use on a regular basis. Select four or five that fit you, and make
them a regular part of your problem-solving method. If you want to read more about problem solving and
heuristics, I recommend How to Model It: Problem Solving for the Computer Age (Starfield et al., 1994)
and Strategies for Creative Problem Solving (Fogler and LeBlanc, 1995).

1.5 Prerequisite Material

No engineering book exists in a vacuum, and some preparatory material is always required. The first
prerequisite, which is often overlooked, is that you must be able to read well. If you don’t read well, get
help immediately.
A second set of prerequisites involves certain mathematical abilities. You need to be comfortable with

algebra and the manipulation of equations, as these skills are used throughout the text. Another required
mathematical skill is graphical analysis, since many of the design methods are graphical methods. You
need to be competent and to feel comfortable plotting curves and straight lines and solving simultaneous
algebraic equations graphically. Familiarity with exponential and logarithmic manipulations is required
for Chapter 7. The only chapters requiring calculus are Section 8.5.2, and Chapters 9 and 15 through 18.

The third area of prerequisites concerns mass balances, energy balances, and phase equilibria. Although
the basics of mass and energy balances can be learned in a very short time, facility with their use requires
practice. Thus, this book will normally be preceded by a course on mass and energy balances. A
knowledge of the basic ideas of phase equilibrium, including the concept of equilibrium, Gibbs’ phase
rule, distribution coefficients, familiarity with graphical representations of equilibrium data, and a
working knowledge of vapor-liquid equilibrium (VLE) correlations will be helpful.
Units are a fourth critically important area. The United States’ NASA program crashed a space craft into
Mars because of failure to convert between the metric and English systems of units. Because conversion

of units will remain necessary throughout your career, I have used data in the units in which they were
originally presented. Thus, you must do conversions throughout the book. Although problem solutions and
Appendix C show conversion factors, it is assumed that you are very familiar and proficient with unit
conversions. This includes conversion from weight to mole fractions, and vice versa.
A fifth area of prerequisites is problem-solving skills. Because the chemical engineer must be a good

problem solver, it is important to develop skills in this area. The ability to solve problems is a
prerequisite for all chemical engineering courses.
In general, later chapters depend on the earlier chapters, as shown schematically in Figure 1-3. Chapters
11, 14, 16, and 17 are not required for the understanding of later chapters and can be skipped if time is
short. Figure 1-3 should be useful in planning the order in which to cover topics and for adapting this
book for special purposes.

Figure 1-3. Chapter interdependency