Page 11 - Chemical process engineering design and economics

vi Preface

sels, this chapter starts with a brief discussion of the mechanical design of vessels.
Although chemical engineers rarely design vessels, a working knowledge of the
subject is needed to communicate with mechanical engineers. The phase separa-
tors considered are: gas-liquid, liquid-liquid, and solid-liquid. The common com-
ponent separators are: fractionators, absorbers, and extractors. This chapter shows
how to approximately calculate the length and diameter of separators. Flowrate
fluctuations almost always occur in processes. To dampen these fluctuations re-
quires installing accumulators at appropriate points in the process. Accumulators
are sized by using a surge time (residence time) to calculate a surge volume. Fre-
quently, a phase separator and a component separator include the surge volume.
This chapter also discusses vortex formation in vessels and how to prevent it. Vor-
texes may form in a vessel, drawing a gas into the discharge line and forming a
two-phase mixture. Then, the two-phase mixture flows into a pump, damaging the
pump.
Chapter 7, Reactor Design, discusses continuous and batch stirred-tank reac-
tors and the packed-bed catalytic reactor, which are frequently used. Heat ex-
changers for stirred-tank reactors described are the: simple jacket, simple jacket
with a spiral baffle, simple jacket with agitation nozzles, partial pipe-coil jacket,
dimple jacket, and the internal pipe coil. The amount of heat removed or added
determines what jacket is selected. Other topics discussed are jacket pressure drop
and mechanical considerations. Chapter 7 also describes methods for removing or
adding heat in packed-bed catalytic reactors. Also considered are flow distribution
methods to approach plug flow in packed beds.
Designing flow systems is a frequently occurring design problem confronted
by the process engineer, both in a process and in research. Chapter 8 discusses
selecting and sizing, piping, valves, and flow meters. Chapter 5 considered pump
selection. Chapter 8 also describes pump sizing, using manufacturer's perform-
ance curves. Cavitation in pumps is a frequently occurring problem and this chap-
ter also discusses how to avoid it. After completing the chapter, the students work
on a two week problem selecting and sizing control valves and a pump from
manufacturers' literature. Many of these problems are drawn from industrial ex-
perience.
Most things in life are not possible without the help of others. I am grateful
to the following individuals:

the many students who used my class notes during the development of the senior
course in process design, and who critiqued my class notes by the questions they
asked
Otto Frank, formally Process Supervisor at Allied Signal Co., Morristown, NJ,
who critiqued a draft of my book from an industrial point of view.

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