It is gratifying as an author to nd that the product of my effort is being put to good
use. In my travels, I’ve seen copies of the rst edition of the Air Pollution Control
Equipment Selection Guide in a wide variety of libraries and on numerous book-
shelves. Some are in the corporate libraries of consulting rms, some at colleges and
universities, and others in private collections. Some of these copies have dog-eared
pages indicating that the reader must have found something of interest and may want
to return. That is why the rst edition book was produced. It was intended to be a
valuable reference resource over time.
For the second edition, the operative word is listening. Readers liked the gen-
eral format of the rst edition and that format is retained herein. The Device Type,
Typical Applications and Uses, Operating Principles, Primary Mechanism Used,
Design Basics, and Operating Suggestions format for each chapter remains. The use
of this format for each chapter allows the reader to compare within those categories.
If you are familiar with the technology, for example, but want to explore various
applications, you can easily do so. If you are interested in the basics of the design
of a particular piece of equipment, you can go to those sections. The tone remains
conversational rather than scientic.
When asked what additional information they would like to see, readers of the
rst edition mentioned a number of things, which, I hope, have been addressed in
this second edition. For example, they asked for an expansion of the “Air Pollution
Control 101” chapter (maybe it should now be “Air Pollution Control 102”?) to
include comments about dealing with gases that are far aeld from ambient air.
These conditions occur quite often today regarding gasication systems wherein the
gas stream may contain lower molecular weight gases under much higher pressures
than ambient conditions.
For the chapter on cyclone collectors, additional information is provided regard-
ing large diameter, product recovery type cyclones that are used on rotary dryers
and the like.
Where appropriate, additional up-to-date information is provided under the
Typical Applications and Uses sections. For example, the “Fabric Filter Collectors”
chapter was enlarged and rened to include spray dryer fabric lter collector com-
bination systems for acid gas and mercury control. Photos of some existing installa-
tions are provided.
A group of chapters (21–23) is now included featuring Special Applications. The
hybrid type systems noted here may combine various wet or dry scrubbing tech-
niques or form a team of various technologies to solve a specic problem wherein
one technology alone would be insufcient. For other challenges, the use of a spe-
cic technique is modied. As an example, sometimes Venturi scrubbers are used as
evaporators rather than particulate control devices. Their proper design, however, is
required to minimize any particulate generation resulting in air pollution. A special
chapter on Venturi evaporators has therefore been added. Coupled with a packed or
xiv Preface
tray tower device, that Venturi evaporator “hybrid” can also recover the evaporated
water, or recover heat, or both.
It seems that some owners of the rst edition already have air pollution control
equipment and want to improve its performance. Initially, they used the book to
explore alternative technologies to replace the problem device, but given the cost
of replacement, their focus shifted to how to get the most out of their existing
hardware. So, in response, a special chapter was added to address that request.
That new chapter, “System Diagnostics and Testing” (Chapter 24), goes over basic
problem diagnosis for both wet- and dry-type gas cleaning equipment and provides
some remedial suggestions. Therefore, the reader may want to use the second edi-
tion as a resource to select new hardware or to modify and keep what they have. If
you are thinking of salvaging your existing gas cleaning system, you may want to
read the last chapter rst!
Much of the information contained herein derives from the past nearly ve
decades in the air pollution control industry. The industry is dynamic and challeng-
ing. To provide improved content, I turned to the most reliable source, colleagues
and friends met during those decades. I am profoundly grateful for the information,
pictures, and other content supplied by these contributors and hope that the reader is
pleased with the result.

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