Page 47 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

20 1 Air Emissions

engineering applications for pre-combustion fuel cleaning and post-combustion air
cleaning.
The general basic principles in Part 1 are necessary for the understanding of air
emission engineering topics in Parts 2 and 3. Part 2 of the book introduces the
strategies for pre-combustion (Chaps. 7 and 8), in-combustion (Chap. 9) and post-
combustion (Chap. 10) air pollution control, step by step, from a process point of
view. While air dispersion model is a powerful tool for air quality assessment and
impact prediction, air dispersion itself is a measure for air emission control by
dilution. It is elaborated in Chap. 11.
Part 3 includes special topics related to the scope of this book, but they do not
closely fit into the process introduced above. Chapter 12 is devoted to carbon
sequestration and storage, which are of increasing interest to society. Although
debates are still ongoing, it is time to summarize the techniques that have been
developed for GHG control, especially for CO 2 capture and storage. There may be
some overlapping between this chapter and the other parts of this book.
Chapter 13 discusses an emerging topic of air pollution, nano air pollution.
Nanomaterials are now widely used in many industries, for example, improved
combustion efficiency, environmental protection, health, solar panel fabrication.
Once these nanoparticles enter the air, they may have to be separated for the pro-
tection of the environment and health. Engineering approaches to nano air pollution
control is the core emphasis of this chapter. Specifically, the properties of nano air
pollution and its implications on monitoring and filtration technologies are covered.
Indoor air quality is introduced in Chap. 14 as it is also an important emerging
topic. Indoor air quality is related extensively to air pollution. The direct sources are
different from their outdoor counterparts, as are their control techniques.
The last chapter is about air quality and air emission monitoring techniques.
They are commonly needed in industrial practices, government standard enforce-
ment and research and development in a laboratory setting.

1.7 Units and Dimensions

The International System of Units (SI) is used in this book unless stated otherwise.
Typical conversion factors are listed in Table A.3 in the Appendices. For example,
the dimension of length (e.g., particle diameter) and mass may take different units
and the conversions are as follows:

• 1 mm = 1000 micrometer (μm)
• 1 μm = 1000 (nm)
• 1 gram (g) = 1000 milligram (mg) = 1,000,000 microgram (μg)

Concentrations of air pollutants and GHGs can be presented in several dimen-
sions, including mass per volume, volume ratio and mass ratio. Mass per volume is
3
3
3
usually presented with units of kg/m , mg/m or μg/m ; and, volume and mass
ratios are measured in units of parts per million (ppm) and percentages. At a low