Page 85 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

Chapter 3
Basics of Gas Combustion

Combustion or burning is a complex sequence of chemical reactions between a fuel
and oxygen. The main purpose of combustion is to produce energy and, occa-
sionally, light. In a combustion reaction, the reactants are fuels and an oxidizer, and
the products include various air pollutants and carbon dioxide. Meanwhile heat is
generated for other engineering applications such as boiling water for steam pro-
duction, engine powering, and space heating by raising the temperature of the air.
Topics to be covered in this chapter include the properties of air as a combustion
oxidizer, combustion stoichiometry, thermodynamics of a combustion system,
flame temperature calculation, and combustion chemical equilibrium. After reading
this chapter, a reader is expected to be able to
• Understand the basics of gas fuel combustion;
• Explain how air pollutants are formed during fossil fuel combustion with air;
• Theoretically predict what and how much air pollutants can be formed by simple
combustion of fuel with known chemical formulae;
• Theoretically calculate the temperature of combustion and energy production;
• Be ready to understand topics related to combustion of other fuels in Part 2.

3.1 Air–Fuel Ratio

Air–fuel ratio (A=F) is the amount of air to the amount of fuel in the combustion
mixture. The amount can be quantified by mole or mass. If the air-to-fuel ratio is
mole based, the value will be different from the one based on mass. In this book, we
use only mole ratio to explain the basic concept, although mass ratio is important
too. The mole air fuel ratio is determined by the mole numbers of the components
of the mixture as
P
n a ð n i Þ a
ð A=FÞ ¼ ¼ P ð3:1Þ
n f ð n i Þ f

© Springer Science+Business Media Singapore 2014 59
Z. Tan, Air Pollution and Greenhouse Gases, Green Energy and Technology,
DOI 10.1007/978-981-287-212-8_3