Page 280 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

Chapter 9
In-combustion Air Emission Control

In-combustion air emission control is accomplished by proper design and operation
of a combustion device, either a burner or an engine. The existing process of
in-combustion control is primarily limiting the formation of NO x by modifying the
combustion temperature and other conditions. This chapter starts with an introduction
of typical combustion processes followed by specific in-combustion air emission
control technologies, including low-NO x burner, sorbent injection for in furnace SO 2
capture, and approaches to reduce soot formation, and so on.

9.1 Stationary Combustion Devices

9.1.1 Pulverized Coal/Biomass Combustion

Combustion of solid fuels takes place in a variety of stationary systems, such as
home heating stove and industrial furnace. In a stove, solid fuels are burned directly
without extensive size reduction. In industrial furnaces such as boilers for power
generation, their sizes have to be reduced to a certain level for continuous feeding
operation. This size reduction is also referred to as pulverization. A comprehensive
description of pulverized coal combustion can be found in the book by Smoot and
Pratt [14].
In a typical pulverized coal combustion system, coal is ground to fine particles
and separated using a mesh screen before being fed to the burner. Pulverized coal
particles have a mean diameter of 50 μm with the majority smaller than 200 μmby
mass. Then, these coal particles are fed into the furnace by mixing with oxidants
(mostly air). And combustion takes place in the flame in the open space of the
furnace.
As introduced in previous chapters, ash and other pollutants are formed during
solid fuel combustion. The coarse ash particles fall down to the bottom of the furnace
as a solid waste, and this is referred to as bottom ash or slag, while the rest of the fine
ash particles are carried along the combustion process with flue gas. In general, the

© Springer Science+Business Media Singapore 2014 257
Z. Tan, Air Pollution and Greenhouse Gases, Green Energy and Technology,
DOI 10.1007/978-981-287-212-8_9