Page 185 - New Trends In Coal Conversion

148 New Trends in Coal Conversion

Reagent
storage

Air/
Heater NH 3
mix
Carrier air
Ceramic
Vaporizer
honeycomb
catalyst
Stack
SCR
catalyst

Injection
grid

Air
precheater
Wind
box

Forced
draft fan
Figure 6.3 Selective catalytic reduction (SCR).
Adapted from Bell, R.D., Buckingham, F.P., 2010. An Overview of Technologies for Reduction
of Oxides of Nitrogen from Combustion Furnaces. MPR Associates.

of NO x to be removed depends on the catalyst used: at high NH 3 /NO x ratios, a high
NO x removal efficiency can be obtained, but simultaneously the amount of unused
ammonia (NH 3 slip) in the clean flue gas increases considerably, producing an addi-
tional environmental impact.

6.2.1.4 Technological challenges
The increasingly restrictive pollutant emissions control regulations require that coal-
fired power plants be equipped with the most novel, less energy-intensive, and efficient
technology. The classic technology is very mature, and its operation processes are well
studied, but they consume a significant amount of energy.
In this area of technological challenges, studies will be shown as examples of the
right direction science should take, according to past points we have seen in this
chapter.
• Air-staged combustion is suggested to be one of the most sophisticated and effective
methods for reducing NO x emissions in recent references such as Fan et al. (2017). In this
study, the major gas species and NO x profiles were measured in a 20 kW down-fired