Developments in NOx Abatement and Control
AUTHOR: Hermine Soud and Kazunori Fukasawa
DATE: August 1996
Environmental legislation to reduce NOx (NO+NO2) emissions from pulverised coal combustion is becoming increasingly stringent world-wide. It is now common practice to install primary measures (or combustion modifications) for NOx control on new and existing plants. In some countries the installation of post-combustion, flue gas treatment processes for NOx control is also a legal requirement. Until the beginning of the decade, post-combustion technologies have been used mainly in Japan and Western Europe but are now being used in other countries such as the USA.
Developments are discussed in the use of primary measures including burner optimisation, air staging (overfire air or two stage combustion), and low NOx burners. Research projects since the mid-1980s have aimed to control NOx emissions through an improved understanding of the combustion process. Computer modelling and simulation are becoming accepted tools for such studies. Progress in the development of flue gas treatment for NOx control is reviewed. This includes selective catalytic reduction (SCR, selective non-catalytic reduction (SNCR), hybrid SCR/SNCR, are combined SO2 and NOx removal processes. Combinations of primary measures and flue gas treatment are discussed. The general costs of developments in NOx abatement and control are presented briefly.