NOx Control Technologies for Coal Combustion
AUTHOR: Anna-Karin Hjalmarsson
DATE: June 1990
The first in a series on the control of nitrogen oxides (NOx) this report describes:
- NOx formation;
- regulations on NOx emissions;
- control of NOx through combustion measures;
- selective catalytic reduction;
- selective non catalytic reduction;
- combined SOx/NOx processes;
- advanced combustion technologies;
- costs of NOx control;
- review of NOx reduction measures in twelve countries.
The first step to control NOx is, in most cases, the use of combustion measures. A large number of boilers are now operating with different types of low NOx burners and air staging, especially in the FRG, Japan and the USA. When the limits for emission cannot be reached by combustion measures, flue gas treatment is added. Selective catalytic reduction is the dominating process in use, with applications in Japan, the FRG and Austria.
Selective non catalytic reduction technologies have recently been developed. Work is continuing on processes for combined sulphur and nitrogen oxide reduction. The activated carbon process is the only combined process that is operating on a commercial scale. New advanced combustion technologies, where emission control is integrated in the process are gaining ground. New for use in utilities are atmospheric and pressurised fluidised bed combustion, integrated gasification combined cycle and slagging combustors.