Development of Pollution Control Technology During Coal Combustion - Simultaneous Multi-Pollutants Removal in Flue Gas by Ozone - page 5

the seawater FGD technology [15] . The process of this technology is relatively
simple, mainly including a spray absorber tower and an aeration tank. Flue gas
reacts with seawater in the spray tower, which is then restored in the aeration tank.
This technology has several advantages. For example, it does not require the
preparation or addition of a desulfurizer and is reliable with low investment and
operation cost, in addition to no wastewater and waste materials needed to be
disposed. Consequently, this technology has received considerable attention all
over the world and is now operating or under construction in Norway, Spain,
Indonesia, United Kingdom, USA, and other countries.
1.2.2 Denitrification Technology
Methods for controlling NO x emissions are usually classified into two categories:
combustion deNO x and post-combustion deNO x technologies. The combustion
deNO x method is applied to diminish NO x formation through the low-oxygen
combustion, staged-air combustion, re-burning, and flue-gas recirculation by
adjusting the primary air and secondary air distribution and changing the
combustion conditions in the furnace. The post-combustion deNO x method utilizes
reagents to reduce NO x in the flue gas. Selective catalytic reduction (SCR) and
selective non-catalytic reduction (SNCR) are usually used and involved in this
category. The following content provides a brief introduction on denitrification
technologies.
1.2.2.1 Low-Oxygen Combustion Technology
As to the low-oxygen combustion technology, combustion is kept at a low excess
air coefficient, both limited oxygen fed into the reaction zone and relative low
flame temperature can inhibit the generation of fuel NO x and thermal NO x on the
basis of the oxygen-sensitive characteristics of fuel NO x .
NO x emissions can be reduced by 15% - 20% through this method. However,
if the excess air coefficient is too low during the real operations, the combustion
stability will be seriously jeopardized. Consequently, the flame center will moved
up and emissions such as CO, soot, and fly ash will increase rapidly, which will
irrefutably lead to dangerous boiler operation conditions.