include nitrogen and sulfur content of fuel for
emission requirements.
Review the Clean Air Act Amendment of 1990 (CAAA)
and other applicable Federal, state, and local
regulations early in the design phase to determine
the appropriate emission limitations and monitoring
requirements.
The CAAA does not require the application of low NOx
burner (LNB) technology for boilers within the size
range of this specification. The CAAA limits SO2
emissions for fuel oil fired boilers over 10.55 gJ
(10,000,000 Btu) to 21.5 kg/nJ (0.5 lb per million
Btu) input or to firing oil with less than 0.5
weight percent sulfur. However, state
implementation plans may place limits on NOx and
particulates and more stringent requirements on SO2.
Many options are available to reduce NOx emissions.
The nitrogen and sulfur content of fuel oil should
be specified in the fuel purchase contract.
Restrictions on the nitrogen content will limit fuel
flexibility. A careful analysis of proposed NOx
reduction technologies must be performed to account
for any required changes to auxiliary equipment and
to identify future increase in O&M costs. Important
questions that should be answered and be a part of
the evaluation include the performance of NOx
reduction over the entire load range, performance
during backup fuel firing, and performance over the
lifetime of the unit.
The majority of NOx control techniques can be
defined as combustion modifications. The goals of
combustion modification include redistribution of
air and fuel to slow mixing, reduction of O2 in NOx
formation zones, and reduction of the amount of fuel
burned at peak flame temperatures.
Combustion modifications primarily deal with the
control of fuel and air. Vertical staging includes
overfire air (OFA) ports above the main combustion
zone. Horizontal staging use registers or other
devices to introduce air at different points along
the flame. Fuel staging establishes a fuel rich
zone above an air lean main combustion zone. Burner
Out of Service (BOOS) techniques direct fuel to
lower burner levels, while operating upper burners
with air only. Flue Gas Recirculation (FGR) reduces
O2 available to react with nitrogen and cools the
flame. In addition to low NOx burners (LNB), OFA
and BOOS other combustion modification techniques
include fuel biasing, low excess air (LEA) and fuel
reburning. Oil fired burners have successfully used
advanced oil atomizers to reduce NOx without
increasing opacity. Oil/water emulsion is a
technique to reduce NOx on smaller industrial
boilers.
SECTION 15569A
Page 22
Previous Page
