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Ammonia flares are of two (2) general types;
a.) emergency (refrigerated ammonia storage terminals, steel mills, food processing) and
b.) process (chemical plant producing ammonia).
The emergency ammonia flare is a NFF-CG™ (NAO Fluidic
Flare - Clear Glow™) which includes
1.) high performance vortex flame retainers (Vortuswirl Vanes™) to assure flame stability and high
combustion efficiency, 2.) reliable pilots for light off of the ammonia gas and 3.) emergency battery
backup ignitor, if required, as is the case for low pressure refrigerated ammonia storage terminals.
Thermal radiation from an ammonia flare is minimal since
ammonia only has nitrogen and hydrogen. Combustion produces
nitrogen and water vapor. Nitrogen is a very poor radiator of heat
and water vapor is a weak radiator. Since ammonia has no carbon
present (which acts as a strong radiator -- BLACK BODY), overall
heat radiation on the storage tank and equipment is not of major
concern. The radiation levels should be calculated and checked
for operator safety concerns only.
Low Pressure Refrigerated Ammonia Storage
Typically, the flare is mounted on top of the access stair support column
along the side of the low pressure
refrigerated storage tank. Operation of the flare only occurs in the event of refrigeration failure or power
failure. Since refrigeration failure is very unlikely, the prime cause of a flare event is a long term power
failure. A short power failure will cause the cooling compressors to shutdown but the thermal mass and
insulation of the storage tank will maintain the ammonia pressure below the safety relief valve settings.
However, a long term loss of power, especially during the summer with high ambient temperatures and
intense solar radiation (sun beating on the surface of the tank), will result in tank pressure build-up and
the opening of the safety relief valve. The flare must be ready for the ammonia gas relief with its pilots
ignited and proven. The flare operation is a simple OFF-ON-OFF operation, i.e., tank pressure normal
-- relief valve closed, pressure build up -- relief valve open, flare ammonia vapor -- reduce tank pressure,
pressure back to normal -- relief valve closes.
Ammonia Emergency Relief -- Nitrating in Steel Mill or Refrigeration in Food Processing Plant
Normally, these flares are NEVER used, except in the
emergency or equipment failure. Typically, the flare
is mounted on a short elevated flare stack or on the roof of the plant. Since radiant heat from the flare is
small, normally stack height is only 10' or 20' depending on the size of the relief load. The pilot(s) and
ignitor are automatically actuated by means of pressure or another remote signal. Backup battery power
and a small LPG cylinder are normally provided for safety and reliability.
A process flare combines the operation of an emergency flare with small
intermittent flows due to process
variation and control. A process flare must be able to handle high emergency flow rates and low flows
(typically 1/10 to 10 percent of the emergency). These low flows are difficult to burn completely due to
their very low exit velocities, low momentum and crosswind dilution/quenching.
NAO has produced two (2) flare models to solve this problem;
1.) Gas assist flare with center and/or ring gas injection -- the flare
produces an intense ring (halo) of fire at
the flare tip to insure complete combustion. The NCGA™ (NAO Center Gas Assist™) and NGR™ (NAO
Gas Ring™ Assist) Flares are used when flaring is normally infrequent, thus minimizing assist gas usage.
2.) For applications, with more continuous flare flows, a Regenerative flare with assist gas is used. The
regenerative flare has a refractory lined tunnel to initiate combustion and restrict excess air/crosswinds.
The amount of assist gas used is reduced with the NRG™ (NAO Regen Flare™). For many gas streams
and mixtures, the regenerative flare only needs assist gas for initial warm up and then is self-sustaining.
Regenerative are available in both elevated and enclosed models. The enclosed regen flare can include
even better air control thus further reducing assist gas needed. The enclosed flare can also be equipped
with sample ports and emissions monitoring to confirm overall performance.
For more information, please call, fax or Email for typical drawings, technical reports, price and brochures.