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Frequently and Questions


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What is BOOS?

BOOS stands for Burners Out of Service and replicates over-fire air with existing equipment(i.e. does not require expensive retrofit).

How much will BOOS increase burner header pressure?

BOOS operation will typically increase burner header pressure on the order of 50%.


What is IFGR?

IFGR stands for Induced Flue Gas Recirculation.

IFGR/BOOS System Design & Fabrication

Does ETEC’s system design depend on using individual burner air registers for balancing and/or control?

The air registers are used for minor trim control adjustment.

What impact will BOOS operation at full load have on burner header gas pressure?

The BHP will increase from 37 to 55 psig

Is flame impingement on the back furnace wall a concern?

Based on the results from similer boiler designs we do not expect this to be a problem.

Will the implementation of IFGR/BOOS impact oil burning and/or flame scanning equipment?

The gas fuel BOOS pattern would be modified to accommodate oil firing, but should not affect flame scanners.

Regarding the design of the new ductwork for the IFGR, what will be the pressure in the new ducts and will the fresh air damper be designed to prevent flue gas blow out?

The duct pressure should be near ambient or slightly negative so no flue gas blowout will be experienced.

Why is CORTEN steel proposed for the ducts? What would be the difference in bid price if carbon steel were used? Specify the wall thickness for the proposed CORTEN steel and for carbon steel (if used)?

ETEC would specify 3/16” CORTEN steel for longevity and strength. Since condensation on the inner duct walls will occur during cooler weather, CORTEN is used to minimize long term corrosion.

How will this effect the bid (price and what alternative material will be proposed)?

CORTEN does not require painting, however, carbon steel does. The cost of CORTEN would be about the same as painted carbon steel.

Does ETEC plan on using air registers for balancing and/or control?

We plan to use the air registers for fine tuning the combustion process during the post outage testing.

Near SCR Technology

Can IFGR and BOOS be integrated to achieve lower NOx emissions?

Yes, since IFGR is based on thermal mechanisms and BOOS is based on stoiciometic mechanisms, they may be very effectively combined to achieve near SCR reduction levels.

NOx Control Technologies

What is NOx Control by Combustion Modification?

NOx Control by Combustion Modification

APTB has performed research and developed technologies for NOx reduction via combustion modification. Techniques such as low-excess air firing, staged combustion, flue gas recirculation, low NOx burners, and reburning have been applied to a wide range of combustion equipment including utility and industrial boilers, industrial process combustors, stationary engines, residential space heaters, and woodstoves. In-house projects include investigations of improved NOx reduction by injection of steam into the reburn zone, evaluations of advanced reburning techniques, and optimization of combustion/flue gas treatment hybrid NOx control techniques.


NOx Control by Combustion Modification Diagram

Field studies include evaluation of reburning (fuel staging) on a 108 MW cyclone coal-fired utility boiler in Ohio and a 300 MW wall coal-fired wet-bottom utility boiler in the Ukraine. APTB is also working with EPA's Office of International Activities to demonstrate coal reburn technology on industrial boilers in Taiwan. This work will continue through 2001. Nitrous oxide (NOx) reductions of over 60% have been obtained using this technology. Reburning is a method of NOx control that uses hydrocarbon radicals to convert nitrogen oxide (NO) to nitrogen (N2) and carbon dioxide (CO2). Reburning is accomplished by diverting a portion of a boiler's fuel, typically 10-20%, to a point above the primary combustion zone where it is injected to create a fuel rich "reburn zone." The remaining combustion air is then injected above the reburn zone to provide the necessary burnout air.

Reburning can be applied to boilers that cannot use standard low NOx combustion modification techniques due to the need to maintain high furnace temperatures, such as wet bottom boilers. In many cases, reburning can be more economical than post combustion NOx controls that would otherwise be used in these instances.

Printed from the EPA website at: http://www.epa.gov/appcdwww/aptb/nox.htm

What is Low-cost NOx control?

A system that reduces oxides-of-nitrogen (NOx) emissions from gas- or oil-fired combustion equipment by up to 75% is being offered by Entropy Technology & Environmental Consultants, Inc. (ETEC, Houston; etecinc.net). The process uses flue gas recirculation (FGR), but saves costs by eliminating the separate fan and windbox mixing devices of standard FGR.

Instead, the Induced Flue Gas Recirculation (IFGR) system uses the boiler or furnace’s main air-inlet fan to draw in fluegas, via ducting connected to the stack. The fluegas and air mix as they pass through the fan. ETEC says the cost is about one-third those of low-NOx burners.



What are the main differences between SO2 and NOx?

SOx and NOx are typically byproducts of combustion of fossil fuels.  Sox or SO2 is generated when fuels are burned that contain high sulfur content. As combustion is an oxidation process, carbon is converted to CO2 and sulfur to SO2.  Controlling the emission will typically require some type of scrubber.  It can be a dry scrubber where the off-gas is mixed in a fluidized bed of lime creating gypsum CaSO4, or a wet scrubber where the off-gas is contacted with an alkaline water solution creating Na2SO4.  In either case, the waste products must be dealt with.


Many power plants have moved to a low sulfur coal to avoid the environmental problems or worked with companies wuch as ours to reduce NOx via effective methods of NOx control such as IFGR and NOx Modications.


NOx on the other hand can not be controlled through fuel and other combustion modifications.  Nitrogen is in the atmosphere and if temperatures in the combustion zone get high, N2 is converted to NO2.  Refer to our section on Other NOx Control Technologies for a overview of the services we offer to control NOx emissions.  Via layered NOx control technologies, we can reduce NOx by up to 90% in some cases.