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Induced Flue Gas Recirculation

IFGR NOx Control Systems ETEC offers a far less costly FGR NOx Control technology than its competitors, eliminating the need for a separate FGR fan and windbox mixing device. This technology, known as induced flue gas recirculation (IFGR), utilizes the FD fan to pull (induce) flue gas from the boiler exhaust duct into the combustion air at the fan inlet. The fan also serves as the mixing device. This NOx Control technology is now covered under ETEC Patents No. 6,599,119 & 6,609,907.

Combustion Modifications

CMODS NOx Control Combustion Modifcations Combustion modification has long been recognized as a very cost effective NOx control technology for reducing NOx emissions. ETEC engineers have applied this technology, very effectively, to scores of combustion devices since the early 1970's. In many cases, one valve provides gas flow to several burners. ETEC modifies this configuration to provide individual burner gas flow via valve and piping modifications enabling more precise combustion performance and further NOx emission reduction.

NOx Modifications

NOx ModificationsETEC engineers have utilized IFGR in conjunction with other NOx control technologies (also known as "Layered Technologies"), e.g., low NOx burners, overfire air, burners out of service (BOOS), etc. in order to provide optimum combustion performance while minimizing NOx emissions or green house gasses. Up to 90% NOx reductions can often be obtained through layered technologies.

Coal to Natural Gas Firing Conversion Technologies

Coal to Natural Gas Conversion Technologies

In the present operating climate, a number of electric utilities are considering converting some of their units from coal to natural gas firing. Along with this conversion, new natural gas fired NOx emissions requirements will be established. Fuel gas fired NOx emissions are formed during the combustion process by thermal fixation of the combustion air nitrogen. One of the most effective combustion NOx control technologies is flue gas recirculation (FGR), which, as a standalone technology may effectively reduce the NOx emissions below the new requirements. If not, then FGR may be augmented with a stoichiometric NOx control technology commonly referred to as Burner-Out-Of Service (BOOS) operation to further reduce NOx emissions. ETEC can help diagnose your project and suggest the right coal to natural gas firing conversion technology to suit your needs.

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Innovative Combustion Solutions

ETEC engineers have a long history in addressing and solving NOx Control emission problems through:

  • Testing, analyzing and defining the combustion processes by which NOx emissions were generated;
  • Providing operational and equipment combustion modifications necessary to reduce NOx emissions; and
  • The pioneering of the NOx reduction technologies of: Induced Flue Gas Recirculation (IFGR); Slip Stream Flue Gas Recirculation (FGR); and additional Hybrid Solutions for NOx Control.

ETEC offers effective NOx reduction technologies to:

FGR has been implemented on scores of boilers in the electrical utility industry as well as the industrial sector as an effective means of NOx control in conjunction with additional combustion modifications (CMODS). Because of the large volumes of recirculation gas involved in a utility boiler, most of these installations have relied on dedicated FGR fans to augment the existing Forced Draft (FD) fans in order to accomplish the mixing of the flue gasses with the combustion air.

Through ETEC's NOx control technologies and expertise, we can help you reduce your NOx emissions by up to 90%.

Innovative Approaches for Achieving Optimal Environmental Synergies

Download ETEC's ETECnology paper on using combined Induced Flue Gas Recirculation (IFGR), Combustion Modifications (C-MODS) and energy efficiency and management programs to ensure NOx emissions compliance and overall significant cost savings.

ETECnology - Innovative Approaches for Achieving Optimal Environmental Synergies


Innovative Approaches for Achieving “Lowest Emissions at the Lowest Cost”
NOx Control Strategies, Optimal Combustion Performance and Plant Energy Utilization Strategies

Our Clients Include:

ETEC clients include Entegy, Exxon Mobil, BASF, Reliant Engery, TXU, Georgia Pacific, LCRA, Excelon, Meadwestvaco, Deltech

ETEC Case Studies

ETEC has developed solutions for Utility, Chemical and Refinery clients and has successfully reduced NOx emissions in both Natural Gas as well as Coal fired boilers.



ETEC has completed Utility IFGR projects from 450mw Electric Utility Boilers to 815mw Electric Utility Boilers reducing emissions up to 90% in combination with Combustion Modifications.


ETEC has completed Refinery IFGR projects for 450klb/hr Refinery Boilers, reducing emissions up to 90% in combination with Combustion Modifications.
Chemical Plants

Chemical Plants

ETEC has completed Chemical IFGR projects for up to 350klb/hr Chemical Plant Boiler, reducing emissions up to 90% in combination with Combustion Modifications.