Thanks to its experience and the technologies it has developed over the years, ELCO offers a wide range of products which use the external FGR technology to reduce NOx emissions and satisfy even the most stringent regulations.
The external recirculation sends a mixture of air and flue gas to the burner combustion head. The gases are mixed upline of the combustion process by the burner fan (for monoblock units) or by the external fan (in case of duoblock burners).
MONOBLOCK BURNERS
The FGR system on monoblock burners provides that the flue gas is drawn in by the burner fan. The installer must therefore install a line connecting the flue gas outlet to the burner fan inlet. The extraction point is generally at the base of the flue pipe, where the pressure is close to zero. A suction is generated in the burner intake box which is a function of the fan curve and the air damper position. In order to ensure an adequate rate of flue gas from the stack and thus to provide the required NOx reduction, the pipeline between the flue and the burner must be sized to minimise the pressure drop.
DUOBLOCK BURNERS (LAYOUT "A")
The FGR system for duoblock burners, since the draught fan is installed far from the burner, needs a layout different from the one of the monoblock ones. On such a layout, the flue duct ends upstream of the draught fan. In order to produce the needed suction to get flue from the stack and to mix it with the fresh air, the air damper is fitted upstream of the draught fan and upstream of the flue duct end, too.
As for monoblock burner, the flue duct has to be properly sized in order to minimize the pressure drop.
DUOBLOCK BURNERS (LAYOUT "B")
An alternative layout to layout "A" provides a further draught fan dedicated to the flue.
It takes the flue from the stack and pushes it into the duct between the burner and the fresh air draught fan. The flue damper is just after the flue fan. The air damper is on burner board and therefore it adjusts the rate of the mixture between the flue and the fresh air.
As for monoblock burner, the flue duct has to be properly sized in order to minimize the pressure drop.
To know more about the ELCO low NOx solutions and the FGR System, download our dedicated brochure:
