The steam or mechanical atomizers on our low-emission utility boiler-burners achieve precisely controlled flame geometry that creates substantial NOx reductions over conventional oil-fired burners. The low-energy-consuming steam atomizer provides a turndown ratio as high as 8:1, with less than 7% steam-to-fuel oil ratio. This atomizer eliminates the need for a more complex constant differential system and operates at a constant pressure.
Raadman WT burners effectively control NOx by staging fuel and air. Using both a multi-poker injector and center-fired gas burner, fuel-rich and fuel-lean zones are created within the flame envelope. The ratio of center-fired gas to poker gas, together with poker orientation and location, is carefully optimized for each application.
Raadman WT burners offer the flexibility of simultaneous gas and oil firing. This gives you the options of firing oil and gas in the same burner, or gas in some and oil in others based on your specific needs. Our burners allow you to switch fuels at various loads without affecting the boiler operation.
In the center of the register, the fuel oil sprayer with swirler is furnished. Surrounding the exterior of this swirler, multiple gas spuds (Spoke nozzle) are furnished, where intimate air/gas mixing is facilitated by primary air flows from outside the swirler.
A small amount of primary air, typically 10 to 20% of the total combustion air, is routed down the center of the burner. New burner designs employ a curved bladed swirler, to impart rotational momentum to this primary air. This swirled primary air creates a rotational vortex in the front of the burner, which serves several functions. It entrains a portion of fuel, creating a fuel-rich region immediately in front of the burner. The swirling primary air also generates a reverse flow in the form of a self-generating annular vortex that helps recirculate hot combustion gases from within the flame zone, thereby providing additional ignition energy to the fuel-air mixture and increasing the mass flow in this region to limit peak temperatures. In addition to controlling NOx formation, operating under fuel rich conditions results in the production of combustion intermediates that can result in the destruction of previously formed NOx. In a reducing environment, NO can act as an oxidizer to react with these combustion intermediates, resulting in the reduction of NO to N2. As such, NO, necessarily formed to satisfy the requirements of establishing a strong flame front, can be scavenged by this mechanism. to achieve complete fuel burnout at minimum excess air, the burner design must provide for fuel-lean zones to directly interact with the center fuel-rich sections. Creating a secondary air zone where the majority of the combustion air is introduced (65 to 90%) accomplishes this. The air injected into this zone is typically injected axially, with little or no swirl.
Blade angle is adjusted with axial movement of the rod connected to an annular plate. Annular plate is linked with swirler vanes that adjust their angle. also adjusted blades can control the flame dimensions.
Opened blade: low swirl; For longer flame shapes
Closed blade: High swirl; For much shorter flame shapes