Ammonium Hydroxide Dilution Fan/Blower Skids

In SCR and SNCR applications, ammonium hydroxide dilution fan skids are the critical transport mechanism that carries atomized aqueous ammonia into the flue gas stream for NOx reduction. Unlike anhydrous systems, these skids must provide a high-volume, high-velocity air stream—typically called "dilution air"—that serves a dual purpose: it acts as the carrier medium for the reagent and provides the necessary thermal energy to ensure the water-ammonia droplets fully evaporate before reaching the catalyst. RM Technologies engineers these skids with high-static pressure centrifugal blowers, often utilizing redundant "lead/lag" configurations to ensure 100% system availability. By integrating VFD-controlled motors and, where necessary, electric duct heaters, our dilution skids maintain a precise air-to-ammonia ratio that prevents "liquid impingement" and the formation of ammonium bisulfate (ABS) deposits. This rigorous control over the dilution air temperature and flow rate is what allows our systems to achieve maximum DeNOx efficiency while keeping ammonia slip within strict regulatory limits.

Selecting the correct blower technology is critical for overcoming the backpressure of the Ammonia Injection Grid (AIG) and ensuring the reagent is carried deep into the flue gas duct. The choice typically depends on the total system pressure drop and the required air volume.

Technical Comparison:

Centrifugal vs. Regenerative Blowers

  1. Centrifugal Blowers (Standard Duty)

Centrifugal blowers are the "workhorse" of the SCR industry. They move large volumes of air at moderate pressures by using a high-speed impeller to throw air outward.

  • The Design: Typically, a backward-curved or airfoil impeller housed in a scroll-shaped casing.
  • The Advantage: Highly efficient at high flow rates. They are generally quieter and more "forgiving" of slight particulate matter in the air stream.
  • The Constraint: They have a relatively "flat" pressure curve. If the AIG nozzles become partially fouled, a centrifugal blower may struggle to maintain the required flow against the increased backpressure.
  • Best For: Large utility SCRs and systems with wide-diameter injection lances where high volume is more important than high pressure.
  1. Regenerative Turbine Blowers (High Pressure)

Regenerative blowers (also known as side-channel blowers) utilize a unique "vortex" design where the air is passed through the impeller blades multiple times to build pressure.

  • The Design: A compact, multi-blade impeller that creates "pulses" of pressure in a circular channel.
  • The Advantage: They can generate significantly higher pressures than centrifugal units of the same size. They have a very "steep" performance curve, meaning they will maintain a constant air flow even if system resistance (backpressure) increases.
  • The Constraint: They are less efficient at extremely high volumes and can be much louder (requiring silencers). They also have tighter internal tolerances, making them more sensitive to dust.
  • Best For: Small-to-medium SNCR systems, "tight" AIG designs with small nozzle orifices, and applications where the injection point is a significant distance from the blower skid.

Engineering Selection Matrix

The RM Technologies Integration Strategy

We don't just provide a blower; we provide a Balanced Air Stream.

  • VFD Control: We equip all dilution fans with Variable Frequency Drives. This allows you to "tune" the blower to the exact pressure required for your specific flue gas velocity, saving energy and reducing wear.
  • Pre-Heat Integration: In aqueous systems, we often place an electric duct heater downstream of the blower. By heating the dilution air to 300°F–400°F, we ensure the ammonia is fully vaporized before it enters the duct, preventing the "rain-out" that leads to ammonium bisulfate ($ABS$) corrosion.
Request a Quote