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Flue Gas Desulfurization

Since the 1970s, LIGHTNIN has supplied mixers to plants all over the world. Our extensive experience enables us to specify the best combination of mixer and impeller for optimum performance in FGD applications.


Download the Flue Gas Desulfurization Mixer Overview

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Mixing in the FGD Process

Mixing is essential in every stage of the FGD process:

  • Absorber agitators (various scrubber processes)
  • Limestone slurry preparation and storage
  • Absorber drain tank
  • Reclaim water
  • Gypsum slurry handling
  • Area sumps
  • Chloride bleed wastewater treatment / heavy metals removal
  • Fly ash make-down and storage
  • Lime slaking and storage

Suspension of varying percentages of fly ash, limestone and gypsum is required at all stages. Mixer selection and system specification depend on:

  • Particle size distribution
  • Percentage of solids in the slurry
  • Degree of suspension required
  • The ration of liquid height to vessel diameter

Specifying and Sizing Forced Oxidation Systems

  • Grid Systems use side entering mixers for solids suspension and blending, but do not play any part in gas dispersion/mass transfer. The grid increases the power required to generate the same degree of suspension as a system without a grid.
  • Lance systems are used for solids suspension, blending, gas dispersion and mass transfer, as well as prevention of pump plugging. The power required to disperse the gas usually determines power requirements. Location and size of the lance is critical, and LIGHTNIN specifies the correct parameters to ensure that the system meets dispersion or mass transfer requirements.
  • LIGHTNIN has the largest installed population of Top Entry Agitators in JBR® (Jet Bubble Reactor) service worldwide. With applications from 30-150 HP and installed since the early 1980s, LIGHTNIN’s experience with the Chiyoda CT-121 process is unrivaled.

LIGHTNIN Innovation Improves Performance in FGD Systems

The introduction of the laser-designed LIGHTNIN A310 impeller in the early 1980s significantly

Products for FGD Applications

The following mixers are typically used in FGD systems:

  • Series 10 mixers for sumps and small tanks.
  • Series 70 and 700 mixers for large applications.
  • Side entering VSF Mixers for absorbers and drain tanks.

Materials of Construction

Due to the high chloride content and abrasive nature of the slurries, the wetted parts of the agitator must be either rubber-covered or of high alloy construction. Top entering mixers operate at low peripheral speeds and have rubber covered wetted parts. Side entering mixers operate at higher speeds and require materials such as 6% Moly (254SMO or Zeron 100) and Duplex Stainless (SAF2507, 2205).

Seals

The seals are a critical component of mixer design in FGD applications. LIGHTNIN recommends the use of mechanical seals on side entering mixers in FGD systems. LIGHTNIN’s FGD Seal uses hard faces, open architecture, duplex alloy and an outside shutoff to provide a guaranteed minimum 16,000 hours seal life without the use of flush water.

Radial Bearing

By supplying a radial bearing in the seal housing, we reduce seal deflection and extend life.

Need More Information?

Contact your local LIGHTNIN Sales Representative to discuss your FGD application.