• Effective removal of selenium within the WFGD Absorbers
    Effective removal of selenium within the WFGD Absorbers

  • MercSelAs or MSA

    WFGD Coupled-Control of Se & Hg 

    WFGD Absorber Provides:

    • pH Control
    • Absorption
    • Crystallization
    • Sub-saturation
    MSA slurry in the erlenmeyer flask and MSA solution in the graduated cylinder.
  • WFGD finds a friend in geochemistry

    In 2017, two Japanese geochemists studied the use of barite as a sequestering agent for selenite and selenate.  One of the many things that study showed was how both selenite Se(IV) and selenate Se(VI) were structurally fixed in the precipitates.  Could MSA be used in WFGD absorbers to incorporate selenium into a gypsum/barite co-crystal?

    WFGD finds a friend in geochemistry
  • MSA – 5% Solution

    MercSelAs or MSA are the trademarks for our patent-pending chemical intermediary used as an additive in WFGD for Se, As and Hg control.  For our full-scale utility MSA testing, we have been delivering the MSA material as a granular solid, in 1-metric tonne bulk bags.  It is then slurried (TSS ~1%) in a mix tank, before injection directly into the WFGD Absorber Recirculatoin Tank ART.

    MSA – 5% Solution
  • WFGD Se Capture

    Theory

    • Kinetics:  Aggregation vs. Orientation Velocity
      • Gypsum supersaturation favors aggregation
    •  T&T researchers – SeO4 uptake strongly SO4 dependent
      • T&T show structurally fixed precipitates
    • SO4, SeO4: Similar Ionic Radii
      • Co-crystal is stable
    • Gypsum Supersaturation:
      • BaSO4 crystal formation slows
      •  BaSeO4 crystal formation speeds up
    WFGD Se Capture
  • Bleed Slurry Test Results
    • First Beaker Test
      • 48% Se Reduction
    • First WFGD Module Test
      • 56% Se Reduction (~300 ppb)
      • 44 hours
    • Second WFGD Test: ~3,000MW
      • Intermittent Operation
      • Inconsistent Data
    • Second Beaker Test
      • 50% Se Reduction (1,200 ppb)
    • Third Full-Scale test (~3,000MW)
      • Upset Conditions/Insufficient MSA
      • 60% Se Reduction in WWTS
    • Fourth Full-Scale Test
      • January 2022
    Bleed Slurry Test Results
  • Secondary Clarifier Overflow

    Third Full Scale Testing Impacts

    • Bleed Slurry
      • Se impacts minimal
    • Secondary Clarifier Overflow
      • 60% Se Reduction in 10 days
    • Ba-SeO3-SeO4-SO4 Crystal
      • Growing along the flow path
    Secondary Clarifier Overflow
Overlays