Plasma Electrodynamics

1
Electron Scrubbing of Flue Gases to Remove
Unwanted By-Products

• History of electron beam dry scrubbing(EBDS)
  system
• EBDS Process Description
• e-Scrub Requirements
• SOx and NOx removal requirements
• EBDS cost estimates and technology comparison
• HPTA technology vs. conventional electron-beam
  guns
• HPTA Technology Development
• DOD technology overview
• HPTA technology overview
• Power-conditioning subsystem description
• Electron-beam gun design
• e-Scrub Project Description

2
What is EBDS ?

• A single-step method for the simultaneous
  removal of SOx and NOx from flue emissions
• Appropriate for use by boilers burning
  high-sulfur coal or incinerators burning
  municipal solid waste (MSW)
• Removal efficiencies of approximately 90 for
  both SO2 and NOx at high overall process energy
  efficiency and low-energy consumption
• In coal burning facilities, the flue gas with
  small amount of ammonia is irradiated with an
  electron beam, causing reactions that convert the
  SO2 and NOx to ammonium sulfate or ammonium
  sulfate-nitrate (salts)
• --gt salts collected by the conventional methods
  such as moving-gravel-bed filters or wet
  electrostatic participators(ESP) may be sold as
  fertilizer
• For flue gases from MSW incinerators, the EBDS
  process uses either sodium or calcium hydroxide
  for the reagent

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History of EBDS System
Need update !
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Alternative Technologies of EBDS

• Wet limestone slurry scrubbing for removing SO2
  (de-SOx) plus selective catalytic reduction (SCR)
  for removing NOx (de-NOx)
• Advanced limestone wet scrubbing combined with
  advanced SCR
• ( Low energy electron scrubbing by corona
  discharges )
• Advantages of EBDS
• Increased efficiency as the sulfur contents of
  coal increases
• Highly efficient removal of both SO2 and Nox
  from flue gas in a single process.
• Easily controlled and has excellent
  load-following capability
• Stack gas heat is not required
• The pollutants and by-products are converted
  into a marketable agricultural fertilizer

5
Obstacles and Promising Design of EBDS

• Obstacles of conventional electron-beam
  generators
• Too small a module power (factor of 5-10)
• Too large a module size (factor of 2)
• Too great a module cost (factor of 3-4)
• New design
• DOD in 1992 developed a design for a
  high-average-power electron-beam generator based
  on high-power transformer accelerator (HPTA)
  technology
• 1993 initiation of e-Scrub program
• develop a cost-effective, high-average-power
  electron-beam generator using HPTA technology
• integrate EBDS technology with the new
  electron-beam generator in a power plant
• ultimately provide for a complete technology
  transfer to the private sector

6
Simplified Flow Schematic of the EBDS Process
exhaust
Electrostatic participators
salts
Lower Tg add humidity
fertilizer
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Reaction Mechanisms of EBDS Process
Genuario and Brown (1993)
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EBDS Process Characteristics

• SO2 removal efficiency gt 95
• comparable to that of an advanced wet scrubbing
  process
• depends on gas relative humidity, NH3
  stoichiometry ,and electron-beam dose (energy
  absorbed per mass of flue gas, 1Mrad10kGy4.13Btu
  /lb)
• mostly by a thermal reaction with the NH3 and
  water vapor, remainder by the radiation-induced
  oxidation of SO2 to SO3 via reaction with OH
• Ammonium sulfate by-product likely forms from a
  heterogeneous reaction between gaseous ammonia
  and nucleating sulfuric acid droplets
• NOx removal efficiency
• primarily dependent on electron-beam-initiated
  chemistry via the formation of specific oxidative
  radical species such as OH and HO2
• Ammonium nitrate by-product directly formed
  homogeneously from gaseous nitric acid and
  ammonia
• non-linearity with the electron-beam dose
• positive impact of increased initial SO2
  concentration

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EBDS Process Summary
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SOx and NOx Removal Requirements
To meet already strict SO2 removal requirements
as well as the looming potential for very strict
NOx reduction, a combination of low-NOx burner
(LNB) and EBDS to achieve 85-91 NOx and over 90
SOx removal levels is envisioned.
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EBDS Cost Estimates
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EBDS Cost Estimates
FGD (wet limestone flue-gas desulfurization) SCR
(selective catalytic reduction) for de-NOx
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Cost Comparison with fertilizer by-product value
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Cost Comparison with electron gun cost
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Cost Comparison with e-Scrubber by-product value
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Cost Comparison
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DOD Technology Overview
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(No Transcript)
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Power-Conditioning Subsystem Description
20
Electron-Beam Gun Design
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E-Scrub Project Description