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Metal Media Filters, AG-1 Section FI
Duane J. Adamson
Savannah River National Laboratory
32nd International Nuclear Air Cleaning Conference
June 18, 2012 SRNL-STI-2012-00311-S
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METAL MEDIA HEPA FILTERS
• Metal media HEPA filters have strength and endurance capabilities different from ASME AG-1, Section FC glass fiber HEPA filters
• As such, Section FI filters may be utilized in broader applications than Section FC filters
Higher temperatures Resistant to high humidity and water Higher pressure Better chemical resistance
• The design of metal media HEPA filters can have a cylindrical, flat panel or pleated configuration.
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Glass Fiber HEPA Filters Limitations
The traditional HEPA filter is a reliable, well understood and economic solution to environmental protection, but is limited by it’s vulnerability to;
• High dust levels
• Humidity
• Temperature
• Environment damage
• Mechanical strength
DNFSB Tech-23, HEPA filter concerns
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U Glass Fiber HEPA Filters Life Cycle
Life cycle cost expensive Installation/removal and solid waste disposal
Bergman et al. concluded millions $ in cost
Glass fiber HEPA filters are disposed of
high differential pressure occurs
radiation level on filter is high
Exposure to personnel during change out
Small amount of dust results in a large volume for low level solid waste disposal
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METAL MEDIA FILTERS • Metal media filters are not for all nuclear filtration applications
• Metal media filters are intended to be used in hostile nuclear air cleaning processes
protecting workers, the public and the environment from hazardous and radioactive particles
• A ASME AG-1, FI Standard has been under development for over a decade
• Metal media filters & housing shall be designed and constructed to in accordance with the AG-1 FI Standard
Fiber Metal
Sintered Powder Metal
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Issues Addressed by FI on Metal Media
Different types of metal media Sintered metal powder
Sintered metal fiber
Metal mesh
Unique attributes of metal media Tensile strength
Rigidity of filter elements
Differential pressure
Resistance to moisture and chemicals
High temperature operation
Cleanable or renewable in situ
Range of filtering efficiencies
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Panel Metal Media HEPA Filters Allowed by FI
Direct substitute for FC fibrous glass media HEPA filters
Built over a decade ago at LLNL Bergman et al.
Tested at ORNL
Panel metal media HEPA filters have been standardized
Dimensions
Flow rating
Pressure drop
Improvement in metal media Metal fiber media can be pleated
Increase surface area
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FI Allows Flexibility for Unique Filtration Application
Flexibility of design and deployment of new metal media filtration system
Owner/designer specification of fabrication and performance criteria
• Flow range
• Temperature
• Pressure
• Chemical of process
• In situ cleaning or regeneration • May not be covered by the FI Standard
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In situ Cleanable Sintered Metal Media System, Aqueous Solution
Sintered metal filter elements
Filter Housing
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In Situ Regeneration of Metal Media
• Very different dP
• 2,000 hr challenge test
• In situ regeneration
• After cleaning filter returns to original dP
• Filter media does not degrade from cleaning
• Particle retention remained outstanding
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Media Particle Retention Testing
Sintered metal filter elements tested
0.3 µm di-octylphthalate
HEPA retention > 99.97%
34 of 38 metal filters passed
Filters had > 99.99% eff.
Post simulant testing DOP test
Returned to Oak Ridge FTF
No change in particle retention
Metal media did not degrading Efficiency Testing, Oak Ridge FTF
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Pulsed Jet Metal Media Filter In Situ Cleaning
• Cleans In situ
• Metal fiber can be pleated
• Increased filter surface area
• Cleaning pulse ≈ 0.25 second
• Doesn’t interrupt process flow
• Returns dust to the user
• Minimising pressure loss
• Operates at a stable dP plateau
• reliable
Ref.: Porvair Nuclear Filtration Brochure
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Time Lapse Cleaning by Pulse Jet
Total sequence time: 0.2 sec
Ref.: Porvair Nuclear Filtration Brochure
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Example Design Criteria for Metal Media Filters in FI Dimensions Length, width, depth
Operating Conditions Temperature and pressure range Initial and max dP Relative humidity range Media velocity (max, min) Volumetric flow (min, max)
Materials of Construction Gasket material Filter media material Adhesive material Filter housing material
Mounting frame/housing Allowable materials (corrosion resistance, durability) Structural requirements -deflection limits -impact loading -stress limits -equipment design verification
Access Filter housing, filter element Location of filter
Filter media Filtering efficiency Unique challenge conditions (NOx, HCl, etc.)
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Path Forward for Obtaining Qualification Data
•Metal Media Test Stand Mississippi State University (MSU)
• Airflows up to 250 ft3/min
• Operating pressures up to 10 lb/in2
• Appropriate design of filter housing and ductwork
• Metal media filters Mott – sintered powered metal filter
Provair – metal fiber filter
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Test Metal Media Filter at MSU
• FI Team will travel to MSU to support planning
• Data collection at MSU will include the following • Resistance to rated air flow
• Aerosol penetration at rated air flow and at 20% rated air flow
• Resistance to pressure
• Test housing/tube sheet leaks
• Filter loading
• Resistance to heated air flow
• MSU talk on Metal Media Test Stand
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Conclusions • Work ongoing at MSU to obtain
qualification data for FI Standard • Metal Media Test Stand
• Data will be obtained in FY12
• FI Standard will support metal filters for the nuclear industry as HEPA Applications
Customer or owner of facility
Designer
Manufacturer
• FI supports unique applications of the process
• Simplify the design process
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