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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