Fiber metal gas filtration.High strength and flow,precisely formed toyour application.

mott corporationP r o c e s s S y s t e m s

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Fiber metal.The high-flow, low-pressure drop alternative.

Unique filtrationmedia.

Mott offers integrated, innovative solutions for manygas filtration problems, based on the uniqueadvantages of fiber metal media:

• High permeate flux• Very low pressure drop• Excellent mechanical strength• Easy to clean• High corrosion resistance• Long on-stream life• High-temperature resistance (up to 1000°C)• Design flexibility (e.g. tubes, candles, discs)

What are metal fibers?Metal fibers are very thin metal filaments, with diametersranging from 1 to 80 micrometers. As a comparison:human hair has a diameter between 70 and 100micrometers. A wide variety of product forms can beproduced, such as:

• Continuous bundles• Yarns• Needle felts• Chopped fibers and pellets• Sintered porous media

Metal fibers and processed products are available invarious alloys, such as stainless steel, high tempera-ture resistant alloys, Nickel and Nickel alloys.

Standard diameters: 1.5, 2, 4, 6.5, 8, 12and 22 micrometers.

Overall diameter range: 1 to 100 micrometers.

Dependability with options.

Fiber metal has an extensive track record in highlydemanding applications where extremely high porosity,high efficiency and a long on-stream lifetime need to becombined with exceptional cleaning ability and corrosionand temperature resistance. Two basic types of fiber metalare offered, with further options such as material andfiber density to adapt media performance to specificapplications needs.

Bekiflow® HGBekiflow® surface media isdesigned using layers ofmetal fiber with a mesh sup-port. The design creates an upperfiltration layer of very fine fibersand a support layer of coarserfibers below the mesh.

Higher porosity and smaller thickness allows easiercleanability of the filter. Bekiflow® HG also provideslower pressure drop over the filter and alleviatesclogging by means of surface filtration.

The standard alloy is 316L stainlesssteel. Specialty alloys such asInconel® 601 and Fecralloy® areavailable for severe temperaturesand corrosive environments.

Inconel® is a registered trademark of Special Metals Corporation.Fecralloy® is a registered trademark of UKEA, UKBekiflow® is a registered trademark of N.V. Bekaert S.A.2

Humanhair

22µm 12µm 6µm 4µm 2µm 1µm

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Process gas filtration usingMott fiber metal filters.

High flow and efficiencyFiltration ratings as low as 1µm can be achieved, whileeven smaller particulate can be filtered out with a highpercentage due to dust cake formation. Metal fiberfiltration media achieve porosities between 70% and87%, providing high-efficiency particle capture withminimal pressure drop and maximum flow rates.

Fiber metal features and benefits:• Heat and corrosion resistant• Excellent cleaning through backpulsing• High porosity• Low initial pressure drop• Solid construction, enabling high filtration velocitiesand long on-stream life

• Broad filtration range available• Customized dimensions upon design or request• Flexible in design• Lightweight elements• Rigid filtration media

The ideal media for sustaining flow.

Process gas filtration is a unique challenge. In additionto potentially high temperatures and, in many applica-tions, caustic elements, there is often the need forsustaining high flow rates and minimizing pressuredrop. Fiber metal filtration systems and elements fromMott can provide the solution.

Filter elements composed of metal fiber are extremelystable and offer extended performance without needfor replacement. Cartridges are completely weldedand are not subject to cracks which can be causedby severe vibrations in chemical filtration systems. Inaddition, metal fiber elements are easily cleanable andcan be used in applications where Cleaning-In-Place(CIP) is required since there is no trespassing of dustwhen the filter element is cleaned by backpulsing.

High-strength all-metal mediaFiber metal elements are solid and rigid and are,therefore, not subject to any wear by movement orfriction. They are also resistant to damage by abrasionof penetrating particles. Fiber filter elements madefrom 316L stainless steel can be used in environmentsup to 350°C/650°F, while even higher temperaturescan be tolerated with elements made of Inconel 601(to 560°C/1040°F) or Alloy HR (to 600°C/1100°F ).Through extensive research, fiber elements have alsobeen developed to resist temperatures to 1000°C/1800°F through the use of Fecralloy.

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Process gas filtration.

In process gas filtration, the gas stream is heavilyladen with solids which must be removed from thefilter in place (in-situ), or the filters must remain online with periodic cleaning in place. Mott precisionporous media is ideally suited to this type of servicedue to its uniform permeability, precise bubble-pointcontrol, and mechanical integrity.

Gas filtration dynamics.

Starting with a clean filter at time zero, the particlecapture mechanisms are identical to those of the trapfilter. After some time, differential pressure increasesas solids are captured on the surface of the elementforming a filter cake. This stable surface cake becomesthe “real” filter media. Blowback occurs at a terminaldifferential pressure which is appropriate for each spe-cific application.

Surface filtration.

Surface filters are a more practical proposition thandepth filters for long-term operation of industrialprocesses with high dust concentrations.

The surface cake is the “real” filter, which preventsclogging. Through blowback techniques, periodic cakeremoval from the filter surface enables stable operat-ing conditions without shutdown. Even very fineparticles only penetrate into the surface layer and notinto the support body. A filtration condition will bereached after a certain number of back-cleaningactions, which enables a constant residual pressuredrop profile to be maintained.

Final/depth filtration.

Final or depth filtration is generally used in a relativelyclean gas stream where there is no need for in-situblowback cleaning. This type of filtration assures pro-tection of downstream equipment or processes, andprotects the downstream system from catastrophicfailure of an upstream piece of equipment, or aprocess upset. Usually a specific nominal or absoluteparticle-removal requirement is given, along with aclean differential pressure. A particular media can beselected to meet the removal requirements, and aface velocity is selected to meet the clean differentialpressure (and practical process) limits.In these applications, the filter may remain in service

for months, or for the duration of a process campaign.Then the elements are removed and cleaned forreuse. Cleaning methods can be chemical, controlledatmosphere burnout, or ultrasonic.

InterceptionElectrostaticDeposition

FlowStreamlines

InertialImpaction Diffusion

ElementCross

Section

Thickness of Porous Media

SurfaceFiltration

DepthFiltration

(CakeFormation)

FinerLayer

CoarserLayer

CoarserLayerMesh

4

Depth filtration

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Filter configurations.

Mott Corporation offers several filter configurations tomeet specific process requirements. The GS or GST trapfilter, the GSP plenum blowback filter, and the GSV ven-turi pulse blowback filter.

GS or GST FilterGS or GST filters used for depth filtration allow the userto remove the elements from the vessel for cleaning ordisposal. This type of filtration is used particularly in applica-tions where the stream produces low solids loading. Forhigher solids loading applications, Mott offers two types ofprocess filtration designs, the GSP and GSV models.

Blowback of porous metalThere are two types of in-situ blowback cleaning methodsfor gaseous process filters – the reverse blow plenumblowback, and the venturi pulse blowback. With theplenum blowback, it is necessary to isolate the filter, or asection of the filter, from service during the cleaningprocess. With the venturi pulse blowback, the entire filtercan remain on forward flow with no interruption of service.

With a Mott GSP plenum blowback, the filter inletand outlet valves are closed, the solids outlet valveopened, then the reverse blow gas valve is opened. Thisgas passes from the inside to the outside of the elements,removing the solids and expelling them through the solidsoutlet valve. The reverse blow should be at a velocitybetween one-half and equal to the forward flow velocity ofthe filter in service. Duration of the blowback can be from2 - 3 seconds or up to 15 seconds, depending on thecharacteristics of the solids and process requirements.

With a Mott GSV venturi pulse blowback system,each element has a venturi throat with a nozzle pointinginto the venturi. In most filters the elements would bemanifolded, and the manifolds blown back sequentially.The fundamental principle of the venturi pulse blowbackis the use of a fast-acting gas valve, such as a pilot-oper-ated diaphragm valve, to create a shock wave throughthe blowback piping and nozzles.

The blowback gas pressure should be 90 psi/6 barabove the system pressure. The blowback pulse duration(valve opening) should be from 0.25 up to 0.5 seconds.This gas flow is directed from the nozzle into the elementventuri; at the same time, it educts additional clean gasthrough the venturi to create a wave down the element,which “pops” the cake from the filter media back into thefluid bed reactor or solids collection tank.

OUTLET

SOLIDSOUTLET

I INLET

BLOWBACKGAS IN

SOLIDSOUTLET

BLOWBACKGAS IN

OUTLET

INLET

GSP PlenumBlowback Filter

GSV Venturi PulseBlowback Filter

GS or GST(no blowback)

INLET

OUTLET

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AvailableAlloys

MaximumOperationalTemperature

AISI 316L SS INCONEL 601 ALLOY HR FECRALLOY

350-380°C 560°C 600°C 1000°C650-720°F 1040°F 1100°F 1800°F

Connection flange =outlet of filtered gas

Fixation of the filtration mediato the supporting structure

Block flange Welded & fixed Demountable

Filtration velocity> 0.05 m/s (> 10 ft/min)

Flat flange

Filter element configurations,materials and properties.

Formed to your specificationsFilter elements made of metal fibers can becustomized. The length can vary from 300mm(11.81 inches) up to 3m (9.84 feet). Theelements are manufactured with a weld-on

metallic carrier in case high filtration velocitiesmust be met. The type of mounting flangeof the element on the base plate can bespecified by the customer.

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Applicationsand industries.

Application overview

Because of its high strength, flexibility in form anddesirable flow characteristics, fiber metal has beenused by many industries in a great number ofapplications all over the world. Some of these include:

Biochemical industry

Food and beverage sector

Chemical industry

Waste treatment

Pharmaceutical industry

Water treatment

Hot gas cleaning

Chemical and catalyst recovery

Oil and gas filtration

HEPA filter media

Medical and pharmaceutical industries

Nuclear venting

Aerospace

Process applications

Several drivers support the significance of usingporous metal fiber in process applications:

• Recovery of high-value product ina process

• Environmentalprotectionrequirements

• Cleaning of processgases beforeadditional use

Hot gas filtrationFiber metal offers highpermeability and lowpressure drop, making itideal for particulate sepa-ration in hot gases. Mediaperformance is furtherenhanced by its excellentthermal-mechanical char-acteristics, particularly incomparison with ceramics.

Hot gas applications include:• Catalyst recovery in chemical processes• Clean process gases in chemical processes• Clean combustion gases and waste incineration• Power generation – coal gasification

Specific applications within specialized industries include:Petrochemical:• Polyolefins• Polypropylene• Polyethylene• Melamine

General Chemical:• Catalyst production• Nitric Acid• Pigments• Others: Acylonitrile, Ammonia, Aniline,Fumed silica, Maleic anhydride

Refinery:• Fluid catalytic cracking• Steam cracker• Continuous catalytic reforming/regeneration• Catalytic dehydrogenation

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