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FILTRATION NEWS May/June 2014Volume 33 No. 3www.filtnews.com

Rosedale Products’ Solids/Liquids SeparatorsRosedale Products’ Solids/Liquids Separators

– Economical Production of Ultrafine Thermoplastic Fibers for Filtration

– From Production of Viscose to Fully Automatic Filtration in the Sugar Industry

– Filter Problems, and Why Filters Fail

2 • June 2014 • www.filtnews.com

Published byINTERNATIONAL

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Editorial DepartmentKen Norberg, Editor in Chief, [email protected]

Adrian Wilson, Intl. CorrespondentChen Nan Yang, China CorrespondentEditorial Advisory Board, See page 4

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Advertising Sales RepresentativesUSA

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Publication DataFiltration News (ISSN:1078-4136) is publishedbi-monthly by International Media Group, Inc.Printed in U.S.A., Copyright 2014.This publication has a requested and controlledsubscription circulation - controlled by the staff ofFiltration News; mailed bi-monthly as PeriodicalsPostage Paid (USPS 025-412) in Novi MI andadditional mailing offices.Filtration News is not responsible for statementspublished in this magazine. Advertisers, agenciesand contributing writers assume liability for allcontent of all submitted material printed andassume responsibility for any claims arisingthere-from made against publisher.

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IN THIS ISSUEMay/June 2014, Vol. 33, No. 3

Association | NewsAFS Conference Growth Continues 6

Industry | NewsExperts Predict Filtration and Separation Will Make China Greener 10

Cover Story | Rosedale ProductsSolids/Liquids Separators as Pre-Filter 12

Fiber | EngineeringEconomical Production of Ultrafine Thermoplastic Fibers for Filtration 14

Filter | ApplicationFrom Production of Viscose to Fully Automatic Filtration in the Sugar Industry 18

Testing | LaboratoryNew Technology from Porous Materials Improves Large Pore Detection 24

Filter | TroubleshootingFilter Problems, and Why Filters Fail 28

Company | NewsMonadnock Offers Pilot to Production Program 36Advanced In-Place Filter Testing Workshop 37

Testing | MethodsTesting Activated Carbon Performance for DifficultAdsorbates: Trace Capacity Numbers 38

Cover courtesy of Rosedale Products, Inc.


Editorial Advisory Board

Editorial Board ChairmanEdward C. Gregor, ChairmanE.C. Gregor & Assoc. LLCTel: 1 803 431 [email protected]&A, Filtration Media

Haluk Alper, PresidentMyCelx Technologies Corp.Tel: 1 770 534 3118Fax: 1 770 534 [email protected] Removal – Water and Air

Jim JosephJoseph MarketingTel/Fax: 1 757 565 [email protected] Filtration

Robert W. McilvaineTel: 1 847 272 0010Fax: 1 847 272 [email protected]. Research & Tech. Analysis

Dr. Graham RidealWhitehouse Scientific Ltd.Tel: +44 1244 33 26 26Fax: +44 1244 33 50 [email protected] and Media Validation

Tony ShucoskyPall MicroelectronicsTel: 1 410 252 0800Fax: 1 410 252 [email protected], Filter Media,Membranes

Scott P. YaegerFiltration and SeparationTechnology LLCTel/Fax: 1 219 324 3786Mobile: 1 805 377 [email protected], New Techn.

Robert BurkheadBlue Heaven TechnologiesTel: 1 502 357 0132 Cell: 1 502 819 0204Email: [email protected] Filtration product develop-ment and performance testing

Dr. Bob BaumannAdvisory Board Member Emeritus

Andy RosolGlobal Filtration Products Mgr.FLSmidth [email protected]: 1 800 826 6461/1 801 526 2005Precoat/Bodyfeed Filter Aids

Clint ScobleFilter Media Services, LLCTel: 1 513 528 0172Fax: 1 513 624 [email protected] Filters , Filter Media, Baghouse Maintenance

Henry Nowicki, Ph.D. MBATel: 1 724 457 6576Fax: 1 724 457 [email protected] Carbons Testing,R&D, Consulting, Training

Richard JacobsEaton Corporation Tel: 1 732 212 4747Email:[email protected] Filtration Technologies

Dr. Ernest Mayer E. Mayer Filtration Consulting, LLC Tel: 1 302 981 8060Fax: 1 302 368 [email protected]

Wu ChenThe Dow Chemical CompanyTel: 1 979 238 [email protected] Filtration (liquid/gas)Equipment and Media

Peter R. Johnston, PETel/Fax: 1 919 942 [email protected] procedures

Peter S. Cartwright, PECartwright Consulting Co.Tel: 1 952 854 4911Fax: 1 952 854 [email protected], RO,Ultrafiltration

Katariina MajamaaThe Dow Chemical CompanyTel: 1 952 897 4357Email: [email protected] filtration, wastewater reuse, industrial water treatment


Association | News

he AFS Oil & Gas and Chem-ical Processing Filtration andSeparations Conference was

held March 24-26 at the MarriottWestchase Hotel in Houston, TX. Con-ference attendance continued to growfrom previous years following the eco-nomic downturn in recent years. Theevent attracted attendance from a widenumber of European and Asian coun-tries, along with the United States,Mexico and Canada. There were sevenconference sponsors: AWC, Chemical

Engineering magazine, Dexmet, Fiber-web, Franklin Adhesives, IBR Labora-tories and International FiltrationNews along with 24 exhibitors limitedby available space.

The event began Monday, March 24,with 10 short courses designed for bothnewcomers to the industry and techni-cally-proficient journeymen includingcourses in the Basics in [each] Air, Liq-uid and Ultrafiltration, MicrofiltrationMembrane, Reverse Osmosis SystemDesign, Nanofiltration Technology,

Centrifugation, Coalescing Principalsand Applications, and Filtration MediaUse and Market.

This spring’s conference chairs wereDavid Engel and Van Barclay, industry-leading names in the oil & gas andchemicals industry. Plenary andkeynote speakers were Professor Kuo-Lun (Allan) Tung, lead organizer forthe 2016 Word Filtration Congress inTaipei, Taiwan, and Doug Heguy, QixinZhu and Lihong Du. The conferencewas organized with 18 separate session

T

AFS Conference Growth Continues

Student poster displays shown at the AFS Conference.

Xinxiang Tiancheng Aviation Purification Equipments Co. Ltd.

Our company specializes in designing & manufacturing and supplying many kinds of filters,

complete filtrating equipments and their elements with different materials according to your

drawings or new & old samples.

Xinxiang Tiancheng Aviation Purification Equipments Co. Ltd.

Chuangye Road No.1, Dvelopment Area, Xinxiang City 453003, Henan

P.R. China

Contact Person in China: Mr. Li Minghao

Tel: +86-13673735086 Fax: +86-373-3520026 Website: www.tchkjh.comEmail: [email protected] • [email protected]

For airplane For special vehicle

For coal machinery

For fluid cleaning systemFor dust collector of cement industry

For ultrafilter


Association | News

topics along with a panel discussion ofexperts who responded to a wide rangeof audience questions.

Many of the industry’s most recog-nized names participated as modera-tors, including: Colin Tyrie, WenpingLi, Vic Norton, George Chase, PeterCartwright, Chris Wallace, ShaguftaPatel, Van Barclay, Thad Ptak, PavlosPapadopoulos, Jay Keener, John Sabey,Ali Arshad, Kenneth Winston, MartinLehmann, Mary King, Biplab Mukher-jee, David Engel, Christine Sun, RahulBharadwaj, and Rob Bender.

At the 2014 AFS Awards luncheon,the AFS 2014 Young Scientist Awardwas presented to Sneha Swaminathanwith Hollingsworth & Vose. WenpingLi with Agrilectric Research was pre-sented the 2014 Frank Tiller Award,and the 2014 Wells Shoemaker Awardwas given to Raymond Collins withDow Chemical Company. The Corpo-rate Sponsor 2013 New Product of theYear, Filtration Media Category waspresented to GKD-USA. The 2013 NewProduct of the Year, Biotechnology Cat-

egory, went to Parker Hannifin Do-minick Hunter Division, and NewProduct of the Year in the FiltrationSystems Category was won by ParkerHannifin Hiross-Zander Division.Needless to say, not taking away fromthe GKD-USA Award, Parker Han-nifin had a particularly good year,walking away with two categoryawards.

Tuesday afternoon the AFS Corpo-rate Sponsors met and several newprojects were introduced along withtechnical writer Nick Basta who will or-ganize and write future AFS MarketLandscape Reports as well as the newAFS Point of View white paper. Follow-ing the Corporate Sponsors meeting areception was held for all attendeesalong with a student poster competi-tion and displays. First place posteraward was presented to Mutiara Ayu,University of Houston; second placewent to Andrew Davis, Brigham YoungUniversity; and third place went toHyeon Shin, University of Akron.

At the request of over 50 percent of

attendees at the 2013 Fall AFS Confer-ence in Cincinnati, Ohio, the AFS willhost its first-ever back-to-back repeatconference on the subject of FiltrationMedia this fall at the Hilton Rose-mont/Chicago O’Hare Airport, October13-15. This event could well be a sell-out. Therefore, organizers encourageanyone with an interest in filtrationmedia to register early. Looking for-ward, the 2015 AFS Spring Conferencewill focus on the subject of Filtrationin Power Generation in the proclaimed“Energy Cluster” city of Charlotte, NCwhere 29,000 energy equipment, con-sulting and construction company en-gineers are employed.

The American Filtration & Separa-tions Society is the largest filtration so-ciety in the world and the principaleducator of the industry.

For additional AFS information contact: Lyn Sholl, AFS Executive ManagerTel: 1-615-250-7784Email: [email protected]

Needle felts

2014 Award Honorees (left to right): Sneha Swaminatha; Wenping Li; Peter Wirtz; Mark Willingham; 2014 AFS Chairman,Ron Fall; Keith Anderson; and Raymond Collins.

FN


Industry | News

he China International Filtra-tion Technology Conventionand Industry Exhibition held

April 15 – 17 in Beijing, China, at-tracted experts and executives fromChina and other parts of the world todiscuss trends of the filtration and sep-aration industry.

The filtration event was a part of theChina (Beijing) International Technol-ogy Transfer Convention 2014 (ChinaITTC 2014). Over 4,000 delegates frommore than 40 countries attended.

The China ITTC was first held in2011. But this was the first time it in-cluded a special event for the filtrationand separation industry. The filtration

event included five forums and an ex-hibition on the first floor of the BeijingInternational Convention Center withan area of 1,000 square meters.

At the five forums, more than 40 ex-perts spoke about recent developmentsof filtration and separation markets andtechnologies.

In some of the forums, Chinese ex-perts described the challenges and op-portunities of the industry. Forexample, Chai Fahe, vice president ofthe Chinese Research Academy of En-vironmental Science, spoke about thechallenges and solutions of China’s at-mospheric particulate pollution. Hesaid many of the solutions were contin-

gent on the developments of the filtra-tion and separation technologies.

Wallace Leung, professor at HongKong Polytechnic University, described inone of the five forums, the different typesof technologies for the filtration and sep-aration of particulate matter 2.5 (PM2.5)and particulate matter 10 (PM10) used inthe past decade. He said low dropout andhigh-efficiency filters made fromnanofibers had overcome most of the de-fects and had success in the market.

Professor Richard Wakeman, a U.K.expert specializing in fluid and particleseparation, talked about the experienceof air control in the U.K in pastdecades. He believed this experience

Experts Predict Filtration and Separation Will Make China GreenerBy Jason Chen, China Correspondent

TMore than 4,000 delegates visited the premier filtration event in China.

could help China tackle the growingchallenges from air pollution.

Filtration and separation materialsfor various industries were also dis-cussed in the forums. Professor ZhangWeidong, Beijing University of Chemi-cal Technology, introduced the use ofpolytetrafluoroethene (PTFE) in the fil-tration and separation of air qualitycontrol, medical protective clothing, oildehydration, and carbon dioxide sepa-ration in the Chinese market.

Fiber and textile processing technolo-gies for filtration and separation materi-als were discussed in the forums as well.Cai Weilong, technology director of Xi-amen Savings Environmental Co. Ltd.,discussed the recent developments of fil-ter materials made through needlepunch and spunlace technologies.

There were more than 30 exhibitorsat the filtration event. The organizersaid the exhibitor number was small be-cause this was the first time the ChinaITTC included filtration and separationtopics, but they expected the number

would grow at the next year’s event.Fujian Longking Co., Ltd. was one

of the exhibitors. Longking has bene-fited from China’s efforts seeking im-proved air filtration in the last fewyears. In 2013, Longking’s sales andnet profits increased 31.32% and56.92%, respectively, from their 2012level. Longking’s growth was mainly

from its success of hybrid electric andbag filters. Coal-fired power plants,iron and steel manufacturers and ce-ment producers have become Longk-ing’s main clients since Chinaincreased the environmental stan-dards for these industries, accordingto Chen Peimin, secretary of Longk-ing’s board of directors.

Beijing International Convention Center, the venue for CITTC 2014.

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he centrifugal-action separatorcan remove grit, sand, metalchips, fines, and other solids

from liquids. It is perfect for use as a pre-filter to extend the life of fine filtrationsystems. These units require little or nomaintenance, as there are no movingparts to wear out, or filter media to re-place. The unit only requires a simplepurging, eliminating downtime. It han-dles flows from 6 gpm and retention rat-ings to 50 micron.

Typical Applications• Cooling towers• Process water • Food processing • Chemical processing • Well water • Pulp & paper mills• Mining operations • Steel mills • Petrochemical industry • Power plants • Protection of spray nozzles and other small orifices

• Chip removal from cutting coolants

• Car and vehicle wash systems• Paint spray booths• Heat exchangers• Spray nozzle protection• Industrial laundries• Solids recovery• Parts washing systems• Pump protection• Domestic water• Recirculating cooling water• Sprinkler systems• Quench water• Pre-filter for seawater

FEATURES• Low constant pressure drops• Piped housings• Carbon steel or stainless steel (304 or 316) construction

for housings• All housings are electro-polished to resist adhesion of dirt and scale

• ASME code stamp available• Pipe sizes 3/8 through 10-inch (larger sizes also available)

Options• Different outlet connections• Special materials

INSTALLATIONThe Separator should be installed in

a near vertical position. The unitshould be supported by means otherthan the inlet/outlet piping. First, con-nect the outlet of the unit to the outletpiping. Then install any supports, suchas U-bolts or legs. Next, connect the

inlet piping to the inlet. Test for leaksand separation. The unit is now readyfor operation.

PURGING AND MAINTENANCESeparators must be purged regularly.

If they are not, the separated solids willaccumulate and overflow the collectionarea, affecting performance and con-taminating effluent.

Users can manually, automatically, orcontinuously purge the collection area ofthe separator. Manual purging requiresthat the operator open a simple valve andempty the contents. Automatic purgingcan be done many different ways, but thesimplest is setting a timer to open andclose the valve, purging the contaminanton a regular basis. Continuous purging

Cover Story | Rosedale Products, Inc.

Solids/Liquids Separators as Pre-Filter By Dan Morosky, Rosedale Products, Inc.

TSeparators extend the life of fine filtration systems.

www.filtnews.com • June 2014 • 13

simply requiresleaving a manualvalve partially openat all time, lettingthe contaminantleak out at a con-trolled rate. For bestresults, all purgingshould be donewhile the separatoris in operation.Avoid purging “up-hill,” which will re-sult in buildup andclogging, affectingperformance andoperation.

Simple rules of maintenance includechecking the purge valve regularly forclogging, scale, and buildup. If the unitis installed in an area where the ambi-ent temperature is below freezing, thecollection area and all purge pipingshould be kept from freezing while op-erating. If left in idle state under freez-ing conditions, the entire unit must bedrained of liquid, and the collectionarea must be purged of solids.

HOW IT WORKS Fluid enters the

pressure vesseltangentially athigh velocity. Acentrifugal actionis created, whichforces the solids toseparate and enterthe sump, whilethe clean liquidexits up throughthe standpipe. Thesolids collect inthe sump, and caneasily be purged.The operation isso simple, it can beset to automati-cally purge on atimed interval.

FLOW RANGE – GPMModel Pipe 5 10 Inlet/ DrainNo. Size (inch) PSID PSID Outlet Size (inch)Sep-6 3/8 3 6 NPT 1Sep-11 1/2 7 11 NPT 1Sep-25 3/4 15 25 NPT 1Sep-35 1 30 40 NPT 1Sep-75 1-1/4 55 75 NPT 1Sep-80 1-1/2 60 80 NPT 1Sep-130 2 90 130 NPT 1Sep-140 2-1/2 96 140 NPT 1Sep-275 3 200 275 NPT or Flanged 1SEP-553 4 425 553 Flanged 2SEP-1265 6 985 1265 Flanged 2SEP-2210 8 1715 2210 Flanged 2SEP-3410 10 2640 3410 Flanged 2

Separator Sizing:Separators are generallysized so that there is atleast a 5 PSID pressuredrop across the unit.Separation efficiency in-creases as pressure dropincreases. Shown here,flow ranges for each unitbased on 5 and 10 PSID.Choose a unit based on aflow/efficiency balance.

For more information contact:Rosedale Products, Inc.

3730 W. Liberty Road | Ann Arbor, MI 48103 Tel: 800-821-5373 or 734-665-8201 | Fax: 734-665-2214

Email: [email protected] Website: www.rosedaleproducts.com

FN

Separators haveno moving parts orfilter media.

Cutaway shows flow


Fiber | Engineering

ompared with conventionalmicrofiber structures, theunique advantages of ultra-

fine fiber webs for filtration applicationsare their enormous specific surface areaand fine pores.

For many years the meltblownprocess has been used for the produc-tion of nonwovens in a typical mi-crofiber range of 1-20 µm. Because oftechnology limitations, fiber diametersbelow 1 µm have so far not been pro-duced in a productive manner.

This constrains the application areaand the material efficiency, for exam-ple, in the filtration industry. For theeconomical production of a defect-freeweb it is crucial to optimize the stan-dard meltblown process.

Consequently, the aim of this workwas the development of a meltblownprocess that goes beyond state of theart – a process that allows the eco-nomic production of ultrafine fibers in

a range of 0.1-1.0 µm with thermoplas-tic polymers.

Experimental results have been cor-related with simulation-based data fora better understanding of the fiber-forming process. Because rheologicalaspects are not completely understood,capillary rheometry was used.

All our findings were combined inthe NaBlo process. The optimized set-ting enables the production of ultrafinethermoplastic fibers using low-viscouspolypropylene (PP) and polybutyleneterephthalate (PBT) polymers.

PROCESSIn many publications [2, 3, 4] the “slip

flow effect” is described as an impor-tant factor to improve filtration effi-ciency. This effect is responsible for thelow friction of the air at the surface ofsubmicron structures. Thus, it takes ef-fect in ultrafine fiber webs during dustseparation.

Fibers in the submicron range leadto much higher filtration efficiency offine particles, while the pressure droprises at a relatively low level.

Currently, the major technology toproduce fine fiber webs is melt blow-ing. The major advantages of the melt-blown technique are its broadindustrial availability, low-priced rawmaterials and high productivity in con-trast to solution-based electro- and cen-trifuge-spinning processes.

Submicron fiberglass papers areoften used for high-efficiency filtrationapplications; in the future these mate-rials could be replaced by new melt-blown nonwovens.

A major advantage of combinedthermoplastic materials is their cor-rectly sorted disposal. Other importantbenefits include their low brittleness,low density, high flexibility, easy ther-mal lamination and possibility for elec-trostatic charging.

Economical Production of Ultrafine Thermoplastic Fibers for FiltrationBy T. Batt, M. Dauner and H. Planck, Institut für Textil- und Verfahrenstechnik Denkendorf (ITV), Germany

C

Figure 1. Left: Cross-sectional view of a meltblown system. Nozzle consists of two air blades beneath a die forming typical(Exxon) geometries for meltblowing. Right: 500 mm wide meltblown line at ITV Denkendorf.

Further, micro-fiberglass papershave been criticized because of therisk of exposure to the smallest fiberdust with a high potential for morbid-ity [1], which could be avoided bypolymeric webs.

Over the past 50 years, meltblownresearch has been focused on loweringthe mean diameter to improve webquality and performance, for example,for filtration applications.

After extrusion of a low-viscouspolymer through the capillaries, themelt can be stretched to ultrafine fibersdown to 100 nm in diameter by thedrag of a high-speed and turbulent hotair stream (Figure 1).

Many factors determine the distribu-tion of fiber diameter in a meltblownweb: melt viscosity, feed rate, air veloc-ity and temperature, die geometry, etc.

Rheological characterizations of thelow-viscous polymers uncovered shearthinning and strain hardening behav-ior of the materials. These give someexplanation for the good spinning sta-bility of the materials despite high

drag rates.Online rheometrical measurements

were used to control viscosity due tothermal degradation and adding of re-active additives. The results underlinedthe importance of a low viscosity forforming ultrafine fibers, but also iden-tified limitations of the process.

Optimized process parameters andparameter combinations wereachieved on a single-capillary nozzle-system using a “design of experi-ment” approach. For the first time asystematic study of die geometries ofthe meltblown process was accom-plished therein.

Different low-viscose PP types wereused. A comparison between standardZiegler-Natta catalyzed PP and thenewer metallocene catalyzed types wasexamined and polymer blends and ad-ditives have also been explored.

With these low-viscous polymers itis possible to produce average fiber di-ameters in a range of 250-500 nm(Figure 2). The production of ultra-fine fibers using PBT also shows

promising results.The present experiments and studies

were supported by computational fluiddynamics (CFD) simulations at theFraunhofer Institut für Techno- undWirtschaftsmathematik (ITWM).

Examination of the fiber drag mech-anisms by high-speed videos andFraunhofer ITWM simulations led tothe construction of an optimizedprocess on a 500 mm wide meltblownline. This process allows the produc-tion of ultrafine fibers with high pro-ductivity.

The up-scaling of the results hasbeen successfully realized on 0.5 mwide lines at ITV and by Oerlikon Neu-mag. Until now, comparable resultshave only been shown from a handfulof companies or institutes [5, 6, 7]. Today,the enormous potential of the econom-ical production of ultrafine thermoplas-tic fibers is beyond doubt.

To support the evaluation of thefinest fiber webs, ITV and FraunhoferITWM established a scanning electronmicroscope (SEM) picture-based



Fiber | Engineering

method for objective and repeatablemeasurement of the fiber diameter.

ITWM developed an automatic soft-ware tool for this specific reason.

The automatic fiber diameter analy-sis is supplemented by the measure-

Figure 2. Left: SEM picture with manually measured diameters (in µm) along intersections with two diagonal lines of anultrafine fiber meltblown web. Right: Histogram with classified fiber diameter distribution in nm gained in an automaticanalysis of SEM pictures compared to manual achieved data for the same images.

ment of the pore size and the air per-meability. Depending on the density ofthe web there are strong correlationsbetween median fiber diameters, poresize and air permeability. Only the neg-ative effects of extreme highpolymer/air-ratios (shots or fiber-fly)can influence this correlation.

Additional filtration tests haveshown the same trend. Thus, there is anadvantage for ultrafine fiber webs forfiltration of fine dust particles.

CONCLUSIONMeltblowing is a complex process in

which many parameters interact witheach other. Further, rheological aspectsas well as the fiber forming processhave not yet been completely under-stood.

Within the NaBlo project, a consor-tium from industry and researchworked together during three and ahalf years to bring the meltblowntechnology to another level. It is pos-sible to install the developed setup on

existing machines.If diameters in the micron range

are required, it gives the possibilityto produce them with higher produc-tivity and lower energy consumptioncompared with conventional ma-chines.

Current research is focusing on theindustrial scale-up of the process andon technical polymers like polypheny-lene sulfide (PPS) and polyetherether-ketone (PEEK) using the NaBlotechnique.

ACKNOWLEDGEMENTThis research was funded through

a grant by the German Federal Min-istry of Education and Research inthe collaborative project NaBlo(BMBF FKZ. 13N9861 and13N9862). The authors wish tothank Fraunhofer ITWM, Freuden-berg Filtration Technologies and Oer-likon Neumag for their help andeffort completing this research aspart of the NaBlo project.

References[1] T. Batt, M. Dauner, H. Planck, ITV Denk-endorf, “Experimentelle Grundlagen zurFaserbildung im Meltblown-Verfahren”, 25.Hofer Vliesstofftage, November 2010.[2] S. Goldstein, “Modern Developments inFluid Dynamics”, vol. 2, p. 676, Dover, NewYork, 1965.[3] K. Graham, M. Ouyang, T. Raether, T.Grafe, B. McDonald, P. Knauf: “PolymericNanofibers in Air Filtration Applications”Donaldson C., Inc., Fifteenth Annual Techni-cal Conference & Expo of the Filtration &Separation Society, Galveston, Texas, April2002.[4] L. Cheng, S. Rief, A. Wiegmann, Fraun-hofer ITWM Kaiserslautern, 10. Symposium“Textile Filter” – Chemnitz, March 2010.[5] A. Wilkie, Hills Inc., West Melbourne,Florida, “Nanofiber Meltblown Fabric”,www.hillsinc.net/nanomeltblownfabric.shtm,February 2007.[6] C.J. Ellison, A. Phatak et al., “Melt blownnanofibers: Fiber diameter distributions andonset of fiber breakup”, Polymer 48, April2007.[7] G. Bhat et al., “Nanofiber”, NonwovensResearch Laboratory, University of Ten-nessee-Knoxville (UTNRL), Nonwovens In-dustry, April 2011.


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Filtration | Application


ometimes it’s worth lookingbeyond existing, establishedprocesses, visible at the ex-

ample of Lenzing Technik GmbH, aninternationally operating engineeringcompany with headquarters inSalzkammergut, Austria.

As a subsidiary of the Lenzing AG– the market leader in the productionof cellulosic fibers with wood as araw material – the Lenzing TechnikGmbH has been focusing on thevalue chain from cellulose to the fin-ished viscose fiber. The company’s

portfolio ranges from engineeringservices to development and manu-facturing of processing equipment aswell as turnkey facilities. Even wholeviscose production plants have beenengineered and built.

A small team of experts at theSolid-Liquid Separation Division ofLenzing Technik has been engaged inthe filtration of viscose, a homoge-nous, but contaminated high-viscos-ity fluid with honey-like appearance.Until the first filtration systems withautomatic sludge discharge were de-

veloped, viscose was filtered with fil-ter presses. In a typical viscose plantup to 100 such presses were in-stalled, frequently taking up severalthousand square meters of filter area.

The filter presses were equippedwith filter cloths made of cotton,needle felt or pulp sheets. Filtrationwas usually targeted at a fineness of20µm. Similar to bag filters, whichare still in use for smaller filtrationtasks; the cloths were perfused byviscose. After their dirt holding ca-pacity had been reached, they neededto be removed manually and replacedwith new cloths.

The first automatic systems wereintroduced in the 1970s, but did notreach market penetration. Especiallyworth mentioning are horizontal discfilters, which use filter aid tobuild/precoat a cake on a package ofhorizontally placed, round filterplates. After finishing the filtrationcycle, the disc package was put intorotation and thereby discharged thefilter cake. Although still in opera-tion in the beverage industry, thissystem could not establish itselfwidely for several reasons such as thehigh complexity and costs for appa-ratus and installation, the discontin-uous filtration as well as filter aidsconsumption and its regeneration.

At about the same time, the firstbackwash filters (mainly using metalfiber fleece as filter media) were in-

From Production of Viscose to Fully Automatic Filtration in the Sugar IndustryBy Stefan Strasser and Stefan Schoepf, Lenzing Technik GmbH

Figure 1: Filter press

S

troduced to the market. Generallyconsidered a suitable technology, thefirst systems failed due to several sig-nificant disadvantages. Some usedextremely complex and expensive fil-ter elements, which needed periodicthermic regeneration, as they werenot efficiently back washable. Otherunfavorable ones needed up to 20%of the filtrate flow to clean the filterfrom impurities (referred to as “re-ject”). Hence, further complex filtra-tion facilities for processing of thereject were necessary.

The development of the “Kolben-Korb-Filter” (KKF) filter by LenzingTechnik GmbH allowed inexpensive,automated filtration of high amounts ofviscose at a fineness of 20µm and min-imum backwash quantities. The “Kol-ben-Korb Filter” has been a marketleader in the global viscose industryever since, and soon achieved successin other fiber-producing industries aswell.

In viscose filtration several require-ments need to be strictly met, whichare also reflected in sugar processing.

RELIABILITYPerhaps more in viscose plants

than in sugar processing, the reliabil-ity of apparatuses is essential.

If the production process of vis-cose as a fluid is interrupted for sev-eral hours, it hardens – andcoagulation takes place. Devices andtanks that are filled with coagulatedviscose need to be cleaned in aminer’s fashion, as there is no way todissolve coagulated viscose.

A similar thing happens in sugarprocessing where unintended crystal-lization of sugar at least involves ef-forts for re-starting the productionprocess. Due to the timely limitedmanufacturing cycles, additionalproduction downtimes are especiallycritical. Furthermore, the continuousdownstream process of evaporation,crystallization and separation shouldnot be discontinued due to a stillstand in the filtration step.

LOWEST REJECT QUANTITIESNot only in viscose production, but

also in sugar manufacturing, the fluid

(thick juice or standard liquor) repre-sents the valuable substance. Mini-mum losses (=“reject” amounts) werethe key success factors of the “Kolben-Korb-filter” in the viscose industry.

FILTER FINENESSBeing considered a spinning solu-

tion, viscose is pressed through ex-tremely small holes of the so-called“spinning jets” (usually at a fineness

of approx. 50µm) after filtration.Downstream from the spinneret thereis a chemical precipitation bath lead-ing to a coagulation of the viscosefiber, which is then drawn throughthe spinning bath by peeling rollsand frequently drawn down to a fiberdiameter of only 20µm.

In sugar processing, an efficientfiltration has positive effects on thedownstream vaporization process as




well as helping to improve productquality of refined sugar. Details onthe reached filter fineness in thickjuice and standard liquor are de-scribed in the course of this report.

EFFICIENT BACKWASHA good viscose/sugar filter runs

continuously, while filtration is notinterrupted during the backwashprocedure.

It is not uncommon, that 100,000backwashes and more can be exe-cuted, before the filter material needsto be changed for the first time.

The increased viscosity of thick

juice and standard-liquor, whichforced other systems to backwashwith external media, did not repre-sent a challenge for the engineers ofLenzing Technik. Quite contrary tothis, the KKF filter concept evenneeded to be adapted to the lowerviscosity of the sugar solution. The

Figure 3: Metal fiber fleeceFigure 2: Stainless steel fabric

Figure 4: Working principle Lenzing OptiFil

result of this adaption is meanwhilepatented and established in a varietyof different applications andprocesses under the name “LenzingOptiFil®.”

LOW OPERATING COSTSBoth, viscose (apart from specialty

types) and sugar have become mass-produced goods. In today’s globalizedmarkets, cost leadership also definesthe market position of a company –applying not only to investment butalso especially to operating expenses.

Mostly, the investment costs forthe integration of processing plantsare multiplied by the costs for instal-lation (e.g., set-up, control system,piping, valves, installation area, etc.).In this respect, the OptiFil has the ad-vantage of an easy system construc-tion with only one automatic valveper filter. While the filter is able tomanage relatively high flow rates, itdoes not require more installationarea than a parking motor scooter.

The patented Lenzing OptiFil is afully automatic, continuous systemthat works according to the principleof depth, surface or cake filtration,depending on the selected type of fil-ter material. A metal or syntheticfiber fabric or fleece (see Figures 2and 3) is used as filter media, retain-ing particles of different sizes eitherinside or on its surface.

After the pre-determined degree ofcontamination has been reached, thefilter material is cleaned by back-washing a small quantity of filteredmedium, with continuous filtrationduring backwashing.

In detail, the filter material of theLenzing OptiFil is installed outside aperforated supporting structure(“perforated drum”). In case of cakefiltration, a very thin filter cake (oftypically 0.5 – 2mm) is formed insidethe holes of the perforated drum dur-ing the filtration from the inside(Room P1) to the outside (Room P2).During the partial backwash from

“Room P2” (Filtrate) to “Room P3”(Reject), the cake is completely dis-charged within a few seconds, usinga small amount of filtrate to force itout of the filter. New cake formationalready starts during backwash and istypically finished resulting in clearfiltrate within less than 10 seconds.

TRADITIONAL FILTRATION METHODS To date, two different systems for

filtration of Standard Liquor havebeen in use in the sugar manufactur-ing process, where both, candle pre-coat filters as well as disposable bagfilter elements show significant dis-advantages in comparison to theLenzing OptiFil.

CANDLE PRECOAT FILTRATIONIn order to achieve an economic

flow rate, the candle precoat filters haveto be operated with precoat (= first con-ditioning of the filter material with athin layer of filter aid) as well as body-feed (= continuous dosing of filter aid).




This required a consumption of 15 kghigh quality filter aid per hour in thespecific process. As a result, tremen-dous operating costs as well as signif-icant expenses for handling andlogistics incurred.

At a specific flow rate of only 2,9m³/m²*h, an enormous filter area wasneeded to handle the total flow rate.So the 8 required candle precoat fil-

ters (each taking up 125 m²) causedconsiderable investment costs as wellas a huge space requirement.

CLEANING BY ROTATING NOZZLESBackwash filters with rotating noz-

zle cleaning systems were installed inseveral cases of thick juice filtration.These types of filter systems have beendeveloped in Israel, originally in-

tended for separation of coarse parti-cles from water in agricultural irriga-tion. Due to their construction design,which is known to have a gap betweenthe backwash nozzles and the sievebasket, they were not able to handlebackwashing of the high viscositythick juice and therefore needed toadd external medium (thin juice orwater) to execute the backwash. This,in turn, led to an increased number ofvalves and pipework. Furthermore,the equal space between the differentnozzles resulted in high losses duringbackwash. As a countermeasure, thefilters are equipped with very coarse(50µm) sieve baskets. These indeedreach large intervals between the back-washes, but operate at the expense offiltrate quality.

DISPOSABLE BAG FILTRATIONA seemingly feasible process, be-

cause a non-expensive alternative tocandle precoat filters has been real-ized in another case of thick juice fil-tration. Needle felt bags, whichfeatured a nominal separation rate of1µm, showed on closer examination

Figure 6: Standard-Liquor Filtration with the Lenzing OptiFil

Figure 5: Solid content bag filter & Lenzing OptiFil


that nearly no analytically verifiableseparation happened (see Figure 5).

Despite the insufficient filtratequality, the differential pressure builtquickly, so that an average of 24 bagsof the two used multi-bag filter hous-ings had to be changed during everyshift. Therefore, bag filtration is noreal alternative for the filtration ofthick juice, although the level of in-vestment costs would be lower.

PROCESS PARAMETERSThe Standard Liquor (originating

from a mixture of thick juice and re-turn flows of crystallization) has atemperature of approx. 95°C and asugar content of about 70%. Thesolid content prior to the filtrationinlet fluctuates between 8 and 14mg/L. By using a 10-micron stainlesssteel filter fabric at a flow rate of 50m³/h per filter unit OptiFil-250-0720, the solid content was averagely

reduced to 3 mg/L or even below.

EFFICIENCYDespite the high unit flow rates at a

filter fineness of 10µm, the medium lossis extremely low with 2,5 liters every 5minutes – due to the efficient backwashsystem. These minimum reject amountsof less than 1% of the filtrate flow differ-entiate the Lenzing OptiFil significantlyfrom other filtration systems. Originatingfrom filtration of high viscosity fluids, theOptiFil easily cleans the filter materialusing internal medium. Due to the pro-duction capacity, the customer decidedon a larger system (OptiFil-350-1080)after the pilot trials. This one unit nowfilters 100 m³/h of Standard Liquor at afineness of 10µm and requires only oneautomatic valve. This allows vast savingsin complexity and space, as well as in-vestment costs in comparison to tradi-tional filtration systems.

COSTS FOR FILTRATIONWhile the operating costs for can-

dle precoat filters are enormous onlybecause of the filter aid consump-tion, and bag filtration requires sev-eral manual bag changes every workshift, the Lenzing OptiFil is charac-terized by nearly no running costsfor operation. The filter material canbe backwashed several thousandtimes without changing. Even if it isblocked once (mostly after finishinga production cycle) it can be changedeasily. As it is made out of untailoredflatware, the filter material used is in-expensive and each change does nottake more than 30 minutes.

For more information contact:Stefan Strasser, Product ManagerLenzing Technik GmbHFiltration and Separation TechnologyTel: +43-(0)-7672-701-2702Email: [email protected]

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orous Materials, Incorpo-rated has utilized new tech-nology to improve methods

of largest pore detection. The com-pany has revolutionized the art of car-tridge filter bubble point testing withtheir new product, The AdvancedCartridge Bubble Point Tester (ABPT-2020-FI). This machine works byslowly pressurizing filter cartridges ata controlled flow rate using a massflow controller. Using a mass flowcontroller allows for much slowerrate of pressure increase at low pres-sures and, therefore, maximum accu-racy in first bubble detection at lowpressures when compared to simplerregulator only systems. This methodallows a high accuracy electronicpressure transducer to detect bubblepoint pressures as low as 0.02 Psi ±0.15%, which translates to approxi-mately a 330 micron pore size.

The Advanced Cartridge BubblePoint tester is a customizable ma-chine that performs testing on filtercartridges according to the ARP-901Standard. Just like standard bubblepoint testers, the Advanced CartridgeBubble Point tester works by pressur-izing samples until the sample startsto bubble and record the pressure atwhich the first bubble occurred.From this, it can calculate the poresize. So what makes this bubble pointtester special compared to the rest?

Testing | Laboratory

New Technology from Porous MaterialsImproves Large Pore DetectionBy Jazmin M. Logrono and Scott P. Whitlow, Porous Materials, Inc.

Dual Chamber ABPT-2020 equipped to test cartridges as large as 40cm x 40cm.

Manual Control Screen displaying system schematic for one sample chamber.

P


ADVANCED FEATURESFrom the beginning to the end of

each test, this machine works auto-matically. The operator simply loadsthe sample, sets the testing parame-ters, and starts the test. The machinehas a motor installed, which is usedto rotate the cartridge. This elimi-nates the need for manual rotation,required by some testing standards.Rotation during bubble point car-tridge testing allows for detection ofthe first bubble at any point aroundthe circumference of the cartridge.This is especially important duringQuality Control testing due to thepossibility of seam flaws being lo-cated in the initial lower portion ofthe filter. The company’s softwarecan be programmed to have a car-tridge rotate constantly or, exactlywhen a client needs it to rotate.

The machine is equipped withpumps that supply head pressure tofill and drain the sample chambers;this can also be done automatically.The software is configured so that themachine is able to pump fluid fromthe reservoir into the sample chamberwith just the click of a button. Drain-ing the sample chambers is just aseasy as filling them. The pumps workto fill and drain the sample chamberwith the wetting fluid. To simplifythings even further, each samplechamber has a level sensor installed,which has been calibrated to specificheights. Users are able to input thediameter of a filter cartridge into thesoftware and have it automaticallysubmerge the sample without excessfluid depth above it or risk of overfill-ing due to operator error.

Each machine includes a reservoirthat holds a wetting fluid. Each bub-ble point testing standard for car-tridge testing requires a specifictesting fluid. ISO 2942 requires usingisopropyl alcohol as a wetting fluidat a specific temperature of 22+/5˚C.The temperature is maintainedthrough the use of a closed loop heatexchanger and high capacity liquidheater-chiller system. The use of aheat exchanger helps reduce theprobability of contaminating the wet-ting fluid. However, wetting fluids

like isopropyl alcohol are highlyvolatile; this introduces the possibil-ities of health concerns with pro-longed vapor exposure.

In order to maximize safety foroperators, Porous Materials has in-stalled a ventilation system. In eachchamber, there is a vent that, using afan, moves air to the cold trap,through a desiccant filter, and ex-hausts clean air. Each chamber is also

equipped with a lid and a door. Thelid is used to prevent evaporationand contamination of the wettingfluid. The door contains the fumesinside of the sample chamber to pro-vide the operator with minimal vaporcontact.

CUSTOMIZABLE OPTIONSAlthough this specific model has

two chambers, these machines are


Testing | Laboratory

customizable to meet customer’sneeds. The dual chambers provide ef-ficiency in a fast paced environmentallowing companies to test multiplesamples of various sizes at once with-out major modifications; simpleadapter plates and gaskets are pro-vided for every size cartridge neededin a particular installation. As a re-sult, productivity and throughput areincreased allowing fewer techniciansand machines to handle more of theworkload. However, for smaller facil-ities or single product assembly lines,it is possible to have a single cham-bered machine sized to specific di-mensions.

Porous Material’s software can betailored to satisfy any customer’s spe-cific needs. If there is a specific stan-dard that a company needs to abideby, this software can be manipulatedto perform any specific testing proce-dure. The software can be used onthree different modes: SupervisorMode, User Mode, and QC mode. Su-pervisor mode allows full control of

60 gallon wetting liquid reservoir allows simultaneous testing in all chambers.

CapRep, the program used to analyze results, is integrated with the software usedto run the machine.


the testing parameters and options.User mode is meant to be used bycommon users. Except for samplename, it does not allow any parame-ters to be changed. QC mode doesnot allow any parameters to bechanged; the user would simply pressa button to begin tests. These optionsare designed to allow the machine tofunction in both research and indus-trial settings, allowing a knowledge-able operator to set customparameters or, ensuring consistentuse of identical parameters over timeby different operators. Tests can alsorun on a pass/fail basis; the operatorwould simply set the criteria that willcause a sample to fail.

CapRep is the program used to an-alyze results; the report program isintegrated with the software used to

run the machine. Porous Materials,Inc. is open to adapting the reportprogram to the user’s specific needs.This includes converting units andanalyzing reports according to spe-cific cartridge filter testing standards.Bubble point data can easily be ex-ported to Excel or Tab documents.

General Specs:• Up to 100 Psi• Flow controllers 30 Sccm

to 200 SLPM• Cartridge Sizes:• Diameters: 2.54cm - 40cm• Lengths: 2.54cm – 150cm• Cartridge flow inlet size

0.5cm - 5cm

For more information contact:Porous Materials, Inc.Tel: 1-607-257-4267Email: [email protected]: www.pmiapp.com

FN


hat are the common fil-ter problems and why dothey happen? Often the

filter is a process equipment compo-nent that is ignored until it fails to per-form to meet process requirements forclarity, flow rate and cycle time. Whenperformance problems occur, the oper-ators send their distress call to theprocess or plant engineer and the chal-lenge to solve the problem begins.

If a process can function well with-out a filter, somebody is ahead of thegame. But most likely, if there is a liq-uid with suspended solids as part ofthe process, then a filter is essential. Ofthe problems that can happen with fil-ters, they can be grouped as follows:

Group 1 – Problems with filter equipment or components.

Group 2 – Problems with filter ancillary equipment.

Group 3 – Problems with filter operational procedures.

EQUIPMENT AND COMPONENTS Undersized Filter: Often initial

investment cost plays a large role inselecting the filter, so a less expen-

sive or undersized filter is purchasedto meet a budget. The undersized fil-ter is not capable of handling theprocess flow or the total amount ofsuspended solids overwhelms the fil-ter solids capacity before the cycle iscomplete. Photos 1 and 2 show theeffect of too large a solids load for fil-ter cake space.

Filter cleaning operating instruc-tions should not start with “once thepressure is released, grab a shovel,and start digging to find the filter el-ements.” Overloading the filter cakespace with solids, as illustratedabove, will cause bridging of the fil-ter cakes between the filter leaves,warping the leaves and causing me-chanical damage.

The solids buildup in the filterduring filtration is based on the flowvolume and the total percent of sus-pended solids in the feed to avoidoverloading situations like shown inPhotos 1 and 2.

Sometimes the initial tests per-formed on a test solution to determinethe filter requirements do not repre-sent the actual process feed composi-tion. If a process starts on a production

scale with a different feed from whatwas originally tested, an undersized fil-ter causes production problems.

Internal Support: Sometimes theinternal support of the filter leaves af-fect the filtration flow and the pressuredrop through the filter. Photo 3 showsone filter leaf with a solid internal sup-port so that the liquid, as it passesthrough the filter cloth, flows on topof the solid corrugated sheet. In Photo4, to prevent the filter cloth from ad-hering to the solid support, a coarsewoven honeycomb support is laid be-tween the solid support and the filtercloth cover, Photo 5. By adding thisinternal support, filtration flow is im-proved; the filter cloth is separatedfrom the drainage support with the honeycomb. Field reports have shownan improvement in some cases of a25% higher flow when the honeycombinternal supports are installed underthe filter cloth bags. This drainagesupport also helps cushion impacts onthe filter cloth protecting the clothfrom tears when hit against a sharp orblunt object.

Maintenance: Lack of propermaintenance is a major cause of filter

Filter | Troubleshooting

Filter Problems, and Why Filters FailBy Jose M. Sentmanat

Photo 1. Solids buildup Photo 2: Overloaded filter

W

problems. A good preventive mainte-nance program will maintain the fil-ter system in good condition andproblem free. Care in proper cleaningof filter leaves is very important.

Leaves that are dirty cause low fil-tration flow rates and high differen-tial pressure due to flow restrictionscaused by reduced internal drainagein the filter leaves. See Photos 6 and7. Photo 6 shows very dirty filterleaves with actual damage to the wiremesh. Photo 7 on the right shows afilter leaf that appears to have cleanwire mesh. However, process condi-tions of low flow and high-pressuredrop were experienced. A section ofthe wire mesh was removed and ex-amination showed the internal sup-port was dirty and clogged withsolids buildup. This result demon-strates that surface cleaning of themedia covering the filter leaf was notsufficient. A good thorough internalcleaning is necessary to keep the in-ternal structure of the leaf clean andfree of solids buildup that obstructsinternal flow and causes high differ-ential pressure. For cleaning filterleaves, it is recommended that asoaking in a 2% caustic bath at about150 F for a couple of hours be per-formed, followed by high pressurehosing to thoroughly dislodge thesolids built up in the internals; thenwash the leaves well. In the worst-case scenario, ultrasonic cleaning by

a specialized shop is necessary.In the repair of mesh filter leaves

by welding the wire mesh to the filterleaf, care during the welding processis essential to ensure that the weldingis good and free of gaps or pinholes

that would cause bypassing duringfiltration. Photos 8 and 9 illustratesome of these problems. Photo 8shows poor welding of the wire meshleaving a gap (where the blade of thepocket knife is inserted). This gap at


Photo 3: Solid support Photo 4: Honeycomb support Photo 5: Cloth bag

the poor weld causes bleed throughand prevents the proper buildup ofthe filter cake during precoating andsubsequent filtration. Photo 9 showschanneling in the filter precoatcaused by pinholes in the welding ofthe wire mesh. Bypassing of the flowthrough holes prevents the filter cakefrom properly forming on the filterleaf, causing the channeling effectthat is shown.

Sometimes operators use im-

proper tools to scrape the filter cakeoff the leaves to complete dischargeof the filter cake. Photo 10 showssome typical improper tools used byoperators. These tools, when made ofmetal and used in a hurry can causedamage to the filter wire mesh asshown in Photo 11 where there is ahole in the wire mesh. This hole willcause bleed through and improperfilter cake formation during precoatand filtration.

Repair of holes in wire mesh or re-placement is required to prevent clarityproblems during filtration. Sometimesthe wire mesh covering the filter leafdevelops holes due to corrosion, wear,or erosion by the abrasiveness of the fil-ter aid passing through the wire meshduring initial buildup of precoat. Pro-tection of mesh from impact with sharpobjects when plates are outside the fil-ter is another consideration. Periodicinspection of the leaves is needed to en-



Photo 6: Very dirty filter leaves Photo 7: Dirty internal

Photo 8: Pocket knife in welding gap Photo 9: Channeling through pinhole

Photo 10: Improper scraping tools Photo 11: Tear in wire mesh from tools

sure that there is no damage to the wiremesh. Photo 12 and 13 illustrate wiremesh holes from damage due to corro-sion, photo 14 shows warped and dam-aged filter leaves and photo 15 showsgood filter leaves properly precoatedwith evenly formed filter cake.

Process Variables: Another filterproblem is the selection of improperfilter equipment because of inade-quate consideration of the flux of theprocess liquor, inaccurate knowledge

of the total suspended solids in thesolution, the particle distribution orthe nature of the solids. Without aproper analysis of the actual processliquor conditions, trouble looms onthe horizon. When consulted about afilter problem, a very common find-ing is that the filter user has no crit-ical data on the solution to befiltered. Particle analysis is not avail-able with important informationsuch as particle size, nature of the

solids particles, and if the solids arecompressible or not compressible.

Ignoring temperature and pressurefluctuations that affect behavior ofthe process liquor and its filterabilityoften happens with consequent filterproblems. Sudden changes in tem-perature affect the viscosity of theprocess liquor and the solubility andamount of solids.

Baffling: Improper baffling of theprecoat and feed liquid flowing into the


Photo 12: Wire mesh holes from corrosion

Photo 13: Wire mesh hole from corrosion

Photo 14: Warped and damaged filterleaves



filter will upset the cake and cause ero-sion of the filter cake and loss of clarity.Some horizontal filter plates have blankareas to serve as a baffle. However, pre-cise stacking of the plates and correctalignment of the plate bundle with thebaffle area opposite the inlet nozzle inthe tank is necessary.

Filter Media: Sometimes the filtermedia is not the right grade for theapplication whether paper, cloth orwire mesh is used. The right filtermedia for the application is deter-mined in the bench scale testing ofthe process liquid and selected tomeet the process requirements.

PROBLEMS - ANCILLARY EQUIPMENT Ancillary filter equipment can

cause problems when incorrectly

specified or integrated in the system.Lacks of proper instrumentation, in-correct piping, agitators or pumpsare factors in filter problems.

Pressure Gauges: Pressure gaugesare needed on the inlet feed pipeahead of the filter and on the dis-charge outlet line of the filter to cal-culate the differential pressure acrossthe filter system during operation.Too high a differential pressure willdamage filter leaves. Too low a differ-ential pressure causes uneven cakedistribution and loss of clarity.

Check Valves: A check valve inthe outlet piping of the filter preventsback flow to the filter and prematurefall off of the filter cake and loss ofclarity. Any back flow to the filtertank not only affects the filter cake,

but also can damage the filter leavesand wire mesh media or cloth covers.

Precoat and Bodyfeed: One defi-nite cause of problems with the filteris the lack or improper precoatand/or bodyfeed operations. Benchscale testing of the process liquor de-termines the proper grade of filteraids for precoating for initial clarityand body-feeding to keep the cakeopen to meet the process cycle time.

Agitators: Improper agitation inthe feed tank causes settling of thesolids and instead of a gradual feedof the suspended solids to the filter,lumps of the solids go to the filterthat disrupt the filter cycle.

If the agitation of the liquid in thefeed tank is too fast, the suspendedsolids and bodyfeed particles un-

Photo 15: Good filter cake Photo 16: Air bubbles in spotty filter cake

Photo 17: Cartridges with missing springs Photo 18: Dirty vertical filter leaves

dergo size reduction, due to abrasion,which affects the filterability ofsolids from the process liquor.

Pumps: The selection of wrongprecoat and/or feed pumps is a causefor problems with the filter. For pre-coating and feeding the filter themost common pump is an open im-peller centrifugal pump. For highviscosity liquids a positive displace-ment pump is better. For bodyfeed adiaphragm type pump is best. Avoidusing a pulsating pump that causes astop and go type flow that affects fil-

ter performance by upsetting thecake. Avoid getting air into the filterfeed and use proper venting of tanksto avoid air blocks. Photo 16 showsa spotty filter cake caused by air inthe feed to the filter. Air bubblestrapped in the filter cake will burstcausing the filter cake to break, leav-ing bare spots on the media. Thiscondition causes clarity problemsand affects the performance of the fil-ter. Bare areas of filter cake are sub-ject to bypassing with no filtration,and the solids become imbedded in

the filter media and inside the filterleaf structure. Sometimes the liquidvelocity through the filter is so highthat the suspended solid particles areforced through the filter cake, whichaffects the clarity of the filtrate.

PROBLEMS - OPERATIONAL PROCEDURESWhen consulted about a filter

problem, a very common finding isthat the filter operator has no criticaldata on the process solution for fil-tration. Data such as the total quan-tity of suspended solids, the nature


Photo 19: Sealant patches (black dots) on wire mesh Photo 20: Sealant on edges with leaks

of the solids, or particle analysis isnot available to give important infor-mation for particle size, nature of thesolids particles, or if the solids arecompressible or not compressible.

Common causes of filter problemsare inadequate operator training andprocedures, not following instruc-

tions or simply a disregard for properoperation of the filter. Photo 17shows filter cartridges where the op-erators failed to insert the compres-sion springs on some cartridgescausing the filter to malfunction.These missing springs were foundlying in the bottom of the filter tank.

Photo 18 shows the top view of avertical tank, vertical leaf filter; theleaves are dirty due to lack of goodhousekeeping practices of cleaningthe leaves and the filter internals ona regular basis.

In shift operations, there are in-stances where operators have inten-


Photo 21: Cake drop-off due to pump problem Photo 22: Lumpy precoat problem


tionally throttled the filter feed valveto continue running the filter to keepthe differential pressure switch andinstrumentation from stopping the fil-ter on their shift. Thus, they postponethe work of pulling the filter off pro-duction for cleaning to the next shift.

At times operators have draggedthe filter leaves on the floor whilehandling them during installation inthe filter, causing tears and wearspots on the filter media. Or simplecarelessness with the handling of thefilter leaves causes damage to the fil-ter leaves and/or to the filter media(paper, cloth or wire mesh).

Often when wire mesh covered fil-ter leaves develop cracks or wearspots, causing bleed through of solidsduring filtration affecting clarity andcontaminating the filtrate with solidsthat pass through the holes or cracks,operators try to do quick repairs byusing sealants to cover such holes andcracks as shown in Photos 19 and 20.

The time and effort spent in doingthese short lived “quick” patchingoperations on leaves is much betterinvested by having the leaves re-paired by a qualified and experiencedshop or simply buying a new set ofleaves, if the leaves are old enough towarrant replacement.

Photos 21 and 22 are of the same ro-tary vacuum pressure filter. Photo 21shows where the precoat and filter cakehas prematurely dropped off due toproblems with the vacuum pump. If thepump starts having problems, interrupt-ing the continuous flow, the cake simplydrops off the drum. The operator mustthen stop the filter and thoroughly cleanthe filter drum to get it ready for thenext cycle. This operation is not onlytime consuming but also a loss in pro-duction. Having ancillary equipment ingood working condition by good pre-ventive maintenance during plant shutdowns avoids production problems.

Photo 22 shows what can happenwhen the filter is not cleaned thor-oughly including the filter trough. Ifthe trough is dirty and not properlycleaned the precoat liquid will pickup the impurities left in the trough.Then the precoat cake is irregularwith lumps of unwanted impurities,

which definitely affects the filter per-formance. The operator will have tostop the filter and thoroughly cleanthe entire filter drum and feedtrough. Operator attention and un-derstanding of the process andequipment needs is important.

Based on experience, the filterconsultant or troubleshooter is calledwhen filter problems are difficult andnot easily resolved by plant person-nel. Before calling the consultantand/or troubleshooter, do goodhomework by having full data on theapplication. Know the percent of sus-pended solids, nature of solids, par-ticle analysis, physical data such asspecific gravity of liquid, density ofthe solids, temperature and feedpressure. Have the piping and instru-mentation drawing (P&ID) of theprocess indicating capacities and de-scription of all related ancillaries.Consulting trouble-shooting serviceis paid by the hour and days on thejob trying to resolve the problems.

The person coming to help shouldnot get paid for sitting around wait-ing for the plant personnel to gatherthe necessary information required toproperly assess the situation to solvethe filter problem.

For more information contact:Jose M. Sentmanat, Owner/Manager LIQUID FILTRATION SPECIALIST, LLC PO BOX 1064CONROE, TX 77305-1064Email: [email protected]: www.filterconsultant.com

ACKNOWLEDGEMENTSThe following people contributed to this article withinformation and photos:Bill Boyd of LEEM/LSS FILTRATION, RAMSEY, NJ,www.leemfiltration.comJan Hermans, SULPHURNET, CULEMBORG, THENETHERLANDS, www.sulphurnet.comAlan Greig, GREIG FILTERS, INC., LAFAYETTE, LA,www.greigfilters.comTom Bevins, FILTER ALL, INC/SEWN WELD IN-DUSTRIES, INC, MAGNOLIA, TX,www.filterallinc.comJulio Mauricio Pineda Marroquin, Consultant,GUATEMALA, [email protected]

FN

Company | News


onadnock Non-WovensLLC offers a “Pilot to Pro-duction” program aimed

at developers of fine fiber melt blownpolypropylene seeking to transitionfrom proven R+D scale production toindustrial scale manufacturing.

The program is ideally suited for de-velopers who have innovative ideas formedia or composites. There is a bigleap from small lab sized concept to in-dustrial scale production. This is whereMonadnock’s experienced team andright-sized melt blown and calendaringmachines are real assets. “There is aconsiderable difference in running meltblown media under test conditions torunning heavy duty industrial quanti-ties,” said Keith Hayward, managing di-rector of Monadnock Non-Wovensbased in Mount Pocono in NE Pennsyl-vania. “Our unique combination offlexible polypropylene melt blown op-

erations and combining technologywith many years of practical experienceis ideal for marketers with new prod-ucts seeking process development.”

This program is suitable for productdevelopers seeking characteristics orspecial properties in the fast growing al-lergen barrier, anti-microbial or odorremoval applications often used in fab-ric, homeland security, medical devicesand some consumer products.

Monadnock Non-Wovens has ex-pertise in prototype to industrial tran-sitions involving polypropylene meltblown with or without a wide range ofadditives and combined materials. Thesize and flexibility of the company per-mits relatively low cost and rapid de-velopment of roll goods media suitablefor further converting or direct sale.

“The elegance of our Pilot to Pro-duction program is that once approvedby the market, the client has a ready

made home for subsequent productionwith established processes and coststructures supported by an ISO9001Quality System” said Hayward. “Pilotprograms can involve renting machinetime, toll converting or conventionalpurchase.”

Monadnock Non-Wovens, a sub-sidiary of Monadnock Paper Mills, Inc.of Bennington, NH, was established in1999 to manufacture nonwoven mate-rial for the fast growing filtration, face-mask, healthcare, consumer andhomeland security markets. It suppliesroll goods non-woven media to con-verters around the world matching ad-vanced fiber technology and thedemands to meet Global standards.

For more information contact:Monadnock Non-Wovens LLCTel: 1-570-839-9210Website: www.mpm.com/nonwoven

Monadnock Offers Pilot to Production Program

FN

MMonadnock’s meltblown and calendaring machines used in the company’s pilot to production program.


FN

FiltrationMergers, Acquisitions

and DivesturesGL Capital, LLC

We understand the nuances ofthe domestic and internationalfiltration industry and bringover 70 years of combinedbusiness, technical and finan-cial expertise. The current eco-nomic climate is an ideal timefor sellers to locate buyersseeking to diversify and forbuyers to identify growth op-portunities through acquisition.

For a confidential conversation contact:

Edward C. Gregor803-431-7427

[email protected]

P. John Lovell719-375-1564

[email protected]

n In-Place Filter TestingWorkshop is scheduledfor August 11-15 in

Boston, MA, through HarvardSchool of Public Health Executiveand Continuing Professional Educa-tion. The program offers hands-on,practical solutions to in-place filtertesting technology and is taught byleaders in the field of filtration.

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Testing | Methods

new Trace Capacity Numbergas-phase or TCN testmethod is available to help

determine the best activated carbon forremoval of trace concentrations ofwater-soluble small molecules and gas-phase applications. TCN drinkingwater applications include removingmethyl-tertiarybutyl ether (MTBE), tri-haolmethanes, vinyl chloride, methyl-ene chloride, methanol and other smallwater-soluble molecules. TCN can beused to evaluate adsorptive trace capac-ity of activated or reactivated carbons.TCN is designed to complement theGravimetric Adsorption Energy Distri-bution or GAED full characterization(1) test method. Figure 1 shows thechallenge gas as chemical structuresused in the two test methods.

TCN values correlate directly withaqueous MTBE removal from drinkingwater, but iodine numbers do not corre-late. Published test procedures to deter-mine iodine activity numbers ofactivated carbons produce results that donot correlate with field studies for targetsmall molecule removal from drinkingwater. Tetrafluromethane (TFM) or car-bon tetrafluoride activity or TCN is theratio (g/100 cc of activated carbon) massof tetrafluromethane adsorbed by a vol-ume of activated carbon sample whenthe carbon is saturated withtetrafluromethane under conditions ofthis test method. An activated carbonbed of known volume and mass is satu-rated with tetrafluoromethane vapor.The mass adsorbed at saturation is meas-ured and reported as mass of tetrafluo-romethane per unit volume of carbon.

TRACE CAPACITY NUMBER - GAED Trace capacity number or TCN test

method is a logical extension of earliertest method Gravimetric Adsorption

Energy Distribution or GAED full char-acterization of physical adsorbents testmethod (1). GAED determines the poresizes of adsorption spaces, and theircorresponding adsorption energy dis-tribution from the largest to the small-est adsorption spaces, but the GAEDequipment is relatively complex andexpensive. The term pore and adsorp-tion space are used interchangeably.GAED provides the characteristic curvefor a material, which can be describedby its polynomial equation, to yieldisotherms for compounds of interest atany temperatures desired (1).Isotherms provide the most importantinformation, it is a GO or NO GO car-bon application and it provides esti-mate of carbon use rate. GAED alsoprovides pore size distribution, BETsurface area, thermogravimetric analy-sis, trace- and mid-capacity numbersfor the tested sample. The TCN methoddescribed in this article uses relativelylow cost readily available equipmentcompared to GAED. TCN equipmentset-up is accepted to provide ASTM In-ternational butane and carbon tetra-chloride activity numbers (2), see

Figures 2 and 3.Since TCN activity (g/100 cc) values

are lower than butane activity, becauseonly the smallest adsorption spaces,which have the highest adsorption en-ergy, are capable of physical adsorptionof tetrafluoromethane at 25oC. Labora-tory sample preparation techniques toincrease TCN resolution have been in-corporated to deal with relatively lowmass TFM loadings on activated car-bons. Accurate TCN activity values de-pend on these highest adsorptionenergy (HAE) pore spaces cleanliness:no adsorbates present, water or concen-trated air in the HAE pores. Activatedcarbons can concentrate ambient at-mosphere air about seven fold in thesehighest adsorption energy pores. Waterloading needs to be less than 0.1 wt %,and these pores need to be empty of ad-sorbates including concentrated air andchar, when the pre-weighed sampletube, see Figure 3, is re-weighed withthe sample. This necessary sample con-ditioning is accomplished by weighingthe sample warm, while the sample isover 70oC, when filling the sampletube, Figure 3.

Testing Activated Carbon Performance for Difficult Adsorbates: Trace Capacity NumberBy Henry Nowicki, Ph.D., MBA

A Figure 1:Structure of 1,1,1,2-Tetrafluoroethane orTFE for Gravimetric Ad-sorption Energy Distri-bution or GAED fullcharacterization runs forphysical adsorbents likeactivated carbons andTetrafluoromethane orTFM for Trace CapacityNumber or TCN runs forthe smallest adsorptionspaces or micro-porecharacterization.


Granular activated carbon (GAC)TCN values are about 5-10 timessmaller than butane activity values.These 5-10 times comparative values ispreliminary and need more industrycollaborative evaluations. StandardASTM International butane activityruns flow butane in a bottom to topflow, see Figure 3. But, for TCN runsflowing tetrafluoromethane (TFM)needs to be reversed top to bottom, thisflow uses the fritted disk or equivalentin the bottom of the sample tube tocontain any carbon dust. With the rel-atively small TFM loading mass, notlosing any GAC sample mass is impor-tant to assure accurate TCN values. Itis also important to tightly pack the ac-tivated carbon sample into the sampletube; a vibrating plate is used as de-scribed in ASTM method D 2854 to ac-complish proper packing.

It is important to know that popularphysical adsorption specifications, io-dine number and BET surface area,have little relevance to activated carbonadsorption performance for small mol-ecule applications. Apparently this istrue, because most of the iodine andsurface area value, mg/g and m2/g re-spectively, are derived from irrelevantlarger pore sizes not needed for smallmolecule applications. The TCN testmethod has more relevant specificitycompared to iodine and surface areavalues, because TCN only evaluates thepore sizes needed for these difficult ad-sorbate applications.

This TCN method is a gas-phase testmethod used to predict aqueous-phaseGAC performance in addition to pre-dicting gas-phase applications. Acti-vated carbons are used in both aqueous-and gas-phase applications. Sometimesthe same activated carbon is used inwater-, solvent-, or gas-phase applica-tions. Typically particle sizes are largerfor gas-phase applications compared toliquid applications to maintain highflow rates and avoid high pressure.Polanyi provided original seminal workto connect gas-phase and aqueous-phase physical adsorption phenomena(3). Polanyi concepts are embedded inthe GAED test method. Polanyi, andmany later scientists intellectual workproduct enables today’s marketplace to

use either gas- or aqueous-phase testmethods to predict performance foraqueous-, solvent-, or vapor-phasephysical adsorption applications.

In aqueous applications it is very im-portant to assure complete wetting ofgranular activated carbon or GACporous structures. The smaller the pore,the harder it is to wet, because it hasmore compressed air that needs to bedisplaced with water. The small micro-pores contain seven atmospheres of airpressure above ambient. Incompletewetting is the most common reason forcarbon not working (4). Aqueous ad-sorbates must diffuse from bulk waterto active adsorption sites with 1- to 5-nm wall-to-wall graphitic platelet ad-sorption spaces, or pores. To assurecomplete micro-pore wetting it is rec-ommended that GAC is soaked in waterfor 72-hours with several draining andrefills with water, before field use to as-sure complete wetting (4). Hot waterwetting decreases this needed time, be-cause hot water penetrates GAC better.Users can also purchase properly wettedactivated carbon instead of dry; this al-lows the carbon to be used immediatelyin the field by eliminating the wettingprocess. Once compressed air bubblesare formed in the bowels of carbon par-ticles, trapped compressed air can sta-

bilize for a long time, even years, whicheffectively eliminates their needed ad-sorption spaces and results in pre-ma-ture adsorbate breakthrough. If asignificant portion of a GAC columnhas trapped compressed air, the waterflows around the collective air bubbleand loses carbon contact. So if the GAChas a high TCN value, but field opera-tions do not properly wet the GAC, itwill not perform to its potential smallmolecule capability.

MTBE UNINTENDED CONSEQUENCESMethyl-tertiarybutyl-ether (MTBE)

was added to gasoline as a fuel additiveto facilitate ignition and improve airquality. MTBE has contaminated(groundwater) drinking water sources,because it is very water-soluble and mi-grates relatively quickly from under-ground leaks compared tohydrocarbons, from leaking storagetanks. It has a bad taste and odor indrinking water at low trace concentra-tions and thus needs to be removed.GAC removes MTBE, but its perform-ance lot-to-lot or vendor-to-vendor isnot predictable using iodine or butanenumbers. Iodine numbers do not predictMTBE loading capacity for GAC sup-plies, but Trace Capacity Numbers docorrelate, see Table 1. Iodine and butane

Table 1.

Comparison of Trace Capacity Numbers (TCN) and Iodine Numbers to GAC Methyl-tertiarybutyl ether (MTBE) Loading

MTBE Loading mg/cc CN mg/cc Iodine No mg/g0.045 4.90 11610.063 5.15 6050.071 6.52 9600.121 7.58 7500.134 8.29 6750.145 9.01 10500.160 10.02 10160.170 10.50 12000.185 11.17 10050.203 12.25 9270.239 12.86 10000.280 13.51 8100.285 15.02 9050.301 15.42 8900.356 16.99 935


ASTM tests fill a wide spectrum of ad-sorption spaces, but tetrafluoromethaneis only taken up by small high adsorp-tion energy adsorption spaces. Thus, io-dine is best used as a performancepredictor when the real-world applica-tion fills up the total pore volume andTCN is more appropriate for specific ap-plications that need selectively onlysmall HAE adsorption spaces.

COMPARISON OF NUMBERSTrace levels of aqueous MTBE adsorp-

tion are unpredictable for commercial ac-tivated carbons based on iodine numbers,because MTBE is very water soluble andpresent low ppb concentrations. The morewater soluble a potential GAC adsorbate isthe more difficult it is to adsorb, and itsloading capacity is lower. The closer theadsorbate is to saturated concentration,the higher the GAC loading above satura-tion, you get two phases of liquids. GAChas a low and variable MTBE removal ca-pacity when compared to iodine, but load-ing capacity is more predictable whenTCN is used as the correlation with MTBE

removals from water. Results of this com-parative evaluation are shown in Table 1for several activated carbon samples. Thisdata set tells us that TCN values go upwith MTBE increased loading or capacityand the iodine number does not correlatewith MTBE loading.

The data in table 1 shows that differ-ent activated carbon samples TCN cor-relates directly with MTBE removalfrom clean water. It also clearly showsthat the Iodine Number has no correla-tion with MTBE removal performance.

This trace capacity number testmethod is expected to be most usefulfor drinking water from ground watersupply sources. Surface water sourcestend to have more organic contami-nants and thus we expect competitionfor the limited number of high ad-sorption energy sites. HAE sites arerequired for physical adsorption ofsmall water-soluble organic com-pounds, like MTBE, THM, vinyl chlo-ride and other small water-solublecompounds. Since about half of theU.S. drinking water sources are

ground water supplies, TCN testmethod should be useful.

DISCUSSIONAccurate test methods to predict ac-

tivated carbon’s specific users applica-tions performance are critical foractivated carbon users and manufactur-ers to select the best carbon. Activatedcarbon has an amazing long list of ap-plications. All carbons are not thesame, so users need to choose wisely. Acarbon, which lasts 2-3 times longerthan a competitor carbon in a given ap-plication, is more useful, than a carbon,which has an earlier breakthrough.Early GAC breakthrough results in re-purchase of unused carbon and changeout of the spent used carbon and itsdisposal. The MTBE used GAC morelikely than not still has a good iodinenumber, when the TCN has been con-sumed and the MTBE filled microporesare not available to provide moreneeded MTBE physical adsorption. Ob-viously MTBE relatively lightly usedcarbon can be reactivated for many

Testing | MethodsFigure 3

1. Ground glass stopper, hollow, medium length, 14/20, from Kontes Catalog No K-89100 Schwartz adsorption tube, or equivalent.

2. 5-mm rod, brace.3. 17-mm outside diameter (O.D.) x 1.2 mm standard wall tubing.

4. Coor=s perforated porcelain disk or extra coarse fritted disk, or equivalent.

5. 10-mm O.D. x 1.0 mm standard wall tubing.6. Right angle stopcock, Kontes Catalog No. K-84700, size 4, 10 mm O.D. stem, with Kontes Catalog No. 89340 size B serrated host connector, or equivalent.

7. Dimension corresponding to a volume of 16.7 ml above the retainer plate.

“Reprinted, with permission, from ASTM D5228-92(1996) Standard Test Method for Determinationof Butane Working Capacity of Activated Carbon,copyright ASTM International, 100 Barr HarborDrive, West Conshohocken, PA 19428A copy of the complete standard may be obtainedfrom ASTM International, www.astm.org."


uses or the municipality could use thisMTBE used carbon at their municipalwastewater plant. Presently municipalwastewater plants do not provide sig-nificant tertiary treatment with acti-vated carbon, yet their effluents arewell known to have deleterious organiccompounds that could be removed verywell with activated carbon (1).

It is generally accepted that adsorp-tion space or pore needs to be 1.3 to 1.8times larger than the adsorbing mole-cules volume. Thus, small moleculesare best adsorbed in the smallest highadsorption energy pores. The term poreand adsorption space are used inter-changeably. Physical adsorption ofsmall molecules is a nanotechnologyphenomenon. Adsorption of moleculesdepends on a power of three moleculardistance between adsorbate andgraphitic platelet, i.e., one-molecularlayer away is a relative adsorption forceof 1, two-molecular layers the relativeforce is 1/8, and three-molecular layersaway from the GAC graphitic plateletthe relative adsorption force comparedto one-molecular layer is one twenty-seventh (1/27) and three molecular lay-ers away from graphitic platelet resultsin negligible physical adsorption (1).The mass ratio of adsorbate to solid be-comes of significant magnificationwhen a significant fraction of the atomsof the solid is at a surface.

Physical adsorption of solvents outof water is enhanced liquid faction, i.e.,the adsorbate comes out of the water asa liquid-like state in micro-pores wellbefore it is concentrated to saturationin micro-pores. Adsorbates are concen-trated in specific adsorption spaces byLondon force fields from graphiticplatelets (5). Polarizability of adsor-bates determine how well they comeout of water as liquid or solids, like thephysical state of the molecules in bot-tles in the chemical store room. Polar-izability is a direct reflection ofrefractive index.

CONCLUSIONIf users are having problems getting

expected GAC performance (gallonstreated per pound or volume of acti-vated carbon) removing small watersoluble target molecules using iodinenumbers as the predictor to evaluate in-coming GAC, one needs to considerTCN test method to help solve thisproblem. Even if a user is not havingthis problem, they need to know aboutTCN and GAED advanced testingmethods and what they can do for fu-ture physical adsorption process appli-cations. TCN uses common industrystandard equipment used for ASTM In-ternational butane and carbon tetra-chloride activity tests. GAED fullcharacterization also enables determi-

nation of TCN values, but uses morecomplex equipment and software.

For more information contact:Henry Nowicki Tel: 1-724-457-6576Email: [email protected]: www.pacslabs.com

References1. Henry Nowicki, see articles in WC&P

(type in Nowicki) on GAED testing at www.wcponline.com.

2. ASTM International standards of activated carbon test methods: D 5742 - Test method for Determination of Butane Activity of Activated CarbonD 5228 - Test Method for Determination of Butane Working Capacity of Activated CarbonD 3467 - Test method for Carbon Tetrachloride Activity of Ac

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