KONTROLA FUGITIVNE PRAŠINE NA PRESIPNIM MESTIMA

7/29/2019 KONTROLA FUGITIVNE PRAINE NA PRESIPNIM MESTIMA

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FUGITIVE DUST CONTROL AT CONVEYOR TRANSFERPOINTS A SOLUTION FOR PUZZLE

KONTROLA FUGITIVNE PRAINE NA PRESIPNIM MESTIMATRANSPORTERA - REENJE ZA SLAGALICU

Dejan MIRAKOVSKI1, Zoran DESPODOV11 Faculty of Mining and Geology, tip, Macedonia

1 INTRODUCTION

Controlling fugitive dust at conveyor transferpoint has been a problem since their introductionin the industry. This issue turns in one of thelimitations for more widely use and developmentof this otherwise highly economic and efficienttransportation means.

Cleaning up material lost from conveyors, dayafter day, consume expensive labor hoursincreasing operating costs. Loosing a portion ofalready processed material like airborne dust,simply mean blowing a huge amount of money tothe wind, which could be especially extensive in

systems conveying minerals with lower specificgravity (coal, industrial minerals etc.). Premature

1 UVOD

Kontrola fugitivne praine na presipnim mestimatransportera postala je problem jo sa njihovimuvoenjem u industriju. Ovaj problem je jedna

prekretnica u ogranienju za iru upotrebu iusavravanjem ovih, za razliku od ostalih, visokoekonominih i uspenih transportnih sredstava.

Svakodnevno ienje izgubljenog materijala iztransportera, potroi skupe radne sate

poveavajui trokove, iz godine u godinu.Gubljenje dela ve preraenog materijala uobliku lebdee praine jednostavno znaigubljenje novca na vetru, koji bi mogao biti

naro

ito obiman u sistemima za transportminerala sa malom specifinom teinom (ugalj,

Abstract: Efficient and economic operation in modern mineral industry is not possible without addressingthe problem of dust control through the material handling and processing operations. Health and safetyrisks, environmental concerns and public pressure, as much as operational problems connected withexcessive dust emissions, urge proper solution for this problem. The paper presents the causes andcountermeasures, including independent review of latest dust control technologies available to the market.

Key words: dust control, transfer points, containment, suppression, collection

Apstrakt: Efikasno iekonomino poslovanje u modernoj mineralnoj industriji je nemogue bez reavanja

problema sa kontrolom praine u operacijama transporta i prerade mineralnih sirovina. Zdravstveni ibezbednosni rizici, problemi sa zagaenjem ivotne sredine, pritisak javnosti, kao i problemi safunkcionisanjem opreme povezani sa visokim emisijama praine, zahtevaju hitno reenje. Ovaj rad opisujeuzroke i kontramere, ukljuujui jedan neutralni pregled najnovjiih tehnologija za kontrolu prainedostupne na tritu.

Kljune rei: kontrola praine, presipna mesta, zadravanje, suzbijanje, skupljanje

UDC: 622.063.8:622.807.5

The International Journal ofTRANSPORT& LOGISTICS

Meunarodni asopisTRANSPORT I LOGISTIKA


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D.Mirakovski, Z.Despodov, FUGITIVE DUST CONTROL AT CONVEYOR T&L - 07/04

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worning and damage of conveyor components byfugitive dust, simply pumping the maintenance

budgets to unacceptable levels. Costs forunplanned brake downs and manpower engagedexceed millions of dollars throughout theindustry.

But with overall rise in awareness in industry(and in the general public) of the problemscaused by airborne dust and other fugitivematerials concerning the health -safety hazardsand environmental pollution issues, a newdimension of this edge old problem was given.In the light of government regulations mandatingimprovements in air quality a costs for avoidablesafety hazards, unwanted community attention,and preventable regulatory citations continue to

escalate.For any industry, unnecessary and repetitive costslike before mentioned can no longer be toleratedand much different approach to controlling dustmust be adopted.

Unfortunately, applicable dust controltechnologies in general still stay in the area ofdark box and expert knowledge filed, and thereis a desperate need for scientific and educationalefforts to put a new light and make them routine

knowledge available for all engineers involved inthe industry. Moreover, todays market offer ahole set of applicable engineered dust controlsystems, which properly combined and appliedcould provide efficient and economic solution forthe problem. So it is time to collect the pieces andsolve the puzzle.

2 DUST CONTROL TECHNOLOGIES SENT CONDITION

The most widely accepted classification for alldust control technologies, categorize them intothree major groups, depending on the appliedapproach to the solution; - containment,suppression, and collection.

- dust containment consists of set ofmechanical and other means (systems)applied to keep material inside thelimited space around the transfer point.

- dust suppression systems increase thecohesion between small particles(preventing them to become airborne)and mass of suspended dust particles,

industrijski minerali i sl.). Prerano habanje ioteenje delova transportera zbog fugitivne

praine, prosto poveava budet odravanja naneprihvatljiv nivo. Trokovi za neplaniranezastoje i upoljavanja dodatne radne snage

prevazilaze milione dolara irom industrije.

Meutim, sa ukupnim porastom svesti uindustriji i optoj javnosti o problemimaizazvanim lebdeom prainom i drugimfugitivnim materijalima u pogledu zdravlja sigurnosti i problemima sa zagaenjem sredine,data je nova dimenzija ovom "starom"

problemu. U svetlosti poboljanja vaeihvladinih propisa u pogledu kvaliteta vazduha,trokovi koji se mogu izbei, rizike, nepoeljne

panje javnosti i preventivni sudski pozivi

produavaju da eskaliraju.Nijedna industrija ne moe dalje tolerisatinepotrebne i ponovljive trokove kao to su

pomenuti. Zbog toga se mora usvojiti drugaijiprilaz u pogledu kontrole praine.

Na alost, postojee tehnologije za kontrolupraine generalno su jo uvek u zoniekspertskog znanja, zbog ega se javlja hitna

potreba od naunih i edukativnih napora zanjihovu iru primenu koje bi bile raspoloive

za sve inenjere ukljuene u ovu industriju,naroito, zbog toga to dananje trite nudiiroki spektar sistema za kontrolu praine koji,kada se pravilno kombinuju i primene moguobezbediti efikasno i ekonomino reenje ovog

problema. Znai, dolo je vreme da se skupesvi komadii i slagalica sastavi.

2 TEHNOLOGIJE ZA KONTROLUPRAINE - SADANJE STANJE

Najira prihvaena klasifikacija svihtehnologija za kontrolu praine u zavisnosti od

primenjenog prilaza klasifikuje ih u tri glavnegrupe: zadravanje, suzbijanje i skupljanje.

zadravanje praine obuhvata kompletmehanikih i drugih sredstava (sistema)

primenjenih da zadre materijal unutarogranienog prostora pretovarnog mesta,

sistemi za suzbijanje praine poveavajukohezije izmeu malih estica(spreavajui ih da ponu da lebde) imase estica, suspendirane praine


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(allowing them to fall from the air stream).- dust collection is the mechanical capture

and return of airborne material after itbecomes airborne from the main materialbody.

In the past, these three approaches have alwaysbeen seen as separate solutions, competing in themarketplace. Each system claimed its owntechnology was the best, providing the mosteffective, most cost-efficient, most maintenance-free solution, pointing to the other systemsweaknesses. But, in reality, many plantsthroughout the industry face with failure and poor

performance of this separate systems approach.Its become obvious that no single technologycan provide a satisfactory solution, especially

from the standpoint of health and environmentalproblems which force more efficient control offine particles (below 10 micrometers).

In order to assure successful dust control programthe three different technologies should not beseen as a competitors, but as interrelatedcomponents working together for success. Allthree systems should be carefully evaluated, one

by one and together to determine the mosteffective and economic way to control thefugitive dust.

3 DUST CONTROL TECHNOLOGIES BASIC DESCRIPTION

As we mention before, only integrated solutionwhich use the best from each different dustcontrol approach, could achieve the goal forefficient and economic dust control. Containingthe material within main material flow andreducing the air movement inside the transfer

point zone is a key for successful operation of

dust suppression or collection systems.Applications of suppression or collection aredetermined by specific conditions of process,equipment and material. More detaileddescription of each different system follow.

3.1 DUST CONTAINMENT

The containment as most fundamental step mustbe accomplished by careful selection of effective

mechanical and other means to keep the material

(meajui ih da padnu sa vazdunog toka), skupljanje praine je mehaniko

zarobljavanje i vraanje lebdeeg materijalaka glavnom telu toka materijala.

U prolosti ova tri prilaza bila su razmatrana kaoizdvojena reenja koja konkuriu medjusobno natritu. Svaki dobavlja promovisao je da jenjegova tehnologija najbolja i da obezbeujenajveu efikasnost, ekonominost i odrivost,istovremeno ukazajui na slabosti ostalih sistema.Meutim, u realnosti, mnoga postrojenja uindustriji suoena su sa neuspehom i loim

performansama svakog izdvojenog sistema.Postalo je oevidno da nema pojedinanetehnologije koja bi mogla obezbeditizadovoljavajue reenje, naroito sa aspekta

zdravlja i problema ivotne sredine koji viezahtevaju uspenu kontrolu finih estica (esticaispod 10 mikrometara).

Sa namerom da se obezbedi uspenost programaza kontrolu praine, ove u osnovi raznoliketehnologije ne treba da budu posmatrane kaokonkurencija, ve kao meuzavisne komponentekoje bi radile zajedno do uspeha. Sva tri sistematrebalo bi paljivo proceniti, izdvojeno ilizajedno kako bi se odredio efikasniji iekonominiji nain kontrole fugitivne praine.

3 TEHNOLOGIJE ZA KONTROLUPRAINE - OSNOVNI OPIS

Kao to smo pomenuli ranije, samointegralno reenje koje e iskoristiti najbolje od

pojedinih razliitih prilaza, moe postii ciljeveza efikasnu i ekonominu kontrolu praine.Zadravanje fugitivnog materijala u glavnomtoku i smanjenje kretanje vazduha unutar zone

presipnih mesta je jedini klju uspenosti sistemaza suzbijanje i/ili skupljanje praine. Primena

postupaka za suzbijanje i/ili skupljanje praine jeodreena specifinim uslovima procesa, opreme imaterijala. U daljem tekstu sledi detaljniji opissvakog pojedinanog sistema.

3.1 ZADRAVANJE PRAINE

Zadravanje kao osnovni korak mora bitiostvareno paljivim izborom efikasnih

mehanikih i drugih sredstava koji e zadrati


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on the conveyer and reduce air movement inloading zone. Effective containment couldsignificantly reduce dust generation anddispersion potential, and improve performance ofsuppression or collection systems. Since eachconveyor and each loading zone has uniquecharacteristics of the material and components atthat given conveyor and load zone, the sources offugitive material must be properly identified andcontrolled. The sources of fugitive materialinclude:

belt carry back, conveyor side spillage, tail area spillage, and exit area dust creation.

3.1.1 Cary back

The material which adhering the belt and pass thedischarge point is best controlled by applyingmultiple cleaning systems. These consist of a

precleaner on the face of the head pulley toremove the majority of material and one or moresecondary cleaners to perform final precisioncleaning. The secondary cleaner(s) are installedat the point where the belt leaves the head pulleyor further along the conveyor return.

materijal na transporteru i smanjiti kretanjevazduha u utovarnoj zoni. Efikasno zadravanjemoglo bi znaajnije smanjiti generisanje praine i

potencijal njenog irenja i poboljati performansesistema za suzbijanje ili skupljanje. Imajui uvidu da svaki transporter i da svaka utovarnazona imaju unikatne karakteristike materijala ikomponente, izvori fugitivnog materijala moraju

biti osobno identifikovani i kontrolisani. U izvorefugitivnog materijala se ukljuuju:

vraanje materijala sa trake, bono prosipanje materijala sa trake, prosipanje u zoni povratne stanice i irenje praine iz izlazne zone.

3.1.1 Vraanje materijala sa trake

Materijal koji se lepi na traku i prolazi nepadajuina istovarno mesto najbolje je kontrolisati

primenjujui viestruke sisteme za ienje. Ovisistemi obuhvataju jedan primarni ista na elu

pogonskog bubnja za skidanje veine materijala ijedan ili vie sekundarnih istaa sa ciljem daizvre finalno precizno ienje. Sekundarniistai su montirani na mestu gde traka naputa

pogonski bubanj ili dalje uzdu povratne granetransportera.

Figure 1 Cleaner systems consist of a precleaner on the face of the head pulley, and one or more secondary

cleanersslika 1 Sistemi za ienje, sastavljeni od primarnogistaa na elu pogonskog bubnja i jednog ili vie

sekundarnih istaa

3.1.2 Side spillage

Conveyor side spillage is best controlled by athree-part program consisting of; proper beltsupport, wear liners inside the chute to protect thesealing system and multiple-layer edge seals tocontain any escaping fines.

3.1.2 Bono prosipanje materijala

Bono prosipanje materijala sa trake najbolje jemogue kontrolisati trojnim programom kojiobuhvata: prikladnu (odgovarajuu) potporutrake, habajue zatitnike unutar uta koji titezaptivni sistem i viestruke iviaste zaptivaekoji slue da zadre neki umaknuti sitne.


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Proper belt support consists of cradles(Figure 3) installed in-line with the carryingidlers to absorb impact and to eliminatefluctuations at the belt line. This impactabsorbing systems support belt through theloading zone preventing the belt sag(Figure 2) and maintain effective seal.

Prikladnu potporu trake sainjavaju gumenegredice (slika 3), montirane u liniji sa noseimslogovima, sa funkcijom da prihvate udare ieliminiu odstupanja trake od ose transportera.Ovi sistemi za prihvatanje udara podupiru traku uutovarnoj zoni spreavajui ugib (slika 2) trake iodravajui efikasno zaptivanje.

Figure 2 Belt sag allows spillage and risks material entrapment and belt damageslika 2 Ugib trake koji doputa prosipanje materijala i oteenje trake

Figure 3Impact absorbing belt support cradlesika 3 Potpora sa gumenim segmentima za prihvaanje udara

Wear liner is a flat sacrificial surface placedinside the chute wall to form a long-lastingbarrier to protect the edge seals (Figure 4).Liner materials could be mild or stainlesssteel, abrasion-resistant plate, ceramic facedor hard-faced steel, rubber, urethane, or

plastic, depending on the specifies of theapplication.

Habajui zatitnik je jedna ravna rtvujua povrinasmetena u unutranosti zidova uta koja formiradugotrajnu barijeru i koja titi iviaste zaptivae(slika 4). Materijal za izradu zatitnika moe bititopljeni ili nerajui elik, abrazivno-otporne ploe,obraena keramika ili grubo obraeni elik, guma,uretan ili plastika u zavisnosti od specifinostiaplikacije.

Figure 4 Wear liners installed inside the chute to protect the sealing

slika 4 Habajui zatitnik montiran unutar uta


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It is critical that wear liners be installed as asmooth seamless layer that does not interferewith flow

The main goal of sealing is to effectively containmaterial fines and to keep material on the belt.This is typically accomplished by installing aflexible elastomer strip on the sides of the skirt

board to close the space between the steelstructures and the moving belt.

Bitno je da habajui zatitnici budu montiranikao glatki sloj koji nee remetiti tokmaterijala.

Glavni cilj zaptivanja je da efikasno zadri sitnematerijala i da zadri materijal na traci. Najeese ostvaruje instaliranjem trake od elastinogelastomera na bokovima, kako bi se zatvorio

prostor izmeu eline strukture i trake ukretanju.

Figure 5 Multiple-layer sealing systemslika 5 Viestruki zaptivni system

3.1.2 Control of air movement

Conveyor loading zones and discharge points areprime sources for the creation and release ofairborne dust. Depending on a number of factors,

including the nature of the material carried theheight of drop and the speeds and angles ofunloading and loading belts, various systems tocontrol airborne dust should be installed atconveyor loading and unloading zones.

The essence of this system is to actually reducedust generation and dispersion potential. In thesimplest form this could be accomplished byfollowing this three design parameters:

- limit air coming into the enclosure andthe material stream.- reduce the creation of dust inside theenclosure.

- lower air velocities within the enclosure,allowing suspended dust to fall back onthe conveyor belt.

Air is stopped from entering the enclosure at thehead pulley of the discharging conveyor byconventional rubber curtain seals at the beltsentrance to the enclosure and by keeping thematerial in a consolidated stream as it moves

through the transfer point.

3.1.2 Kontrola kretanja vazduha

Utovarne zone i istovarna mesta trakastogtransportera su primarni izvori za stvaranje ioslobaanje lebdee praine. U zavisnosti od

brojnih faktora, uklju

uju

i prirodutransportovanog materijala, visinu pada, brzine iuglove istovarnih i utovarnih traka, mogu bitiinstalisani razliiti sistemi za kontrolu lebdee

praine na utovarnim i istovarnim zonamatransportera.

Sutina ovog sistema je da trenutno smanjigenerisanje i potencijal irenja praine. U

jednostavnoj formi ovo moe biti ostvarljivo krozrealizaciju dole pomenutih projektnih

parametara:

- ogranienja dolaska vazduha u ograenipotok materijala,

- smanjenja stvaranja praine unutarograde,

- snienja brzine vazduha u ogradi,doputajui suspendovanoj praini daopet padne na transportnu traku.

Vazduh je stopiran od ulazne vodilice ograde napogonskom bubnju istovarnog transportera saklasinom gumenom zavesom na ulazu trake ka

ogradi i sa zarobljavanjem sitnea u tokumaterijala koji se kree kroz presipno mesto.


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Keeping the material in a consolidated body willreduce the amount of air that will be entrained orcarried along. Best results are achieved by use ofhood and spoon design (Figure 6).

Zarobljavanjem materijala u konsolidovanomtelu smanjie se koliina vazduha koja e bitivoena ili transportovana uzdu. Najboljirezultati su ostvareni upotrebom sistema

poklopac - kaika (slika 6).

Figure 6 hood and spoon chute minimizes the air entrained with the material, and so reduces airborne dust.slika 6 ut izvedbe poklopac-kaika

The hood minimizes the expansion of thematerial body while the spoon provides a curvedloading chute so the material slides down to theloading zone. By reducing the velocity and forceof material impacting the load zone, the dustgeneration and air speed are significantlyreduced.

The final phase of this system is to lower the airspeed in the enclosure. The goal is to quiet airvelocities in order to let dust settle and fall backonto the belt. This is accomplished by making theenclosure large enough and then slowing the airmovement. Typically a rubber dust curtainshanging from the top are used. (Figure 7) Theserubber exit curtains inhibit the amount andvelocity of air passing out of the loading zone,and so minimize the escape of dust.

Poklopac minimizuje irenja tela materijala dokkaika obezbeuje zakrivljeni utovarni ut takoda materijal klizi ka utovarnoj zoni. Smanjenjem

brzine i sile materijala koji udara na utovarnuzonu, stvaranje praine i brzina vazduha suznatno smanjeni.

Zavrna faza ovog sistema je snienje brzinevazduha u ograenom prostoru. Cilj je smanjitibrzinu vazduha sa namerom pribrati prainu i njuvratiti na traku. Ovo je ostvarljivo postavljanjemdovoljno velike ograde i zatim usporavanjemkretanja vazduha. Koriene su tipine gumenezavese za prainu koje vise na vrhu (slika 7).Ovaj izlaz od gumene zavese spreava koliinu i

brzinu vazduha koji prolazi kroz utovarnu zonu itako minimizira bekstvo praine.

Figure 7 Dust curtains

slika 7 Zavese za zadrvanje praine


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3.2 DUST SUPPRESSION SYSTEMS

In a dust suppression system a water/chemicalsare used in a form of spray/fog/foam to increasecohesiveness (agglomeration) between particlesand prevent dust generation, as much as toincrease mass of already suspended particles andknock them down to the material body.

There are a number of mechanical systems usedfor this purpose, ranging from simple sprays tosophisticated, automated systems.

3.2.1 Water

The water spraying is the oldest dust control

system in which by adding the moisture to thematerial, weight/mass ratio and cohesiveness ofthe material is increased, so it is less likely for the

particles to become airborne. Efficiency of watersuppression systems varies widely and usually ahuge amount of moisture (1% to 10%) is neededto achieve satisfactory results. On the other side,excessive moisture can produce problems withmaterial handling/processing (add weight,screens blinding, belt slippage, materialfrosting....) and to adversely affect materialquality/performance (reduce coal thermal

power....). But the biggest limitation of thesesystems is their poor performance in control ofsmall (respirable) dust particles. Thereforemodern operation really uses these systems, so afurther elaboration in this paper will be omitted.

3.2.2 Chemical additives / wetting agents

Wetting agents are surfactant formulations thatimprove the ability of water to wet andagglomerate fine particles. Wetting agents

designed for dust control generally improve bothwetting actions (spread and capillary wetting

phenomena). Available products range fromsingle component commodity surfactants tospecialty chemical formulations that contain

blends of surfactants with organic and inorganicadditives. Binding agents may also be includedfor long-term (residual) dust control effects.

Although use of these additives can increase theoperation costs of dust control systems, residualdust control throughout the materialtransportation and storage could bring great

3.2 SISTEMI ZA SUZBIJANJE PRAINE

Kod sistema za suzbijanje praine mogue je koristitivodu ili neke hemikalije u obliku spreja, magle ili

pene, kako bi se poveala kohezivnost (aglomeracija)izmeu estica materijala i spreilo stvaranje

praine.Time se poveava masa ve ranijesuspendovanih estica i vri njihovo obaranje namaterijal.

Postoje brojni sistemi koji se koriste u tu svrhu, poevod jednostavnih sistema za rasprskavanje, pa sve dosofisticiranih automatskih sistema.

3.2.1 Voda

Prskanje vode je najstariji sistem za kontrolu prainekod koga se kroz poveanje vlanosti materijalapoveava teina i kohezivnost izmeu estica, pa ih jetee suspendovati u vazduhu. Efikasnost sistema zasuzbijanje praine vodom varira u irokim granicama inajee su potrebne vee koliine vode u iznosu od 1do 10% kako bi se postigli zadovoljavai rezultati. Sadruge strane, viak vode moe prouzrokovati

probleme sa transportom, prerade (kao to su:poveanje mase, zaepljenje sita, proklizavanje trake,smrzavanje materijala) i negativno uticati na kvalitetmaterijala (smanjenja toplotne moi uglja i sl.). No,

najvea ogranienja u primeni ovih sistema su njihovenemogunosti kontrolisanja sitnih respirabilnihestica. Zbog toga savremena postrojenja ree koristeove sisteme, i zato e njihova dalja elaboracija u ovomradu biti izostavljena.

3.2.2 Hemijski aditivi (kvaljivci)

Kvaljivci su smee surfaktanta koji poboljavajusposobnost vode u kvaenju i aglomeraciju sitnihestica materijala. Ove hemikalije dizajnirane za

kontrolu praine poboljavaju oba fenomenavlanjenja (vlanjenje irenjem i kapilarnovlanjenje). Na tritu se mogu nai od

jednokomponentnih surfaktanata do specijalnihhemijskih formulacija koji sadre surfaktanteorganskog i neorganskog porekla. Vezivni aditivimogu biti iskorieni za obezbeivanje dugotrajnihefekata.

Pored toga to upotreba ovih aditiva moepoveati operativne trokove, njihov rezidualanefekat kroz celokupni transportni sistem i sistemskladiranja materijala obezbeuje znatnu korist


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benefits for extensive systems (like coal operations).Of course, additional (and continuing) cost of theadditive and the impact of the chemical on thematerial's eventual use must be carefully considered.

3.2.3 Foam

Foaming agents are used to convert water and airinto foam. Dust control foam is dry, stable,small-bubbled foam with a consistency similar toshaving cream. Foaming agents are primarilyhigh foaming surfactants, and may also containwetting and binding agents. Dust control foamfunctions similarly to liquid spray wetsuppression, in that the foamed liquid wets andagglomerates fine particles.

The advantages of foam over liquid sprays areimproved liquid distribution, resulting in lowerliquid feed rates; and improved fine particlecapture, which reduces breathable dust. Improvedliquid distribution is realized by the largeincrease in liquid surface area. The improved fine

particle capture is believed to be due to thefoam's ability to engulf and wet fine particles,and/or the "shrapnel" effect, where fragments of

bursting bubble films contact, wet andagglomerate fine dust particles.

Because foam dust control mechanisms involvethe contact of foam with dust particles, foam isused primarily for bulk agglomerationapplications. This mechanism provides carryon dust control effect over longer transportationdistances and several transfer points. Withaddition of residual agents (binders andtackifiers) dust control over the entire process oftransportation, storage and reclaiming could beachieved.

kod velikih sistema, kao na primer, sistema zatransport i skladiranje uglja. Svakako da dopunski(tekui) trokovi aditiva i uticaj hemikalija na buduuupotrebu materijala moraju biti paljivo razmotreni.

3.2.3 Pena

Penuavci su aditivi koji se koriste da bipretvorili vodu i vazduh u penu. Pena koja seupotrebljava za suzbijanje praine je suva,stabilna, i sa sitnim mehuriima. Penuavci su

primarno visoko penuavi surfaktanti, a mogusadrati aditive za kvaenje i vezivanje. Tretman

penom je slian sa vodenom supresijom sarazlikom to penuasta tenost na vlai iaglomerira sitne estice.

Prednosti tretiranjem penom u poreenju savodenim sprejem su: poboljana distribucijatenosti (to prouzrokuje manje zahteve za vodu)i poboljano hvatanje sitnih estica, ime seredukuje respirabilna praina. Bolju distribucijutenosti je mogue realizovati kroz poveanje

povrine raspoloive tenosti, a bolje hvatanjevrstih estica je rezultat sposobnosti pene zazarobljavanje i kvaenje sitnih estica i/ilitakozvani rapnel efekat, kada komadii ispucalihmehuria pene dodiruju, vlae i aglomeriraju

sitne estice materijala.

Imajui u vidu da mehanizam funkcionisanjapene ukljuuje kontakt pene i sitnih estica zbogtoga se pena generalno koristi za aglomeracijumaterijala. Ovaj mehanizam obezbeujetakozvani rezidualni (carry on) efekat kod duihtransportnih trasa i kroz vie presipnih mesta.Dodavanjem rezidualnih aditiva (bindera itakifera) mogue je postii kontrolu praine ucelokupnom procesu: transporta, skladiranja iutovara materijala.

Figure 8 Dry foam applied at conveyer transfer point.

slika 8 Suva pena primenjena na presipnom mestu transportera


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Moisture addition from foam dust suppressionsystems ranges from 0.08% to 0.2% by weight.At these reduced levels of added moisture, theadverse affects associated with excess moistureare greatly reduced or eliminated.This make the foam dust control very convenientin cases where excess of moisture is notacceptable and flexibility and high efficiency arecrucial.

3.2.4 Fog

Fog suppression systems are new level of classicwater spray systems. These systems use specialnozzles to produce extremely small waterdroplets in a dispersed mist. (Figure 11.3) The

fog system atomizes the water to reduce thesurface tension of the water droplets, whileincreasing the number of droplets in a given area,which consequently provide better contacting andagglomeration of already suspend fine particles.The increased weight of combined particlesallows them to settle back to the water whileminimizing the amount of water added to the

product.

There are two methods of producing finelyatomized water fog. One method produces fog

from water and compressed air by passing themtogether through a two fluid nozzle. The othersystem uses an ultra-fine stream of water pumpedat high pressure through single-fluid atomizingnozzles.

A well-designed fogging system can provideexcellent control of dust at reasonable operatingcosts. But because of the small orifice size of thenozzles, they can easily plug if not serviced atrequired intervals. Also, for truly effective

performance, fog dust suppression systems

require tight enclosure of the transfer point,which is not always easy to obtain. Another

potential drawback of a fogging application isthat dust control is achieved only at the point ofapplication (no carry on effect). So, a capitalinvestment can be very high for complexconveyor systems with multiple transfer points.

3.3 DUST COLLECTION SYSTEMS

Dust collection system utilizes mechanical powerto collect air passing trough the point of dustgeneration/liberation. Collected air is then passed

Dodatak vlage kod apliciranja pene kree se uintervalu od 0.08 do 0.2 teinskih procenata. Kodovog smanjenog nivoa dodatka vlanosti negativniefekti zbog vika vlage su znatno smanjeni ilieliminisani u celosti. Ove injenice ukazuju na to da

je kontrola praine sa penom prioritetnija usluajevima gde je viak vlage neprihvatljiv, afleksibilnost i vee performance su od sutinskogznaenja.

3.2.4 Magla

Sistemi za suzbijanje praine sa maglom su vii nivood klasinih vodenih sprej sistema. Ovi sistemiupotrebljavaju specijalne mlaznice da bi proizveliekstremno male vodene kapljice u jednu

disperzovanu sumaglicu. Magleni sistem raspravavodu da bi smanjio povrinski napon vodenimkapljicama, pri poveavanju broja kapljica u jednom

prostoru, koji zbog toga obezbeuje bolji kontakt iaglomeraciju ve suspendovanih finih estica.Poveana masa kombiniranih estica dozvoljava imda se taloe ponovo u vodu to dovodi dominimiziranja koliine vode koja se pridodaje

proizvodu.

Postoje dve metode za stvaranje fine rasprivanevodene magle. Jedan metod proizvodi maglu od

vode i komprimiranog vazduha koje prolaze zajednokroz jednu dvofluidnu mlaznicu. Drugi sistem koristijedan ultra-fini mlaz vode ispumpavan pod visokimpritiskom kroz jednofluidne atomizirajue mlaznice.

Dobro projektovani magleni sistem moe obezbeditiodlinu kontrolu praine sa umerenim operativnimtrokovima. Meutim, imajui u vidu da mlazniceimaju otvore sa malom veliinom, oni se mogu lakozapuiti ako nisu servisirane u zahtevanimintervalima. Takoe, za zaista efikasne performanse,sistemi za supresiju praine maglom zahtevaju

zaptivnu ogradu na presipnom mestu, koju nije svakiput lako realizovati. Drugi potencijalni nedostatakjedne maglene aplikacije je to to kontrola praine sepostie jedinstveno na mestu aplikacije (nema carryon efekta), tako da, jedna kapitalna investicija moe

biti mnogo visoka za kompleksne transportnesisteme sa vie presipnih mesta.

3.3 SISTEMI ZA SKUPLJANJE FILTRIRANJE PRAINE

Sistemi za skupljanje praine koriste mehanikusilu da bi usisali vazduh koji prolazi kroz zone


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through some form of filtration device(electrostatic percipator, bag filter, cyclone,and scrubber) to remove dust particles and afterreleased in the atmosphere. Beside thesesystems there are passive systems, which usethe positive pressure inside the chute enclosureto allow the air to pass through the filters,Figure 9.

stvaranja/disperziranja praine. Usisani vazduh,zatim, prolazi kroz neki ureaj za filtraciju(elektrostatiki percipator, vreasti filter, ciklon,skruber i sl.), u koji se estice praine odstranjuju, aisti vazduh isputa u atmosferu. Pored ovih,

postoje i takozvani pasivni sistemi koji koristepozitivni pritisak u kuitu sipke da bi omuguilivazduhu da proe kroz filterske ureaje, slika 9.

Figure 9 Mechanical collection system (left) and passive collection system (right)slika 9 Mehaniki sistemi za skupljanje ( levo) i pasivni sistemi (desno)

Dust collection system usually provideshigh efficiency if properly designed andconstructed. Tight enclosure of transfer

point and correct assessment of air that mustbe pulled through the system is fundamental

for efficient and economical dust collection.

Due to the movement of material throughthe transfer point, three types of airmovement can be observed; displaced airinduced air and generated air. Therefore,totals air flow in a given transfer point can

be determined with the following equation:

Qtot = Qgen + Qdis + Qind , (1)

Where: Qtot - total air movement,

Qgen - quantity of generated air,Qdis calculated displased air,Qind Calculated induced air,

Qind = 32

10D

SRAu

, (m3/s) (2)

Au - open area at upstream end at the point whereis air induced into the system by action offalling material, (m2),

R - rate of material flow, (kg/ s),S - height of material free fall, (m),D - average material diameter, (m),

Sistemi za skupljanje praine najee obezbeujuvisoku efikasnost ukoliko se pravilno projektuju iinstaliraju. Hermetino zatvaranje presipnih mesta i

pravilna procena koliine vazduha koje treba usisati usystem, su od sutinskog znaaja za efikasnost i

ekonomi

nost ovih sistema.

Kao rezultat kretanja materijala kroz presipno mestojavlja se kretanje vazduha, koje u zavisnosti od uzrokanjegovog stvaranja moe biti: izbacivanje vazduha,inducirano i generisano kretanje vazduha. Ukupnukoliinu vazduha koja se kree kroz odreeno presipnomesto mogue je odrediti sledeom jednainom:

Qtot = Qdis+Qind+Qgen, (1)

gde su: Qtot ukupna koliina vazduha,

Qgen generisana koliina vazduha,Qdis proraunati izbaeni vazduh,Qind-proraunati inducirani vazduh,

Qind= 32

10D

SRAu

,(m3/s) (2)

Au otvorena povrina ulaznog dela sipke gde sevazduh inducira, (m2),

R kapacitet transportovanog materijala, (kg/s),

S visina slobodnog pada materijala, (m),D srednji dijametar zrna materijala, (m),


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Qdis =( )

( )3kg/mdensitybulkkg/sproductconveyed

, (m3/s).

Generally, a mechanical dust collection systemwill be required when the total air flow in the

loading zone exceeds 0,5 (m3/s) or if the airvelocity in the enclosure cannot be lowered toless than 1.25 (m/sec).

After all design parameters are carefullyevaluated, then the type of dust collection systemshould be selected. There are three basicapproaches to dust collection systems: central,unit, or integrated systems. In central method allthe individual collection points are by means ofducting connected a single filter in a singlelocation. The unit systems consist of self-contained dust collectors for individual or smalland conveniently grouped dust generation points.A logical extension of the unit concept is theintegrated system, where insert able filters areinstalled within the dust generation point itself.

Qdis = kapacitet/nasipna masa, (m3/s).

Generalno, mehaniki sistemi za skupljanjepraine su neophodni kada je ukupna koliinavazduha koja prolazi kroz presipno mesto iznad0.5 m3/s, odnosno kada se brzina vazduha ukuitu sipke ne moe smanjiti ispod 1.25 m/s.

Kada su svi projektni parametri paljivoprocenjeni tada bi trebalo izabrati tip sistema zaskupljanje praine. Postoje tri osnovna sistema zaskupljanje praine: centralni, jedinini iintegralni. Kod centralne metode sveindividualne take skupljanja su povezanecevovodom u centralni filter. Jedinine sistemisadre kompletne sisteme za skupljanje i

filtraciju praine za pojedina

na ili mala pogodnogrupisana mesta za generisanje praine. Logikiproduetak jedininog koncepta je integriranisistem, gde su filtri umetnuti u zonu stvaranja

praine.

Figure 10 a) Central Dust Collection System; b) Integrated Dust Collection System;c) Unit Dust Collection System

slika 10 a) Centralni sistem za skupljanje praine, b) Integrirani sistem za skupljanje praine,

c) Jedini

ni sistem za skupljanje praine


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Collection systems are proven and high efficientsolution, but their installation involve largerspace requirements, modification of existingsystems and extensive set ofmechanical/electrical and control equipmentwhich make them expensive to install. Also theoperating and maintenance costs are highcompared to alternative suppression systems. Thecollected dust must be returned to the materialflow (or otherwise disposed of), which may allowthe dust to be re-entrained into the air and thenre-collected at the next pickup point.

4 CONCLUSIONS

Given the differences in dust control

technologies, one of the most critical decisionsis to choose proper components and integratethem in one system which can assure the mostefficient and economic dust control solution.Only an in-depth look of causes for fugitivematerial occurrence can provide the engineerwith enough information how to solve the

problem.

Proper containment measures are fundamentalfor success of suppression and/or collectionsystems. Well designed dust control must

provide reduction of fugitive dust within theregulation limits and eliminate neighborcomplains and regulatory problems. Additional

benefits will include reduced maintenance costs,material losses, material flow and freezing

problems, as much as improved operationssafety, workforce moral and productivity.

Sistemi za skupljanje praine su dokazana ivisoko efikasna reenja, no njihova instalacijaukljuuje zahteve za vei prostor, modifikaciju

postojeih sistema i produenje kompletmehanike/elektrine i kontrolne opreme, to ih

pravi skupe za instaliranju. Takoe, operativni itrokovi odravanja su visoko uporedljivi saalternativnim sistemima za supresiju. Skupljena

praina mora biti vraena u tok materijala (ili nadrugi nain izbaena), to moe dozvoliiti da ta

praina bude ponovo usisana na sledeomusisnom mestu.

4 ZAKLJUAK

Zbog razlika koje postoje u tehnologijama za

kontrolu praine bitno je pravilno izabrati njihovekomponente i iste integrisati u jedan sistem koji bimogao obezbediti najsigurniju i najekonominukontrolu praine. Samo detaljnija analiza svihuzroka pojave fugitivne praine moe obezbeditiinenjeru dovoljne informacije da bi on reio ovaj

problem.

Ispravne mere za zadravanje praine su baza zauspenost sistema za suzbijanje ili skupljanje

praine. Dobro projektovani sistem za kontrolupraine mora obezbediti smanjenje koncentracije

praine u zakonskim dozvoljenim granicama i daeliminie albe javnosti i inspekciskih organa.Dopunske dobiti ukljuuju smanjene trokoveodravanja i materijalne gubitke, izbegavanja

problema sa smrzavanjem, kao i poboljanusigurnost kod operacija i povean moral i

produktivnost radnika.

Reviewal / Recenzija: prof. dr Milo Gruji

REFERENCES / LITERATURA

[1] Godbey, Thomas, Selecting a dust control system (PartI), Powder and Bulk Engineering, CSCPublishing, Minneapolis, October 1989, p. 37-42.[2]Godbey, Thomas, Selecting a dust control system (PartII), Powder and Bulk Engineering, CSC

Publishing, Minneapolis, November 1989, p. 20-30.[3] Mirakovski, Vrencovski, Doneva, "Sovremeni tehnologii za zatita od fugitativnata praina",

Meunarodno sovetuvawe - Cement 2002, 15-18 Maj 2002, Struga.[4] Mirakovski, "Kontrola na fugitativnata praina vo rudarskata industrija", Zbornik na Trudovi na

Rudarsko geolokiot Fakultet, Juni 2002, tip[5] Swinderman, Goldbeck and Marti, FOUNDATIONS -3, The Practical Resource for Total Dust &

Material Control, Martin Engineering, Neponset, Illinois,U.S.A., 2002

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KONTROLA FUGITIVNE PRAŠINE NA PRESIPNIM MESTIMA