Triboelectrostatic Rétthafi urðunarfluga Ash WOCA 2015

Triboraffastan rétthafa á

Land fyllt fljót aska

L. Baker, A. Gupta, og S. Gasiorowski

ST Equipment & Tækniskólinn LLC, 101 Hampton Avenue, Prjóninn MA 02494 Bandaríkin

Ráðstefnu: 2015 Heims um koll Ash – (www.worldofcoalash.org)

Leitarorð: Triboelectrostatic, Rétthafa, Fly Ash, Urðun endurvinnslu, Þurrkaðir, aðskilnaður, Carbon

Óhlutbundnar

Triboelectrostatic separation has been used for the commercial beneficiation of coal combustion fly ash to produce a low carbon product for use as a cement replacement in concrete for nearly twenty years. With 18 separators in 12 coal-fired power plants across the world, ST Equipment & Technology LLC ' s (STET) patented electrostatic separator has been used to produce over 15 Million tonnes of low carbon product.

To date, commercial beneficiation of fly ash has been performed exclusively on dry “run of station‿ ash. Recent environmental legislation has created, in certain markets, a need to supply beneficiated ash in times of low ash generation. Þessi, coupled with a requirement in some locations to empty historical ash landfill sites, has created the need to develop a process to beneficiate historically landfilled ash.

Previous studies have shown that the exposure of fly ash to moisture, and subsequent drying influences the triboelectrostatic charging mechanism, with carbon and mineral particles charging in the opposite polarity to that experienced with run of station ash. Studies have been performed by the authors to determine the effect of moisture exposure on separation efficiency of several ashes that have been reclaimed from landfills and dried. Charge reversal was experienced following drying, but overall separation efficiency was achieved equivalent to that experienced with fresh run of station ash.

The effect of dried ash feed relative humidity on triboelectrostatic separation efficiency was examined, and sensitivity was greatly reduced compared to that experienced with run of station ash, lowering overall process costs.

KYNNING

The American Coal Ash Association (ACAA) annual survey of production and use of coal fly ash reports that between 1966 og 2011, Yfir 2.3 billion short tons of fly ash have been produced by coal-fired utility boilers.1 Of this amount approximately 625 million tons have been beneficially used, mostly for cement and concrete production. þó, the remaining 1.7+ billion tons are primarily found in landfills or filled ponded

impoundments. While utilization rates for freshly generated fly ash have increased considerably over recent years, with current rates near 45%, um það bil 40 million tons of fly ash continue to be disposed of annually. While utilization rates in Europe have been much higher than in the US, considerable volumes of fly ash have also been stored in landfills and impoundments in some European countries.

Nýverið, áhugi á að endurheimta þetta losaði efni hefur aukist, að hluta til vegna eftirspurnar eftir hágæða Fly Ash fyrir steypu og sementframleiðslu á tímabili með minni framleiðslu sem kol-rekinn máttur kynslóð hefur minnkað í Evrópu og Norður-Ameríku. Áhyggjur af langtímaumhverfisáhrifum slíkra urðunarstaðanna eru einnig tafarlaus tól til að finna gagnleg forrit fyrir þetta geymda Ash.

LAND FYLLT ASH GÆÐI OG NAUÐSYNLEGUR VIÐTAKENDUR

While some of this stored fly ash may be suitable for beneficial use as initially excavated, the vast majority will require some processing to meet quality standards for cement or concrete production. Since the material has been typically wetted to enable handling and compaction while avoiding airborne dust generation, drying will probably be a minimal requirement for use in concrete since concrete producers will want to continue the practice of batching fly ash as a dry powder. þó, assuring the chemical composition of the ash meets specifications, most notably the carbon content measured as loss-on-ignition (LOI), is a greater challenge. As fly ash utilization has increased in the last 20+ Ára, most “in-spec‿ ash has been beneficially used, and the off-quality ash disposed. Thus, LOI reduction will be a requirement for utilizing the vast majority of fly ash recoverable from utility impoundments.

LOI REDUCTION BY TRIBOELECTRIC SEPARATION

Þó ýmsir starfsmenn hafa notað brennslu aðferðir og flotlaug ferli fyrir LOI minnkun batna landfyllingar og tjóð Fly Ash, ST Equipment & Tækni (STET) hefur komist að því að staðlað vinnslukerfi þess, lengi notað fyrir viðtakendur nýmynduðum fljúgandi Ash, er jafnárangursríkt á endurheimtu ösku eftir hentugar þurrkun og deagglomeration á lægri rekstrarkostnaði í heild.

Á rampur-allt að auglýsing umsókn um STET vinnslukerfi fyrir Fly Ash, STET-vísindamenn prófuðu aðskilnaðinn á þurrkuðum landfylltum ösku. Þessi endurheimti Ash aðskilin mjög álíka að nýmynduðum ösku með einum óvæntan mismun: í agnahleðslu var snúið úr því að ferskari aska með kolefnislífhleðslu neikvæð í tengslum við steinullarmagnið.2 Aðrar rannsóknir á rafstöðuskilrúmum á Fly Ash kolefni hafa einnig fylgt þessu fyrirbæri.3,4,5

YFIRLIT YFIR TÆKNI – FLJÚGANDI KOLEFNISATÓMINN AÐSKILNAÐUR

Í STET Carbon Skilrúm (Mynd 1), efni er fóðraður í þunna bilið milli tveggja samsíða planar rafskaut. Þær agnir sem eru mjög hlaðnar með interagnið snertileysi. Hið jákvæða innheimt kolefni og neikvæð innheimt steinefni (í nýmynduðum ösku sem ekki hefur verið bleytt og þurrkuð) eru dregnar saman á móti rafskaut. Agnirnar eru síðan sópaðar upp af samfelldu hreyfanlegum beltum og settar í gagnstæðar áttir. Beltið flytur agnir sem eru samliggjandi við hverja rafall í átt að gagnstæðum endum skiltisins. Hár beltahraði gerir einnig mjög mikil gegnumsnúningshraði, allt að 36 tonnum á klukkustund á einni skilvindu. Litla bilið, háspennulínur í háaleit, Teljari núverandi flæðis, kröftug agna-agnir og sjálfhreinsiverkun beltisins á Rafskaut eru afgerandi Eiginleikar STET skilju. Með því að stýra ýmsum ferlistikum, eins og beltahraði, straumur punktur, og straumhraði, STET ferlið framleiðir lágt LOI fljúga ösku á kolefnisinnihaldi minna en 1.5 að 4.5% from feed fly ashes ranging in LOI from 4% að yfir 25%.

Mynd. 1 STET Separator

The separator design is relatively simple and compact. Vél hönnuð til vinnslu 36 tonn á klukkustund er u.þ.b. 9 M (30 Ft.) Langur, 1.5 M (5 Ft.) wide, og 2.75 M (9 Ft.) Hár. Beltið og tengd rollinum eru einu Hreyfðu hlutar. Rafskaut eru kyrrstætt og samsett úr viðeigandi varanlegum efnum. The belt is made of non- conductive plastic. The separator’s power consumption is about 1 kílóvattstund á tonn af efni sem unnið er með mest af krafti sem neytt er af tveimur mótorum sem aka beltinu.

Ferlið er algjörlega þurrt, requires no additional materials other than the fly ash and produces no waste water or air emissions. The recovered materials consist of fly ash reduced in carbon content to levels suitable for use as a pozzolanic admixture in

steinsteypa, and a high carbon fraction useful as fuel. Nýting beggja afurðastrauma veitir 100% lausn til að fljúga aska förgun vandamál.

RECOVERED FUEL VALUE OF HIGH-CARBON FLY ASH

In addition to the low carbon product for use in concrete, brand named ProAsh®, the STET separation process also recovers otherwise wasted unburned carbon in the form of carbon-rich fly ash, branded EcoTherm™. EcoTherm™ has significant fuel value and can easily be returned to the electric power plant using the STET EcoTherm™ Return system to reduce the coal use at the plant. When EcoTherm™ is burned in the utility boiler, the energy from combustion is converted to high pressure / high temperature steam and then to electricity at the same efficiency as coal, typically 35%. The conversion of the recovered thermal energy to electricity in ST Equipment & Technology LLC EcoTherm™ Return system is two to three times higher than that of the competitive technology where the energy is recovered as low-grade heat in the form of hot water which is circulated to the boiler feed water system. EcoTherm™ is also used as a source of alumina in cement kilns, displacing the more expensive bauxite which is usually transported long distances. Utilizing the high carbon EcoTherm™ hæhæ annað hvort á orkuverksmiðju eða sementsbundið Kiln, hámarkar orkuendurheimt frá afhentu grófu, draga úr þörfinni til minja og flytja viðbótareldsneyti til aðstæðna.

STET ' s Raven Power Brandon Shores, SMEPA R. D. Morrow, NBP Belledune, RWEnpower Didcot, EDF Energy West Burton, og RWEnpower Aberthaw flís ristaðar plöntur, allar eru með EcoTherm™ Skilakerfi. Nauðsynlegir þættir kerfisins koma fram í mynd 2.

Mynd. 2 EcoTherm™ Skilakerfi

STET RISTUÐ PROCESING AÐSTAÐA

Controlled low LOI fly ash is produced with STET’s technology at twelve power stations throughout the U.S., Canada, the U.K., poland, and Republic of Korea. ProAsh® fly ash has been approved for use by over twenty state highway authorities, sem og margar aðrar tilgreiningar stofnana. ProAsh® has also been certified under Canadian Standards Association and EN 450:2005 gæðastöðlum í Evrópu. Ash processing facilities using STET technology are listed in Table 1.

Table 1. STET Commercial Operations

COAL ASH RECOVERED FROM LAND FILLS

Two sources of ash were obtained from landfills: sample A from a power plant located in

the United Kingdom and sample B: from the United States. Both these samples consisted of ash from the combustion of bituminous coal by large utility boilers. Due to the intermingling of material in the landfills, no further information is available concerning specific coal source or combustion conditions.

The samples as received by STET contained between 15% og 20% water as is typical for landfilled material. The samples also contained varying amounts of large >1/8 inch (~3 mm) material. Að undirbúa sýnunum fyrir kolefnisaðskilnað, mikið rusl var fjarlægt með skimun og sýnin síðan þurrkuð og deagglomerated áður en Kolsýringur. Ýmsar aðferðir til þurrkunar/deagglomeration eru metnar í því skyni að hagræða heildarferlinu. Almennt ferli flæðablað er sett fram á mynd 3.

Mynd 3: Vinna flæðablað

Eiginleikar tilbúinna Sýna voru vel innan marka fljúga Ash fengin beint frá venjulegum gagnsemi Kötlum. Viðeigandi Eiginleikar fyrir bæði aðgreiningarstrauma og afurðir eru teknar saman í töflu 2 ásamt endurheimtu vöru.

KOLEFNISSAÐSKILNAÐINN

Carbon minnkun rannsóknir með STET triboelectric belti skilju leiddi mjög gott bata á Low LOI vöru. Það áhugaverða fyrirbæri sem fram hefur komið var bakfærsla hleðslustöðva á kolmunna rædd hér að ofan. Á meðan þessi hegðun hefur komið fram áður hjá STET og öðrum vísindamönnum, the mechanism that changes the relative work functions and thus contact charging behavior of the material is not understood. One suggested mechanism is the redistribution of soluble ions on the mineral and

Eftirfarandi tafla tekur saman efnahvörf fyrir sýni úr uppruna B. Prófun á upprunaefni hefur ekki verið lokið.

Table 4: Ash efnafræði Low LOI Ash.

Styrkja þróun á 20% substitution of the low LOI fly ash in a mortar containing 600 lb / yd3 showed the material derived from landfilled ash performed somewhat better than material from fresh production. Sjá töflu 5 below.

Table 5: Compressive strength of mortar cubes.

CONCLUSIONS

After suitable scalping of large material, drying, and deagglomeration, fly ash recovered from utility plant landfills can be reduced in carbon content using the commercialized STET triboelectric belt separator. The efficiency of the STET system is essentially equivalent for ashes obtained freshly from boiler operations and dried landfilled material. The separator product is suitable for use in concrete production without further beneficiation with nearly identical performance properties. The recovery and beneficiation of landfilled ash will provide a continuing supply of high quality ash for concrete producers in spite of the reduced production of “fresh‿ ash as coal-fired utilities reduce generation. Additionally, power plants that need to remove ash from landfills to meet changing environmental regulations will be able to utilize the process to alter a waste product liability into a valuable raw material for concrete producers.

TILVÍSANIR

[1]American Coal Ash Coal Combustion products and Use Statistics: https://www.acaa-usa.org/Publications/Production-Use-Reports/

[2]ST internal report, ágúst 1995.

[3]Li,T.X,. Schaefer, J.L., Ban, H., Neathery, J.K., and Stencel, J.M. Dry Beneficiation Processing of Combustion Fly Ash, Proceedings of the DOE Conference on Unburned Carbon on Utility Fly Ash, maí 19 20, Pittsburgh, PA, 1998.

[4]Baltrus, J.P., Diehl, J.R., Soong, Y., Sands, W. Triboelectrostatic separation of fly ash and charge reversal, Fuel 81, (2002) pp.757-762.

[5]Cangialosi, F., Notarnicola, M., Liberti, L, Stencel, J. The role of weathering on fly ash charge distribution during triboelectrostatic beneficiation, Journal of Hazardous Materials, 164 (2009) pp.683-688.

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