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STET 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 20 years….
Sækja PDFF. Hrach, S. Gasiorowski, H.Guicherd
ST Equipment & Tækniskólinn LLC (STET), 101 Hampton Avenue, Prjóninn MA 02494 Bandaríkin
Ráðstefnu: Vietbuild Ho Chi Minh borg – júní 2015
Leitarorð: Triboelectrostatic, Rétthafa, Dry Fly Ash, Carbon Separation ABSTRACT
STET 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. STET’s electrostatic beneficiation technology reduces the carbon content of coal fly ash, producing consistent, low carbon ash for use as a substitute for cement. Fly ash with carbon levels up to 25% have been used to produce ash with a controlled carbon level of 2 ± 0.5%. A carbon-rich product is simultaneously produced to recover the fuel value of the carbon.
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, um það bil 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 continues 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. An excessive amount of unburned carbon in fly ash is the most common problem. The American Association of State Highway and Transportation Officials (AASHTO) and European Standards (EN 450 Category A) require that the amount of unburned carbon in fly ash, measured by loss on ignition (LOI) not exceed 5% by weight. þó, starting in the mid-1990s, installation of mandated NOx control equipment at coal-fired power plants increased the carbon (LOI) content of much of the previously marketable fly ash. Further requirements to reduce NOx and other power plant emissions have resulted in the contamination of fly ash with ammonia. As a consequence, while understanding the benefits of using fly ash in concrete continues to increase, the availability of suitable quality fly ash is decreasing. Processes to economically beneficiate off-quality fly ash are thus also of increasing interest to the power and concrete industries. STET has pioneered such processes for both carbon and ammonia removal from fly ash.
YFIRLIT YFIR TÆKNI – FLJÚGANDI KOLEFNISATÓMINN AÐSKILNAÐUR
Í STET Carbon Skilrúm (Mynd 1), the material is fed into the thin gap between two parallel planar electrodes. The particles are triboelectrically charged by interparticle
contact. 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, countercurrent flow, kröftug agna-agnir og sjálfhreinsiverkun beltisins á Rafskaut eru afgerandi Eiginleikar STET skilju. Með því að stýra ýmsum ferlistikum, eins og beltahraði, the feed point, 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 nonconductive 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 wastewater or air emissions. The recovered materials consist of fly ash reduced in carbon content to levels suitable for use as a pozzolanic admixture in concrete, 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 silica and alumina in cement kilns, displacing the more expensive raw materials, such as shale or bauxite, which are used in cement production. 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 Talen Energy 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 ASH PROCESSING FACILITIES
Controlled low LOI fly ash is produced with STET’s technology at twelve power stations throughout the U.S., Canada, the U.K., poland, og Lýðveldið Kórea. ProAsh® fly ash
has been approved for use by over twenty state highway authorities, sem og margar aðrar tilgreiningar stofnana. ProAsh® hefur einnig verið Vottað samkvæmt kanadíska Staðlasamtökum og EN 450:2005 gæðastöðlum í Evrópu. Ash processing facilities using STET technology are listed in Table 1.
Table 1. STET Commercial Operations
| Gagnsemi / Power Station | Staðsetning | Upphaf Auglýsing Aðgerðir | Facility Details |
|---|---|---|---|
| Duke Energy – Roxboro Station | North Carolina Bandaríkin | Sept. 1997 | 2 Skiltákn |
| Talen orka - Brandon Shores Station | Maryland Bandaríkin | apríl 1999 | 2 Skiltákn 35,000 ton storage dome. Ecotherm™ Return 2008 |
| ScotAsh (Lafarge / Scottish Power Joint Venture) - Longannet-stöðin | Scotland Bretlandi | október. 2002 | 1 Skiltákn |
| Jacksonville Electric Authority - St. John’s River Power Park, FL | Florida Bandaríkin | maí 2003 | 2 Skiltákn Coal/Petcoke blends Ammonia Removal |
| South Mississippi Electric Power Authority R.D. Morrow Station | Mississippi Bandaríkin | Jan. 2005 | 1 Skiltákn Ecotherm™ Return |
| New Brunswick Power Company Belledune Station | New Brunswick, Canada | apríl 2005 | 1 Skiltákn Coal/Petcoke Blends Ecotherm™ Return |
| RWE npower Didcot Station | England Bretlandi | ágúst 2005 | 1 Skiltákn Ecotherm™ Return |
| Talen Energy Brunner Island Station | Pennsylvania Bandaríkin | desember 2006 | 2 Skiltákn 40,000 Ton storage dome |
| Tampa Electric Co. Big Bend Station | Florida Bandaríkin | apríl 2008 | 3 Skiltákn, tvöfaldur passi 25,000 Ton storage dome Ammonia Removal |
| RWE npower Aberthaw Station (Lafarge Cement UK) | Wales Bretlandi | September 2008 | 1 Skiltákn Ammonia Removal Ecotherm™ Return |
| EDF Energy West Burton Station (Lafarge Cement UK, Cemex) | England Bretlandi | október 2008 | 1 Skiltákn Ecotherm™ Return |
| ZGP (Lafarge Sement Pólland / Ciech Janikosoda JV) | poland | mars 2010 | 1 Skiltákn |
| Korea South-East Power Yeongheung Units 5&6 | Suður-Kórea | September 2014 | 1 Skiltákn Ecotherm™ Return |
| Lafarge Sement Pólland Warsaw | poland | 2016 | 1 Skiltákn |
CONCLUSIONS
Maximizing the utilization of fly ash as a cement substitute in concrete production substantially reduces the carbon dioxide emissions associated with construction activity. þó, pollution control systems implemented by the coal-fired power stations have resulted in a reduction of available fly ash meeting concrete-grade specifications. Further degradation of fly ash quality is expected due to further reductions in allowable gas emissions. In order to avoid loss of this valuable resource of material for concrete production as well as reduction of greenhouse gas emissions associated with concrete construction, processes for restoring the quality of the fly ash in an economic and environmentally viable way are needed.
The beneficiation of fly ash with STET processes further increases the supply of this important material. The STET beneficiation processes continue to be the most extensively applied methods to upgrade otherwise unusable fly ash to high-value materials for cement replacement in concrete. Eighteen SETT carbon separators are currently in place with over 100 machine-years of operation.
ProAsh® has found wide acceptance in the concrete industry as a premium fly ash requiring far less monitoring of air entrainment requirements due to less LOI variability than other ashes. Returning the high-carbon concentrate from the STET process to the boiler at a power plant allows recovery of the recovered carbon fuel value at an efficiency similar to coal. STET offers economical means to recover ash for high-value use that would otherwise be landfilled. Electrostatic carbon separation and Ecotherm™ return to the boiler provide a modular solution to a utility’s fly ash needs. These processes can be implemented in phases, or as a single project.
TILVÍSANIR
[1] American Coal Ash Coal Combustion products and Use Statistics:
https://www.acaa-usa.org/Publications/Production-Use-Reports/
