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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….
Download PDFF. Hrach, S. Gasiorowski, H.Guicherd
Sen ekipman & Teknoloji LLC (STET), 101 Hampton avni, Needham MA 02494 NAN ETAZINI
CONFERENCE: Vietbuild Hô-Chi-Minh-vil-jen 2015
MOTS: Triboelectrostatic, Beneficiation, 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, Sen ekipman & Teknoloji LLC a (STET) technologie séparateur électrostatique ki te itilize pou pwodwi sou 15 Milyon tòn pwodwi ti kabòn.
Dat, 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.
YON TI RALE
Asosyasyon Ash chabon Ameriken (ACAA) ankèt anyèl pwodiksyon ak itilize chabon vole ash te rapòte ke ant 1966 ak 2011, sou 2.3 billion short tons of fly ash have been produced by coal-fired utility boilers.1 Of this amount, apeprè 625 milyon tòn te beneficially itilize, sitou pou pwodiksyon siman ak beton. Sepandan, ki te rete a 1.7+ milya tòn premyèman ap jwenn nan décharges oubyen te ranpli ponded impoundments. Pandan tout tan pousantaj itilizasyon yo pou prije généré mande pou vole te anpil anpil nan ane resan, ak yon pousantaj aktyèl tou pwe 45%, apeprè 40 million tons of fly ash continues to be disposed of annually. Pandan tout tan pousantaj itilizasyon yo an Ewòp te genyen pi wo ke nan Etazini, konsiderab volumes a vole te tou te sere nan décharges ak impoundments nan kèk peyi Ewopeyen yo. 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. Sepandan, 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.
TEKNOLOJI KOURIKOULÒM-MANDE POU VOLE CARBON SEPARASYON
Nan rele STET séparateur kabòn (Figi 1), the material is fed into the thin gap between two parallel planar electrodes. The particles are triboelectrically charged by interparticle
contact. Kabòn pozitivman accusé a ak a accusé négative ineral (nan prije généré mande sa yo ki pa te humide e secs) a pou opoze électrodes. Matyè yo lè sa a te baleye pa yon senti dwa kontinyèl, transmis nan direksyon yo bò. Kouwa a deplase matyè adjasan pou chak lektwòd anvè toupatou bò la séparation. Gwo vitès senti anwo nan syèl la tou permet débits trè wo, jiska 36 tòn pa è sou yon moun ki pa marye séparateur. A ti gap, anwo nan syèl la vòltaj jaden, countercurrent flow, wòdpòte renn-renn ajitasyon ak pwòp tèt nettoyage aksyon senti sou électrodes yo vizaj kritik a rele STET séparateur. Pa okipe kay yo plizyè karakteristik pwosesis, tankou senti vitès, the feed point, ak manje bèt yo ki te konn, pwosesis la te rele STET pwodwi ba LOI vole ash kabòn sa ki nan liv la nan mwens ke 1.5 pou 4.5% nan manje vole sann ki sòti nan LOI de 4% pou fini 25%.
Pye fig. 1 STET Séparateur
Plan séparateur relativman senp ak kontra. Yon machin ki fèt pou travay 36 tòn pa lè se apeprè 9 m (30 .) lontan, 1.5 m (5 .) lajè, ak 2.75 m (9 .) anwo nan syèl la. Kouwa ak asosye woulèt se sèl kalite manm. Électrodes èstasyone ak reyalize yon materyèl ki fè a se sa dirab. The belt is made of nonconductive plastic. Pouvwa konsomasyon la séparation se osijè de 1 Kilowatè tòn pa materyèl ki te trete ak pi fò nan pouvwa consommée pa de motè mete senti a.
Pwosè a chèch nèt, 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. Itilize nan toulede kouran pwodwi bay yon 100% solisyon vole sann dispozisyon pwoblem.
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™ ash either at a power plant or a cement kiln, maximizes the energy recovery from the delivered coal, reducing the need to mine and transport additional fuel to the facilities.
STET’s Talen Energy Brandon Shores, SMEPA R.D. Demen, NBP Belledune, RWEnpower Didcot, EDF Energy West Burton, and RWEnpower Aberthaw fly ash plants, all include EcoTherm™ Return systems. The essential components of the system are presented in Figure 2.
Pye fig. 2 EcoTherm™ Return system
STET ASH PROCESSING FACILITIES
Controlled low LOI fly ash is produced with STET’s technology at twelve power stations throughout the U.S., Kanada, the U.K., Poloy, and the Republic of Korea. ProAsh® fly ash
has been approved for use by over twenty state highway authorities, as well as many other specification agencies. ProAsh® has also been certified under the Canadian Standards Association and EN 450:2005 quality standards in Europe. Ash processing facilities using STET technology are listed in Table 1.
Tab 1. STET Commercial Operations
| Itilite / Power Station | Kote yo ye | Kòmanse Komèsyal Operasyon | Facility Details |
|---|---|---|---|
| Duke Energy – Roxboro Station | North Carolina NAN ETAZINI | Sept. 1997 | 2 Separateur yo |
| Talen Energy - Brandon Shores Station | Maryland NAN ETAZINI | Avril 1999 | 2 Separateur yo 35,000 ton storage dome. Ecotherm™ Return 2008 |
| ScotAsh (Lafarge / Scottish Power Joint Venture) - estasyon longannet | Scotland RETIRE | Okt. 2002 | 1 Separateur |
| Jacksonville Electric Authority - St. John’s River Power Park, fl | Florida NAN ETAZINI | Me 2003 | 2 Separateur yo Coal/Petcoke blends Ammonia Removal |
| South Mississippi Electric Power Authority R.D. Demen Station | Mississippi NAN ETAZINI | Jan. 2005 | 1 Separateur Ecotherm™ Return |
| New Brunswick Power Company Belledune Station | New Brunswick, Kanada | Avril 2005 | 1 Separateur Coal/Petcoke Blends Ecotherm™ Return |
| RWE npower Didcot Station | England RETIRE | Out 2005 | 1 Separateur Ecotherm™ Return |
| Talen Energy Brunner Island Station | Pennsylvania NAN ETAZINI | Desanm 2006 | 2 Separateur yo 40,000 Ton storage dome |
| Tampa Electric Co. Big Bend Station | Florida NAN ETAZINI | Avril 2008 | 3 Separateur yo, doub pase 25,000 Ton storage dome Ammonia Removal |
| RWE npower Aberthaw Station (Lafarge Cement UK) | Wales RETIRE | Septanm 2008 | 1 Separateur Ammonia Removal Ecotherm™ Return |
| EDF Energy West Burton Station (Lafarge Cement UK, Cemex) | England RETIRE | Oktòb 2008 | 1 Separateur Ecotherm™ Return |
| ZGP (Lafarge Siman Poloy / Ciech Janikosoda JV) | Poloy | Mas 2010 | 1 Separateur |
| Korea South-East Power Yeongheung Units 5&6 | Kore di sid | Septanm 2014 | 1 Separateur Ecotherm™ Return |
| Lafarge Siman Poloy Warsaw | Poloy | 2016 | 1 Separateur |
CONCLUSIONS
Maximizing the utilization of fly ash as a cement substitute in concrete production substantially reduces the carbon dioxide emissions associated with construction activity. Sepandan, 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.
REFERANS
[1] American Coal Ash Coal Combustion products and Use Statistics:
https://www.acaa-usa.org/Publications/Production-Use-Reports/
