Clean Coal Technologies

Transcript

1 Corso di Laurea Magistrale in Ingegneria Chimica/ Ingegneria Energetica Anno Accademico Formazione e Controllo di Inquinanti nella Combustione Impianti di trattamento effluenti Clean Coal Technologies Prof. L.Tognotti Dipartimento di Ingegneria Civile e Industriale Recycle streams R1 ash, H2O, SO2, CO2 R2 H2O, SO2, CO2 R3 SO2, CO2 R4 CO2

2 Outline The role of coal in the energy scenario The drivers for innovation in clean coal technologies The processes associated with PC firing Burners and boilers Ash related problems Oxy-coal combustion

3 The role of coal 6% 6% 24% 25% 38% 17% 18% 19% 39% Nuclear Hydro and other renewable Natural gas Coal Primary energy demand 7% Power generation Oil Coal covers approximately 1/4 of the world energy demand Coal demand increases up to 40% in the power sector Font: IEA World Energy Outlook 2004 and BP Statistical Review 2004

4 Requirements for future power generation Primary energy sources for electricity production Primary energy (Gtoe) % 19 % 2000 Renewables 20 % 43 % Nuclear Oil Gas Coal 12 % 13 % 29 % 40 % 2020 Source: World Energy Outlook 2002 Demand for new power plants until 2020: EU: 200 GW world: 2000 GW Developing countries: additional demand Europe: replacement Huge investments are needed in the next 20 years to replace the aging infrastructure and to continue BAU: billion euros in EU billion euros in the world

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7 Age of Coal-Fired Power Plants in Europe Percentage of Installed Ccoal- Fired Capacity in Europe >40 Years 37 % 63 % Number of Plants

8 Sustainable coal: drivers Innovation is the most important instruments for long term success of coal in power generation sector. The main items are : Increase of efficiency. Abatement of pollutants. Reduction of CO2 emission. Social acceptance.

9 Increase of efficiency Development of Coal Fired Power Stations Today technology is proven for 280 bar, 600/610 C and is ready for 300 bar, 630/630 C. Japan has a competitive advantage of about 5 years on large stateof-the-art installations.

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12 Net efficiency, % (LHV) Measures to improve efficiency 46 0,003 MPa ,15 1,25 Air ratio 120 C 130 C Stack gas temperature 30 MPa 600 C 25 MPa 540 C Steam conditions Double reheat Single reheat Reheating 0,0065 MPa Condenser pressure

13 DCO 2 ~ 30% P.f. ultra-supercritical boilers, CO 2 emissions 1200 CO2 emissions g/kwh Plants to be replaced Current average EU countries Average EU countries 2010 Thermie AD % 30% 35% 40% 45% 50% 55% 60% Net efficiency, % (LHV) Source: PowerGen Europe 2003

14 New clean coal power Europe-wide and in the world Power plant Company Capacity (MWe) Steam temperature ( C) Tsuruga 2 Hokoriku EPCo (J) 700 Steam pressure 24.1 (MPa) 593/593 Start-up 2000 Tachibana -wan 1&2 J-Power (J) 1050 x / /2001 Avedore 2 Energy E2 (DK) / Hekinan 4&5 Chubo EPCo (J) 1000 x / /2002 Tomatoh Atsuma 4 Hokkaido EPCo (J) / Niederhaussem RWE (D) / Isogo 1 J-Power (J) / Reihoku 2 Kyushu EPCo (J) / Hitachinaka Tokyo EPCo (J) / Maizuru 1 Ka n sai EPCo (J) / Hirono 5 Tokyo EPCo (J) / Genesee 3 EPCOR (CAN) / Council Bluffs 4 Mid American Eco (USA) / Yuhuan Huanen Pow. Int. (C ina ) 1000 x / Weston 4 Wisconsin PServ. (USA) / Torvaldaliga 2,3&4 Enel (I) 660 x / /2008/2009 Elm Road Wisconsin E Power (USA) 677 x / /2009 Isogo 2 J-Power (J) / Boa 2&3 Neurath RWE 2x / /2010 Walsum 10 Steag (D) / Datteln 4 E.ON (D) / Boxberg R RWE 1x Hamm RWE 2x / /2012 Moorburg Vattenfall 2x /2012 Maasvlackte E.ON (D) /

15 Enel Torrevaldaliga Nord power plant Coal storage State-of-the-art Performance Boilers Turbine housing Fabric filter Wet FGD Efficiency (LHV, net) ~45% P SH 242 bar T SH (turbine inlet) 600 C T RH (turbine inlet) 610 C Cond. back pressure bar Very Low Emissions (mg/nm 6% O 2 ) SO (200) NO x 100 (200) Dust 15 (30) ( ) EU Directive 2001/80/EC First unit in service late 2008, will be the first 600 C SH unit in Europe.

16 Factors driving clean coal technology Environmental issues Emissions: limit trends for coal power stations mg/nm 3, 6% O SO 2 NO x PM USA 609/EC USA 81/EC USA Italy Japan Hawthorn Torre Nord 3ten

17 Factors driving clean coal technologies Environmental issues Micropollutants: Heavy metals and fine particulate 0,3 No limits Hg+Cd+Tl 300 Hg 0,2 Cd+Tl VOC 200 0,1 Present limits 2000/76/EC DM EU Directive (2004/107/EC): Limit values of arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air link to PM10 and PM2.5

18 Processes associated with PC combustion Fundamentals

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20 Coal Combustion Products

21 Pollutant abatement ΔNOx = 30-70% ΔNOx = 80-90% ΔSOx = 97% Boiler DeNOx FF DeSOx GGH Gypsum LJ Fly ash Δdust = 99,9% Liquid drain TSD

22 PC Boiler terminology

23 La centrale termica 23

24 24 La caldaia Generalità e principi di funzionamento La caldaia ha il compito di trasferire il contenuto energetico del combustibile al ciclo acqua/vapore mediante opportuni meccanismi di scambio termico. Il bruciatore (singolo o in schiera) è il dispositivo più importante del sistema di combustione di caldaia sia per la funzione in sé, che consiste, appunto, nel bruciare il combustibile, sia per quanto riguarda la performance dell intero impianto in termini di efficienza e di emissioni. La missione primaria di un bruciatore è formare un getto di combustibile e aria che possa essere acceso in un solo colpo in modo da produrre una fiamma in grado di autosostenere la combustione e mantenere con stabilità opportune caratteristiche chimico-fisiche (temperatura, lunghezza, spessore). Alcune criticità legate alla tipologia e all esercizio dei bruciatori: la stabilità di fiamma le emissioni di NOx e CO il tenore di incombusti nelle ceneri

25 25 La caldaia Scambio termico: componenti principali

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27 27 La caldaia Scambio termico: calore asportato dalle diverse sezioni Tratto da NRWPP700 Final Report

28 Efficienza Lorda, (% LHV) 28 Evoluzione e stato dell arte degli impianti a vapore Rendimento di impianto CON CORPO CILINDRICO A UNICO PASSAGGIO 260 bar 600 C 170 bar 538 C VAPORE SUBCRITICO VAPORE SUPERCRITICO Tratto da Evaluation of coal-based power generation in an uncertain context - UCL Université catholique de Louvain

29 29 Evoluzione e stato dell arte degli impianti a vapore Stato dell arte degli impianti a carbone

30 La caldaia Problematiche Focus su materiali - Creep, short term overhating, ossidazione lato vapore, corrosione lato fumi Caso della C.le di TVN, assetto CMC Camera di combustione (spiral walls) - Tin = 345 C - Tout = 410 C ca - materiali: 16Mo3, 15NiCuMoNb Risurriscaldatore secondario - Tin = 530 C - Tout = 612 C - materiali: S 304H, P92 Temperature acqua-vapore per Generica Caldaia USC 30

31 31 La caldaia Danneggiamenti

32 La caldaia Tipologie di caldaia

33 FRONTE RETRO 33 La caldaia Sistemi di combustione frontali Il metodo del reticolo valle ECO per il bilanciamento aria/combustibile dei bruciatori Fronte caldaia Retro caldaia Configurazione frontale contrapposta

34 La caldaia Esempio di disposizione bruciatori su caldaia frontale (TVN)

35 35 La caldaia Sistemi di combustione tangenziali Aria OCD Aria Carbone Aria OCD Aria

36 La caldaia Piano 2 carbone Confronto tra sistemi frontali e tangenziali Piano 3 carbone Naso caldaia Fireball Fiamma definita per singolo bruciatore Naso caldaia Tangenziale Frontale contrapposto 36

37 37 La caldaia Dimensioni in base al tipo di combustibile utilizzato Carbone Olio Gas Gli ampi volumi a disposizione e le basse velocità in gioco rendono piuttosto semplice l ottenimento di una combustione ad altissima efficienza. I generatori tradizionali sono interessati da camere di combustione costituite da numerosi bruciatori che realizzano fiamme di diffusione. Generalmente si opera in eccesso di aria. La preparazione del combustibile diventa problematica in presenza di combustibili liquidi e solidi (carbone). Le dimensioni della camera sono legate alle caratteristiche del combustibile e alla emissività dei fumi corrispondenti.

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41 Coal Flames

42 IFRF Aerodynamically Air-Staged Burners (AASB) Type 0 Type 1 Type 2

43 IFRF classification of Swirling Flames Fricker and Leuckel,

44 Pulverised coal Burners TEA-C Low-NO X Burner Secondary and tertiary air with independent swirler Fuels: NG, oil, coal

45 Coal burner technology

46 Low NOx burners

47 Burner Arrangements in PC Boilers

48 Tangential Burners for a PC Boiler Advantages - PC particles sweep around furnace volume, with longer residence time. Improved coal particle burnout; Fuel-rich zone in inner region, surrounded by O2-rich SA outer Low NOx: By detaching high T & high O2, two necessary conditions for NOx; Oxidizing atmosphere along furnace water-wall (reducing one is very corrosive)

49 Low-NOx combustion: in-furnace measures PRIMARY AIR SECONDARY AIR TERTIARY AIR DNOx 40% F LEAN RICH F F LEAN RICH LEAN LNB DNOx 50% DNOx 70% OFA Reburning

50 Burners and OFA

51 Combustione ed ossicombustione industriale del carbone Oxycombustion Leonardo Tognotti University of Pisa, Italy

52 Oxy-coal combustion: scope Briefly identify problem and potential role of oxy-coal combustion Focus on pulverized coal configurations rather than on circulating fluid bed combustors, and other systems Identify current state of the technology and critical research issues.

53 The power to reduce CO 2 emissions Ref EPRI Technology Assessment Center 2007 CO2 emission mitigation through carbon capture and sequestration

54 What is Carbon Dioxide Capture and Storage (CCS)? Carbon dioxide (CO 2 ) capture and storage (CCS) is a process consisting of separation of CO 2 from industrial and energy-related sources, transport to a storage location, and long-term isolation from the atmosphere.

55 The options for carbon sequestration Deep saline formations estimated capacity: 1000 Depleted oil and gas fields estimated capacity: 100 Deep coal seems estimated capacity: 10

56 Trapping mechanisms and storage security Storage security depends on a combination of physical and geochemical trapping Over time, residual CO 2 trapping, solubility trapping and mineral trapping increase

57 CO2 capture options and systems Overview Schematic of CO2 capture diagram processes of possible and CCS systems systems SRCCS Figure TS-3

58 Oxycombustion: characteristics of the process 1. The oxy-combustion process eliminates N 2 from reaction zones 2. Combustion process requires recirculation of significant amounts of flue gases 3. High concentration of triatomic gases like CO 2 and H 2 O with physical and chemical properties different than N 2 4. High CO 2 content in flue gases makes easier the further CO 2 sequestration INECSE

59 Advantage of Oxyfuel is its Potential for Retrofit to Existing Boilers. Options for Points from which to Recycle Flue Gas for Pulverized Coal Boiler (Adapted from Stromberg) Recycle streams R1 ash, H 2 O, SO 2, CO 2 R2 H 2 O, SO 2, CO 2 R3 SO 2, CO 2 R4 CO 2

60 Conventional vs. Oxy- coal plants

61 Oxy-coal combustion: Two overarching issues O 2 supply energy penalty Current cryogenic technology can consume 15-20% of energy produced Purity of CO 2 flue gas for sequestration Is it a waste? Or a resource? Regulatory and legal issues. Directives issued for comment from EU, Japan, and US EPA (July, 2008) Does it have commercial value for tertiary oil recovery? What impurities are allowed? Corrosion during transportation to disposal site? Compression cost limitations? Technology for purification, if required.

62 The main combustion/heat transfer issues

63 Retrofitting The fundamental parameter is the recycle ratio, the mass fraction of flue gas recycled into the furnace = mass of recycled flue gas per time unit = mass of product flue gas per time unit Changing the recycle ratio is possible reproduce the normal air combustion conditions

64 Recycle ratio Adiabatic Flame temperature and flue gas volume vs Recycle Ratio

65 The ratio R of recirculated CO 2 to Oxygen is around 3 if heat flux for air combustion is to be matched Case O 2, eff T AF K p c p w, T=1500 K L=15 m q max, kw/m 2 Air 21% O 2 R=1 O 2 R =2 O 2 R=3 51% ,946 35% ,140 27% The recycle ratio will depend upon furnace size, oxygen purity, coal type, temperature of recycle and will be reduced by solid recycle in FBC (Alstom)

66 Gas compositions (omitting non-condensables) and volumes for bituminous coal (CH 1.1 O 0.2 N S ) fired with air and oxygen CO 2 Air Firing 17 % by volume Oxy-Firing 64% H 2 O 8.9% 34% NO x 2770xCR* ppm 10,700xCR* ppm SO x 2470 ppm 9400 ppm Moles CR* = fractional conversion of coal nitrogen to NO x

67 Different properties of the gaseous atmosphere at oxy-combustion processes Gas property ratios of CO2 and N2 at 1200K [T. Wall 2008]

68 Oxy-coal combustion research outputs 1. Enabling technology for retrofit in conventional, but new, high efficiency, air-tight, air-fired units that have been proven for air firing (short term). 2. Enabling technology for oxy-coal application to new units that were never planned for air firing, but still look (somewhat) like boilers (intermediate term) 3. Research for development of new technologies which do not look at all like current boilers (long term).