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Making oxy-fuel combustion

Making oxy-fuel combustion 7
New Developments in Combustion Technology Part III: Making oxyfuel combustion an advantage Geo. A. Richards, Ph.D. National Energy Technology Laboratory U. S. Department of Energy 2014 PrincetonCEFRC Summer School On Combustion Course Length: 6 hrs June 2223, 2014 Presentation Identifier (Title or Location), Month 00, 2008 This presentation Updated, expanded from 2012 CEFRC lecture: – Inherent carbon capture: chemical looping combustion (Day 1) – Stepchange in generator efficiency: pressure gain combustion (Day 2) – Frontier approach (): making oxyfuel an efficiency advantage (Day 2) Sampling Diagnostics RDC Flow Pgain rig NETL ‹› Making oxygen for oxyfuel …reprise • Oxygen can be supplied today by commercial Air Separation Units (ASU) based on established cryogenic separation. • The energy needed to separate oxygen from air is significant (see below) • In conventional oxycombustion, we dilute the purified oxygen to maintain the same boiler flame temperature as in aircombustion. 1 mole of air 0.21 moles oxygen Dilute again Air p = 1 atm with CO or steam O2 2 0.21 moles oxygen Separation p = 0.21 atm O2 Unity 0.79 moles nitrogen (ASU) 0.79 moles nitrogen p = 1 atm N2 p = 0.79 atm N2 C + O  CO 2 2 DH DG = 394 kJ/gmol (C or O 2) Reversible separation work: 6 kJ/gmol O produced In efficient powerplants we convert 2 less than ½ of DH to work. Thus200kJ/gmol O2 work produced Current actual process: 18kJ/gmol O produced 2 Roughly 1/10 of that is needed for ASU. e.g, the change in gibbs energy for ideal mixing (Sandler, Chemical Engineering Thermodynamics (1989) pp. 313. See Trainier et al., “Air Separation Unit…..” Clearwater Coal Conference, 2010. ‹› Making Oxyfuel an Advantage • Producing pure oxygen requires a lot of energy • If one could find a way to make significant extra power because of the available oxygen, oxyfuel would be an advantage. • Oxyfuel already provides an advantage for process industries that benefit from high temperatures (e.g., glass making, steel). • Oxyfuel already provides advantages in propulsion (rocket engines) • How can you make oxyfuel an advantage for power generation ‹› Efficiency 100 A) Existing Supercritical Pulverized Carnot w/r to 293 K 90 1 Coal (23.9MPa/866K/866K steam) 80 B) Advanced UltraSupercritical 70 Pulverized Coal (34.5 Mpa/1005K/1033K 1 60 steam) D 50 C) Simple Cycle Gas Turbine (as C reported, LMS 100, working fluid temp 40 2 estimated from exhaust and pressure ratio) B 30 A D) Combined Cycle Gas Turbine (as 20 reported, MPCP2(M501J), working fluid temp 10 3 estimated similar to case C) 0 0 500 1000 1500 2000 2500 Approximate combustion temperatures Oxyfuel Combustion Temp. Working fluid temp. Temperature (K) PC Coal Combustion Temp. Working fluid temp. Note: boilers report HHV efficiency; Gas Turbine Combustion Temp. = Working fluid temp. turbines report LHV 1 Current and Future Technologies for Power Generation with PostCombustion Carbon Capture, DOE/NETL2012/1557 2 Gas Turbine World 2012 GTW Handbook, Vol. 29, Pequot Publishing pp74 3 Gas Turbine World 2012 GTW Handbook, Vol. 29, Pequot Publishing pp89 ‹› Efficiency Magnetohydrodynamic Power Generation • The high temperatures A Turbogenerator possible with oxyfuel can be Hot Vapor N used to operate an MHD or Gas Brushes “topping” cycle: + – Topping cycle power possible Moving because of the oxygen S Conductors – MHD exits to conventional Forming Coil steam boiler system External Current Field (“bottoming cycle”). B MHD Generator • How does MHD work – Conductive, hightemperature N Electrode gases play the role of an Cathode electrical conductor moving Source of Hot, Electromotive through a magnetic field. Electrically Force Conducting Gas Motion – Generates power directly from S of Gas the moving gases. ‹› A combined cycle • For reasons that will be clear later, most MHD concepts only produce power ABOVE 2600K (which is….HOT). • Thus, it needs to be a combined cycle to extract energy from the whole temperature spectrum. Topping Work Output W T Bottoming Work Output W B Air separation Air unit High efficiency Oxygen MHD Power Unit steam boiler Fuel 2600 K combustion products MHD “topping” cycle including the oxygen production 45 efficient today best cases Example Enthalpy into the “top” = mass flow of fuel x HHV = Q h = 0.1 (10) Work from the top : W = h Q T T T h = 0.45 (45) B Enthalpy into the “bottom” = Q – W = Q ( 1 – h ) T T Combined Work from the bottom: W = h (Enthalpy into the bottom) = Q ( h – h h ) B B B T B Efficiency: Combined cycle efficiency: (W + W )/Q = h h – h h .1+.45 – (.1)(.45) T B T + B T B = 0.50 (50) ‹› Past MHD topping efforts • Concept proven in both U.S. and USSR in 70s and 80s – US DOE 1978 1993 – Electricity transferred to grid • Economic downfall : key factor being materials – Electrode damage – Seed material use MHD U25RM diffuser channel (USSR) 1970s From Petrick Shumyatsky 1978. ‹› Direct Power Extraction The “new” MHD: making oxyfuel an advantage New benefits, new approaches, new technology: Legacy MHD program Today Comments Oxyfuel combustion developed for No CO capture CO Capture 2 2 capture enables MHD. Validated models for different Large demos Simulation validation generator concepts, not demos. ASU power requirements have Preheated air Efficient oxygen production dropped 40 since 1990. No emissions Use oxyfuel gas SOx and NOx control Capture GPU processing unit (GPU). Advanced magnets exist today. Magnets 6 Tesla Magnets 6 Tesla Electrode arcing could be controlled Analog electronics Solidstate inverters/control with digital devices. Simulations can compare multiple Linear generator Radial, Linear, others geometries. New channel construction Conventional manufacturing Advanced manufacturing approaches. Aspirational – use nanosecond Seeded flows New goal: injected plasma pulse discharge to ionize gas ‹› Related technology – combustion, ionized flames, and plasma • Nonequilibrium plasma may benefit new aspects of combustion: Starikovsky, A. Aleksandrov, N. (2013). PlasmaAssisted Ignition and Combustion, Progress in Energy and Combustion Science, Vol. 39, pp. 61110. Ignition in demanding applications Pulse detonation engines, gas turbine relight, HCCI engines, others • Alternating current excitation of flames has recently demonstrated significant hydrodynamic changes in flame structures: Drews, A. M., Cademartiri, L., Chemama, M. L., Brenner, M. P., Whitesides, G. M., Bishop, K. J. M (2012). AC Electric Fields Drive Steady Flows in Flames, Physical Review E 86, pages 0363141 to 4. “…AC fields induce steady electric winds….localized near the surface of the flame….these results suggest that ac fields can be used to manipulate and control combustion processes at a distance….” • Flame ionization can be used for sensors and diagnostics. Benson, K., Thornton, J. D., Straub, D. L., Huckaby, E. D., Richards, G. A. (2005). Flame Ionization Sensor Integrated Into a Gas Turbine Fuel Nozzle, ASME J. Eng. Gas Turbines and Power, Vol. 127, No. 1, pp. 4248. Proposes detection of dynamics and combustion conditions with flame ionization • New propulsion concepts include plasma MHD “bypass” or electric thrust propulsion: Schneider, S. (2011). Annular MHD Physics for Turbojet Energy Bypass, AIAA20112230. Longmeier, B. W., Cassady, L. D., Ballenger, M. G., McCaskill, G. E., ChangDiaz, F. R., Bering, E. A. (2014). Improved Efficiency and Throttling Range of the VX200 Magnetoplasma Thruster, Journal of Propulsion and Power, Vol. 30, No. 1 pp. 123 – 132. • Nonequilibrium plasma: a key technology for the future Plasma Science: Advancing Knowledge in the National Interest (2010). This National Academies report provides status and motivation to use plasma – including combustion applications. MHD enthalpy MHD accelerator extraction Inlet Plasma television display MHD Bypass Concept Turbojet ki/Plasmadisplay Mach 7 ‹› Fundamentals of Electromagnetics • Electric field E is a vector (units: volt/meter) • E can be described by the voltage potential V; E = V • By convention, minus sign means E points to low voltage 2 • Magnetic Induction B is a vector (units: Tesla = voltsec/m ) F E F B Experimental observations of charge Q in electric Field E (left) and moving E Charge Q at velocity u in B (right). u Q B Q F = Q E F = Q (u x B) E B Q “Another” E Electric Force on Q Magnetic Force on Q E = F /Q u x B = F /Q E Q B Thus in 1D E = V/L E = E + u x B NET Q L = distance. ‹› A Simple Generator j Flowing conductive k gases i B u b R L u x B = uB k • Gas (conductive) flows with bulk velocity u i • Magnetic filed B k is applied as shown. • The resulting “induced” electric field is –uB k • This field can drive a current flow in the external circuit. • How is this similar to a conventional generator ‹› How Much Current Flows Important Nomenclature Note: The current flux is proportioned to E : E (zero sub) is NET 0 applied by the external load does not J = σ E ; σ = conductivity of media Amps/(voltmeter) NET include magnetic 2 induced field J = current flux vector Amps/meter 2 A = electrode area meter j b J = σ E = σ ( E + u x B) = σ ( E – uB) j NET 0 0 CHANNEL HEIGHT i R = b/sA is the resistance to current flow through i V the plasma – shown “oddly” disconnected since L E 0 J uB drives current in the same place. R R uB i L From E = V E = (V – V ) /b I 0 0 L H V H (V = Low Voltage V = High Voltage) SIMPLE GENERATOR FROM PREVIOUS PAGE L H E = (V – V ) /b = IR /b (Ohm’s Law) 0 H L L Define open circuit R  infinite, then J = 0 implies E = uB from above. L 0 Then, V = uBb (open circuit voltage) OC uBb V OC R ≡ internal resistance I = = ; i R + R b/ σ A + R i L L Note : as typical, V is a voltage difference while V and V are measured relative to ground oc H L ‹› Limiting Cases Open Circuit V L E 0 O = J = σ ( E – uB) E = uB 0 0 (V – V )/b = E = uB uB H L 0 V ≡ uBb OC V H Generating Circuit V L E 0 E uB; J = σ ( E – uB) J R R 0 0 i L uB I = V /(R +R ) oc i L V H Short Circuit V = V H L E = 0 E = (V – V )/b = O 0 J R 0 H L i R = O L uB V V OC OC I = = R + R =O R V = V i L i H L ‹› Electrical Analogy R i R V = E b L Load 0 G V = uBb OC I V IR R E Load L L 0 Define K = = = = V I (R + R ) R + R OC uB i L L i Several interpretations for K: 1. Ratio of load to O.C. voltage 2. Ratio of load resistance to total resistance 3. An efficiency (why Multiply by I/I  load power/total power) 4. A ratio of the “applied” field E to “generated” field uB 0 ‹› Electrical Analogy – Power Produced R i R V = E b L Load 0 G V = uBb OC I V IR R E Load L L 0 Define K = = = = V I (R + R ) R + R OC uB i L L i The power to the load is power = (current x load voltage): I = A J ; I = A s (E uB) = A s uB ( K – 1 ) 0 V = b E = b uB K Load 0 2 2 x Power = I V; Power = Ab s u B K ( K 1 ) 2 2 Power density = Power/(Ab) = s u B K ( K 1 ) ‹› Next slides overview What you just heard: J = σ (E – uB) a simple generator y 0 What you will hear next: • A complication arises from the Hall Effect …the flowing current also interacts significantly with B • Thus, we find: σ J = (E  B E uB) 2 x 0x e 0y I +  B e σ J = (E –uB+  B E ) 2 y 0y e 0x I +  B e • You can impose E or E by applying different electrical 0x 0y boundary conditions via electrode geometry ‹› Complications From the Hall Effect • Most MHD: charge is carried by electrons • By convention, electrons move against E • The electron current flow has an associate charge velocity u e • Must account for the interaction between u and B (Hall Effect) e j u u B B electrons i k electrons u + + u u + e + + + u x B Hall Effect u x B e No Current : u x B charge velocity = bulk velocity u Hall Effect “Tilts” the Field – How Much Caution: note this is a simplification for clarity; u may not be aligned with the yaxis e ‹› Some Cyphering • The velocity of electrons in a field is u =  (E + u x B ) (i) e e net e • The mobility  is related to conductivity as n e = σ e e e • The B field is assumed independent of current flow B = B k E net,y u =  (E i + E j + u x B) e e net,x net,y e Straightforward E net,x algebra and u = u i + u j Also assume e ex ey B substitutions in equation (i). J = J i + J j x y • Notice that J = n e u ; J = n e u x e ex y e ey σ J = (E –  B E ) e x 2 2 net,x net,y I +  B e Nomenclature σ 3 n = electron density (per m ) J = (E +  B E ) e y net,y net,x 2 2 e I +  B e e = fundamental charge 1.602 E19 C/electron m V  = electron mobility / E = E e s m net,x 0x E = E – u B net,y 0y ‹› The Simple Faraday Generator j y i x • The electrodes are long, continuous k z • Thus, E = 0 0x σ σ J = (E ) = (E uB) u y y,net 0y 2 2 2 2 I +  B I +  B e e Notice that the simple generator analysis (without Hall Effect) gave (J ) = σ (E uB) y 0y No Hall 1 Thus, the Hall Effect reduces the y current by: 2 2 I +  B e What is the magnitude of meaning of J x σ σ J = (0  BE ) = ( B E uB) =  B J 2 2 x e net,y e 0y e y I +  B 2 2 e I +  B e The Hall effect leads to an xcurrent that is  B times the ycurrent. e How big is  B (Next Slide) e ‹› The Magnitude of  B e Consider the xdirection force on the electron between collisions time  du u , e e mean F = m ; eE  m ( ) (i) e e x e  dt But, we also write: (ii)  E = u e x e, mean E = E i x (iii) Combining (i) and (ii) :  = e/m e e x We can also express a magnetic field in terms of a “cyclotron frequency” , next: y F = e(u x B) B e F B In the absence of other forces/collisions, the electron will experience a force at right angles to its motion  circular orbit r , consider the force: L u e 2 F = m u / r B e e L x Define cyclotron frequency u m e e 2 eu B = m u / r  = B e e e L r e  = u / r  B =  m /e (iv) L e L e B Combine (iii) and (iv) :  B =  “Hall parameter” e r L  1  lots of cycles before collisions  1  collide one cycle  1  lots of collisions before a cycle is complete ‹› Return to Faraday Generator E 0y y With  B = : Recall K = e uB x σ uB σ J = E uB = (K 1) y 0y 2 2 I + () I + () J =  (J ) x y For practical MHD 1  10… implies: 1) Significant reduction in J versus “simple” model y 2) Large axial (x) current flow – creates ohmic losses How could you improve this situation ‹› Segmented Electrodes Break up the xcurrent so that J = 0: x (why does this stop the Hall current) σ (1) J = (E  E ) = 0 x 2 x,net y,net 2 I +   u σ (2) J = (E +  E ) y y,net x,net 2 2 I +   From (1): E =  E (3) Individual loads x,net y,net y  x σ E σ y,net 2 2 2 2 z (out of plane) J = (E +   E ) = (1+  ) y 2 2 y,net y,net 2 2 I +   I +   J = σ E = σ (E uB) Same as “simple” generator y net,y o Notice that the axial voltage gradient is potentially very large (eqn. 3) What practical disadvantages exist with this concept ‹› It has no return path. Hall Generators Here, you use the axial hall current for power. Notice E = 0 by short circuit. yo (applied) E = E uB y,net yo Solve for currents and voltage as before. E =  uB open circuit oc short circuit LOAD Notice the open circuit voltage is larger than uB Disk Geometry (very clever) E  K = (Defined) ox H  uB LOAD Flow in u x B current (short circuit) + u Hall current B Flow out State one huge practical advantage of the disk (Hint: count the number of wires) ‹› An intermediate approach: Slanted (diagonal) electrode connections • Electrode connections establish E and E so that the 0x 0y E 0 electrons experience a force from the Hall field that is E 0y E 0x balanced by the E imposed by the electrodes. 0x • Thus, the current only flows vertically in the channel. • This balance exists at just one operating condition. Note that the E includes –uB in the ydirection. net The electrons move vertically in response to (E uB) 0y B points out of the page u Load Load Force from Note the slanted electrode frames visible in the duct (E uB) See Hill and Peterson 0y Force from “Mechanics and Hall effect Thermodynamics of Propulsion” Third Printing, Force from 1970, AddisonWesley Publishing, pp. 122. Helpful xelectric field From: Quarterly Technical Progress Report, July 1 – Sept 30, 1985, Component Development and Integration Facility Avg. drag Work performed under DOE DEAC07781D01745; Original Reports currently available only at NETL . discussion of the force Electron force from balance. velocity collisions ‹› Fluid mechanics and thermodynamics ‹› 1D Energy Balance Treating J as a negative scalar (current flowing down): Area Flow B Ohmic loss: A Velocity per u unit volume: R (i) Voltage: Height V = E b 0 Electrical power output from the volume: G b E per 0 unit Volume: volume: (ii) V = b A . Note: in a 2 or 3D problem the output is the dot product of vectors J E . Current: Resistance: 0 Care must be used on the sign of scalars in simple balance laws, and I = J A R= b/(As) distinguishing output (MHD generator) versus input (MHD pump) Mechanical energy input to the volume (xbody force times xvelocity u): xbody force The vector product points left Force on a charge Q = (e) per unit volume: Note u has only xcomponent; Charges per unit volume (iii) Thus, mechanical energy input per unit volume: Use the earlier definition of load factor K; recall 0 K 1, use (i – iii) ; As expected : (1) + (2) = (3) A summary of mass, momentum and energy (1D simplification, steady flow, constant area duct, neglect thermal conduction and viscous effects) For a comprehensive development of the governing equations, see for example: Hughes W.F., Young, F. J. (1989). The nd Electrodynamics of Fluids, 2 Edition, Robert E. Krieger Publishing. Again, treat J as a negative scalar Continuity: Familiar Momentum eqn: Note JB is the body force from last page. With negative J, what does this do to pressure along X Energy eqn: note this is written with the source term (right side) as the negative of the output defined on the last page. What does the source = (output) term do to the enthalpy of the flow along X J U The real situation: Describe the flow near the electrodes Electrodes ‹› Conductivity in the gaseous media • In conventional electrical generators, a long copper wire moves at a relatively slow speed through a modest magnetic field. • The conductivity of the gases in MHD is comparatively low, even when “seeded”, next slide. • MHD power extraction is practical only because of the high velocity U, strong field B, large volume conductor, and “adequate” conductivity 2 2 Power output density = J • E = σ U B K (K1) 0 7 Copper s = 6 x 10 Siemen/m Seeded MHD s = 10 Siemen/m Siemen = 1/ohm ‹› Gas Conductivity: Seeding Data from Swithenbank, J, (1974), Ionization Potentials Current flow depends on Magnetohydrodynamics and Electrodynamics of Combustion Systems, in “Combustion Technology: Some Species Ionization Modern Developments” Palmer, H.B., Beer, J.M. eds conductivity J = σ E potential Academic Press. Conductivity is for JP4oxygen combustion products with 1 K seed. E (eV) i Simple generator: Power density 100 2 2 Li 5.39 P = J • E = σ U B K (K1) 0 Na 5.14 K 4.34 The power density is maximum at Cs 3.89 2 2 K = ½ ∴ P = σ U B /4 He 24.58 max Ne 21.56 Reasonable Design: A 15.76 3 10MW/m = P ; UB = 2000V/M H 15.6 10 max 2 O 12.05 2 σ ≈ 10 S/m (S=Siemen = 1/ohm) O 13.61 N 15.6 2 Two points: NO 9.26 1. The magnitude of the conductivity with CO 14.1 temperature: operating temp 2600K CO 14.4 2 H O 12.6 2 2. The slope versus temperature: very sensitive 1 OH 13.8 1500 2500 3500 U 6.1 Temperature (K) J The real situation: Describe the conductivity near the electrodes Electrodes ‹› Condcutivity (S/m) Plasma Conductivity Experiments Fundamental Combustion Lab – NETL • Oxymethane Hencken burner used for high temperature (3000 K) flame generation – Began operation in Feb 2014 • K CO seeded in fuel ionizes to 2 3 create thermal plasma – K seed density quantified via KPLIF or spectroscopy Conductivity Probe Dye Laser • Conductivity measured point wise with Langmuir probe Nd:YAG Laser • Nd:YAG and dye lasers for optical diagnostics – Rayleigh thermometry Ar O 2 Hencken Preheater N 2 temperature measurement Burner Camera for OHPLIF, H 2 KPLIF, Rayleigh K CO – Quantitative OHPLIF 2 3 CH 4 Temperature Seeder CO Slide courtesy Nate Weiland, Clint Bedick, Rigel Woodside netl Reaction Mechanism • Elements K and e (Electron) added • Species K, K+, KO, KOH, OH, and Electron added • K/O/H reaction data added from: P. Glarborg, P. Marshall, “Mechanism and modeling of the formation of gasous alkali sulfates”, Combustion and Flame 141, 2239 (2005) K + O + M = KO + M K + OH + M = KOH + M K + HO2 = KOH + O K + HO2 = KO + OH K + H2O2 = KOH + OH K + H2O2 = KO + H2O KO + H = K + OH KO + O = K + O2 KO + OH = KOH + O KO + HO2 = KOH + O2 KO + H2 = KOH + H KO + H2 = K + H2O KO + H2O = KOH + OH KO + CO = K + CO2 KOH + H = K + H2O • Ionization reaction data added from: D.E. Jensen, G.A. Jones, “Reaction rate coefficients for flame calculations”, Combustion and Flame 32, 134 (1978) K+ + Electron + M = K + M (factor of uncertainty = 5) OH + Electron + M = OH + M (factor of uncertainty = 100) Slide courtesy Nate Weiland, Clint Bedick, Rigel Woodside netl 1D Flame Modeling in Cantera • Steady state simulation composition 0.45 CEA Equilibrium 0.4 matches CEA equilibrium fairly well; Cantera Steady State 0.35 Cantera case is burner stabilized flame, 0.3 noting T T : ad 0.25 – CEA: 3022 K 0.2 0.15 – Cantera: 2815 K (burner stabilized heat loss) 0.1 • Major species reach equilibrium in 1 mm 0.05 0 O2 H2O CO2 CO OH O H 0.6 0.01 CEA Equilibrium CH4 O2 H2O 0.5 Cantera Steady State CO2 CO OH 0.4 0.001 0.3 0.2 0.0001 0.1 0 0.00001 0 0.2 0.4 0.6 0.8 1 K KO KOH K+ OH e Axial Position (mm) Slide courtesy Nate Weiland, Clint Bedick, Rigel Woodside netl Species Mass Fraction Species Mole Fraction Species Mole Fraction Conductivity Seed Density Measurements • Conductivity Measurements • KPLIF Imaging – Using a commercial Langmuir Double – Need quantitative measure of seed Probe from Impedans, Ltd. density for correlation to plasma conductivity – Custom shaped platinum probe tips to 2 achieve 1 mm resolution in flame – KPLIF used by Lengel Linder (1990) – Shape of induced current profile vs. – Use Katom transition at 578.2 nm probe voltage differential used to (Monts, 1995) with existing laser dye obtain electrical conductivity, electron temperature, and ion density (Osaka, Hencken 2008; Wild, 2012) Burner Intensified Camera Custom platinum probe tips Power Monitor Probe Potential (V) 578.2 nm Cyl. Cyl. Sph. 1 mJ Lens Lens Lens Dye 532 nm Laser Nd:YAG Laser 2ω Gen 70 mJ Slide courtesy Nate Weiland, Clint Bedick, Rigel Woodside netl Probe Current (μA) Seeding – not the same today • Seeding is used to raise the conductivity of the combustion products. • The seed recovery was a major cost item and technical barrier in earlier MHD programs. • Would this change in a carbon capture scenario where the entire flue gas was sought for capture • Nonequilibrium plasma generated would be a game changer if : – Energy to generate was low enough. – Recombination rate was low. – Studies for propulsion applications, using nano second discharge pulses: about 2 order of magnitude greater ionization needed () Schneider, S. (2011). Annular MHD Physics for Turboject Energy Bypass”, AIAA20112230 ‹› Electrodes • Cooled electrodes must operate with high surface temperature to reduce quenching conductivity and heat loss near the walls. • Complicated by thermal, chemical, and electrical attack. • Some tests suggest reasonable life is possible in slag free (gas fuel operation) or with better slag removal. • Advances in materials and material processing for conductive solid oxides – Field Assisted Sintering Technology currently under investigation at NETL. • Current instability can lead to arcing – concentrated current flows – burning the surface. – State of the art electronics may reduce this problem Compress Sintered material can include Pulse DC Voltage conductive ceramics with unique properties S. Chanthapan, A. Rape, S. Gephart, Anil K. Kulkarni, J. Singh (2011). Industrial Scale Field Assisted Sintering Is an Emerging Disruptive Manufacturing Technology ADVANCED MATERIALS PROCESSES, pp. Cooled electrode from legacy test program, 2126, Published by ASM. Damage from arcing evident. ‹› Layout of a Power Plant Configuration What would be different in a carbon capture scheme What might be removed for future electric grids General arrangement plan and elevation view for the MHD plant Petrick, M., Shumyatsky, Y.A. (1977) ‹› Research issues/ideas • Various literature citations suggest different efficiency benefits of the concept. – Enthalpy extraction from the combustor to MHD exit is a key. – Conductivity vs. temperature in existing concepts limits on the enthalpy extraction. – Kayukawa (2004) reviews some interesting options for efficiency gains. • The actual component behavior and performance needs to be understood before development is pursued. – A ideal application for cybercombustion – Validated simulations – where do we get the data to validate • Can we develop a different approach for Direct Power Extraction – Unsteady flow (e.g. – periodic) – Nonequilibrium plasmas – how about behind a detonation Kayukawa, N. (2004). OpenCycle magnetohydrodynamic power generation: a review and future perspectives. Progress in Energy and Combustion Science , Vol 30, pp. 3360. ‹› MHD literature background – A source of validation data • The legacy MHD program was managed by DOE’s PETC (NETL predecessor). – In 1994, Congress wanted DOE to archive the information learned in the program so “costs and time to reestablish a viable MHD effort could be minimized” • Ninety boxed documents scanned and digitized at NETL during 2013. • This may be the largest set of information on MHD (for power) anywhere. • Contact NETL for information/access. ‹› Discussion/thinking/homework 1. Using a simple drawing, show what can happen to the Hall current in a Disk Generator what you add swirl to the inlet flow 2. Go to the internet and find the account of Michael Faraday trying to measure MHD voltage in the Thames river. – Estimate the voltage he should have measured – Can you think of any other situations in nature where MHD physics might be significant Disk generator Swirl B ‹› Summary • Direct Power Extraction from hightemperature oxyfuel flames is possible using magnetohydrodyanmics. • The concept has been explored in the past. • New drivers of CO2 capture and progress in oxyfuel combustion suggest a “new look” may be worthwhile. • In a combined cycle, the efficiency could be very high, but: – Power extraction is limited by conductivity versus lower temperature for traditional seeded flows – Need to address technical challenges of seed recovery, electrode life….or find a new innovation • Computational models offer a new approach to development that did not exist in earlier programs. • In progress: Simulations and validating experiments with new technologies, material processes. ‹›
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