Highly fuel efficient Automobiles via Promoted NO x Decomposition (PND) by Electro Catalytic Honeycomb (ECH)

Transcription

1 Highly fuel efficient Automobiles via Promoted NO x Decomposition (PND) by Electro Catalytic Honeycomb (ECH) Ta-Jen Huang, Professor (tjhuang@che.nthu.edu.tw) Department of Chemical Engineering National Tsing Hua University Hsinchu, TAIWAN 1

2 Issues How to achieve high fuel efficiency of automobiles Highest possible combustion temperature highest possible fuel efficiency [thermal efficiency] Complete combustion of all precursors of combustible pollutants Gasoline direct injection compression ignition (GDCI)engine fueled with light gasoline [light un branched open chain hydrocarbons (HCs)] no PM (particulate matter) *** Immediate solutions: Lean burn at best economy for gasoline engines Deleting EGR (exhaust gas recirculation) of diesel engines for highly increased fuel efficiency Zero pollution of CO, HCs & PM. The remaining issue is high NO x control. Removal of high to low concentration NO x under oxygen rich condition Removing very high NO x to near zero & completely oxidizing CO & HCs. NO x emission control at engine cold start No delay on NO x control. No consumption of reducing agent on NO x control No remain of the reducing agent, e.g. NH 3, to cause secondary pollution. All these issues solved by Electro Catalytic Honeycomb (ECH). 2 The real world applicability of PND by ECH is confirmed by experimental data shown in the following.

3 How to increase the fuel efficiency of current gasoline automobiles? For gasoline cars, simply change the Air Fuel Ratio from 14.7 (stoichiometric burn) to 16.2 (lean burn for Best Economy*) [*as shown on the right]. This only needs to replace the Three way Catalytic (TWC) converter with the ECH. 3

4 How to increase the fuel efficiency of current diesel automobiles? For diesel cars, deleting EGR to highly increase the fuel efficiency and also to highly simplify the aftertreatment system (to one ECH only). This only needs to replace the Diesel oxidation catalyst (DOC) converter to the ECH and For new cars: deleting all other units (including all sensors) in the aftertreatment system. For old cars: simply close EGR and stop operating all other units (including all sensors electrical heating) in the aftertreatment system. 4

5 Gasoline direct injection compression ignition (GDCI) engine for very high fuel efficiency with zero pollution EGR is not needed via ECH-deNOx GDCI can be for 2 & 4 cycle engine GDCI engine fueled with light gasoline [light un branched openchain hydrocarbons cetane] can have a fuel efficiency higher than current gasoline engine by 50% [S. Chu, A. Majumdar, Nature 488 (2012) 294; M.A. Ghadikolaei, Int. J. Res. Eng. Tech. 3 (2014) 335][a reduction of greenhouse gas emission by 50%] with zero pollution of CO & HCs without PM. Light un branched open chain HCs [cetane]: alkane molecules with a cetane number of 100 can ignite very easily under compression. Fuels with higher cetane number have shorter ignition delays more complete combustion less HCs & CO emission zero pollution higher combustion temperature higher expansion power higher NO x welcome by PND less engine knocking more smooth and quiet engine Current 2 cycle gasoline engine GDCI can increase the fuel efficiency by 60% & be pollution free 5 [intake fuel vapor intake air]

6 Electro Catalytic Honeycomb (ECH) deno x a real world device for Promoted NO x Decomposition (PND) Lower emission of greenhouse gases (GHG) needs higher fuel efficiency, i.e., lower fuel (energy) consumption cost down via PND. Currently, fuel efficiency is inhibited by difficulty in deno x technologies (SCR reductant supply, NSR storage capacity limit )to treat an exhaust with high NO x concentration. TWC can not treat lean burn exhaust. Higher combustion temperature leads to higher fuel efficiency but also higher NO x concentration in the exhaust. This is inevitable since the following reactions occur during combustion using air (N 2 + O 2 ): Initiation: O 2 2O (thermal cracking providing O for combustion) Chain reaction: O + N 2 NO + N; N + O 2 NO + O Termination: NO + O NO 2 This deno x difficulty has been resolved by PND with ECH promoted NO x decomposition for automotive emission control. 6

7 Electro-catalytic honeycomb (ECH) enables saving health & fuel Diesel exhaust causes cancer (WHO ) World Health Organization -- Diesel engine exhaust fumes are a definite cause of lung cancer. soot NOx outdoor air pollution also (WHO ) What should we do? Not driving diesel automobiles? Deleting EGR needing diesel particulate filter ** NO X soot trade off during EGR of diesel engine [A. Maiboom et al., Energy 33 (2008) 22] Old tech e.g. SCR (Selective Catalytic Reduction) Current diesel engines have sacrificed the fuel efficiency to lower NO x concentration by exhaust gas recirculation (EGR) Deleting EGR Increase combustion temperature in engine Increased NO x (%) soot: particulate matter (PM) Deleting EGR New tech (PND) preferred ** Note: The very small particulates, which can go through the filter, can penetrate deep into the lung. [American Lung Association/Calif.] Deleting EGR : saving both health & fuel Increasing fuel efficiency at least by burning more soot precursor in the engine reduce soot emission 7

8 The most efficient lean burn combustion processes are that of gasoline engine being converted from stoichiometric-burn to lean-burn & that of diesel engine deleting EGR for best economy >30% auto s fuel saving deno x by Electro-Catalytic Honeycomb (ECH) ECH looked the same as TWC (Three way Catalytic) converter -- for stoichiometric-burn engine ECH-deNO x reactor for lean-burn engine Engine exhaust pipe 8

9 promoted NO x decomposition electrochemical cell (generating emf) Electro-Catalytic Honeycomb (ECH) for lean NO x emission control The ECH works on Promoted NO x Decomposition (PND), i.e. emf-promoted direct NO x decomposition, NO x (NO+NO 2 ) N 2 +O 2 electrochemical cell (generating emf) promoted NO x decomposition 10: Electro-catalytic honeycomb (ECH) 11: Anode, forming ECH structure 111 & 112: outer & inner surface of the anode structure 12: Exhaust flow channel 13: Shell, covering the outer surface of the anode structure 20: Electrolyte layer, coated on the inner surface of the anode structure 30: Cathode layer, facing the exhaust flow channel for exhaust treatment Electromotive force (emf) is generated when there is a difference in oxidation/reduction potentials of Cathode/Anode and increases with potential difference. The EDC consists of two electrochemical cells. [electrochemical double-cell] ECH [EU patent EP & other patent applications] [as automotive catalytic converter] Typical deno x characteristics of PND are*: No consumption of reducing agent or else [purely decomposition] Care free Higher O 2 concentration results in higher deno x rate [due to increased promotion with emf] Simultaneous oxidation of hydrocarbons, CO & Particulate Matter (PM) feasible Higher NO concentration can result in higher deno x rate [obeying reaction kinetics] Highly fuel efficient engines Relatively constant deno x rate at very low NO x concentration [due to a specific reaction mechanism] near zero NO x emission can be achieved No temperature window & effective deno x from ambient temperature no treatment delay & deno x at cold weather Presence of H 2 O & CO 2 beneficial & SO 2 OK; no N 2 O formation No use of precious metal Economical *These characteristics are all based on the inventor s published results.

10 Typical experimental results on promoted NO x decomposition (PND) diesel exhaust [T.J. Huang et al., Appl. Catal. A (2012) 153] diesel exhaust diesel exhaust [T.J. Huang et al., Appl. Catal. B 110 (2011) 164] deno x rate ( mole NO x min -1 cm -2 ) ppm NOx 360 ppm NOx deno x rate ( mole NO x min -1 cm -2 ) Temperature ( C) no treatment delay & no temperature window Very high NO concentration preferred [T.J. Huang et al., Chem. Eng. J. 203 (2012) 193] Relatively-constant deno X rate at low NO X region These are typical characteristic curves for promoted NO x Decomposition for lean deno x of combustion processes 10

11 deno x characteristics of emf promoted decomposition of NO x Very high NO concentration preferred Highly fuel efficient engines & ECH deno x does not need any control on diesel engine operation No consumption of reductant or anything else Care free Effective at high O 2 concentration the higher the better Simultaneous oxidation of hydrocarbons, CO & PM feasible No temperature window & effective deno x from ambient temp no treatment delay & deno x at cold weather Relatively constant deno x rate at very low NO x concentration near zero NO x emission can be achieved ECH similar size to SCR converter (shown next) Very compact size for automobiles No use of precious metal Economical H 2 O & CO 2 beneficial & SO 2 OK; no N 2 O formation Zero pollution 11

12 Real world automotive applications For SCR deno x onboard of heavy duty Diesel vehicles with commercial V 2 O 5 /WO 3 TiO 2 catalyst on standard metal substrates with a cell density (~honeycomb) of 400 cpsi, the highest activity for 1000 ppm NO at 52,000 h 1 & 400 C is 1.24 μmole NO min 1 cm 2 [O. Krocher, M. Elsener, Appl. Catal. B: Environ. 75 (2008) 215] ECH-deNO x double this as shown on the right Note: SCR deno x activity of μmole NO min 1 cm 2 was reported for treating 250 ppm NO with catalyst plate. [X. Fan et al., Catal. Commun. 12 (2011) 1298] ECH-deNO x comparable as shown on the right ECH-deNO x on real engine exhaust The ECH-deNO x activity is comparable to the real-world automotive SCR-deNO x activity. 12

13 Shortages in current automotive deno x technologies Three way catalytic (TWC) converter (honeycomb) Engine operation must be adjusted to accommodate the exhaust treatment. The usage of precious metals. Stoichiometric burn low fuel efficiency. Treatment delay the catalyst is not effective at ambient temperature and thus a heating period is required. [for all current deno x via reduction or storage] Exhaust Gas Recirculation (EGR) To result in low NO x concentration in exhaust at the expense of fuel efficiency. Selective Catalytic Reduction (SCR) The consumption of reducing agents, e.g., ammonia in urea based SCR (costly & inconvenient refilling). The formation of N 2 O from NO, a strong greenhouse gas. with presence of reducing agent NO x Storage and Reduction (NSR) lean NO x trap The consumption of fuel for NO x treatment. Limited storage capacity. Electrochemical NO x Reduction with applied voltage (electrical current) The consumption of electricity with low current efficiency. 13

14 Principle for emf-promoted decomposition NO x : NO & NO 2 NO N + O (previously needing removal by reductant NH 3,CO,HCs) SCR,TWC N 2 O 2 (continuously promoted oxygen desorption PND) NO 2 NO + O O 2 2O SO x : SO 2 & SO 3 SO 2 1/8S 8 + 2O O 2 (promoted oxygen desorption) SO 3 SO 2 + O promoted NO x decomposition--pnd promoted SO x decomposition--psd continuously promoted oxygen desorption by the presence of a voltage (an electromotive force, emf) 14

15 Publications supporting lean deno x by promoted NO x decomposition (PND) underlined is the inventor of the ECH. Ta Jen Huang, C.L. Chou, Electrochem. Comm., 11 (2009) Ta Jen Huang, C.L. Chou, J. Power Sources, 193 (2009) Ta Jen Huang, C.L. Chou, J. Electrochemical Society, 157 (2010) P28 P34. Ta Jen Huang, C.L. Chou, Chem. Eng. J., 160 (2010) Ta Jen Huang, C.L. Chou, Chem. Eng. J., 162 (2010) Ta Jen Huang, I.C. Hsiao, Chem. Eng. J., 165 (2010) Ta Jen Huang, C.Y. Wu, Y.H. Lin, Environmental Science Technology, 45 (2011) Ta Jen Huang, C.Y. Wu and C.C. Wu, Chem. Eng. J., 168 (2011) Ta Jen Huang, C.Y. Wu, C.C. Wu, Electrochem. Comm., 13 (2011) Ta Jen Huang, C.Y. Wu, C.C. Wu, Chem. Eng. J., 172 (2011) Ta Jen Huang, C.Y. Wu, S.H. Hsu, C.C. Wu, Energy Environmental Science, 4 (2011) Ta Jen Huang, C.H. Wang, Chem. Eng. J., 173 (2011) Ta Jen Huang, C.Y. Wu, S.H. Hsu, C.C. Wu, Appl. Catal. B: Environmental, 110 (2011) Ta Jen Huang, C.Y. Wu, Chem. Eng. J., 178 (2011) Ta Jen Huang, C.H. Wang, J. Electrochemical Society, 158 (2011) B1515 B1522. Ta Jen Huang, S.H. Hsu, C.Y. Wu, Environmental Science Technology, 46 (2012) Ta Jen Huang, C.Y. Wu, D.Y. Chiang, C.C. Yu, Chem. Eng. J., 203 (2012) Ta Jen Huang, C.Y. Wu, D.Y. Chiang, C.C. Yu, Appl. Catal. A: Gen., (2012) Ta Jen Huang, C.Y. Wu, D.Y. Chiang, J. Ind. Eng. Chem., 19 (2013) Power generation with NO x substituting O 2 -- NO x decomposition in rich oxygen -- promoted by both voltage & oxygen-ion migration NO x decomposition at (promoted by) open-circuit voltage (electromotive force, emf) 15

16 emf open circuit voltage (OCV) of fuel cell no anode fuel needed with applied voltage oxygen pumping Anode fuel: HCs etc. with power generation solid oxide fuel cell (SOFC) continuous presence of an OCV for power generation 16

17 O 2 + 2e 2O Oxygen can be simply desorbed 2O O 2 without discriminating the source of O NO x O Schematic description of bi pathway dominated oxygen reduction on SOFC cathode [M. Gong, R.S. Gemmen, X. Liu, J. Power Sources 201 (2012) 204] 17

18 at high enough NO concentration Lean deno x by emf-promoted decomposition of NO x NO N + O H 298 = Kcal/mole (exothermic) NO 2 N + O 2 H 298 = -8 Kcal/mole 2NO +[] [ ] N-[O] [O]-N N-[O] [O]-N N 2 + [O] [O] [O] [O] O 2 +[] [ ] 2nd order r N2 = k [NO] 2 Higher NO concentration is highly preferred (according to kinetic law) 2NO N 2 + O 2 The presence of a voltage weakens the chemisorptive bond strength of the O species. [C.G. Vayenas, S. Bebelis, Catal. Today 51 (1999) 581] facile desorption of oxygen for emf-promoted decomposition of NO x 18

19 Principle and proof for emf-promoted decomposition of NO N 2 + O 2 N 2 formation rate ( mol min -1 g -1 ) The deno x rate via emf-promoted decomposition is two orders higher than that over conventional catalyst via direct decomposition solid oxide fuel cell cell at OCV catalyst powder Inlet NO concentration ( ppm ) Inlet NO x concentration (ppm) OCV: open-circuit voltage (solid oxide fuel cell operation without consuming anode fuel, i.e., reductant) ~ electromotive force (emf ) Over the catalyst in a conventional reactor, the formed N species from direct NO decomposition can be easily associated to form N 2 ; however, the formed O species is strongly adsorbed and facile desorption of the O solid oxide fuel cell:lsc GDC cathode catalyst:lsc GDC (La 0.6 Sr 0.4 CoO 3 Ce 0.9 Gd 0.1 O 1.95 ) 14% O 2, 10% H 2 O, 10% CO 2 ; 600 o C species as O 2 into the gas phase is very important. 19 deno x rate ( mole NO x min -1 g -1 ) ECH vs. Catalyst honeycomb ECH Catalyst Room temperature ECH can have a relatively-constant deno x rate while Catalyst honeycomb cannot. [Y. Teraoka et al., J. Chem. Soc. Faraday Trans. 94 (1998) 1887] deno x rate ( mole NO x min -1 g -1 )

20 The fields for applications ofech The application fields of ECH Light Duty Vehicles and Trucks Gasoline passenger cars & Motorcycles Diesel passenger cars (ECH deno x ) Pickup trucks Heavy Duty Highway Engines and Vehicles Compression ignition (CI) engines [GDCI] Urban buses Trucks (ECH deno x ) Long distance buses Recreational vehicles Long haul trucks Spark-ignition (SI) engines Lean burn Nonroad Engines and Vehicles Aircraft CI engines (underground mining, sea oil platform ) Locomotives (ECH deso x & deno x ) Marine CI engines Recreational engines and vehicles Stationary sources Power plant boilers (burner), Gas turbines Fertilizer plants, Cement plants Large boilers (ECH deso x & deno x ) Medium boilers (in Hospitals, Care centers ) Small boilers (Household boilers) Other Combustion exhausts (ECH deso x & deno x ) Schematics of ECH EDC 10: ECH; 11: anode, forming the structure of the ECH; 111 and 112: outer and inner surface of the anode structure, respectively; 12: exhaust flow channel; 13: shell, covering the outer surface 111; 20: electrolyte layer, coated on the inner surface 112; 30: cathode layer, facing the exhaust flow channel for exhaust treatment. (EU patent EP ) Seal* EDC plate for PND testing with or without metal plate Electrochemical double cell (EDC) Electro catalytic honeycomb (ECH) SO 2 1/8S 8 +O 2 Metal plate * The anode side should be enclosed completely by dense layer (seal).

21 Concluding Remarks Lean deno x by promoted NO x decomposition (PND) no consumption of reductant (no NH 3 slip) or other resource Higher O 2 concentration preferred for deno x simultaneous oxidation of hydrocarbons (HCs), CO & Particulate Matter (PM) feasible Very high NO concentration preferred for deno x very high temperature in engine allow deleting EGR minimize HCs, CO & PM formation in engine Relatively constant deno x rate at very low NO x concentration near zero NO x emission can be achieved No temperature window & effective deno x from ambient temperature no treatment delay Thus, especially with GDCI (light Gasoline Direct injection Compression Ignition) engines, ECH deno x can result in zero pollution of automobiles to help Creating Healthy, Livable Cities. 21