Challenges in methanation for biomass based SNG-production

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1 Challenges in methanation for biomass based SNG-production Dipl.-Ing. Thilo Henrich Engler-Bunte-Institut GERG Workshop, Session 5, Other R&D Brussels, 5 th June

2 Structure Motivation Theoretical considerations Monolithic reactors Summary 2

3 Motivation Problems: Finiteness of fossil fuel resources High anthropogenic greenhouse gas emissions Possibilities for the gas industry? Solutions: Improvement and optimisation of energy efficient technologies Methane from renewables Biogas State of the art SNG To be developed 3

4 Motivation Biogas/ Biomethane Manure Biodegradable waste Energy plants Straw Wood Fermentation Low lignin and high water content High lignin and low water content Upgrading Thermochemical CH 4 Gasification Gas conditioning Methanation Upgrading Advantages of the thermo-chemical way: Decoupling of production and consumption Utilisation of non-fermentable biomass SNG directly usable as biogenic fuel (CNG) Adaptation of known coal technology possible High energetic efficiency 4

5 Motivation Efficiencies: Power generation by steam turbine Biomass (100 %) Available heat Combustion (η KW = 85 %) (85 %) Steam turbine (η el = 29 %) Waste heat (15 %) Electricity (25 %) Waste Heat (60 %) Power generation by gasification Biomass (100 %) Clean Gasification (η KG = 72 %) synthesis gas Gasengine (η el = 35 %) (72 %) Waste heat (28 %) Electricity (25 %) Waste Heat (47 %) SNGproduction Biomass (100 %) Clean Gasification (η KG = 72 %) synthesis gas Conditioning (η = 83 %) (72 %) Waste heat (28 %) SNG (60 %) Waste Heat (12 %) The total efficiency depends on the recovery of the waste heat 5

6 SNG-production from coal 6

7 Motivation Great Plains Gasification Plant Power plant Coal mine Synfuel Plant 7

8 Motivation Up to now the only commercially operated plant for SNG-production Byproducts: Carbon dioxide, ammonia, ammonia sulphate, phenol, cresylic acid 2 GW th Source: J.M. Panek, J. Grasser, Report, US DOE, (2006) 8

9 Theoretical considerations for methanation 9

10 Theroretical considerations From the new feedstock wood new boundary conditions arise: Coal is produced centrally Wood is produced decentrally Limited wood availability demands highly efficient technologies For wood as a natural product a sustainable wood economy has to be established Wood gasification plants have to be smaller than coal gasification plants A process development for the feedstock wood for plants up to 100 MW (thermal) is necessary 10

11 Theroretical considerations Process based on the gasification of wood: Compression to injection pressure Raw gas Dust removal Synthesis gas cleaning CO-Shift Methanation SNG conditioning Gas pipeline Alkali metals Tars Halogens Sour gases Heavy metals Adjustment of the H 2 /COratio CH 4 - production CO 2 -removal Drying (Adjustment of the heating value) Catalytic process steps 11

12 Theroretical considerations Reactions involved in methanation: CO-Methanation: CO 2 -Methanation: WGS-Shift: Boudouard-reaction: CO + 3 H 2 CO H 2 H 2 O + CO 2 CO CH 4 + H 2 O CH H 2 O CO 2 + H 2 CO 2 + C (s) Properties of the methanation reaction: Highly exothermic: Formation of methane favoured at low temperatures Decrease in mole-number: An increase in pressure results in a higher methane-yield A slight excess in hydrogen and addition of water prevents carbon deposition from the gas phase Methanation of carbon dioxide only takes place at low CO-partial pressures 12

13 Theroretical considerations Thermodynamics of methanation: Methanation of synthesis gas (allothermic fluidised bed gasification with water): CO-conversion X CO p = 1 bar p = 10 bar Educt gas (dry): CO: 14 vol.-% CO 2 : 27 vol.-% H 2 : 45 vol.-% CH 4 : 9 vol.-% C 3 H 8 : 4 vol.-% N 2 : 1 vol.-% Aspired temperature range p = 50 bar p = 100 bar Temperature T in C Temperature range is restricted! Only small support of methane yield at elevated pressure! 13

14 Theroretical considerations Reactor types that have already been successfully used in methanation: Fluidised bed reactors Offer the advantage of a very intensive heat- and mass transfer; therefore an almost isothermal mode of operation is possible Disadvantageous is the abrasion of the fluidised bed material, which has an adverse effect on the performance of the fluidised bed Currently the PSI focuses on methanation in fluidised beds (PSI: Paul- Scherrer-Institut, Villigen, CH) Fixed bed reactors: Offer the advantage of established construction technology (but expensive) Of adverse effect are the poor heat transfer properties formation of hot spots thermal stress degradation of the catalyst Currently the ZSW focuses on the Fixed-bed-methanation ( Zentrum für Sonnenenergie und Wasserstoff-Forschung, Stuttgart, FRG) 14

15 Monolithic reactors 15

16 Monolithic reactors General design: A system of parallel, catalyst-coated channels Application-areas for monoliths: Exhaust emission control Automotive flue gas cleaning Further application-areas: Strongly endo- or exothermic reactions Flue gas conditioning in the decentralised energy supply by fuel cells Reforming 200 cpsi 1) 400 cpsi 1) Channels per square inch 16

17 Monolithic reactors Special case: Metallic monoliths Advantages: High radial heat conductivity An homogeneous temperature profile Less hot spots Longer catalyst lifetime Low abrasion of the catalyst Low pressure drop Adjustable geometric parameters Numerous reactor concepts can be realised Challenges: Development of a efficient reactor cooling concept Coating of the monolith with the catalyst Reactor design and industrial production Choice of the monolith material 17

18 Monolithic reactors Influence of the material on the maximum reactor diameter: Requirements: T max (r = 0) = 350 C (623 K) T aussen (r = R) = 200 C (473 K) 320 Temperature T in C Al 2 O 3 -Fixed Bed λ eff,rad = 8 W/(m K) r max = 26 mm Stainless Steel λ eff,rad = 10 W/(m K) r max = 29 mm Aluminium λ eff,rad = 96 W/(m K) r max = 89 mm Radius r in m 18

19 Monolithic reactors Estimation of the reactor size Initial point for calculations: Gasification of wood with steam in a fluidised bed Power of the gasifier: 10 MW (thermal) Methanation reactor: Metallic monolith coated with a Nicatalyst (Materials: Steel, Aluminium) Mass- & Heat streams: Educts stream: 9650 m 3 /h (1 bar, 300 C) Thermal power of the reactor: 1.5 MW Monolith: Residence time in the reactor: 0.5 s Number of channels: 1.2 x 10 6 Radial heat conductivity: k St = 2 W/(m K) k Al = 16 W/(m K) Maximum reactor diameter: d St = 48 mm d Al = 144 mm Educt Hot cooling medium Cold cooling medium Product Methanation reactor: Reaction volume: 1.35 m 3 Number of parallel monoliths: Steel ~ 3420, Aluminium ~ 380 source.: 19

20 Summary SNG-production is an interesting way for the gas industry to produce gaseous fuels Wood/lignin-rich biomass is a promising feedstock, which is not used for SNG-production up to now The methanation of a clean synthesis gas is an established process for the feedstock coal The methanation can be carried out at low temperatures with a high CO-conversion The monolith material can enhance the heat transfer properties significantly, which simplifies the reactor design 20

21 Thank you for your attention! Do you have questions? Dipl.-Ing. Thilo Henrich Phone: / ; 21

22 Gesamtprozess Vergasertypen Festbett Partikelgröße: < 400 mm Betriebstemperatur: < 1000 C Betriebsdruck: beliebig Anlagengröße: < 10 MW th Brennstoff Vergasungs-/ Fluidisierungsmedium Zyklon Brennstoff Vergasungs-/ Fluidisierungsmedium Brennstoff Syntheserohgas Syntheserohgas Syntheserohgas Vergasungsmedium Syntheserohgas Brennstoff Vergasungsmedium Wirbelschicht Partikelgröße: < 50 mm Betriebstemperatur: < 800 C Betriebsdruck: beliebig Anlagengröße: MW th Hoher Methananteil im Synthesegas möglich! Flugstrom Partikelgröße: < 100 µm Betriebstemperatur: > 1000 C Betriebsdruck: beliebig Anlagengröße: MW th Brennstoff Schlacke Vergasungsmedium Syntheserohgas 22

23 Methanisierung Katalysatoren Katalytisch aktiv sind: Elemente der VIII. Nebengruppe (sog. Eisen- und Platingruppe) sowie Silber und Molybdän Aktivitäts-Reihenfolge: Selektivität zu CH 4 : Preis pro kg (roh): Ru > Fe > Ni > Co > Rh > Pd > Pt > Ir Pd > Pt > Ir > Ni > Rh > Co > Fe > Ru Rh > Pt > Pd > Ir > Ru > Co > Ni > Fe Nickel ist der beste Kompromiss bezüglich Aktivität, Selektivität und Preis, stellt aber hohe Anforderungen an die Reinheit des Synthesegases (bezüglich Halogenund Schwefelverbindungen), Gefahr der Nickelcarbonyl-Bildung bei Temperaturen < 250 C Stand: 13. März

24 Wärmeübertragung Berechung der radialen Wärmeleitfähigkeit Λ r Ansatz Festbett 1) : Λ λ r f = λ λ s f + Pe d K' Angaben: λ f = 0,176 W/(m K); Wärmeleitfähigkeit des Fluids λ s = 8 W/(m K); Wärmeleitfähigkeit des Feststoffes (Al 2 O 3 ) Pe d = 0,8; Peclet-Zahl K = 7,12; Konstante Ansatz Metallische Wabe 2) : Λ r = λs Angaben: ( 1 ε + ξ) + ε + ξ λ w λ w ( 1 ε + ξ) + ε + ξ ( 1 ε + ξ) + ( ε + ξ ε ) λ s ε + λ s ε λf + λ λ S = 25; 236; 401 W/(m K); Wärmeleitfähigkeit des Wabenmaterials (Edelstahl 1), Aluminium 1), Kupfer 1) ) ε = 0,47 3) ; Leerraumanteil der metallischen Wabe ζ = 0; Porosität des Katalysatorträgers (Anmerkung: kein Washcoat) s ε 1 1) VDI-Wärmeatlas 2) G. Groppi, E. Tronconi, Catalysis Today, 69, 63-73, (2001) 3) X. Huang, Studienarbeit, Engler-Bunte-Insititut,,

25 SNG-Erzeugung in der TBM Holzvergasung Ziel: Selektive CO-Methanisierung bei nahezu atmosphärischem Druck zur SNG-Erzeugung in metallischen Wabenreaktoren 25

26 SNG-Erzeugung in der TBM Förderung durch die Landesstiftung Baden-Württemberg Verbundpartner: ZSW, Stuttgart DVGW-Forschungsstelle, Gastechnologie Zielsetzung: Förderzeitraum: EBI/DVGW: Energetisch effiziente Bereitstellung eines einspeisefähigen Erdgassubstitutes auf Basis der Vergasung von Biomasse 3 Jahre Katalysatorauswahl für Methanisierung Laborversuche zur Methanisierung in metallischen Wabenreaktoren Erstellung eines Verfahrenskonzeptes unter Einbindung der metallischen Wabenreaktoren Methanisierungsversuche mit Gas aus der Holzvergasungsanlage der Technologieplattform Bioenergie und Methan 26

27 Known processes Due to the energy crises in the 1970s numerous processes for SNG-production on basis of the gasification of coal or refinery residues have been developed Name/ Develo per Reactor -type ADAM & EVA Cono- Meth/ Super- Meth CRG Gassynthan Hygas Lurgi TREMP Bi- Gas Comflux IRMA FB FB FB FB FB FB FB WS WS RB- WÜ stages Status of develop ment pressur e (in bar) Pilot Pilot Pilot Pilot Technikum Temperature (in C) Pilot Demo/ Pilot n.s. n.s. Pilot Com m. Chem Systems Bubblecolumn ~ n.s ~ k.a FB: Fixed Bed, FLB: Fluidised Bed, RB-WÜ: Rohrbündelwärmeübertrager 30 ~ ~ 340 In most instances adiabatic, multi-stage fixed bed-reactors have been used 27

28 Wärmeübertragung Einfluss des Materials und der Geometrie auf Λ r Radiale Wärmeleitfähigkeit Λ r Wabe: ε = 0,47 Schüttung aus Al 2 O 3 mit ε = 0,42 Hohlraumanteil ε 28