Experimental Investigation of the Entrained Flow Gasification of a Bituminous Coal and a Lignite

Transcription

1 Experimental Investigation of the Entrained Flow Gasification of a Bituminous Coal and a Lignite M.Sc. Andreas Geißler, M.Sc. Markus Steibel, M.Sc. Federico Botteghi, Prof. Hartmut Spliethoff Institute for Energy Systems Technical University of Munich 8th International Freiberg Conference on IGCC & Xtl Technologies

2 Agenda Motivation and Aim of this Work 2 Experimental Procedure 3 Experimental Equipment and Experiment Matrix Pressurized High Temperature Entrained Flow Reactor (PiTER) High Pressure Thermogravimetric Analyzer (PTGA) 4 Results 5 Conclusion and Future Aspect 2

3 Motivation and Aim of this Work Motivation Pyrolysis CO CO 2 Gasification O 2 CO 2 Reaction gas H 2 O Fuel H 2 Soot C x H y Tars CO H 2 O Synthesis gas H 2 Ash Entrained flow gasification for high conversion rates Fuel properties (e.g. coal rank) and gasification conditions influence conversion behavior Detailed knowledge of occurring phenomena during gasification important for design and performance of efficient gasifiers Experimental data for coals of different rank at conditions comparable to industrial gasifiers necessary for understanding the conversion process and designing gasifiers 3

4 Motivation and Aim of this Work Aim of this work Experimental investigation of entrained flow gasification for two fuels at high temperatures (up to 6 C) and high pressures (up to 2. MPa) Comparison of devolatilization and gasification behavior (overall conversion) Focus on char properties (reactivity and surface area) of the collected samples Comparison of char surface area at different pyrolysis conditions Comparison of intrinsic kinetic data of representative char samples determined in thermogravimetric analyzers (Regime I) Determine and compare the behavior of the fuels in regard to thermal annealing Obtain insights of the gasification behavior of two fuels at condition comparable to industrial scale gasifiers Entrained Flow Conditions TGA: Intrinsic Parameters 4

5 2 Experimental Procedure Fuel Ash Moisture Volatile Content Content Carbon Hydrogen Nitrogen Sulfur wt% (dry) wt% (ar) wt% (dry) wt% (dry) wt% (dry) wt% (dry) wt% (dry) Bit. Coal Lignite Pressurized Entrained Flow Reactor Devolatilization and Gasification Experiments Char Sample Lab Analysis Proximate and Ultimate Analysis Surface Area Measurement Thermogravimetric Analyzers Char gasification kinetics Obtain intrinsic kinetic data for different gasification agents 5

6 Reaction zone Gas Preheating 3 Experimental Equipment Pressurized High Temperature Entrained Flow Reactor (PiTER) Gas inlet Fuel Feeding Technical Data Gasification Agents Ar, N 2, O 2, CO 2, H 2 O Max. Temperature 8 C Reaction tube Max. Pressure 5. MPa Evaluation: Ash-Tracer-Method Quench Sampling probe X Overall = m,daf m daf m,daf = x,ash x Ash x,ash 6

7 3 Experimental Equipment Thermogravimetric Analyzer Gas inlet Technical Data Sample Heating Element Gasification Agents Ar, N 2, O 2, H 2, CO 2, H 2 O, CO Max. Temperature C Max. Pressure 5. MPa Up to % vol. of gasification agent concentration Beam Balance X t = m m t m r obs = m t dm t dt 7

8 3 Experiment Matrix PiTER: Pyrolysis experiment: Gas residence time between s in N 2 Gasification experiments: Constant O/C-Ratio of CO 2 -Gasification: Constant partial pressure of.2 MPa Thermogravimetric Analyzers: PTGA: Lignite and Bit. Coal char from PiTER experiments at similar conditions Investigated temperatures determined by heating rate experiments ATGA (atmospheric): Pyrolysis chars: 5% O 2 ; constant temperature: 375 C Lignite, 425 C Bit. Coal Reactivities in relation to reactivity of reference char (according to DIN 572) 8

9 Overall Conversion [-] Overall Conversion [-] 4 Results Pyrolysis Experiments at Different Pressures and Temperatures Bit. Coal - Pyrolysis Lignite - Pyrolysis C;.5 MPa 2 C;. MPa 2 C; 2. MPa 4 C;.5 Mpa C;. Mpa 2 C; 2. Mpa 4 C;.5 Mpa 4 C;. Mpa 4 C; 2. Mpa 6 C;.5 Mpa Residence Time [s] 2 3 Residence Time [s] Higher volatile content of lignite Bit. Coal: Release of volatiles completed for every investigated residence time Lignite: Influence of temperature and residence time detectable 9

10 Specific surface area [m 2 /g] Specific surface area [m 2 /g] 4 Results Pyrolysis Experiments at Different Pressures and Temperatures 5 Bit. Coal - Surface area 5 Lignite - Surface area C;.5 MPa 2 C;. MPa 2 C; 2. MPa 4 C;.5 MPa C;. MPa 2 C; 2. MPa 4 C;.5 MPa 4 C;. MPa 4 C; 2. MPa 6 C;.5 MPa Residence Time [s] 2 3 Residence Time [s] Surface areas decrease with increasing residence time Bit. Coal: Higher temperature leads to a lower surface area Lignite: Chars more sensititve to reaction conditions

11 Overall Conversion [-] Overall Conversion [-] 4 Results O 2 -Gasification at Different Temperatures: Bit. Coal - O 2 -Gasification 2 3 Residence Time [s] 2 C;.5 MPa 4 C;.5 MPa 6 C;.5 MPa Lignite - O 2 -Gasification 2 3 Residence Time [s] C;.5 MPa 4 C;.5 MPa 6 C;.5 MPa Temperature and residence time influence detectable Bit. Coal: Overall conversion of 8% reached Lignite: Overall conversion of 95% reached

12 Overall Conversion [-] Overall Conversion [-] 4 Results CO 2 -Gasification at Different Pressures and Temperatures: Bit. Coal - CO 2 -Gasification 2 3 Residence Time [s] 2 C;.5 MPa 4 C;.5 MPa Lignite - CO 2 -Gasification 2 3 Residence Time [s] C;.5 Mpa C;. MPa C; 2. MPa 4 C;.5 Mpa 4 C;. MPa Temperature and residence time influence detectable Bit. Coal: Temperature of 2 C too low for the CO 2 -Gasification Lignite: More reactive than Bit. Coal 2

13 r oserved (g/g/min) r oserved (g/g/min) 4 Results HPTGA: Char from PiTER-Experiments (2. MPa, 2 C, 2.5 s) Determine intrinsic kinetic data Modeling with Arrhenius- and Power-Law Approach r observed X, T, p i = S X r int T p i n = S X k exp E A R T p i n Heating rate experiment for determining temperatures for isothermal experiments: Heating rate experiment CO 2 Heating rate experiment H 2 O KOL.5 KOL.2 TBK. TBK Temperature [ C] Temperature [ C] Reactivity of Lignite significantly higher than for Bit. Coal Reactivity towards H 2 O-gasification for both fuels higher than to CO 2 -gasification 3

14 Carbon Conversion [-] Carbon conversion [-] 4 Results HPTGA: Char from PiTER-Experiments (2. MPa, 2 C, 2.5 s) Lignite: CO 2 -Gasification (675 C, 2. MPa) Residence time [min].5 MPa. MPa 2. MPa Bit. Coal: CO 2 -Gasification (8 C, 2. MPa) Residence time [min].5 MPa. MPa 2. MPa Fuel Activation Energy [kj/mol] Reaction order [-] CO 2 H 2 O CO 2 H 2 O Bit. Coal Lignite Reaction order: Bit. Coal more sensitive to partial pressure of gasification agent Activation energy: Less temperature dependency of the reaction with lignite 4

15 4 Results ATGA: Thermal Annealing of Different Pyrolysis Chars Reactivites of char samples is reduced by thermal annealing: 6 Bit. Coal - Annealing 6 Lignite - Annealing r intrinsic/ r Ref,intrinsic Residence time 2 C;.5 MPa 2 C;. MPa 2 C; 2. MPa 4 C;.5 MPa r intrinsic /r Ref,intrinsic Residence time C; 2. MPa 2 C;. MPa 4 C;.5 MPa 4 C;. MPa 4 C; 2. MPa 6 C;.5 MPa Reactivity reduced with increasing temperature and residence time during pyrolysis Lignite much more sensitive to temperature and residence time influence No pressure influence detectable 5

16 5 Conclusion and Future Aspects Conclusion Data of experiments at high temperature and pressure are presented Pyrolysis behavior and surface area development shows higher sensitivity to operation parameters for the lignite than for the bituminous coal Higher reactivity of lignite Higher conversion of the lignite at equal conditions Obtained data can be used for designing large scale applications according to the fuel rank Future Aspects Transfer intrinsic kinetic data with effectiveness-factor approach to entrained flow conditions (Regime II and III) Use data for model validation Test further coals (other ranks such as anthracite) or biomass Create databank with kinetic data and further parameters relevant for gasification 6

17 Thank you for your Attention! M.Sc. Andreas Geißler +49 () Institute for Energy Systems Technical University of Munich This work is part of a project supported by the German Federal Ministry of Economics and Technology and industrial partners (AirLiquide, RWE, EnBW, Vattenfall and Siemens Fuel Gasification) under the Contract Number: A. 7