CFD simulations of an industrial scale entrained flow gasifier: Influence of gasifier design and operating conditions

Transcription

1 Lehrstuhl für Energiesysteme Fakultät für Maschinenwesen Technische Universität München CFD simulations of an industrial scale entrained flow gasifier: Influence of gasifier design and operating conditions Stefan DeYoung Lehrstuhl für Energiesysteme Technische Universität München 9th International Freiberg Conference on IGCC & XtL Technologies 3-8 June 2018, Berlin

2 Content Introduction / Research project HotVeGas CFD modeling approach and validation procedure Definition of the industrial scale test case Results and discussion Conclusion and outlook 2

3 Project: HotVeGas III FLEX Experimental investigations and modeling of coal gasification and gas cleaning Motivation: Development of a fuel database with focus on gasification kinetics as a basis for gasifier design and operation Evaluation of innovative IGCC/polygeneration concepts for high fuel, operational, and product flexibility Fuel particles, reaction gases Product gases Research focus: Studies of gasification kinetics with the pressurized high temperature entrained flow reactor (PiTER) CFD modeling of gasification processes Process and energy system analyses Condensation behavior of trace elements Fixed bed reactor kinetics WGS membrane reactor Volatiles release Gasification reactions Project framework: 01/ /2019 Funded by BMWi and industry partners (RWE, Air Liquide) Cooperation with TUBA Freiberg, FZ Jülich, and GTT Deposition, slag flow Deposition, condensation corrosion 3

4 CFD simulation of entrained flow gasification Goal: Prediction of conversion rates and gas composition in entrained flow gasifiers (dry-fed, oxygen-blown) CFD model development (UDFs) CFD model validation (lab scale, < 100 kw th, 1 20 bar, C) Large scale CFD simulation (Siemens type, MW th ) Source: Schingnitz (2005) 4

5 Modeling approach ICEM CFD + ANSYS Fluent: 3D-Hexa, RANS, SIMPLE, 2nd Order Turbulence: RKE or SKE, Std. WF CO CO 2 Particle tracking: DPM, DRWM H 2 C x H y Particle and gas radiation: DO, WSGGM Soot H 2 O Tars Turbulence chemistry interaction: EDC, ISAT Gas phase reactions: Modified J-L mechanism O 2 CO 2 H 2 O Volatiles release: Single rate or two comp. rates Char reactions: UDFs (PR_RATE, SCALAR_UPDATE) Measured intrinsic rates (nth order, O 2 /CO 2 /H 2 O) + Diffusion / η + Thermal annealing + Particle / pore structure CO H 2 More information: Halama (2015, 2016), Steibel (2017) 5

6 2.3 m m 6.8 m Reactor geometry and computational mesh Number of nodes: 4 million Min. orthogonal quality: 0.5 Max. aspect ratio: 20 V tot = m 3 V min,i = 9e 10 m 3 V max,i = 4.8e 5 m 3 H 2 O, O 2 N 2, Fuel Pilot O 2, H 2 O Fuel, N MW PiTER Base case D = 80% L = 80% L = 80% D = 80% BOOSTER Ø2900 Ø2300 Ø2900 Ø2300 Outlets 6

7 Boundary conditions and characteristic parameters RHL = Rhenish lignite, BHC = Bituminous hard coal, TWB = Torrefied woody biomass P th = 500 MW th, p op = 25 bar Fuel loading = 265 kg fuel /m 3 N2 Re in = 2.6e5 3.4e6, Ma in < 0.25 T wall = 1300 C T f,ash Source: Schingnitz (2005) 7

8 Conversion behavior of different solid fuels High overall conversion of % for all investigated fuels (RHL > TWB > BHC) Similar cold gas efficiencies of 79 80% and comparable heat losses of 1 3 %P th Gas composition is close to the water-gas shift equilibrium at the reactor outlet 8

9 Conversion behavior of different solid fuels Larger influence of thermal annealing on char conversion rates compared to pore closing effects Char reaction with steam is dominant for RHL and BHC, while Boudouard reaction is dominant for TWB 9

10 Particle density distribution along the reactor length (RHL) Char Fuel Ash plane 1 plane 2 [ ] plane 23 Broad particle density distribution at intermediate char conversion levels 10

11 Influence of burner and gasifier design (RHL) Significant influence of burner and gasifier design on char reaction zones and temperature fields inside the reactor 11

12 Influence of operating conditions (RHL) Low influence of steam addition at the considered operating conditions Improved cold gas efficiency at lower O/C ratio, as overall conversion is still high However, temperatures are possibly too low to achieve a smooth slag discharge Optimum 12

13 Conclusion and outlook Conclusion: 3D-CFD simulations of a 500 MW Siemens type entrained flow gasifier (25 bar) using a detailed and validated model for 3 solid fuels lignite, bituminous coal, torrefied wood Investigation of the influences of burner and gasifier geometry, as well as operating conditions Outlook: Sensitivity studies (e.g., mineral and moisture content, operating pressure, part load, model input parameters) Model validation for different solid fuels and fuel mixtures at operating pressures of > 20 bar 13

14 Thank you for your attention! References: Halama, S., Spliethoff, H.: Numerical simulation of entrained flow gasification: Reaction kinetics and char structure evolution. Fuel Processing Technology 138, , Halama, S., Spliethoff, H.: Reaction kinetics of pressurized entrained flow coal gasification: CFD Simulation of a 5 MW Siemens test gasifier. Journal of Energy Resources Technology 138, , Schingnitz, M., Mehlhose, F.: MEGA GSP process, entrained-flow gasification of coal, biomass and waste. International Freiberg Conference on IGCC & XtL Technologies, Freiberg, Germany, Steibel, M., Halama, S., Geißler, A., Spliethoff, H.: Gasification kinetics of a bituminous coal at elevated pressures: Entrained flow experiments and numerical simulations. Fuel 196, , 2017.