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
Introduction / Research project “HotVeGas”
CFD modeling approach and validation procedure
Definition of the industrial scale test case
Results and discussion
Conclusion and outlook
2
Content
3
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
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
Project framework:
01/2016 - 12/2019
Funded by BMWi and industry partners (RWE, Air Liquide)
Cooperation with TUBA Freiberg, FZ Jülich, and GTT
Project: HotVeGas III – FLEX Experimental investigations and modeling of coal gasification and gas cleaning
Volatiles
release
Fuel particles,
reaction gases
Deposition,
slag flow
Product
gases
Deposition,
condensation
corrosion
Gasification
reactions
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 kWth,
1–20 bar, 1200–1600 °C)
Large scale
CFD simulation
(Siemens type, 5–500 MWth)
Source: Schingnitz (2005)
5
Modeling approach
ICEM CFD + ANSYS Fluent:
3D-Hexa, RANS, SIMPLE, 2nd Order
Turbulence:
RKE or SKE, Std. WF
Particle tracking:
DPM, DRWM
Particle and gas radiation:
DO, WSGGM
Turbulence chemistry interaction:
EDC, ISAT
Gas phase reactions:
Modified J-L mechanism
Volatiles release:
Single rate or two comp. rates
Char reactions:
UDFs (PR_RATE, SCALAR_UPDATE)
Measured intrinsic rates (nth order,
O2/CO2/H2O) + Diffusion / η + Thermal
annealing + Particle / pore structure
CO2
CxHy
CO
H2O
Soot
H2
Tars
CO2
H2O
O2
CO H2
More information: Halama (2015, 2016), Steibel (2017)
6
Reactor geometry and computational mesh
54
00
68
00
Ø2300 Ø2900
Base case D = 80% L = 80% L = 80%
D = 80%
Fuel, N2
O2, H2O Pilot
Outlets
H2O, O2
N2, Fuel
Ø2300 Ø2900
500 MW
PiTER
BOOSTER
2.3
m
4.8
m 6
.8 m
Number of nodes: 4 million
Min. orthogonal quality: 0.5
Max. aspect ratio: 20
Vtot = 39.25 m3
Vmin,i = 9e–10 m3
Vmax,i = 4.8e–5 m3
7
Boundary conditions and characteristic parameters
RHL = Rhenish lignite, BHC = Bituminous hard coal, TWB = Torrefied woody biomass
Pth = 500 MWth, pop = 25 bar
Fuel loading = 265 kgfuel/m3N2
Rein = 2.6e5–3.4e6, Main < 0.25
Twall = 1300 °C ≈ Tf,ash
Source: Schingnitz (2005)
High overall conversion of 99–100% for all investigated fuels (RHL > TWB > BHC)
Similar cold gas efficiencies of 79–80% and comparable heat losses of 1–3 %Pth
Gas composition is close to the water-gas shift equilibrium at the reactor outlet
8
Conversion behavior of different solid fuels
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
10
Particle density distribution along the reactor length (RHL)
plane 1
plane 2
plane 23
[…]
Char Fuel Ash
Broad particle density distribution at intermediate
char conversion levels
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
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
13
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
Conclusion and outlook
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
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, 314–324, 2015.
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, 042204, 2016.
Schingnitz, M., Mehlhose, F.: MEGA GSP process, entrained-flow gasification of coal, biomass and waste. International Freiberg Conference
on IGCC & XtL Technologies, Freiberg, Germany, 2005.
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, 210-216, 2017.
