DBFZ Leipzig Fachtagung Prozesssimulation in der Energietechnik Sep Siemens Gasification Technology

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1 DBFZ Leipzig Fachtagung Prozesssimulation in der Energietechnik Sep Siemens Gasification Technology Moser / Pieloth

2 Contents Siemens Flugstromvergaser Simulation der Abtrennung von Restflugasche im Rohgas am Beispiel einer Tauchquenchung Siemens Fuel Gasification Technology overview 3 Quench principles 7 Theoretical background and validation 8 Numerical models 20 Results 23 Summery & Outlook 25 Page 2

3 Siemens Fuel Gasification Technology overview Siemens offers gasifier types for every feedstock Feedstock's with more than 4 wt% ash content Lignite's, Sub-bituminous and Bituminous coals, Hard coals, Feedstock's with less than 4 wt% ash content Petroleum coke, Bitumen, Tars, Oils, Asphaltenes, Biomass, Cooling Screen Design Fuel Oxygen, steam Pressurized Pressurized water water inlet outlet Burner Refractory Wall Design Cooling wall Burner insert Cooling screen Quench water Reactor 1300 to 1800 C Refractory lining SiC layer Cooling water Quench water Total quench Cooled reactor outlet Quench Gas outlet Gas outlet Page 3 Granulated slag

4 Siemens Fuel Gasification Technology overview Cooling Screen Type Gasifier Pressurized water inlet SFG Gasifier (> 4 wt % ash) Cooling screen Qunech water inlet Feedstock Reactor C Quench O 2 H 2 O Pressurized water outlet Burner Qunech water inlet Syn-Gas outlet Fuel flexibility Features Lignite, bituminous and sub-bituminous coal, hard coal, Dry feeding high efficiency (>80%) high carbon conversion rate (>98%) Cooling screen short start-up/shut-down (~2h) Significantly higher lifetime/high availability Full quench simple and reliable ideal for CO sour shift Single main burner with integrated pilot burner Automatic start up without removal of start burner Modular concept for simplified maintenance Pilot burner secures hot stand by under full pressure Granulated slag Page 4

5 Siemens Fuel Gasification Technology overview Features SFG-500 Length: 18 meters Outside diameter (incl. flanges): 4.3 meters Weight: 220 tons Capacity: ~ 2,000 tons of coal daily Syngas output: ~ 3.0 mio Nm 3 /day SFG-500 Gasifier for NCPP Project/China Page 5

6 Siemens Fuel Gasification Technology overview Burner Reaction Chamber Cooling Screen Quench Nozzles Quencher Syngas Outlet Slag discharge Operating Pressure: up to 42 bar

7 Quench principles T in ~ 2000 K Full quench Partial quench Scrubber quench T out ~ 500K proven & reliable desgin SFGT technology Page 7 Technical study Technical study

8 Theory Löffler model of particle deposition on droplets Deposition of dust particles on a droplet due to inertia Cleaning of a raw gas stream can be resolved into three sub processes: a) Particle deposition on a single droplet b) Cleaning of a volume of a single droplet c) Change of dust concentration through the summation of cleaning volumes of all droplets The deposition efficiency of particles on a droplet is defined as the product of collision efficiency and adhesion efficiency h: Wet scrubbers: h Page 8

9 Theory Particle deposition on a single droplet: Map between and (Stokes parameter): The Stokes parameter is defined as: a = f(re d ), b = f(re d ) Droplet - Reynolds number: Specific cleaned volume: Change of dust concentration: a 2 pvrelx p 18 x Re RV d 2 i t t 1 4 v rel 3 2x l x d l t t d 2 1 d,i d l b (t)v rel rel,i (t)dt 2 xd, i (t)v (t)dt Page 9

10 Theory Euler-Lagrange Simulation (Two phases, each phase two* components) Air: Euler Phase (air, dust), Droplets: Lagrange Phase (water, dust) Re Process parameter (e.g. l,v rel ) d v rel i t t x 2 1 l 4 d x l a b p v 18 2 d, id,i (t)v rel,i (t)dt rel l x x 2 p d *more then two, if dust polydispers Re 100 potential flow 100 > Re 50 Re = 60; > Re 30 Re = > Re 5 Re = 10; 20 5 > Re viscous flow Schuch s Parameter a and b Change of dust concentration Page 10

11 Theory Schuch s PhD thesis: - Flow channel (0.1 m x 0.1 m cross section, air velocity v = 5, 7, 15 m/s) - Monodisperse droplets (velocity entering flow channel w 0 = 4, 7, 15 m/s) - Monodisperse dust (x p = 1.6, 2.5, 4.0, 14.8 m) - Measurement of dust collected by droplets Droplet collector Channel Droplet generator Dust v Droplets w 0 Page 11 Schuch (1978) Schuch s experimental setup Modellrechnungen mit ANSYS CFX

12 Theory v = 7m/s, w 0 = 7 m/s Specific cleaned volume RV Droplet diameter x d [µm] Theo. calculations and exp. data Löffler/Schuch Specific cleaned volume RV Page 12 verified with Matlab ANSYS CFX numerical modeling

13 Theory Euler-Lagrange-Simulation - Droplet (rigid sphere ), Dust (Lagrange-Particles) - Droplet - Dust - Collision Deposition efficiency - Mesh ~ 2, Elements, high resolution in the vicinity of droplet s surface - 0,1 Re d 100 (Step size 1), for all 0 < x p / x d < 0,15 high accuracy in adaption of,a,b)- und a,b(re d )-Functions v i rel Re 18 Re d i g d x p g N N d g x x d,i in,i p,i d 2 Particle Page 13 Mesh Droplet

14 Theory Re = 5 Re = 40 Re = 100 Schuch Schuch Schuch Comparison of - dependencies for Re d = 5, 40 und 100, with CFD calculated () - Values, approximated = (Re d ) CFD Values, - - Schuch [1], -- Schmidt [2] [1] G. Schuch, PhD thesis, Universität Karlsruhe, Karlsruhe 1978 [2] M. Schmidt, PhD thesis, Universität Karlsruhe, Karlsruhe 1993 Page 14

15 Theory Page 15 Parameterization of a(re d ) and 1/b(Re d ) curves , , , , , , , , ,2056-0, , , ,29-0,06784

16 Theory / Validation Salt feeder Injector Raw gas (NaCl particles) Water 0 Thermostat m Salt ~ 5 m Rotary sprayer Rotary sprayer Chamfer m Salt 0 Conductivity Measurement Rotary scrubber (pilot plant scale) Page 16 Conductivity Chamfer Measurement Clean gas Rotary scrubber (schematic representation)

17 Theory / Validation Q 3 (x) Jet mill Q 3 (x) Cyclone screened Salt (NaCl) powdered in a jet mill, then screened with a cyclone. Rotary sprayer Page 17 RPM [1/min] Characteristic droplet size generated by the rotary sprayer (LAMROT-Sprayer) used in experimental setup. With higher RPM the PSD shows a smaller span value.

18 Theory / Validation Dust concentration: c 0 Scrubbing Air velocity v = 4.98 m/s Dust concentration c 1 Droplet Trajectories at RPM = 7000 Page 18 RV

19 Theory / Validation Air velocity 4.98 m/s Specific cleaned volume RV RPM [1/min] Page 19

20 Numerical models Full quench Scrubber quench proven & reliable desgin SFGT technology Page 20 Complicate geometry 180 model ~4 mio cells High number of dpm trecking steps requiered ~16000 particles per dpm iteration Requieres much CPU-time Simple geometry 45 model ~0.74 mio cells Less dpm trecking steps requiered ~9000 particles per dpm iteration Less CPU-time Scrubber quench choosen for numerical study on dust absorption models

21 Numerical models Scrubber quench study on dust absorption for non-isothermal flow conditions CFD code: Ansys Fluent 3-D simulation Steady state simulation Turbulence model: k-sst Discrete particle model ( DPM, Lagrange particle tracking ) 4 dust particle fractions Page 21

22 Numerical models Scrubber quench study on dust absorption for non-isothermal flow conditions Inlet: hot raw gas and dust Water nozzles Water nozzles Outlet: cooled raw gas + water droplets Page 22

23 Results Fluid Phase DPM Phase Species inlet outlet diff diff absorb kg/s mass flow -> In-out dpm to massfrac massfrac % in-out % h2o 0, , ,13% 1,06% n2 0, , ,84% h2 0, , ,84% co2 0, , ,84% co 0, , ,84% dg1 0, , ,29% dd1 98,96% dg2 0, , ,11% dd2 97,51% dg3 0, , ,72% dd3 77,87% dg4 0, , ,73% dd4 38,31% Mass balances fulfilled For dust good agreement of Eulerian phase mass balance and Langrangian phase mass balance Inlet-outlet: Page 23 Good fulflillment of species (n2, h2, co2, co) mass balances Deviation in water mass balance due to evaporation of water Because of evaporated H2O Eulerian - Langranian mass balance for H2O fulfilled Increased absorptionrate from dd4 to dd1

24 Results Analysis of dust load on particles Dust load on water droplets usually does not exeeds the range of 10%. Analysis of dust load on water droplets shows that almost no droplet carries a dust load above 10% Numerical outcomes correspondence to experimental findings Page 24

25 Summary Scrubber quench study on dust absorption Study of particle absorption on scrubber quench for non isothermal flows Dust absorption models successful integrated in Ansys Fluent code Outcomes are in the range of expectations Smaller particles are less absorbed than larger particle Unrealistic high loading with dust on water droplets is negligible Page 25

26 Outlook SFGT technology Full quench proven & reliable desgin Implementation of dust absorption models in SFGT full quench model Implementation of load delimiter on water droplets Implementation of models for dry particles (total evaporation of water) Options: 1. Transfer for small dust particles back to Eulerian phase 2. Creation of solid dust particle network on the base of spray drying experience Page 26

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