investigation of 2-phase evaporative reacting flows in micro-scale

2016 ANSYS Convergence Conference30 June, Electra Palace Hotel, Athens, Greece

ANSYS Hall of Fame 2016 Competition Winner - Academic: Investigation of 2-phase evaporative reacting flows in micro-scale

Dr. Nikolaos Nikolopoulos, PhD cand. Ilias Malgarinos, and Prof.Manolis Gavaises

http://www.ansys.com/Other/Hall-of-Fame/CUL

Presentation Outline

Activities Ideas Possibilities

Current Activities

Droplet Dynamics

Fluidized Beds

Ideas (Prospects)

CFD application prospects in FCC industry

Ideas for collaboration

Ansys Convergence 2016, Slovenia

Droplet Dynamics


Drop-gas Solid Surface Phase Change Reactions+ + +

Validated 2-phase flow model VOF in wide range of cases



Model Features

Navier-Stokes Momentum-Continuity

Volume of Fluid Method (VOF) for interphase tracking

Phase change Evaporation Model

Drop motion

Dynamic local refinement

Droplet Dynamics

Surface Reactions


Application in FCC industry


FCC (Fluid Catalytic Cracking), from large scale to micro scale

Large Scale(FCC reactor)

Meso Scale(injection zone)

Micro Scale(drop-particle collisions)




Why study the micro scale?

Investigate the reasons for catalyst pore blocking (due to non-evaporated liquid or coke formed) originating in direct solid-liquid contact

Improve selectivity

Optimize injection strategy

Injection is a micro-scale phenomenon




Parameters investigatedParticle Droplet Gas

Position static moving

D (μm) 75 75-150

U (m/s) 15-30

T (K) 800-1000 550 800

P (atm) 2

Constant conditionsParameters

Cracking Pathway assumed Cracking rates from

Gianetto et al. (1994)

Gianetto, A., et al., Fluid Catalytic Cracking

Catalyst for Reformulated Gasolines. Kinetic

Modeling. Industrial & Engineering Chemistry

Research, 1994. 33(12): p. 3053-3062.C25H52(l) C25H52(g) C7H16(g)




Case 1 (2D), 1 drop – 1 particleDd = Dp 2D

Effect of particle T on collision outcome

thin liquid expanding radially

torus breakup

τ=0.1 τ=0.7 τ=1.1 τ=1.7

Uo = 15m/s

10

00

K8

00

K

Tp

Formation of vapour layer




2D

encapsulation

Dd = 2Dp

15

m/s

Tp = 800K Effect of impact velocity on collision outcome

Case 1 (2D), 1 drop – 1 particle

30

m/s

Uo τ=0.1 τ=0.5 τ=1.0 τ=1.4

thick (compared to the previous where we had a “thin”) ejecta sheet - expanding radially

under specific conditions may lead to satellite droplets detachment




Vapour layer prediction- a decisive parameter (Leidenfrost phenomenon)

Drop is levitated by a vapour layer on hot catalysts2D




Cracking Predictions

Hotter catalysts promote cracking reactions/gasoline production

Low impact velocity promotes cracking reactions/gasoline production

2D




Droplet info

Small over large droplets (compared to catalytic particles) evaporate faster and cool down slightly in the process

2D




Case 2 (3D), 1 drop – 1 particle 3D




Vapour layer prediction-Leidenfrost phenomenon

Drop is levitated by a vapour layer on hot catalysts3D

h




Droplet break-up mechanism in 3D 3DDd = Dp

Uo = 15m/s

Tp = 1000K




Case 3 (3D), 1 drop – many particles 3DDd = 2Dp

Uo = 30m/s

Tp = 1000K




Droplet impact onto a cluster

Many different liquid shapes (ligaments, sheet, fingers)/ Gasoline prediction

3DDd = 2Dp

Uo = 30m/s

Tp = 1000K




Cluster formations promote cracking reactions/gasoline production compared to 1drop-1particle collisions

3DDroplet impact onto a cluster




Droplets on clusters evaporate faster and heat up in the process3DDroplet impact onto a cluster


CUL-CERTH-video-Malgarinos.mpg



3DExhibited Dynamics

CUL-CERTH-video-Malgarinos.mpg



Case 4 (2D), 4 chain drops – 1 particle 2D




Case 4 (2D), 4 chain drops – 1 particle 2D Solution of particle cells for prediction of particle cooling from impact




Particle cooling characterization(4 chain drops on 1 particle)

Similar trend of particle temperature decrease for different chain impact periods and initial particle temperatures

2D

a dimensionless character for time periods up to 12 μs (800 K) a dimensionless character for time periods up to at least 24 μs (1000 K)




Wall heat flux prediction for different chain impact periods (6, 12, 24 μs between each impact) and initial particle temperatures

Particle cooling characterization(4 chain drops on 1 particle)

2D

a higher WHF for 1000 K (compared to 800 K) – this controls the necessary regeneration rate of catalytic particles


Fluidized Beds


Fluidized bed modeling

CERTH/CPERI Expertise

10 Year Experience in Fluidized Bed simulation

Hydrodynamic simulations

Reacting Flows

Full-loop simulations

Custom built model (EMMS) for the formation of clusters


CFD application in FCC industry


FCC (Fluid Catalytic Cracking), large scale reactors

• Investigate back-mixing effects• Investigate Feed spray arrangement; Optimize catalyst / liquid oil

mixing• Use of micro-scale results to predict accurately droplet / catalytic

particles fluid mechanics


CFD application in FCC industry


FCC (Fluid Catalytic Cracking), micro scale

• Help in minimization of coke deposits in the feedstock injection zone originating from droplet-particle direct contact

• Investigate cooling rate for particle cluster• Identify configuration which promote light molecule gas yields

and catalytic particle temperature reduction


Experiments? Correlate particle insertion temperature with deactivated catalyst rate in outlet

Collaboration


Internal Meeting

Experiments? Bring closer the region of injection with the region of particle insertion for increased possibility of drop levitation. Correlate injection/particle insertion regions overlapping with deactivated catalyst rate in outlet

Experiments? Find the optimum temperature of droplet injection for maximization of evaporation rate. Correlate droplet T with deactivated catalyst number in outlet

CERTH CFD competenciesCollaboration with Industrial partners

CERTH CFD competenciesPF and FB combustion

Fluent commercial code (licenses for parallel processing), fully validated UDFs (PF

and FB boilers)

New cluster computing system for parallel processing

House built validated developed models integrated in ANSYS/Fluent:

Char combustion

Devolatilization

Boudouard reaction

Radiation

NOx emissions

Drag Scheme (EMMS)

Full-loop simulation

Reacting flow

Homogeneous and

heterogeneous reactions

NOx emissions

Fluidized Bed TechnologyPulverized alternative fuel Technology

(WRF/SRF, Sludge, Biogenic Fuels)\

Numerical Grid of 2.5 million tetrahedral cells (High computational cost) The true geometry is fully respected. Detailed design of burners

Primary air

Secondary air

Burner wall

OFA

Labels

Recircualation

Ducts

Oil burners

Ag. Dimitrios PP

CERTH CFD competenciesAn example of a Greek PF boiler

CERTH CFD competenciesAn example of a German FB reactor

- The EMMS scheme developed increases the accuracy of the model especially in the dense

bottom region which is hard to model, and in which the majority of CO2 capture takes place.

CFD modeling of plexi-glass cold model (Carbonator) of USTUTT

Real geometry RVE RVE with Backstays

Wall heat flux as a BC

Anisotropic stiffness matrix (xml file)

Far-Field Analysis

CERTH CFD competenciesFEM tubes analysis in a German PP

Far-Field stress/strain fields Near-Field stress field

Near-Field Analysis

CERTH CFD competenciesFEM tubes analysis in a German PP

Thank you for your attention!


The European Commission for funding this work, by the Marie Curie Fellowship (FP7-PEOPLE-2012-IEF), GA No 329500 entitled as “Non Flat

Impingement” is gratefully acknowledged

Appendix

Adaptive local grid refinement

Saves computational cost Increases accuracy at the interface

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