Advanced Multiphase Simulation of Rotary Kilns:
Coupling of ANSYS Fluent and a Third Party Solver
Eero Immonen
Process Flow Ltd Oy
Contents
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Introduction to rotary kilns
Why simulate?
 Optimization (energy consumption,
emissions)
Overview of the simulation challenges
Solution: Coupling of ANSYS Fluent and
KilnSimu by VTT
Samples and illustrations
Benefits of the coupled solution
Rotary kilns in industrial processes
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Rotary kilns are huge (!) pyroprocessing devices used to raise
materials to a high temperature
Primary uses include:
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Manufacturing of pigment, cement, oxides, ...
Lime calciner in the recovery cycle of chemicals (pulping)
Roasting of sulfide ores prior to metal extraction
Slow rotation along
primary axis ~ 1 rpm
Example: Rotary kilns in cement making
Schematic by Prosperity Minerals Holding LTD
Characteristics of rotary kilns
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A critical part of the manufacturing process
 The kiln capacity defines the overall plant capacity
 The main energy-consuming and greenhouse-gasemitting stage of production
 Significant need for understanding the process and its
parameters (e.g. heat transfer to the bed feed along kiln)
 Significant optimization potential (e.g. burner section)
Extreme operating conditions
 High temperatures
Challenging environment
for measurements  simulate!
 Vibration
 Corrosion
Simulation challenges
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True multiphysical environment
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Solid phase phenomena (bed feed)
 Particulate motion, erosion, heat transfer, chemical
reactions (calcination), ...
Gaseous phase phenomena
 Combustion, turbulent flow, multitude of fuels
Coupling of the solid and gaseous phase
 Heat transfer from gas to the walls and bed feed
 Transfer of reaction products (e.g. CO2, H2O, ...)
from the bed feed to the gaseous phase
Introducing KilnSimu by VTT
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KilnSimu is a generic 1D multiphase simulator for rotary kilns
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State of the art resolution of bed chemistry using ChemApp
Cell1
Gas out
Celli
Gas in eq.
Mass transfer of gas species between bed and
gas. Convection and diffusion between gas and
bed.
CellN
Gas in eq.
Gas in eq.
Gas in
Bed in
convection+
diffusion
convection+
diffusion
convection+
diffusion
dust+
volatiles
dust+
volatiles
dust+
volatiles
condensed
Bed in eq.
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condensed
Bed in eq.
Mass transfer of condensed species between
bed and gas. Dusting of solid particles and
formation of liquid phases.
condensed
Bed out
Bed in eq.
Issue: Need a priori information on the combustion
conditions (e.g. flame position) in order to obtain a
realistic overall solution
Solution: Coupling of ANSYS Fluent and KilnSimu
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Gaseous and solid phase simulation in 1D in KilnSimu
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Gaseous phase simulation in 3D in ANSYS Fluent
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General-purpose solver for any rotary kiln application
High-performance multi-phase CFD modeling environment
hosting a leading selection of combustion sub-models
Chemical reaction modeling, especially in turbulent conditions,
has been a hallmark of Fluent since its inception
Coupling of Fluent and KilnSimu: KS  Fluent  KS  ...
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Unit conversions and front-end code for rapid simulation setup
1D  3D  1D geometry interfacing routines with interpolation
Heat and mass transfer treatment on solid-gas interfaces
 - Automated setup of b.c’s and c.z.c’s in Fluent
Built-in postprocessing features
Schematic flow chart of the coupled solution
Geometry
and mesh
KilnSimu
Fluent
Set-up Fluent
and KilnSimu
or read
parameters
Parameter
files *.dat
Simulation
parameters
Read
interface
fluxes
Export
interface
fluxes
Solve gas
domain
Export
interface
heat fluxes
Postprocessing
Solve KilnSimu
domains
Read
interface
heat fluxes
Postprocessing
KilnSimu solution loop
Fluent solution loop
Global solution loop
Illustration of the coupling: KilnSimu  Fluent
Initial data calculated by KilnSimu are transferred to Fluent
A.
B.
A.
Bed feed surface: Temperature boundary
condition
Gas volume: CO2 sources on bed feed
surface
Drum wall (lining): Temperature boundary condition
A.
B.
Drum shell
Drum lining
Gas volume
Feed volume
C.
Ilustration of the coupled solution
Resulting gas temperature profile
Benefits of the coupled simulation
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Fewer a priori assumptions about combustion needed in
KilnSimu to obtain realistic results
Enhanced accuracy in estimating the gas-volume
phenomena compared to the 1D treatment in KilnSimu
Facilitates a detailed analysis, and optimization, of the
burner area - this is not possible in a 1D solution
More accurate description of radiation heat transfer
Possibility of studying a large variety of chemical states in
the feed, and, simultaneously, analyzing the associated gas
volume phenomena
The coupled simulation helps reduce energy
consumption and control emissions in rotary kilns!
THANK YOU!
For more information go to:
http://www.kilnsimu-fks.com/