Advanced Multiphase Simulation of Rotary Kilns:

Coupling of ANSYS Fluent and a Third Party Solver

Eero Immonen

Process Flow Ltd Oy

Contents

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

Rotary kilns are huge (!) pyroprocessing devices used to raise

materials to a high temperature

Primary uses include:

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

A critical part of the manufacturing process

The kiln capacity defines the overall plant capacity

The main energy-consuming and greenhouse-gas-

emitting 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

Vibration

Corrosion

Challenging environment

for measurements simulate!

Simulation challenges

True multiphysical environment

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

KilnSimu is a generic 1D multiphase simulator for rotary kilns

State of the art resolution of bed chemistry using ChemApp

Issue: Need a priori information on the combustion

conditions (e.g. flame position) in order to obtain a

realistic overall solution

Gas in

Bed out

Celli Cell1 CellN

Bed in eq.

dust+

volatiles

Gas out

Bed in

Mass transfer of gas species between bed and

gas. Convection and diffusion between gas and

bed.

Mass transfer of condensed species between

bed and gas. Dusting of solid particles and

formation of liquid phases.

convection+

diffusion

dust+

volatiles

convection+

diffusion

dust+

volatiles

convection+

diffusion

condensed condensed condensed

Bed in eq. Bed in eq.

Gas in eq. Gas in eq. Gas in eq.

Solution: Coupling of ANSYS Fluent and KilnSimu

Gaseous and solid phase simulation in 1D in KilnSimu

General-purpose solver for any rotary kiln application

Gaseous phase simulation in 3D in ANSYS Fluent

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 ...

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

Fluent KilnSimu

Simulation

parameters

Parameter

files *.dat

Set-up Fluent

and KilnSimu

or read

parameters

Solve KilnSimu

domains

Export

interface

fluxes

Read

interface

fluxes

Solve gas

domain

Export

interface

heat fluxes

Post-

processing

Post-

processing

Global solution loop

Geometry

and mesh

Read

interface

heat fluxesFlu

en

t so

lutio

n lo

op

Kiln

Sim

u s

olu

tio

n lo

op

Illustration of the coupling: KilnSimu Fluent

Initial data calculated by KilnSimu are transferred to Fluent

A. Bed feed surface: Temperature boundary

condition

B. Gas volume: CO2 sources on bed feed

surface

A. Drum wall (lining): Temperature boundary condition

Drum shell

Drum lining

Gas volume

Feed volume

A. C. B.

Ilustration of the coupled solution

Resulting gas temperature profile

Benefits of the coupled simulation

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/