Emirates Journal for Engineering Research, 19 (1), 19-25 (2014)

(Regular Paper)

19

MODELING AND SIMULATION STUDY TO PREDICT THE CEMENT

PORTLAND CYCLONE SEPARATOR PERFORMANCE

Ali Alahmer1, Mohammed Al-Dabbas

2

1 Department of Mechanical Engineering, Tafila Technical University, 66110 Tafila, Jordan.

2 Department of Mechanical Engineering, Faculty of Engineering, Mutah University, Mutah, Al-Karak 61710 Jordan.

(Received April 2013 and Accepted October 2013)

من المعروف جيدا أن الفاصل الدوامي هو مفيد إلى حد كبير إلزالة الجسيمات والشوائب من مصنع أسمنت

وشدة، االنعكاسي، وتدفق دوامةال انهيار عوامل مثل عدة الدوامي يعتمد في األساس على الفاصلان . بورتالند

فاصل الدوامي ال على أداء الغازتدفق ، وان هذا البحث يعرض نموذجا يصف توزيع السرعة. عاليةال االضطراب

نافيير رينولدز لقد تم استخدام معادالت متوسط . (CFD)بورتالند باستخدام ديناميات الموائع الحسابية سمنتأل

م خدارب العملية باستاالتج أيضا هذه الدراسة استخدمت. (RSM) رينولدز اإلجهاد االضطراب نموذج مع ستوكس

في االنبعاثات و، الغازي والضغط درجة الحرارة لقياس االنبعاثات المحلل TESTO 350 S / M / XLجهاز

فاصل الدوامي الأن كفاءة التجريبية أشارت النتائجلقد .بورتالند أسمنت مصنع في فاصل الدوامي ال جميع أنحاء

في حالة فاصل الدوامي لل الكفاءة الكلية، زادت وباإلضافة إلى ذلك .جدا وهنالك توافق مع النتائج النظرية جيد كانت

.الصيغتين لكال انخفاض الضغط

It is well known that cyclone separator is substantially beneficial equipment for particle removal

from cement Portland factory. The dynamic behavior of such separators depends basically on

several factors as vortex breakdown, flow reversal, and high turbulence intensity. This manuscript

presents the description of a fully detailed of a Computational Fluid Dynamics (CFD) model flow

to predict the effects of velocity distribution, gas flow on the performance of cement Portland

cyclone. Both Reynolds averaged Navier Stokes equations with the Reynolds stress turbulence

model (RSM) were applied for the sake of analysis. Also, the experimental study uses the Testo

350 S/M/XL portable emission analyzer to measure the gaseous temperature and pressure, and its

emission across the cyclone in Portland cement factory. The experimental results indicated very

good performance parameter. In addition, the overall cyclone collection efficiency increased

while the pressure drop decreased for both formulations.

Keywords: Cyclone, Portland cement, CFD, velocity distribution, collection efficiency.

1. INTRODUCTION

Rising Cyclones separator is a device that uses a

centrifugal force generated by a spinning gas stream

to remove particulates from an air or gas without

using filters. The rotational effects and gravity are

used to separate mixtures of solids and fluids. The

main goal of this cyclone is to create a vortex, which

centrifuges the dust particles to the walls where they

can be moved into the dust collecting hopper away

from the influence of the spinning gases through the

boundary layer[1,2]. Figure 1 displays the

components of cyclone separator which are basically

consist of a cylindrical shell fitted with tangential

inlet through which the dusty gas enters an axial inlet

pipe to discharge the cleaned gas and a conical base

with dust discharge[3]. The significant numbers of

large sized cyclone separators are positively applied

as main process equipment to deal with high

volumetric flow rates of dust laden gases in Portland

cement manufacturing industries as shown in figure

1. The performance of the cyclone separators is

expressed in term of the collection efficiency, or

separation efficiency, which equals the weight ratio

of the dust collected to the dust entering in the

cyclone, and the pressure drop [2]. This process can

be described by the following steps: (i) Air flow

passes through a cylinder called a cyclone to create a

high speed flow of rotation air; (ii) then the air steams

runs in a spiral pattern, starting from the wide end of

the cyclone top and finished at the narrow end of

bottom before it comes out the cyclone in a straight

stream through the cyclone center, then out the top;

(iii) the next step, the heavier particle which have a

higher inertia fails to follow the air stream and strike

the outside wall; and (iv) finally, these particles

dropping to the cyclone bottom and then remove

it[4,5].

The structure of this manuscript starts by discussing

the cyclones separator definition, its components and

cyclone processes in section one, while section two

presents a theory of cyclone separator through a

mathematical model. Section three displays CFD

thermal simulation model. Section four presents the

Ali Alahmer, Mohammed Al-Dabbas

20 Emirates Journal for Engineering Research, Vol. 19, No.1, 2014

results and discussion by studying the velocity

distribution, temperature distribution, cyclone

efficiencies and cyclone measurements; finally

section five summarizes the study findings through

the conclusion.

Figure1. Airflow diagram of simple cyclone separation.

2. CYCLONE THEORY

It is known that the fluid particle velocity moves

spirally. So, the gas velocity can be divided into two

velocity components: a tangential component ( ) and

a radial velocity component ( ) According to Stokes

law [6,7], the drag force on any particle in this inlet

stream is therefore by the following equation:

(1)

Where; Fd is the frictional force or Stokes drag acting

on the interface between the fluid and the particle (in

N), μ is the dynamic viscosity (N s/m2), is the

radius of the spherical cyclone (in m), and is the

radial particle's velocity (in m/s).

The centrifugal force component can be expressed

as [6,7]:

(2)

Where; m is the particle mass (in kg), is the

tangential particle's velocity (in m/s), and is the

particle density (in kg/m3).

Due to the difference between the particle and fluid

densities, it will generate the buoyant force and it can

be displayed as [6,7]

(3)

Where; is the buoyant force (in N), and is the

particle density (in kg/m3).

The force balance can be created by summing the

forces together

Assuming steady state;

(4)

Expansion of equation 4 and it will be developed

(5)

Rearrange the above equation in terms of the particle

radius. The particle radius is

(6)

a. Model Description

To investigate the gas flow arrangement and particle

collection performance, in cyclones separation, the

continuity and momentum balance equations for the

gas phase and the particles were used in the

Lagrangian view. The governing equations for the gas

phase and the particles are shown in [8-10].

i. Gas Phase

The continuity and momentum equations of gas phase

can be written respectively as [7,10-11]:

(7)

=

(8)

Where; U is the fluid velocity vector, ρ is the fluid

density, is Del operator, P is the pressure, μ is the

viscosity, is the Reynolds stresses, is the

Dyadic operator, and T is the transpose operator.

The Reynolds stresses in the equation 8 represent the

turbulence model term, which is widely used in the

solid flow CFX and it is based on the equation

[8-10]

=

(9)

Which can be expressed in index notation as:

=

(10)

Modeling and Simulation Study to predict the Cement Portland Cyclone Separator Performance

Emirates Journal for Engineering Research, Vol. 19, No.1, 2014 21

Where is the Reynolds stress model constant and it

is equal to 0.22, k is the turbulence kinetic energy per

unit mass, is the turbulence dissipation rate, is

the pressure strain rate, and P is the exact production

term and it can be expressed as

(11)

The kinetic energy dissipation can be written as [8-

10]

(12)

Where; and is the Reynolds stress model

constant and its value 1.45 and 1.9 respectively.

The pressure strain correlations can be written in

general as

(13)

Where:

(14)

and

(15)

Where; a is the anisotropy tensor, S is the strain rate,

and W is the vorticity.

ii. Particle Transport

To predict the particle capture performance, it is

necessary to solve for the particle transport. The

particle transport is given by the following equation

[6,7]

(16)

Where; is the drag coefficient, and d is the particle

diameter in (µm)

3. CFD WORKFLOW

After surveying the published papers, many

interesting studies have been used computational

fluid dynamics models to predict the flow field

characteristics and pattern particle trajectories inside

the cyclone as well as the pressure drop. However

most studies referred to the commercial CFD program

Fluent 3-D, which is considered one of the more

robust CFD’s available. In our research a SolidWorks

Flow was used due to its advantages. Firstly it is

relatively cheap with an easy Graphical user

interface. Secondly it allows the browsers more

visualization and discrimination of experimental

results without the need for additional computing

power. Finally, SolidWorks Software Suite allows

maximum quick processing and flexibility for all

researchers’ needs, and also provides a strong and

efficient way for scientists to analyze results for

applications [11]. Figure 2 displays the drawing map

of CFD workflow. SolidWorks solves the flow of a

system using the finite element method by analyzing

a 3-dimensional of meshed CAD model [12].

4. RESULT & DISCUSSION

a. Velocity Distribution inside Cyclone

The radial and tangential pattern motions of particle

inside the cyclone separation with different views are

depicted in figures 3, 4 and 5. These figures indicate

the streamline and velocity distribution of gas flow

near to the vortex breaker. The streamline

configuration indicates significant lower strength of

the swirl below the vortex breaker derived from the

related velocity magnitudes. In addition, the figures

displayed the velocity contours at the two locations

above and below the vortex breaker to show that it

reduces the swirl significantly. Re-circulation zones

can be seen inside the cyclone, and the separation of

particles in it is due to the centrifugal force caused by

the spinning gas stream; this force strikes particles

outward to the cyclone wall [13,14].

Ali Alahmer, Mohammed Al-Dabbas

22 Emirates Journal for Engineering Research, Vol. 19, No.1, 2014

Figure 3. Radial and tangential particle motion patterns

in the cyclone separator.

Figure 4. Front view of cyclone separator flow.

Figure 5. Top view of cyclone separator flow.

b. Temperature Distribution in Cyclone

The temperature distribution inside the cyclone

separation is presented in figure 6. It proves that the

distributed gases temperature within the cyclone

basically depend on the amount of unburned fuel and

particle collision. Because of high collision of

particles, the smaller ones move up toward the

cyclone's top, while the larger ones flow down toward

its bottom, consequently the particulate matter is

concentrated at the bottom of the cyclone.

Figure 2. Drawing map of CFD Workflow.

Modeling and Simulation Study to predict the Cement Portland Cyclone Separator Performance

Emirates Journal for Engineering Research, Vol. 19, No.1, 2014 23

Figure 6. Temperature distribution inside the cyclone

separator.

c. Stress Strain Distribution on Cyclone

The stress strain distributions of cyclone using solid

CFD software are shown in figure 7 and 8. The

cyclone geometry should bear the high thermal stress

of flue gaseous, and the accumulated corrosion of flue

gaseous acid. Consequently the designer must

importantly consider the mechanical properties of the

cyclone (stress-strain distribution) in cyclone's

design.

Figure 7. The strain distribution on cyclone separator.

d. The Particle Capture Efficiency

In the cyclonic flow, the particles move towards

either the wall of the cyclone or its central axis until

the drag, buoyant and centrifugal forces are balanced

as shown in figure 9. Consequentially, the cyclone is

more efficient in capturing large particles, while the

smaller ones escape toward the top of cyclone.

Further, gas flow affects the particle transport, but the

gas phase remains unaffected by particle phase

momentum as a result of the drag and buoyancy

forces. Finally, the coarse solid particles are

accumulated at the bottom of the cyclone, while the

finer non-captured ones exit out of the cyclone

through the vortex tube. The solids are supplied from

the feed silo to the cyclone through a rotary air lock

valve.

Figure 8. The stress distribution on cyclone separator.

Figure 9. The particle capture efficiency.

e. Collection efficiency

The efficiency of collection of any size of particle can

be expressed as [15]:

(17)

Where; is the collection efficiency of particles in

the jth size range (0< <1), dpc is the diameter of a

particle that will be collected 50% of the time, and

dpj is the characteristic diameter of jth particle size

range (in .

The effect of average particle size on the collection

efficiency is depicted in figure 10. As shown as the

particle size increases, the cyclone collection

efficiency increases.

Ali Alahmer, Mohammed Al-Dabbas

24 Emirates Journal for Engineering Research, Vol. 19, No.1, 2014

Figure 10. Effect of average particle size on the

collection efficiency.

f. Cyclone Measurement

Gaseous temperature, pressure and emission

across the cyclone in the Portland cement factory are

measured by Testo 350 S/M/XL portable emission

analyzer as shown in figure 11. The Model 350 is a

self-contained emission analyzer system capable of

measuring oxygen (O2), carbon monoxide (CO),

nitrogen oxide (NO), nitrogen dioxide (NO2), sulfur

dioxide (SO2), hydrogen sulphide (H2S), and

hydrocarbons in combustion emission sources, while

capturing data on pressure, temperature, and flow.

Figures 12 represents the measured gas

temperature along the cement Portland factory versus

time passes. In general, as the time passes, the gas

temperature will decrease

Finally, the pressure drop across the cyclone is a

crucial factor in the evaluation of cyclone

performance and it is a dominant parameter for

cyclone operation and design. It is a measure of the

amount of work that is required to operate the cyclone

at given conditions [1]. Figure 13 depicts the

measured pressure drop along the cement Portland

factory versus time passes. As shown in figure, the

pressure drop decreases significantly with time

passing. This effect is mainly due to the decrease of

the density and the increase of the viscosity of the

gas.

Figure 11. Testo 350 S/M/XL portable emission

analyzer.

Figure 12. Gas temperature versus time across the

cyclone separator.

Figure 13. Gas pressure versus time across the cyclone

separator.

5. CONCLUSION

The manuscript presented the CFD simulation of

cyclone separator in Portland cement developed to

predict the effects of velocity distribution,

temperature distribution, stress strain distribution,

pressure drop and particle separation efficiency on

Portland cyclone. Also, it presents the experimental

study of measurement of the pressure drop and

temperatures across the cyclone versus time and its

effect on the cyclone performance. The findings of

this study indicate that the cyclone's performance

(i.e., pressure drop and efficiency) measurement was

found to be corresponding to the values predicted by

CFD.

NOMENCLATURE

A anisotropy tensor

Reynolds stress model constant (= 1.45)

Reynolds stress model constant and (= 1.9)

drag coefficient

Reynolds stress model constant (= 0.22)

D particle diameter

Dpc diameter of a particle

0

20

40

60

80

100

1 8 15 22 29 36 43 50 57 64 71

Co

llect

ion

Eff

icie

ncy

η (

%)

Average Diameter Particle Size (μm)

T = 15.25t2 - 169.11t + 830.29 R² = 0.951

300

380

460

540

620

700

0 1 2 3 4 5 6 7 Gas

Te

mp

era

ture

(℃

)

Time (h)

ΔP= -0.1226t2 + 3.2845t + 15.8 R² = 0.9114

16

20

24

28

32

36

0 2 4 6 8

Gas

Dro

p P

ress

ure

(m

bar

)

Time (h)

Modeling and Simulation Study to predict the Cement Portland Cyclone Separator Performance

Emirates Journal for Engineering Research, Vol. 19, No.1, 2014 25

dpj characteristic diameter (in

Fb buoyant force (in N)

Fd frictional (in N)

K turbulence kinetic energy per unit mass

M particle mass (in kg)

P Fluid pressure (Pa)

Rp radius of the spherical cyclone (in m)

S strain rate

U fluid velocity vector

radial particle's velocity (in m/s)

tangential particle's velocity (in m/s)

W Vorticity (in 1/s)

particle density (in kg/m3)

pressure strain correlations

collection efficiency of particles

particle density (in kg/m3)

pressure strain rate

Del operator

Dyadic operator

µ dynamic viscosity (N s/m2)

fluid density (kg/m3)

turbulence dissipation rate

T transpose operator

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