numerical investigation of new cooling method for clinker flow...

International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:18 No:03 1

I J E N S 2018 IJENS JuneIJENS © -IJMME-7272-301804

Numerical Investigation of New Cooling Method for

Clinker Flow in Parallel with Air flow at

Different Height Ratios

Nasr A. Jabbar1, M.J. ALshukri1, Wakkas Ali Rasheed1, Ihsan Y. Hussain2

1Department of Mechanical Engineering, Faculty of Engineering, University of Kufa, Najaf, Iraq 2Department of Mechanical Engineering, College of Engineering, University of Baghdad, Baghdad, Iraq

Abstract-- The properties of Portland cement depend on several

parameters, and the cooling method is one of these parameters.

When the effectiveness of cooling method increases, the

properties of Portland cement are enhanced. In the present work,

a new cooling method is suggested and numerical analysis is

made by CFD modeling using (FLUENT 6.3.26). Using the same

dimensions of cooling room in grate cooler, constant mass flow

rate of air and clinker, different porosity of clinker, and different

height ratios ( height of air / height of clinker), the numerical

results were calculated. The results show that the height ratio is

an important factor affecting the new cooling method and can be

used in order to decrease the length of cooling room or the time

of cooling process according to the porosity of clinker. The

maximum temperature of clinker with the lowest possible

porosity is much lower than the maximum temperature of

clinker with maximum porosity at a constant height ratio (H.R.).

Also, when the height ratio (H.R.) increases, the temperature of

clinker decreases at any point, also the rate of change between

clinker and air temperature decreases with increasing the height

ratio (H.R.).

Index Term-- Clinker; Cooling Process; Forced Convection;

Porosity; CFD. 1. INTRODUCTION

The production of Portland cement consists of three

fundamental stages [1,2]: (a) Preparation of the raw mixture,

(b) Production of the clinker, (c) Preparation of the cement.

The requirements of each stage are generally constant in spite

of the changes in properties of raw materials and operation

conditions. The production of the clinker is the most important

stage because there are several variables affecting on it.

Portland cement clinker is a hydraulic material composed

primary of calcium silicates, aluminates, and ferrites and it

remains the essential component of all standardized cements.

A clinker or clinker nodules are homogeneous material

produced from a finely ground, homogenized blend of

limestone, shale and iron ore. The properties of clinker

nodules (the phase composition of the clinker and the

morphology of the individual clinker phases) have a decisive

influence on the cement quality. These parameters are

controlled by the composition of the raw material (first stage),

and also by the combustion and cooling conditions during the

clinker burning process (second stage) [1,3]. One of the most

important parameters affecting in clinker production is the rate

of cooling [4]. Several studies were made to investigate the

effect of cooling rate on the composition and crystal structures

(crystallization of alite and belite) of clinker [5-9].

Generally, there are four types of clinker cooler (Rotary

cooler, satellite cooler, shaft cooler and grate cooler). The

grate cooler is the most important type because of its thermal

efficiency compares with other types of coolers [10]. Several

researchers studied the heat and mass transfer in the grate

cooler in order to control on clinker cooling process.

Touil [11] used finite element to simulate clinker cooling

process in grate cooler. Mujumdar [12] carried on overall heat

balance calculation of double-input and multiple-output to

analyze heat transfer in the grate cooler. Locher [13]

conducted a control model using the heat transfer analysis of

gas through the particle bed. He investigated the influence of

grate speed and particle size distribution on clinker cooling

process. Li [14] studied a chemical reaction of calcining

process of limestone and modeled the heat-mass transfer

coupling in this process. He found that solid particle size, inlet

flow velocity, and inlet gas temperature were important

parameters to the system characteristics. Zhang [15] simulated

using Fluent software and he found the optimal gas flow and

heat transfer in sinter circular cooler. In recent years, the

seepage heat transfer theory used in order to study and control

the clinker cooling as porous media at high temperature

[16,17].

1.1. NEW SUGGESTED COOLING METHOD The grate cooler consists of number of cooling rooms

depending on the size of grate cooler. These rooms arrange as

series and clinker enters each room (see Fig.(1)). The fresh air

(or cold air) generally enters from the bottom of the room and

the hot air sometimes flow parallel to the clinker (cold zone)

and another flow counter to the clinker (warm zone). These

cooling conditions produce sometimes warm clinker due to

change in mass flow rate of clinker and air, properties of raw

materials and working conditions, therefore; the clinker

properties will be bad relatively. In present work, the new

method suggests using the same rooms separately and

controlling on the mass flow rate of air of each room

depending on mass flow rate of clinker, input and output

temperature of clinker and the porosity of clinker.

The new suggested cooling method, used in present work,

assumed that:

1. The dimensions of the clinker cooling room are equal

to the dimensions of one stage in grate cooler (i.e.

height of room is 0.6 m and width of room is 1.8 m).

2. The mass flow rate of air and clinker is constant and

equal to 30 kg/sec [10].

3. The flow of air and clinker are parallel (see Fig.(1)).

4. The clinker is assumed as a porous media with

porosity (0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7).

5. The inlet temperature of cold air is 300K.

6. The inlet temperature of hot clinker is 1600K.



Fig. 1. Scheme of the clinker cooler.

Fig. 2. The Geometry and Conditions of the Cooling Room

In this method, the height ratio (H.R.), which defined as the

ratio between the height of air to the height of clinker

(Hair/Hclinker), is changed as (1, 1.5, 2, 2.5 and 3) in order to

study the effect of air height on the required length of cooler

when the clinker height decreases.

2. MATHEMATICAL METHODOLOGY

“A mathematical model is identified which is appropriate for

the description of steady, two-dimensional, convection in a

fluid-saturated porous medium. For theoretical studies of

convective heat transfer in fluid-saturated porous material, the

following assumptions are often made and used:

The natural convection and the radiation heat transfer

are neglected.

The medium is assumed to have constant, isotropic,

and homogenous characteristics and properties

(permeability, porosity).

It is allowed that the temperature of solid and fluid

phases be different.[18]

The steady-state fully developed forced convection is

desired.

The porosity of the medium is considered to be

uniform and constant.

Local thermal equilibrium (LTE) is valid.

Viscous dissipation are negligible [19].”

2.1. GOVERNING EQUATIONS

In convection heat transfer, the convection process is

governed by the basic conservation principles of mass,

momentum and energy; therefore to determine the flow and

temperature fields, they are in vector form [20]; a schematic of

the physical model and coordinate system is shown in Fig.(3).

Continuity Equation;

Momentum equations;

Energy Equation;

The energy equation describing temperature distribution of the

flow inside the gate is given by

For the solid and air temperature inside the porous medium

two energy equations;

𝑘 − ϵ Equation [21];

The 𝑘 − 𝜖 turbulence model equation is written as:

In these equations, (k) is the turbulent kinetic energy (μt) is the

turbulent viscosity (S) is the modulus of the mean rate-of-

strain tensor (𝑝𝑘) represents the generation of turbulence

kinetic energy due to the mean velocity gradients. (𝑝𝑏) is the

generation of turbulence kinetic energy due to buoyancy.

Fig. 3. Schematic of The Physical Model and Coordinate System

3. NUMERICAL MODEL

FLUENT(6.3.26) software was used to conduct CFD

modeling and simulation. The important part in all CFD is to

design geometry of the problem. GAMBIT software was

employed to draw the geometry and generate mesh. GAMBIT

offers graphical user interface to get inputs from user. The

numerical modeling is achieved by dividing the geometry into

a grid network. The mesh density used in this study was high

enough to assure all relevant flow feature [22]. The numerical

solution is obtained by dividing the domain of interest into a

grid network, The mesh density should be high enough to

capture all relevant flow feature.



The mean cell count deviation (skewnees) for the current

model was 0%. Quadrilateral cells = 10800, and Face count=

21840, The user defined function was used to specify

properties of fluid and porous media ( clinker) (See Table(1)).

Table I

The Properties of Air and Clinker Used in This Work [10] Property Clinker Air

Density(kg/m3) 1350 342.1*t-1.0002

Viscosity(kg/m.sec) ------ 342.1t0.6769 *109 Heat Capacity

(J/kg.K)

0.632+4.62*10-4 t-

0.37*10-7 t2

0.97+1.37*t*10-4-4t2

Thermal

Conductivity

(W/m.K)

0.2 1*t1.6771*10-9

4. VALIDATION OF NUMERICAL MODEL

To belay of the results acquired from the present study, a

comparison was made with the results checked by prior

studies, which insure validity the program, the practical part of

the research [21] was simulated, The experimental

investigation of this research covered a set of experiments

executed to study the forced convection heat transfer from a

heated flat plate embedded in porous media with a constant

heat flux. The inquiry covered values of heat flux of (1000,

2000, 3000, 4000 and 5000 W/m²) and different velocities

values of (V=1.868, 3.451, 5.73 and 6.367 m/s).

The geometry of the design model consists of two regions of

interest. These are: the flow duct with dimensions (L=1872

mm x W=184 mm x H=333 mm). The smaller box with

dimensions (L=270mm x W=130mm x H=70mm), this box:

on base consist of heated Aluminum plate with dimensions

L=250mm x W=90mm and filled with porous media (glass

beads with diameter 12mm), as shown in figure (4). A

comparison between the experimental and theoretical results

has been made for one case, so figures (5a,b,c and d) show the

numerical and experimental results for temperature profile that

compared with each other. This figure is plotted for

temperatures with q"=5000W/m2 and all velocities above for

x-direction in the box. Figures present that the numerical

simulation follows the same trend as the results of

experimental work, with 5.6% variation.

Fig. 4. Model Geometry (all Dimensions in mm)

(a) V= (20%, 2.15 m/s)

(b) V=(40%, 3.451m/s)

(c) V= (70%, 5.73 m/s)

(d) V= (100%, 6.367 m/s)

Fig. 5. Experimental results versus Numerical results for temperature profile at q"=5000 W/m2,V=( 2.15,3.451,5.73 and 6.367 m/s)



5. RESULTS AND DISCUSSIONS

Figure (6) shows temperature distribution in cooling room (air

and clinker) at different height ratios (H.R.) when the porosity

of the clinker is (0.1). The temperature along the length of

cooling room for the solid phase (clinker) decreases in the

incident direction, however, for the fluid phase (air)

temperature; it increases along the length direction.

The response of the temperature to varying values of the

clinker porosity from 0.1 to 0.7 is illustrated in Figures (6) to

(12), and to represent the situation clearly, the temperature

lines for temperature at limited heights and at length of gate is

taken in figures (13) to (17), where the increasing porosity

leads to corresponding decrease in damping properties (the

rate of damping for fluid comes by three components which

are viscous, orifice and friction components) in the flow and

leads to decrease in resistance flow, and on the other side the

temperature of air decreases with an increase in porosity. It is

clear that when the average temperature decreases, it means

that the heat transfer rate increases. Because at low porosities

one observes that the resistance of the convective flow

becomes weaker because of an increase in the flow resistance

from the less permeable outer sub-layers. Also It can be seen

that the clinker temperature decreases when using the variable

porosity material along the length direction.

Also, when the height ratio (H.R.) increases, the temperature

of clinker decreases at any point, because more heat is

removed from the clinker. In the other hand, the rate of change

between clinker and air temperature decreases with increasing

the height ratio (H.R.). Consequently, the maximum

temperature inside the clinker region decreases. Same

behavior is also seen in Figures (7) to (12). This fact can be

Fig. 6. Effect of Height Ratio (H.R.) on Temperature Distribution in Cooling Room When ε=0.1.



seen in Figures (13) to (17) when the height ratio (H.R.)

changes from 1 to 3.

The results also show that at a constant height ratio (H.R.), the

maximum temperature of clinker with the lowest possible

porosity is much lower than the maximum temperature of

clinker with maximum porosity. It is the main reason for

prevention of air flow through the void space of porous media.

In Fig (18), the comparison among temperatures variation at

the end of cooling room due to change in height Ratio (H.R.)

at different height (h) and different porosity (ε) is shown. It is

found that the convection heat transfer increases more slightly

at different height due to change in clinker porosity, which is

due to the high temperature gradient of the solid phase with

changing porosity effect.

This can be attributed to permeability of the porous region that

acts quite similar to a solid obstacle in low permeability vice

versa. The curves in figure (18) show that the maximum

temperature of clinker is inversely proportional with the height

Ratio (H.R), however a higher height Ratio (H.R) is the best

solution due to cooling rate enhancement which are required

as well as that the speed of cooling Clinker is an important

advantage [3, 23] .

Fig. 7. Effect of Height Ratio (H.R.) on Temperature Distribution

in Cooling Room When ε=0.2.



Fig. 13. Temperature Distribution Along Length of Cooling Room

at Different Height (h) When Height Ratio (H.R.)=1.




at Different Height (h) When Height Ratio (H.R.)=1.5.




at Different Height (h) When Height Ratio (H.R.)=2.5.



Fig. 18. Temperature Variation at the End of Cooling Room due to Change in Height Ratio (H.R.) at Different Height (h) and Different Porosity (ε).



6. CONCLUSIONS

The following conclusions may be drawn from this study:

1. The temperature along the length of cooling room for

the clinker is decrease in the incident direction, while

for the air temperature; it increases along the length

direction.

2. When the height ratio (H.R.) increases, the

temperature of clinker decreases at any point, also the

rate of change between clinker and air temperature

decreases with increasing the height ratio (H.R.).

3. With an increase in porosity, the temperature of air

decreases and the clinker temperature decreases

when using the variable porosity material along the

length direction.

4. At a constant height ratio (H.R.), the maximum

temperature of clinker with the lowest possible

5. porosity is much lower than the maximum

temperature of clinker with maximum porosity.

6. The convection heat transfer increases more slightly

at different height due to change in clinker porosity,

which is due to the high temperature gradient of the

solid phase with changing porosity effect.

The maximum temperature of clinker is inversely proportional

with the height Ratio (H.R), however a higher height Ratio

(H.R) is the best solution due to cooling rate enhancement.

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http://cementamericas.com/mag/cement_importance_cement_raw/

numerical investigation of new cooling method for clinker flow...

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