semen 30

Energy Conversion and Management 45 (2004) 3017–3031www.elsevier.com/locate/enconman

Energy and exergy analyses in a rotary burner withpre-calcinations in cement production

€Unal C�amdali a,*, Ali Er_is�en b, F€usun C� elen c

a Development Bank of Turkey, Necatibey Cad., No: 98, Bakanliklar, 06100 Ankara, Turkeyb Kırıkkale University, Engineering Faculty, Mechanical Engineering Department, 71100 Kırıkkale, Turkey

c Metropolitan Municipality, General Directorate of EGO, Gas Department, Maltepe, 06570 Ankara, Turkey

Received 31 May 2003; received in revised form 27 September 2003; accepted 9 December 2003

Available online 24 January 2004

Abstract

Cement production facilities are often located in rural areas and close to quarries, where the rawmaterials required for cement production are present, i.e. limestone and shale.

Although energy analysis, based on the first law of thermodynamics, is used to reduce heat losses or

enhance heat recovery, it does not give any information on the degradation of energy that occurs in the

process. Exergy analysis, based on the first and second laws of thermodynamics, facilitates improvement of

the operation or technology by clearly indicating the locations of energy degradation in the process.

In this study, the applications of energy and exergy analyses are examined for a dry system rotary burner

(RB) with pre-calcinations in a cement plant of an important cement producer in Turkey. The RB includes

thermal and chemical processes. Besides, real figures of the cement factory have been used in this work. Inconclusion, the values of the first and second law efficiencies have been found and compared.

� 2004 Elsevier Ltd. All rights reserved.

Keywords: Energy analysis; Exergy analysis; Cement production; Rotary burner

1. Introduction

By the mid 1970s, the increase in energy resource consumption that occurred in each passingyear was not a source of general concern. However, recurrent fuel shortages, electricity blackouts

* Corresponding author. Tel.: +90-312-2318400; fax: +90-312-2302394.

E-mail addresses: [email protected], [email protected] (U. C�amdali).

0196-8904/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.enconman.2003.12.002

mail to: [email protected],

Nomenclature

A surface area (m2)C flow velocity (m/s)cp specific heat capacity at constant pressure (kJ/kgK)E exergy (kJ), energy (kJ)Eex exit exergy (kJ)Ein inlet exergy (kJ)EL lost exergy due to irreversibilities (kJ)EO outlet exergy (kJ)EQ exergy of heat transfer (kJ)Es exergy of a system (kJ)EW exergy of work transfer (kJ)g specific Gibbs function (kJ/kg)gG gravitational acceleration (m/s2)h specific enthalpy (kJ/kg)h0f specific enthalpy of formation (kJ/kg)h convective heat transfer coefficient (kJ/hm2 K)I irreversibility (kJ)k thermal conductivity (kJ/hmK)l length of RB (m)m mass (kg)P pressure (kPa)Q heat transfer (kJ)QL heat loss (kJ)r radius (m)RB rotary burnerS entropy (kJ/K)s specific entropy (kJ/kgK)T temperature (K)Tin inner temperature of RB (K)Tsur surface temperature of RB (K)V volume (m3), velocity (m/s)W work (kJ)z0 height of flow (m)l chemical potential (kJ/kmol)g energy efficiency (%)w exergy efficiency (%)e specific exergy (kJ/kg)

Subscriptsanz anzast layerbr bricks

3018 U. C�amdali et al. / Energy Conversion and Management 45 (2004) 3017–3031

cond conductionconv convectioncv control volumeex exitf flowgen generationi ith componentin inletL lossrad radiationS-gases stack gasessts steel sheet0 environmental state00 chemical potential at chemical equilibrium with environment

Superscripts

CH chemicalKN kineticPH physicalPT potentialTM thermomechanicalÆ rate– per mole0 standard reference conditions

U. C�amdali et al. / Energy Conversion and Management 45 (2004) 3017–3031 3019

and brownouts, rising prices and so on began to alter perceptions. Many individuals voicedconcern that unless corrective steps were undertaken, difficulties would be encountered in pro-viding energy for future needs [1].

So, energy analyses have been conducted widely in many industries. Energy can be transformedfrom one form to another and transferred by work and heat transfer. The total amount of energyis conserved in all transformations and transfers. The main aim in realizing energy analysis is todetermine the used and lost energies.

Wide application of exergy analysis can lead to reducing the use of natural resources and, as aresult, to decreasing the pollution of the environment. The main purpose of exergy analysis is todetect and evaluate quantitatively the causes of the thermodynamic imperfections of thermal andchemical processes. The exergy method of thermodynamic analysis is based upon the first andsecond laws of thermodynamics together, whereas the energy balance is based upon the first lawonly, which is a conservation principle. It is a feature of the exergy concept to permit quantitativeevaluation of energy degradation [2].

As a result, the energy and exergy concepts may be expressed in the following simple terms: (1)energy is the ability of producing change and (2) exergy is the work producing potential or qualityof different energy forms for a given environment. The laws of thermodynamics may be formu-lated accordingly: (1) energy is always conserved in a process (first law) and (2) exergy is always


conserved in a reversible process, but is always consumed in an irreversible process (second law,the law of exergy) [3].

In this study, the mass analysis is realized. Then, enthalpies going into and leaving the RB arecalculated with heat losses from the RB by conduction, convection and radiation according to thefirst law of thermodynamics. Furthermore, exergy analysis is made based on the second law ofthermodynamics. At the end of the present study, efficiencies depending on both the first andsecond laws are compared.

2. Cement production

The cement industry has an important role in the economy based on its production. Duringthe production of cement, natural resources are consumed in large amounts. The most importantraw materials for the manufacture of cement are limestone (CaCO3) and clay or calcareous clayin which both components are already naturally mixed. The components are milled and driedwith flue gases from the clinker kiln. Depending on the type of cement to be produced, thefollowing products may be added to the dried limestone subsequently: pyrite ash, fly ash fromcoal fired power plants, sandy clay and filter ash from the electrostatic precipitator present. Themixture obtained is ground and subsequently fired in a rotary furnace to cement clinkers. Forheating, various fuels and other combustible materials, e.g. coal dust, petroleum coke, etc., areused. Depending on the type of preheating of the material, it is differentiated between grate andcyclone preheating, whereby the starting materials are preheated to 700–800 �C. The rawmaterials pass through the rotary furnace towards the flame. In the hottest zone, the materialbeing fired reaches temperatures of around 1450 �C. After fast cooling with ambient air, theclinkers are milled, together with gypsum, to give ready cement. A part of the process is given inFig. 1 [4–6].

Materials going into and leaving the RB are seen in detail in Fig. 2, and those materials, theenergy and exergy analysis are accomplished. The process has a two and half hour cycle.

2.1. Chemical analysis occurring in the rotary burner

Chemical reactions occur in the RB by combustion of coal and forming clinker. These are givenas standard reactions in the following [7].

2.1.1. Chemical reactions in combustion of coal

Cþ 1=2O2 ! CO

CþO2 ! CO2

SþO2 ! SO2

Farine coming from pre-heater QL

Gas Coal

Dust Secondary air Primary air

Hot clinker

Fig. 2. Rotary burner (RB) and materials going into and leaving [7].

Fig. 1. A part of cement production process (from Cemex Inc., USA).


2.1.2. Main chemical reactions in formation of clinker

2CaOþ SiO2 ! ðCaOÞ2SiO2

CaOAl2O3 þ 2CaO ! ðCaOÞ3Al2O3

CaOAl2O3 þ 3CaOþ Fe2O3 ! ðCaOÞ4Al2O3Fe2O3

ðCaOÞ2SiO2 þ CaO ! ðCaOÞ3SiO2

MgO ! MgO

K2O ! K2O

Na2O ! Na2O


3. Mass analysis in the rotary burner (RB)

The mass balance of the RB, which is performed according to the chemical reactions, is given intheir chemical components in Table 1. This balance is formed based on the law of conservation ofmass in Eqs. (1)–(1b).

Table

Chem

Ma

FarCaOCOSiOAl2Fe2MgK2OSO3

Na2TotCoa

CSN2

H2

O2

H2OCaOSiOAl2Fe2MgK2OSO3

TotAirO2

ð

N2ð

Tot

Ove

(*): p

4CaO

Xmin ¼

Xmex ð1Þ

where
Xmin ¼ mfarine þ mcoal þ mair ð1aÞ
Xmex ¼ mclinker þ mDust þ mS�gases ð1bÞ

1

ical analysis of materials going into and leaving RB [7–9]

terials going into RB Materials leaving RB

ine (kg/h) Clinker (kg/h)68 948.80 C3S 57 111.30

2 20 467.70 C2S 13 438.50

2 18 924.80 C3A 9104.70O3 5520.70 C4AF 10 955.40O3 3676.50 MgO 1357.80O 1735.80 SO3 232.50

843.80 K2O 660.30241.10 Na2O 139.50

O 180.80 Total 93 000.00al 120 540.00 Dust (kg/h)l (kg/h) CaO 7427.79

5668.25 SiO2 40.30389.50 Al2O3 83.75164.00 Fe2O3 291.79451.00 MgO 410.8461.25 SO3 78.301610.27 K2O 204.0038.95 Na2O 41.30

2 831.28 Total 8578.03O3 297.25 Stack gases (kg/h)O3 215.25 CO2 40 693.43O 32.80 CO 355.00

20.50 SO2 779.0069.70 H2O 5669.30

al 10 250.00 O2ð��Þ 38 206.02

(kg/h) N2ð��Þ 186 558.22

�Þ 56 654.78 Total 272 260.97�Þ 186 394.22al 243 049.00

rall 373 839.00 Overall 373 839.00

rimary air + secondary air; (**): waste air; C3S: 3CaO Æ SiO2; C2S: 2CaO Æ SiO2; C3A: 3CaO ÆAl2O3; C4AF:

ÆAl2O3 ÆFe2O3.


4. Energy analysis in the rotary burner (RB)

The first law of thermodynamics, which is called the law of conservation of energy, is used forthe energy analysis for the RB. When this law is applied to a system in which chemical reactionsare occurring, the following equation can be written:

Table

Const

Sub

CaO

ÆSiOÆSiOAl2O

<Fe

<Fe

<Fe

T ¼ T

Qcv þXin

minðh0f þ Dhþ V 2in=2þ gGzinÞ ¼ Wcv þ

Xex

mexðh0f þ Dhþ V 2ex=2þ gGzexÞ þ QL ð2Þ

The following assumptions are made for the energy analysis:

• Heat ðQcvÞ is not given out of the system.• Electrical energy ðWcvÞ used for the RB to rotate is not included in the analysis.• Kinetic and potential energies of materials going into and leaving the system are neglected.

Eq. (2) can be written as Eq. (3) when the assumptions above are taken into consideration.

Xin

minhT;P ¼Xex

mexhT;P þX

QL ð3Þ

where

hT;P ¼ h0f þ Dh ð4Þ

Dh ¼Z T

298

cp dT ð5Þ

cp ¼ aþ bT þ cT�2 ð6Þ

The a, b and c coefficients in Eq. (6) change with material types. The coefficients of some materialsused in the RB are listed in Table 2.

2

ant pressure specific heat and its coefficients of some substances used in the RB [10]

stance a b c �cp ¼ aþ b � T þ c � T�2 (kcal/kmolK)

11.86 1.08· 10�3 )1.66· 105 11:86þ 1:08 10�3T � 1:66 105T�2

2æ 3.27 24.8· 10�3 – 3:27þ 24:8 10�3T ð298 < T < 390Þ2æ 13.64 2.64· 10�3 – 13:64þ 2:64 10�3T ð390 < T < 2000Þ3 25.48 4.25· 10�3 )6.82· 105 25:48þ 4:25 10�3T � 6:82105T�2 ð298 < T < 1800Þ

2O3>a 23.5 18.6· 10�3 )3.55· 105 23:5þ 18:6 10�3T � 3:55105T�2 ð298 < T < 950Þ2O3>b 36 – – 36 ð950 < T < 1050Þ

31:7þ 1:76 10�3T2O3>d 31.7 1.76· 10�3 – ð1050 < T < 1873ÞðKÞ; Æ æ: solid phase; h ia: a-phase; h ib: b-phase; h id: d-phase.


4.1. Enthalpies of materials going into and leaving RB

The enthalpies of the materials going into and leaving the RB are given for the chemicalcomponents in Table 3. Eqs. (5) and (6) and Ref. [11] are used to obtain these values.

Table 3

Enthalpies of materials going into and leaving RB

Materials going into RB Materials leaving RB

Farine (1065 K) minhin (kJ/h) Clinker (1423 K) mexhex (kJ/h)

CaO �733 180 854.56 C3S �654 910 126.04

CO2 �165 814 978.01 C2S �159 973 113.47

SiO2 �271 205 631.36 C3A �110 598 796.97

Al2O3 �86 066 608.86 ðCaOÞ4Al2O3

Fe2O3

9=;C4AF

�85 641 719.1

Fe2O3 �16 449 763.95 �34 793 961.43

MgzO �24 324 806.88 �14 961 104.20K2O �2 399 007.78 MgO �18 399 058.99

SO3 �1 035 186.96 SO3 �917 059.05

Na2O �1 021 031.84 K2O �1 608 781.33

Total �1 301 497 870.20 Na2O �574 236.41

Coal (318 K) minhin (kJ/h) Total �1 082 377 956.99

C 95 396.65 Dust (1320 K) mexhex (kJ/h)

S 5639.96 CaO �77 148 740.83

N2 3409.56 SiO2 �563 990.44

H2 129 152.87 Al2O3 �1 278 828.16

O2 8570.03 Fe2O3 �1 239 515.17

H2O �21 561 515.30 MgO �5 622 233.45

CaO �440 481.66 SO3 �316 804.15

SiO2 �12 589 378.15 K2O �520 901.76

Al2O3 �4 880 170.24 Na2O �208 668.66

Fe2O3 �1 108 035.97 Total �86 899 682.62

MgO �488 581.26 Stack gases (1373 K) mexhex (kJ/h)

K2O �78 338.70 CO2 �313 599 035.08

SO3 �343 622.39 CO �964 822.55

Total �41 247 954.60 SO2 �2 941 659.80

Air (1373 and 298 K) (kJ/h) H2O �62 819 585.74

O2ð�Þ 59 888 721.99 O2

ð��Þ 42 982 918.68

N2ð�Þ 212 642 102.89 N2

ð��Þ 226 509 662.81

Total 272 530 824.88 Total �110 832 521.68

Reaction energy _E (kJ/h)

C (for CO2) �185 879 172

H2 (for H2O) �56 247 620

S (for SO2) �3 618 141

Total �245 744 933

Overall �1 315 959 932.92

(�365 544 kW)

Overall �1 280 110 161

(�355 586 kW)

(*): primary air + secondary air; (**): waste air; C3S: 3CaO Æ SiO2; C2S: 2CaO Æ SiO2; C3A: 3CaO ÆAl2O3; C4AF:

4CaO ÆAl2O3 ÆFe2O3.


4.2. Heat loss from RB

4.2.1. Heat loss by conduction from wall of RB

The geometric shapes of the RB and RB surface with the electrical analogy of the thermalconductivities of the RB wall are given in Figs. 3–5 in order to calculate the heat losses. Fur-thermore, the thermal values of the RB are tabulated in Table 4 [7]. These values are measured bythe firm authorities. There are three regions based on the temperature in the RB as seen in Fig. 3.

Heat loss by conduction from the surface of the RB is given by the following equation:

_Qcond ¼Tin1 � Tsur1

lnðr2=r1Þ2pkanzl1

þ lnðr3=r2Þ2pkbr�Al2O3l1

þ lnðr4=r3Þ2pkstsl1

þ Tin2 � Tsur2lnðr2=r1Þ2pkanzl2

þ lnðr3=r2Þ2pkbr�MgOl2


þ Tin3 � Tsur3lnðr2=r1Þ2pkanzl3

þ lnðr3=r2Þ2pkbr�Al2O3l3


ð7Þ

4.2.2. Heat loss by radiation from inlet of RB, by convection from surface of RB

Heat loss by radiation from the left and right ends of the RB inlet can be calculated usingEq. (8), by convection from the surface using Eq. (9) and by the total heat loss using Eq. (10):

Al2O3 MgO Al2O3

Steel sheet (r3-r4)Bricks (r2-r3)

Anzast layer (r1-r2)r1 = 1700 mmr2 = 1768 mmr3 = 2168 mmr4 = 2200 mm

43 m 20 m 3 m

Tin1 Tin2

Tsur1 Tsur2 Tsur3

Tin3

Fig. 3. Geometric shape of RB.

Steel sheet (r3-r4

r4

r3

r2

r1

)

Bricks with Al2O3 or MgO (r2-r3)

Anzast layer (r1-r2)

Fig. 4. Physical construction of RB wall.

Bricks with Chrome -nickelAnzast Layer Al2O3 or MgO Steel sheet

lkanz2

1

lkbrπ π2

1

lksts2

1

π

Fig. 5. Electrical analogy of thermal conductivities for RB wall.

Table 4

Thermal values of RB

Thermal properties Numerical values Thermal properties Numerical values

Tin1 1423 K Tsur1 423 K

Tin2 1823 K Tsur2 393 K

Tin3 1473 K Tsur3 473 K

kanz 0.3 kW/mK kbr-Al2O32.09 kW/mK

kbr-MgO 2.32 kW/mK

ksts 36.4 kW/mK l1 43 m

l2 20 m l3 3 m


_Qrad ¼ reðT 4in � T 4

0 ÞA ð8Þ

_Qconv ¼ hAðTsur � T0Þ ð9Þ
X
_QL ¼ _Qcond þ _Qrad þ _Qconv ¼ 9958 kW ð10Þ

4.2.3. Energy efficiencyThe energy efficiency is expressed as the ratio of the energies leaving the RB to the energies

entering the RB. So, the energy efficiency and its result can be written as Eq. (11):

g ¼��X

mex � ðhT;PÞ��

Xmin � ðhT;PÞ

�� ¼ j � 355586j=j � 365544j ¼ 97% ð11Þ

5. Exergy analysis for a control volume

There are many studies applying second law analysis [12–19]. The concept of exergy has beenappearing in the international thermodynamic world with increasing frequency for one or twodecades. Nonetheless, the concept of exergy is uncommon in descriptions of industrial processes.This is unfortunate, particularly since the concept of exergy will be used routinely in processanalysis in the near future. The concept is both readily understood and easy to apply [3].

The various kinds of energy display different qualities. These differences appear in their abilityto feed energy driving processes and to be converted into other kinds of energy [8]. The standardof energy quality is called exergy. So, exergy analysis is a powerful concept for physical andchemical processes. Besides,


• Exergy analysis provides an alternative view on the correct efficiency of a process.• Exergy analysis is very useful to find operations where efficiency improvements are the most

suitable or useful [11].

There are three types of exergy transfer across the control surface of a system:

1. Exergy of work transfer.2. Exergy of heat transfer.3. Exergy associated with the steady stream of matter.

5.1. Exergy of work transfer

The maximum work delivered by the system Wmax is only partly available for use. One partP0DV is spent in order to displace the atmosphere. The remaining part is the exergy of the system.So, the exergy relation can be written as follows:

EW ¼ Wmax � P0DV ð12Þ

5.2. Exergy of heat transfer

Since heat cannot be totally converted into work, heat has a lower exergy compared with work.The exergy of heat at the control surface can be defined as follows:

EQ ¼ Qcv � ð1� T0=T Þ ð13Þ

5.3. Exergy associated with a steady stream of matter (flow exergy)

The exergy of a stream of matter is equal to the maximum amount of work obtainable when thestream is brought from its initial state to the dead state by reversible processes. The specific exergyof a stream of matter (specific form) can be divided into distinct components. These componentsare written in two forms [20,21]:

1. Thermomechanical exergy ðeTMf Þ2. Chemical exergy ðeCHf Þ

These are:

etot ¼ eTMf þ eCHf ð14Þ

where

eTMf ¼ ePHf þ eKNf þ ePTf ¼ ðh� T0sÞ � ðh0 � T0s0Þ þ

C2

2þ gGz0 ð15Þ

eCHf ¼ ðli0 � li00Þ ð16Þ


li0 and li00 can be given by the following Eqs. (16a) and (16b) for reference substances, assumedas ideal gases.

li0 ¼ gi0 þ R � T0 � LnðPi0=P0Þ ð16aÞ

li00 ¼ gi0 þ R � T0 � LnðPi00=P0Þ ð16bÞ

gi0 ¼ hi0 � T0 � si0 ð16cÞ

If some of the species i of the system or of streams do not exist in the environment, li00 will bedetermined by one of the known methods for a gaseous fuel and a mixture [22,23].

5.4. Exergy analysis in RB

The exergy balance for a steady flow system is given by the following equation:

Ein � Eex � EQ � EL ¼ Es ð17Þ
Eq. (17) shows that exergy losses are caused by irreversibilities. If this equation is applied for theRB as seen in Fig. 6, Eqs. (18)–(21) can be obtained. The following assumptions are made toobtain these equations:
1. The system is assumed as a steady state, steady flow process.2. Electrical energy used for the RB to rotate is not included in the analysis in obtaining exergy

equation.3. Stack gases are assumed as ideal gases.4. Pressure effects on enthalpy and entropy of solids are neglected.5. Variations of the potential and kinetic energies are neglected (i.e. eKN

f ¼ ePTf ¼ 0).6. Chemical exergies of the substances are neglected.
X
in

minePHin ¼

Xex

mexePHex þ

XEQ þ EL ð18Þ

where

ePH ¼ ðh� h0Þ � T0ðs� s0Þ ð19Þ

EQ ¼ QL � ð1� T0=TsurÞ ð20Þ

RBΣin

min εinPH

Σex

mex exPH

Σ EQ

ε

Fig. 6. Exergies going into and leaving rotary burner.

Table

Nume

Ma

Far

CaO

CO

SiO

Al2O

Fe2MgK2O

SO3

Na2Tot

Coa

C

S

N2

H2

O2

H2O

CaO

SiO

Al2O

Fe2Mg

K2O

SO3

Tot

Air

O2ð�

N2ð

Tot

Exe

co

C

H2

S

Tot

Ove

(*): pr

ve S a

(****)�e ¼ �g�C3S: 3


EL ¼ T0Sgen ð21Þ

Numerical results of this analysis are given in Table 5.

5

rical results of exergy analysis

terials going into RB Materials leaving RB

in _EPH (kJ/h) Clinker _EPH (kJ/h)

24 813 983.63 C3S 38 982 444.96

2 9 123 681.95 C2S 9 460 417.06

2 8 340 159.36 C3A 6 064 725.29

3 2 459 361.43 ðCaOÞ4Al2O3

Fe2O3

9=;C4AF

22 041 142.08

O3 1 340 304.84 2 447 395.14

O 820 755.67 2 179 805.72482 780.17 MgO 1120 945.36

82 451.37 SO3 141 315.82

O 104 498.78 K2O 581 374.34

al 47 567 977.20 Na2O 246 000.31

l _EPH (kJ/h) Total 83 265 566.08

15 187.18 Dust _EPH (kJ/h)

982.64 CaO 4 044 505.93

516.67 SiO2 27 894.05

16 527.34 Al2O3 78 358.17

2 067.35 Fe2O3 155 909.23

4 948.47 MgO 295 571.35

138.50 SO3 41 262.53

2 3561.51 K2O 160 180.80

3 1492.00 Na2O 42 414.27

O3 892.53 Total 4 846 096.33

O 258.86 Stack gases _EPH (kJ/h)

43.30 CO2 30 088 733.78

249.36 CO 256 417.74

al 46 865.71 SO2 394 416.60_EPH (kJ/h) H2O 7 900 863.40

Þ 35 342 985.70 O2ð��Þ 25 366 122.86

�Þ 125 003 748.25 N2ð��Þ 133 155 929.53

al 160 346 733.95 Total 197 162 483.91

rgy after reaction of

al

_EPHð��Þ (kJ/h) Lost exergy 157 585 277.07

186 284 202.13ð��Þ

44 955 847.20ð��Þ

3 657 797.20ð��Þ

al 234 897 846.53

rall 442 859 423.39 Overall 442 859 423.39

imary air + secondary air; (**): waste air; (***): The exergies values are found by using Gibbs function for C, H2

ccording to chemical reactions below.

: C+O2 !CO2; (*****): H2+1/2O2 !H2O; (******): S+O2 !SO2.

CO2� �gC � �gO2

; �e ¼ �g�H2O � �gH2� 1=2 � �gO2

; �e ¼ �g�SO2� �gS � �gO2

.

CaO Æ SiO2; C2S: 2CaO Æ SiO2; C3A: 3CaO ÆAl2O3; C4AF:4CaO ÆAl2O3 ÆFe2O3.


5.5. Exergy efficiency

The exergy efficiency is a measure of how effectively the input exergy is converted into theexergy of the products. So, exergy efficiency is defined by the following equation:

w ¼X

mexeex=X

minein ¼ 1�X

EL=X

mineinh i

¼ 1� ½157585277:07=442859423:39� ¼ 0:644 ð22Þ

6. Conclusions

• Heat losses by conduction, convection and radiation from the RB are about 3% of the heatcoming into the system. Although this ratio is seen to be low, the total amount is very conside-rable from the viewpoint of process duration. So, it is significant to reduce heat losses by usinginsulation materials for the RB.

• Dust and stack gases occurring in the system transport the most significant amount of energyout of the RB. Some of this energy is used in the pre-heater system. The amount of energy thatis not used in the pre-heater system can be utilized in various sections of the plant as processheat.

• Waste air also transfers a very important amount of energy from the RB. Accordingly, theamount of air coming into the RB should be controlled.

• The percent of lost exergy is 35.6% of the total exergies. This is the highest ratio after the exergypercent of stack gases. The exergy losses in the RB are caused by chemical reactions, forming ofclinker, heat transfer and other reasons.

• Stack gases and the waste air in them have a considerable amount of exergy. It is possible to usethe unused portion of this energy in other applications.

• Although the energy efficiency is about 97%, the exergy efficiency is 64.4%. So, it is seen thatexergy analysis accounts for the operation, indicating the locations of energy degradation inthe process.

• The exergy efficiency at another plant in Turkey was obtained to be 64.5% [5]. This value isclose to the value obtained in this study.

References

[1] Moran MJ. Availability analysis. New Jersey: Prentice-Hall, Inc.; 1982.

[2] Morris DR, Szargut J. Standard chemical exergy of some elements and compounds on the planet earth. Exergy

1986;11(8):733–55.

[3] Wall G. Exergy flows in industrial processes. Energy 1998;13(2):197–208.

[4] C�elen F. Exergy analysis in a Rotary Burner With Pre-Calcination In Dry System Cement Production. Kırıkkale

University Institute of Science & Technology, M.S. Thesis, 1998.

[5] Kolip A, €Uzt€urk _IT, K€ose R, Arıkol M. Energy and exergy analysis for cement factory. In: Proceedings of the

Workshop on the Second Law of Thermodynamics, Erciyes University and Turkish Soc. Thermal Scis. and Tech.

(T.S.T.S.T), August 27–30, 1990, Kayseri, Turkey.


[6] G€ur€uz HK. Mass and energy balances in cement factories. J Chamber Chem Eng (Turkish) 1977;84.

[7] C�amdalı €U, C�elen F, Eris�en A. Thermodynamic analysis in the rotary burner with pre-calcination in dry system

cement production. J Chamber Chem Eng (Turkish) 1999;(157):16–20.

[8] C�amdalı €U, C�elen F, Eris�en A. Exergy analysis in the rotary burner with pre-calcination in dry system cement

production. Thermodynamic Journal (Turkish). Doga Publication; No: 157, Dec. 1999. p. 71–80.

[9] Weast RC, editor. CRC handbook of chemistry and physics. 54th ed. Cleveland, OH: CRC Press; 1973.

[10] Kubaschewski O, Evans EL, Alcock CB. Metallurgical thermo-chemistry. Pergamon Press; 1989.

[11] Barin I, Knacke O, Kubaschewski O. Thermochemical properties of inorganic substances. Berlin: Springer Verlag;

1973. supplement (1977).

[12] Chengxu S, Jianming X. The exergy analysis of a glass tank furnace. Glass Technol 1996;32(6).

[13] Rosen MA. Evaluation of energy utilization efficiency in canada using energy and exergy analyses. Energy

1992;17(4):339–50.

[14] Morris DR. Exergy analysis and cumulative exergy consumption of complex chemical processes: the industrial

chlor-alkali processes. Chem Eng Sci 1991;46(2):459–65.

[15] Sergio A, Jose I. Minimum energy requirements in industrial processes: an application of exergy analysis. Energy

1990;15(11):1023–8.

[16] Faleh S, Basil I. Exergy analysis of major recirculating multi-stage flash desalting plants in Saudi Arabia.

Desalination 1995;103:265–7.

[17] McGovern JA, Harte S. An exergy method for compressor performance analysis. Int J Refrig 1995;18(6):421–33.

[18] C�amdalı €U, Tunc� M, Dikec� F. A thermodynamic analysis of a steel production step carried out in a ladle furnace.

Appl Thermal Eng 2001;21:643–55.

[19] C�amdalı €U, Tunc� M, Karakas� A. Second law analysis of thermodynamics in the electric arc furnace at a steel

producing company. Energy Convers Manage 2003;44:961–73.

[20] Szargut J, Morris R, Steward FR. Exergy analysis of chemical and metallurgical processes. Hemisphere Publishing

Corporation; 1988.

[21] Kotas TJ. The exergy method of thermal plants analysis. London: Butterworths; 1985.

[22] G€o�g€us� Y, C�amdalı €U. General exergy balance of a system with variation of environmental conditions and some

applications. In: Proceedings of Energy Systems and Ecology Conference (ECOS) 2000, July 5–7, 2000. p. 1117–

1130.

[23] G€o�g€us� Y, C�amdalı €U, Kavsao�glu MS�. Exergy balance of a general system with variation of environmental

conditions and some applications. Energy 2002;27:625–46.

semen 30

Documents