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ENERGY AND EXERGY EFFICIENT GRATE CLINKER COOLING SYSTEM
MUHAMMAD IRFAN BIN SHAHINUDDIN
FACULTY OF ENGINEERING UNIVERSITY OF MALAYA
KUALA LUMPUR
JULY 2011
ENERGY AND EXERGY EFFICIENT GRATE CLINKER COOLING SYSTEM
MUHAMMAD IRFAN BIN SHAHINUDDIN
RESEARCH REPORT SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS
FOR THE DEGREE OF MASTER OF ENGINEERING
FACULTY OF ENGINEERING UNIVERSITY OF MALAYA
KUALA LUMPUR
JULY 2011
ii
UNIVERSITI MALAYA ORIGINAL LITERARY WORK DECLARATION
Name of Candidate: Muhammad Irfan bin Shahinuddin (I.C No: 850715-10-5043)
Matric No: KGH090005
Name of Degree: Master in Mechanical Engineering by Coursework & Research
Title of Dissertation: Energy and Exergy Efficient Grate Clinker Cooling System
Field of Study: Energy Efficiency
I do solemnly and sincerely declare that:
(1) I am the sole author/writer of this Work;
(2) This Work is original;
(3) Any use of any work in which copyright exists was done by way of fair dealing and for permitted purposes and any excerpt or extract from, or reference to or reproduction of any copyright work has been disclosed expressly and sufficiently and the title of the Work and its authorship have been acknowledged in this Work;
(4) I do not have any actual knowledge nor do I ought reasonably to know that the making of this work constitutes an infringement of any copyright work;
(5) I hereby assign all and every rights in the copyright to this Work to the University of Malaya (“UM”), who henceforth shall be owner of the copyright in this Work and that any reproduction or use in any form or by any means whatsoever is prohibited without the written consent of UM having been first had and obtained;
(6) I am fully aware that if in the course of making this Work I have infringed any copyright whether intentionally or otherwise, I may be subject to legal action or any other action as may be determined by UM.
Candidate’s Signature Date
Subscribed and solemnly declared before,
Witness’s Signature Date
Name:
Designation:
iii
ACKNOWLEDGEMENT
The completion of this research report is not without the help or assistance received
from other individual(s) or parties. I would therefore like to take this opportunity to
express my sincerest of gratitude towards these helpful hands.
First and foremost, I would like to thank my supervisor, Assoc. Prof. Dr. Saidur
Rahman for the aid and support given throughout the two semesters of preparing this
dissertation.
Secondly, I would like to thank my university mates and friends for the
information shared and the technical help provided, making learning a more
meaningful experience along the way.
Lastly, I would like to thank my family for all the direct and indirect assistance
given throughout the entire duration of undertaking this task.
iv
ABSTRACT
The cement production ranks among the most energy intensive industrial
processes, for which energy expenditure alone typically accounts for 30-40% of the
production cost. It also contributes towards atmospheric pollution via the emission of
major air pollutants such as nitrogen oxides, carbon monoxide and particulate matter,
and greenhouse gas carbon dioxide. The goal of this study is to improve the efficiencies
of a grate clinker cooling system through the optimization of its operational parameters,
which consequently reduces the cost of thermal energy and the emissions of air
pollutants and greenhouse gas. The study uses two approaches, i.e. the conventional
energy analysis as well as the exergy analysis of the system’s operational parameters,
i.e. mass flow rate of cooling air, cooling air temperature, mass flow rate of clinker and
grate speed, through simulated air and clinker temperature profiles. It was found that
the energy efficiency and the energy recovery efficiency can be increased by an
average of 2.3% and 1.6% respectively, while the exergy efficiency and the exergy
recovery efficiency by an average of 2.5% and 1.9% respectively, for every 5%
optimization of the operational parameters of the system. The exhaust heat recovery
alone contributes to 21.5% of energy recovery efficiency and 9.4% of exergy recovery
efficiency. The cost benefit analyses suggest that decreasing the mass flow rate of
clinker is the most beneficial way to improve the system’s efficiencies, with USD 0.196
per tonne of clinker of cost saving, 6.1 months of payback period, an investment
present value of USD 483,141.00, and a cost of USD 0.41/GJ energy conserved.
Results from the emission reduction analysis also prove that decreasing the mass flow
rate of clinker contributes the most towards emission reduction per unit clinker
produced, i.e. 0.037 kg of NOx/tonne, 0.029 of CO/tonne, 0.002 kg of PM/tonne, and
4.393 kg of CO2/tonne.
v
ABSTRAK
Proses pengeluaran semen merupakan di antara proses yang paling banyak
menggunakan tenaga, di mana penggunaan tenaga sahaja merangkumi 30-40% kos
pengeluaran. Proses tersebut juga menyumbang kepada pencemaran udara melalui
pembebasan gas-gas pencemar seperti oksida-oksida nitrogen, karbon monoksida dan
habuk, serta gas rumah hijau karbon dioksida. Tujuan kajian ini adalah untuk
meningkatkan efisiensi-efisisensi penyejuk klinker jenis memayang melalui
pengoptimalan parameter-parameter operasinya. Ianya akan menyumbang kepada
pengurangan kos tenaga haba dan pembebasan gas-gas pencemar serta gas rumah hijau.
Kajian ini menggunakan dua kaedah, iaitu analisis tenaga dan analisis eksergi bagi
parameter-parameter operasi yang terpilih seperti kadar jirim udara penyejuk, suhu
udara penyejuk, kadar jirim klinker, dan kelajuan memayang, berlatarkan profil suhu
udara dan klinker yang disimulasikan. Kajian mendapati efisiensi-efisiensi prinsip
pertama dapat ditingkatkan sebanyak 2.3% dan 1.6% secara purata, manakala efisiensi-
efisienci prinsip kedua sistem sebanyak 2.5% dan 1.9% secara purata, bagi setiap 5%
pengoptimalan parameter-parameter operasi sistem. Penggunaan kembali tenaga haba
yang terkandung di dalam udara ekzos secara puratanya menyumbangkan 21.5% dan
9.4% daripada effisiensi-efisiensi prinsip pertama dan efisiensi-efisiensi prinsip kedua
sistem. Analisis-analisis kos menunjukkan bahawa pengurangan kadar jirim klinker
merupakan kaedah terbaik bagi meningkatkan efisiensi-efisiensi sistem, dengan
pengurangan kos sebanyak USD 0.196 setiap ton klinker, 6.1 bulan bayaran balik
pelaburan, USD 483,141.00 nilai pelaburan semasa, dan USD 0.41/GJ kos tenaga yang
diselamatkan. Analisis pengurangan pembebasan gas pencemar juga menyarankan
pengoptimalan kadar jirim klinker dapat mengurangkan 0.037 kg NOx, 0.029 kg CO,
0.002 kg PM, dan 4.393 kg CO2 bagi setiap ton klinker dihasilkan.
vi
TABLE OF CONTENTS
Page
ABSTRACT iv
ABSTRAK v
TABLE OF CONTENTS vi
LIST OF FIGURES x
LIST OF TABLES xiii
LIST OF SYMBOLS & ABBREVIATIONS xviii
CHAPTER I: INTRODUCTION
1.1 Introduction 1
1.2 Motivation of Study 3
1.3 Objectives 5
1.4 Scope of Study 7
1.5 Research Report Structure 8
CHAPTER II: LITERATURE REVIEW
2.1 Cement Industry and Cement Production Energy 10
2.2 Air Pollutants and Greenhouse Gas Emissions from the Cement 11
Production Process
2.3 Cement Process Description 13
2.4 Clinker Cooler 14
2.5 Energy Efficiency Improvement Opportunities for Grate Clinker Coolers 16
2.6 Energy Analysis of the Grate Clinker Cooler 17
2.7 Exergy and Entropy Production Analysis of the Grate Clinker Cooler 18
2.8 Operational Parameters of the Grate Clinker Cooler 20
vii
CHAPTER III: METHODOLOGY
3.1 Energetic & Exergetic Analyses 23
3.1.1 Energy & Exergy Analyses Data 24
3.1.2 First Law Analysis of the Grate Clinker Cooler 26
3.1.3 Second Law Analysis of the Grate Clinker Cooler 28
3.2 Cost Benefit 30
3.2.1 Potential Energy & Cost Savings 30
3.2.2 Payback Period 31
3.2.3 Present Value 32
3.2.4 Capital Recovery Factor 32
3.2.5 Cost of Conserved Energy 32
3.3 Emission Reduction 33
CHAPTER IV: RESULTS & DISCUSSIONS
4.1 Energy Analysis of the Base Case Clinker Cooler 34
4.1.1 Mass Balance 34
4.1.2 Energy Balance 35
4.2 Exergy Analysis of the Base Case Clinker Cooler 36
4.2.1 Exergy Balance 37
4.3 Operational Parameter: Mass Flow Rate of Cooling Air 40
4.3.1 Change in First & Second Law Efficiencies of the 40
Grate Clinker Cooling System
4.3.2 Electrical Energy Requirement with Increment in 46
Mass Flow Rate of Cooling Air
viii
4.4 Operational Parameter: Temperature of Cooling Air 49
4.4.1 Change in First & Second Law Efficiencies of the 49
Grate Clinker Cooling System
4.4.2 Heat Energy Requirement with Increment in Temperature of 52
Cooling Air
4.5 Operational Parameter: Mass Flow Rate of Clinker 54
4.5.1 Change in the First & Second Law Efficiencies of the 54
Grate Clinker Cooling System
4.5.2 Energy Requirement with Decrement in Mass Flow 58
Rate of Clinker
4.6 Operational Parameter: Grate Speed 61
4.6.1 Change in First & Second Law Efficiencies of the 61
Grate Clinker Cooling System
4.6.2 Energy Requirement with Increment in Grate Speed 69
4.7 Heat Recovery of Exhaust Air 65
4.7.1 Change in First & Second Law Efficiencies of the 67
Grate Clinker Cooling System
4.7.2 Use of Exhaust Air Recovery to Pre-heat the Raw Materials 70
4.8 Potential Energy & Cost Savings 72
4.9 Payback Period 76
4.10 Present Value 79
4.11 Capital Recovery Factor 80
4.12 Cost of Conserved Energy 82
4.13 Summary of the Cost Benefit Analyses 84
4.14 Emission Reduction 86
ix
CHAPTER V: CONCLUSIONS & RECOMMENDATIONS
5.1 Conclusions 90
5.2 Recommendations 92
REFERENCES 94
APPENDICES 97
Appendix A: Mass Flow Rate of Cooling Air Energy & Exergy Analyses 98
Appendix B: Cooling Air Temperature Energy & Exergy Analyses 103
Appendix C: Mass Flow Rate of Clinker Energy & Exergy Analyses 107
Appendix D: Grate Speed Energy & Exergy Analyses 113
Appendix E: Heat Recovery of Exhaust Air Energy & Exergy Analyses 119
Appendix F: Energy & Cost Saving Analyses 120
Appendix G: Incremental Operations Cost Analyses 121
Appendix H: Economic Analyses 123
Appendix I: Emission Reduction Analysis 125
x
LIST OF FIGURES
Figure No. Page
1.3 Objectives & methodologies 6
2.3 Flow diagram of typical dry process in cement production 14
2.4 Grate clinker cooler schematic 15
2.6 Energy flow diagram of the clinker cooling system 18
2.7 Exergy flow diagram of the clinker cooling system 19
3.1.2 Energy balance schematic of the grate clinker cooler 27
3.1.3 Exergy balance schematic of the grate clinker cooler 29
4.3.1 (a) Variation of average caloric temperature of the clinker along the
length of cooler at different mass flow rate of cooling air
40
4.3.1 (b) Variation of air temperature at freeboard region along the length
of cooler at different mass flow rate of cooling air
41
4.3.1 (c) Variation in first law efficiencies of the grate clinker cooler with
increment in mass flow rate of cooling air
43
4.3.1 (d) Variation in second law efficiencies of the grate clinker cooler
with increment in mass flow rate of cooling air
45
4.4.1 (a) Effect of inlet temperature ratio on entropy production in the
grate clinker cooler
49
4.4.1 (b) Variation in second law efficiencies of the grate clinker cooler
with change in temperature of cooling air
50
4.4.1 (c) Variation in first law efficiencies of the grate clinker cooler with
change in temperature of cooling air
51
4.5.1 (a) Variation of clinker temperature along the length of cooler at
different mass flow rate of clinker
54
xi
4.5.1 (b) Variation in first law efficiencies of the grate clinker cooler with
decrement in mass flow rate of clinker
56
4.5.1 (c) Variation in second law efficiencies of the grate clinker cooler
with decrement in mass flow rate of clinker
57
4.6.1 (a) Variation of air temperature along the length of cooler at different
grate speeds
61
4.6.1 (b) Variation in first law efficiencies of the grate clinker cooler at
different grate speeds
62
4.6.1 (c) Variation in second law efficiencies of the grate clinker cooler at
different grate speeds
64
4.7.1 (a) Variation in energy recovery efficiency of the grate clinker cooler
with varying operational parameters
68
4.7.1 (b) Variation in exergy recovery efficiency of the grate clinker cooler
with varying operational parameters
69
4.7.2 Energy balance of the grinding mill for the drying process of raw
materials
71
4.8 Energy saving contribution of the operational parameters 72
4.9 Payback period of the investment made for every 5%
optimization of the operational parameters of the grate clinker
cooler
77
4.10 Present values of the investment made for every 5% optimization
of the operational parameters of the grate clinker cooler
79
4.12 Cost of conserved energy for every 5% optimization of the
operational parameters of the grate clinker cooler
82
4.14 (a) Average emission reduction for every 5% optimization of the
grate clinker cooler’s operational parameters
87
xii
4.14 (b) Average CO2 emission reduction for every 5% optimization of
the grate clinker cooler’s operational parameters
88
xiii
LIST OF TABLES
Table No. Page
2.1 Global energy consumption for cement production 11
2.2 Global carbon emission from cement production 12
2.3 Energy required by different process phases 13
2.7 Summary of results, discussions and conclusions of the grate
clinker cooler computational modelling
21
3.1.1 Summary of input and output data of the base case clinker cooler 25
3.1.2 Energy input & output of the clinker cooler 26
4.1.2 Energy analysis summary of the base case clinker cooler 35
4.2.1 Exergy analysis summary of the base case clinker cooler 38
4.3.2 Additional fan electrical energy requirement for every 5%
increase in mass flow rate of cooling air
48
4.5.2 Additional energy requirement for every 5% decrease in mass
flow rate of clinker
60
4.8 (a) Energy saving summary for every 5% optimization of the
operational parameters
72
4.8 (b) Cost saving summary for every 5% optimization of the
operational parameters
73
4.8 (c) Energy and cost saving comparison between operational
parameters of clinker cooler and the exhaust air heat recovery
74
4.9 Summary of the costs incurred to optimize the operational
parameters of the grate clinker cooler
76
4.13 Summary of the cost benefit analyses
84
xiv
4.14 Average emission reduction for every 5% optimization of the
grate clinker cooler’s operational parameters
86
A1 (a) Base case clinker cooler 98
A1 (b)
A1 (c)
5% increase in mass flow rate of cooling air
10% increase in mass flow rate of cooling air
98
98
A1 (d) 15% increase in mass flow rate of cooling air 98
A1 (e) 20% increase in mass flow rate of cooling air 99
A1 (f) Energy efficiencies 99
A1 (g) Average improvement in energy efficiencies 99
A1 (h) Energy recovery efficiency with exhaust heat recovery 100
A1 (i) Average energy saving 100
A2 (a) Base case clinker cooler 101
A2 (b) 5% increase in mass flow rate of cooling air 101
A2 (c) 10% increase in mass flow rate of cooling air 101
A2 (d) 15% increase in mass flow rate of cooling air 101
A2 (e) 20% increase in mass flow rate of cooling air 102
A2 (f) Exergy efficiencies 102
A2 (g) Average improvement in exergy efficiencies 102
A2 (h) Exergy recovery efficiency with exhaust heat recovery 102
B1 (a) Base case clinker cooler 103
B1 (b) 5% decrease in cooling air temperature 103
B1 (c) 5% increase in cooling air temperature 103
B1 (d) Energy efficiencies 104
B1 (e) Average improvement in energy efficiencies 104
B1 (f) Energy recovery efficiency with exhaust heat recovery 104
B1 (g) Average energy saving 104
xv
B2 (a) Base case clinker cooler 105
B2 (b) 7.4% increase in exergy destruction with every 5% decrease in
cooling air temperature
105
B2 (c) 7.4% decrease in exergy destruction with every 5% increase in
cooling air temperature
105
B2 (d) Exergy efficiencies 106
B2 (e) Average improvement in exergy efficiencies 106
B2 (f) Exergy recovery efficiency with exhaust heat recovery 106
C1 (a) Base case clinker cooler 106
C1 (b) 5% decrease in mass flow rate of clinker 107
C1 (c) 10% decrease in mass flow rate of clinker 107
C1 (d) 15% decrease in mass flow rate of clinker 108
C1 (e) 20% decrease in mass flow rate of clinker 108
C1 (f) Energy efficiencies 108
C1 (g) Average improvement in energy efficiencies 108
C1 (h) Energy recovery efficiencies with exhaust heat recovery 109
C1 (i) Average energy saving 109
C2 (a) Base case clinker cooler 110
C2 (b) 5% decrease in mass flow rate of clinker 110
C2 (c) 10% decrease in mass flow rate of clinker 110
C2 (d) 15% decrease in mass flow rate of clinker 111
C2 (e) 20% decrease in mass flow rate of clinker 111
C2 (f) Exergy efficiencies 112
C2 (g) Average improvement in exergy efficiencies 112
D1 (a) Base case clinker cooler 113
D1 (b) 9.1% increment in grate speed 113
xvi
D1 (c) 18.2% increment in grate speed 113
D1 (d) 27.3% increment in grate speed 114
D1 (e) 36.4% increment in grate speed 114
D1 (f) Energy efficiencies 114
D1 (g) Average improvement in energy efficiencies 114
D1 (h) Energy recovery efficiencies with exhaust heat recovery 115
D1 (i) Average energy saving 115
D2 (a) Base case clinker cooler 116
D2 (b) 9.1% increment in grate speed 116
D2 (c) 18.2% increment in grate speed 116
D2 (d) 27.3% increment in grate speed 117
D2 (e) 36.4% increment in grate speed 117
D2 (f) Exergy efficiencies 117
D2 (g) Average improvement in exergy efficiencies 118
E1 Varying mass flow rate of cooling air 118
E2 Varying temperature of cooling air 119
E3 Varying mass flow rate of clinker 119
E4 Varying grate speed 119
F1 Energy saving 120
F2 Cost saving 120
F3 Exhaust air recovery 120
G1 Cooling air mass flow rate upgrades 121
G2 Clinker mass flow rate upgrades 121
G3 Fan power consumption 122
H1 Monthly cash flow 123
H2 Economic appraisal 123
xvii
H3 Investment costs 123
H4 Energy cost 123
H5 Cost of conserved energy 124
H6 Cost estimation 124
I1
I2
Average emission rate
Average emission reduction
125
125
xviii
LIST OF SYMBOLS & ABBREVIATIONS
Symbols/ Abbreviation Meaning
A Annual Net Cash Flow
ACC Annualized Capital Cost
C Specific Heat
CCE Cost of Conserved Energy
ck Clinker
cmh Cubic Meter per Hour
CO Carbon Monoxide
CO2 Carbon Dioxide
CRF Capital Recovery Factor
CS Cost Saving
°C Degree Celcius
Df Specific Drive Force of Cooler
d Discount Factor
EM Emission
EC Energy Cost
ES Energy Saving
E Rate of Energy
Ex Rate of Exergy
e� Specific Exergy
F Force
Ga Grate Surface Area
IC Incremental Cost
IIC Initial Investment Cost
I Rate of Irreversibility
kg Kilogram
xix
kN Kilo Newton
kWh Kilowatt Hour
Lm Life Span of Upgrade
lit Liter
mm Millimeter
m2 Square Meter
m3 Cubic Meter
m Mass Flow Rate
mbar Millibar
MJ Mega Joule
N Strokes per Minute
No. Number
NOx Nitrogen Oxides
P Pressure
P Power
PE Percentage of Electricity
PJ Petajoule
PM Particulate Matter
PV Present Value
Q Rate of Heat
S Stroke Length
SPP Simple Payback Period
T Torque
T Temperature
Tg Teragram
ton Tonne
USD United States Dollars
VSD Variable Speed Drive
xx
W Rate of Work
η Efficiency
ψ Flow Exergy
π Phi
Ʃ Summation