Title Page
Contents
Abbreviations 16
Abstract 17
Chapter 1. Introduction 19
1.1. The Present and Future of Ammonia 21
1.1.1. Application of ammonia in hydrogen production 22
1.1.2. Ammonia production 23
1.1.3. Properties of ammonia as a carbon-free energy source 25
1.2. Literature review/theoretical framework 28
1.2.1. Fundamentals of ammonia combustion 28
1.2.2. Challenges of ammonia combustion 28
1.3. Reactions Mechanisms of Ammonia Combustion 30
1.3.1. Ammonia-air flames propagation and characteristics 31
1.3.2. The ignition characteristics of ammonia combustion 37
1.3.3. The formation of nitrogen oxides (NOₓ) 39
1.3.4. The influence of equivalence ratio on NOx emission 42
1.4. Ammonia Combustion Technologies 45
1.4.1. Characteristics of flameless combustion 47
1.4.2. Heat release characteristics of flameless ammonia-air combustion 47
1.4.3. The lean blow-off limit of ammonia flame 49
1.5. Hazards and Safety Issues of Ammonia Fuel 51
1.5.1. Ammonia accidental fire and explosion hazard 51
1.5.2. Ammonia corrosion risk 53
1.5.3. Health hazards of ammonia 54
1.5.4. Ammonia safety management 57
Chapter 2. Ammonia Combustion Stability 61
2.1. Combustion Stability 61
2.1.1. Ammonia flame stability condition and limits 62
2.2. The Effective Factors of Ammonia Combustion Stability 72
2.2.1. Effect of ammonia laminar flame speed on combustion stability 72
2.2.2. The extinction of ammonia combustion flame 72
2.2.3. Effects laminar burning velocity of ammonia on combustion stability 77
2.2.4. Effects of ignition temperature on ammonia combustion stability 79
2.2.5. Effects of heat released on ammonia combustion stability 80
2.2.6. Effects of swirl number on ammonia combustion stability 80
2.2.7. Effects of residence time on ammonia combustion stability 83
2.2.8. Effects of O₂ concentrations on ammonia combustion stability 83
2.2.9. Effects of fuel composition and species on ammonia combustion stability 85
Chapter 3. Ammonia Combustion Instability 86
3.1. The Characteristic of Ammonia Combustion Instability 86
3.2. Thermal Diffusive Instability of ammonia Combustion 88
3.3. Hydrodynamic Instability characteristics of ammonia Combustion 92
3.4. Thermoacoustic Instability characteristics of ammonia Combustion 97
3.5. The Spectrum of Ammonia Combustion Species 99
Chapter 4. Research Methods and Apparatus 109
4.1. Research Motivation and Objectives 109
4.1.1. Experimental set-up and configuration of flat flameless furnaces 111
4.1.2. The geometric and detailed design of flat flameless ammonia combustor 113
4.1.3. Measurement of ammonia combustion flue gas composition 114
4.2. Elemental Analysis of Combustion Flow and Instability 115
4.3. Experimental Condition and Parameters 117
4.4. Optical Setup of Experimental System 119
4.5. Safety and Hazard Analysis of Ammonia in Flameless Combustion 123
4.5.1. Hazard identification 123
4.5.2. The health and safety assessment of ammonia combustion process 125
Chapter 5. Results and Discussion 127
5.1. Experimental Results of Ammonia Flameless Combustion 127
5.1.1. The real-time temperature data 127
5.1.2. The emission characteristics of ammonia combustion flue gas 129
5.1.3. The evaluation of ammonia combustion stability limits 133
5.2. Optical Study of Ammonia Combustion Processes 136
5.2.1. The emission spectroscopy of ammonia flameless combustion 138
5.2.2. The UV,Visible and IR spectrum from ammonia flameless combustion and species in each of the regions 142
5.2.3. The Effect of equivalence ratio on the spectra of ammonia combustion. 151
5.3. Safety Analysis and Risk Assessment of Ammonia Combustion 153
5.3.1. Ammonia flameless combustion safety hazard identification 153
5.3.2. Evaluation health hazard of ammonia combustion 156
5.3.3. Safety evaluation of released ammonia in exhaust gas 159
5.3.4. Safety evaluation of released hydrogen in exhaust gas 161
5.3.5. Safety evaluation of NOx emission in exhaust gas 162
5.4. Safety risk assessment of experimental ammonia flameless combustion 163
5.4.1. The risks associated with each components of experimental ammonia flameless combustion 163
5.4.2. Summery of risk assessment of ammonia combustion hazards 165
5.5. Control measures for safe use of ammonia in combustion 167
5.5.1. The layers of protection analysis (LOPA) for safe use of ammonia gas 167
5.5.2. Preventive measures for safe handling of ammonia gas and fire suppression system 168
Chapter 6. Conclusion remarks 170
References 176
초록 190
Appendices 191
Appendix 1. [Technology of hydrogen production from ammonia] 191
Appendix 2. [Health hazards and safety of ammonia] 192
Appendix 3. [Utilizing ammonia combustion technology for Carbon Neutrality] 193
Appendix 4. [Process of Converting Ammonia to Hydrogen] 194
Appendix 5. [Green Hydrogen Production Technologies from Ammonia Cracking] 195
Table 1-1. The fundamental combustion characteristics of ammonia. 25
Table 1-2. Comparing properties of ammonia with other fuels. 27
Table 1-3. Ammonia thermodynamic characteristics of compare to other fuels. 29
Table 1-4. The constant parameters of laminar burning velocity of fuel-air mixtures (with methanol, propane, isooctane, and indolene) in terms of equivalence ratio, and... 32
Table 1-5. The possible overall reaction of ammonia and air combustion. 40
Table 1-6. The kinetics model reaction mechanisms of OH* formation and chemiluminescence corresponding rate parameters. 43
Table 1-7. Ammonia exposure symptoms according to the concentration. 55
Table 1-8. The flammability limits and explosion pressures of ammonia. 56
Table 4-1. Overview of a variety of experimental setups and configurations used in the pretest 110
Table 4-2. Experimental condition parameters of lab scale ammonia flameless combustion 117
Table 4-3. Model and specification of high-speed digital camera 119
Table 4-4. Model and specification of spectrometer 120
Table 4-5. The spectral data of species emission intensity corresponding to their wavelengths 120
Table 4-6. The scaling of probability and severity of the risk of ammonia combustion hazards 125
Table 4-7. The assessment matrix for evaluating the likelihood and impact of ammonia risk 126
Table 5-1. Temperature data (℃) at different measuring points of the combustor 128
Table 5-2. The exhaust gas composition of ammonia flameless combustion at different equivalence ratios (0.2 - 1.2). 132
Table 5-3. The effects of turbulence on the stability of ammonia flameless combustion 134
Table 5-4. Characteristics wavelengths of detected species of ammonia 139
Table 5-5. Categorization of the potential hazards of ammonia and its components before, during and after the ammonia combustion process using PHA method 157
Table 5-6. Safety limits of ammonia based on TLV and NFPA 86 standards 158
Table 5-7. The concentration of measuring ammonia, in exhaust gas and in vicinity envirnment of combustion system 159
Table 5-8. Standard for ammonia safety and health evaluation at flue gas and Environment 160
Table 5-9. The experimental result of hydrogen concentration at exhaust gas 161
Table 5-10. The risks associated with NH₃ of experimental ammonia flameless combustion 163
Table 5-11. The risks associated with NOx of experimental ammonia flameless 164
Table 5-12. The risks associated with hydrogen of experimental ammonia flameless combustion 164
Table 5-13. Risk level of hazards with experimental ammonia flameless combustion 165
Table 5-14. Summary of QRA risk assessment of ammonia combustion hazards 165
Figure 1-1. The comparison of greenhouse gas emissions from fossil fuels and industry from 1900-2020. 21
Figure 1-2. An overview of moving from fossil fuel toward hydrogen-based energy. 22
Figure 1-3. Schematic of the 1000 Nm³/hr scale of hydrogen production process from ammonia cracking 23
Figure 1-4. Ammonia production methods based on energy supply for production 24
Figure 1-5. Comparison of ammonia and hydrogen in terms of their energy density with carbon-based fuels. 26
Figure 1-6. The variation of species concentrations and temperature on the flame axis for ammonia methane combustion at different equivalent ratios((a) 0.8, (b) 1.0,... 31
Figure 1-7. Summarizes the ammonia laminar flame characteristics according to the oxygen ratio and equivalence ratio in the oxidizing agent at 1 atmosphere. 33
Figure 1-8. Relationship between laminar burning velocity of NH₃/H₂/air combustion and hydrogen fraction. 33
Figure 1-9. The comparison of the laminar flame velocities of NH₃/H₂/air at different pressure (0.1,0.3,0.5 MPa) and various equivalence ratios with simulation results. 34
Figure 1-10. Comparison of flame velocities of NH₃, H₂, CH₄, and NH₃/H₂ in air at atmospheric pressure and ambient temperature. 34
Figure 1-11. Comparison laminar flame speed ammonia air combustion, in different equivalent ratios, at T=300 K and 1 atm. 35
Figure 1-12. The flame structure of a premixed turbulent combustion. 35
Figure 1-13. The laminar flame velocity (SL) of the ammonia/air mixtures, NH layer thickness (δL,NH), and laminar flame thickness (δL), under various equivalence...[이미지참조] 36
Figure 1-14. The planar laser-induced fluorescence (PLIF) imaging for ammonia laminar premixed flame propagation. 36
Figure 1-15. Comparison of minimum ignition energy of NH₃, H₂, over various equivalence ratio [18,67]. The symbols are □: H₂; ○: NH₃; ·: NH₃/H₂/N₂ (8 vol% H₂,...[이미지참조] 37
Figure 1-16. The adiabatic flame temperature of ammonia, DME, hydrogen, methane, and syngas at equivalence ratios (0.1 - 2.5). 38
Figure 1-17. Comparison of ammonia auto ignition temperature, power, and energy density with other fuels. 38
Figure 1-18. The ignition delay time of ammonia combustion at different temperature (a), and laminar flame speed in terms of equivalence ratio at different pressures (b) 39
Figure 1-19. The NOx formation and reduction in ammonia combustion. 41
Figure 1-20. NOx concentrations for of O₂-rich NH₃/air flames with respect to equivalence ratio. 41
Figure 1-21. comparison of NOx emission from premixed and non-premixed ammonia-methane-air combustion at different equivalence ratio. 42
Figure 1-22. Emission analysis apparatus for exhaust gas and NOx concentration of the NH₃-air combustion and the SCR in gas turbine power generation system. 44
Figure 1-23. A comparison of temperature fluctuations for a flameless combustion compared to a classical diffusion flame in conventional combustion. 46
Figure 1-24. Combustion stability in terms of various mixture velocity: (a) unstable, vmix=30-35 m/s, (b) stable, vmix=50 m/s, (c) unstable, vmix=55-70 m/s.[이미지참조] 47
Figure 1-25. Heat release change of lean pre-mixed flame of NH₃ -CH₄ - air in a model gas turbine with different phase angles. The pressure change is measured by... 48
Figure 1-26. Ammonia safety issues and accidents in ammonia plants and related facilities, explosion of ammonia tank (Bangladesh,2016), India2005, and liquid rocket... 52
Figure 1-27. The anodic voltage E(v) compare to standard hydrogen electrode (SHE), relative corrosion velocity (K) of materials at variety pH diagram. 54
Figure 1-28. The diagram of the steps for effective risk management processes 58
Figure 1-29. The steps of a dynamic QRA and online sensitivities process for hydrogen production using ammonia combustion 59
Figure 2-1. The comparison of different flame stability zones (A: stable flame, B: unstable flame, C: flameless condition) in terms of the exhaust gas recirculation ratio... 61
Figure 2-2. Stability map of the premixed ammonia-air tubular flame in terms of equivalence ratios 63
Figure 2-3. The premixed ammonia-air tubular flame and NO emission, in multistage staging tangential fuel injection combustor. 63
Figure 2-4. Stability limits of premixed NH₃/air flames at various equivalence ratio(0.8-1.4) at 3O0K and 0.1 MPa. The dotted lines represent heat values. 64
Figure 2-5. The stability limit as a function of the exit velocities corresponding to equivalence ratio. 64
Figure 2-6. A reduction in stability limits and NO emission of a two-stage NH₃/air premixed flames influenced by secondary air injection at various equivalence ratios... 65
Figure 2-7. The of ammonia air and hydrogen mixtures at different equivalence ratios (a) the flashback limit and (b) the laminar burning velocity at 483 K, 101 kPa... 67
Figure 2-8. Comparison of premixed ammonia air laminar flame flow velocity at boundary layer flashback, 293 K and 101 kPa. 67
Figure 2-9. Flame stability diagram based on equivalence ratio corresponded to molar fraction of ammonia. The triangle symbols indicate flashback conditions and... 68
Figure 2-10. The combustor utilizes swirling flows to stabilize the flame 69
Figure 2-11. Comparison stability limits of ammonia- hydrogen with ammonia- methane flames. 70
Figure 2-12. Blowout based on inverse of Damkohler number. 71
Figure 2-13. The stability diagram of laminar counterflow diffusion flames obtained by varying the air (Ua=1 the blue line) and fuel velocities (red line Uf=1)[이미지참조] 74
Figure 2-14. The extinction stretches rate (εext)of ammonia air premixed flame for various equivalence ratio at atmospheric pressure.[이미지참조] 75
Figure 2-15. The flame extinction in terms of Karlovitz number at the critical value of Peclet number Pe 77
Figure 2-16. The laminar burning velocity in terms of equivalence ratio 78
Figure 2-17. The flammability limits of premixed and diffusion flames based on concentrations of fuel vapor /air mixture at different temperature. 79
Figure 2-18. Diagram and flame regime maps of a low-swirl vane burner with different swirl numbers and air flow rates 81
Figure 2-19. Comparison of stability limits of non-premixed flames with swirl stabilized quarl and non-quarl. The flow velocity of air is Ua and fuel is Uf. 82
Figure 2-20. The swirling ammonia-air combustion under a wide range of flow conditions (a), swirl-stabilized burner (b). 82
Figure 2-21. Laminar burning velocity of NH₃ equivalence ratio at various oxygen level. 84
Figure 3-1. The flame stability of NH₃-CH₄ combustion at different equivalence ratio as a function of ammonia fraction (XNH₃).[이미지참조] 89
Figure 3-2. The influences of initial pressure and equivalence ratio on flame propagation and experimental set up. Where Ld is the unburned gas Markstein length.[이미지참조] 89
Figure 3-3. Spectra of turbulent kinetic energy of premixed ammonia combustion blends of NH₃/H₂/N₂/H₂O - air. E10-H75-S09 represents the equivalence ratio 1,... 93
Figure 3-4. Flame extinction, intensity curve and stability limits at various equivalence ratios, lip velocities and extinction time. 94
Figure 3-5. The he Darrieus-Landau in terms to different order of k the wavenumber and ω the growth rate. 96
Figure 3-6. The spectrum of ammonia combustion species (including NOx emissions NO, N₂O and NO₂ species) in different equivalence ratios. 99
Figure 3-7. The relationship between the ammonia premixed flames chemiluminescence and equivalence ratio find by infrared thermographic image processing. 100
Figure 3-8. Spectral bands and intensity of ammonia combustion flames in the vacuum UV Range (250 to 530 nm) 101
Figure 3-9. Comparison spectrum of premixed ammonia-methane-air flame at different equivalence ratio (0.70 ≤ ϕ ≤ 1.35). 102
Figure 3-10. The comparison of chemiluminescence intensities of OH*, CH*, CN*, and NH* radicals at various XNH₃ in (a) Premixed and (b) Non-premixed CH₄/NH₃/air flames[이미지참조] 103
Figure 3-11. Comparison of premixed and non-premixed ammonia-methane-air flame and the analysis method for chemical species concentrations 103
Figure 3-12. Chemiluminescence spectrum of (a) Premixed and (b) Non-premixed CH₄/NH₃/air flames at various XNH₃.[이미지참조] 104
Figure 3-13. The OH emission spectrum of ammonia/hydrogen blends varying the air and the equivalence ratio. 105
Figure 3-14. Flameless combustion of NH₃-H₂ under varying equivalence ratios and air injector sizes. 106
Figure 3-15. The absorption spectra of the three gases (NH₃, NO₂, and NO) in flue gas, by a Fourier transform infrared analyzer, at ϕ=1 and 1/70 s exposure time, the... 107
Figure 4-1. The diagram of experimental research methodology 109
Figure 4-2. The combustion stability of premixed and non-premixed ammonia flame compares with flameless mode, in cylindrical co centered, Swirl, and RAI(Reversed... 110
Figure 4-3. The experimental setup for ammonia flameless combustion system and for real-time measurement apparatus for temperature, gas concentration, and optical analysis 111
Figure 4-4. Schematic flow diagram of the 2.5 kw flat flameless combustor and apparatus for real-time measurement Schematic flow diagram of a 2.5kw flat... 112
Figure 4-5. Schematic and detailed design of a 2.5kw flat flameless furnace for ammonia combustion (volume 90x360x250=0.09m3), Qin/Volum=27.7 kw/m3 113
Figure 4-6. Position of thermocouples ports and observatory window 114
Figure 4-7. Schematic setup for ammonia flameless combustion spectroscopy 121
Figure 4-8. The screening equipment for the ammonia gas detection and measurements 124
Figure 5-1. The temperature distribution at different parts of ammonia flat flameless combustor 127
Figure 5-2. Temperature fluctuation of ammonia flameless combustion at different points of the flat flameless combustor 128
Figure 5-3. Temperature of ammonia flameless combustion at different equivalence ratios 129
Figure 5-4. NOx emission of pure ammonia flameless combustion at different equivalence ratios of 0.2-1.2. 130
Figure 5-5. The relation of temperature and NOx emission of pure ammonia flameless combustion as a function of equivalence ratios φ 131
Figure 5-6. The transition from premixed flame to flameless mode for ammonia air flame at equivalence ratio conditions(0.8-1.2) and 0.1 MPa. Exposure time 6-10 ms,... 136
Figure 5-7. The combustion instability of ammonia in cylindrical premixed flame, swirl diffusion flame, and flameless mode, at equivalence ratio 0.8-1.2, dynamic... 136
Figure 5-8. Comparison of hazardous situations of flashback into the burner of premixed flame, blow-off at high flow rates in swirl diffusion flame, and the stabilized flameless 137
Figure 5-9. The spectrum of ammonia flameless combustion in terms of normalized intensity of light emitted as a function of wavelengths, at different equivalence ratios... 141
Figure 5-10. UV Spectrum of NH₃ combustion at different equivalence ratios and temperature 142
Figure 5-11. The visible Spectrum of NH₃ combustion at different equivalence ratios and temperature 144
Figure 5-12. IR Spectrum of NH₃ combustion at different equivalence ratios and temperature 145
Figure 5-13. The safe area limits for ammonia released in exhaust gas 158
Figure 5-14. Unburned ammonia concentrations measured in exhaust gases as a result of an accident 159
Figure 5-15. The safe area limits of H₂ released in the exhaust gas 161
Figure 5-16. Protection layer for response to leaks of ammonia and hydrogen gas include leak and fire detection 167
Figure 5-17. Possible scenarios for preventing leaks from pipes connectors and their consequences 168
Figure 5-18. Ammonia safety storage cabinet equipped with the fire suppression System. 169