The thesis primarily focuses on the pressure influence on the reaction rate of char gasification using laboratory thermogravimetric analysis (TGA). It discusses also the gasification of char with a mixture of gasifying agents (CO2 + steam) under a pressure of 40 bar and temperatures up to 1100°C, which has not been reported in the literature to the best of found knowledge.
The first section investigates the pressure impact on char gasification kinetics by varying the total and partial pressure of the gasifying agent. The second section investigates the effect of gasifying agent at 40 bar and combining the pyrolysis step in the investigation, which was done in-situ under inert atmosphere. Then, mixtures of the two gasifying agents were used for the gasification in separate experiments. The third section uses raw coal as material and gives attention
to the char structure formed after the pyrolysis under the high pressure. The fourth section includes measurements for char characteristics during the gasification reaction and compares them with the reference char data performed previously in this research group under atmospheric pressure.:Abstract
1. Introduction 1
1.1 Scope of the thesis 1
1.2 Layout of the thesis 2
2. Literature Review 4
2.1 Background 4
2.2 Coal and gasification 5
2.2.1 Coal classification and characteristics 5
2.2.2 Introduction to gasification process 7
2.2.3 Coal Analysis 10
2.2.4 Pyrolysis 13
2.2.5 Gasification reactions 13
2.2.6 Mechanism of solid-gas reaction and Thermodynamic background 14
2.2.7 Regimes of gas-Solid Reactions 17
2.2.8 Summary 19
2.3 Effect of Pressure on gasification process 20
2.3.1 Advantages of high-pressure operation 20
2.3.2 Influence on the pyrolysis step 20
2.3.3 Effect of Pressure on coal swelling 21
2.3.4 Pressure influence on char morphology 23
2.3.5 Effect of pyrolysis pressure on char surface area 23
2.3.6 Effect on reaction order n 24
2.3.7 Summary 24
2.4 Pressure influence on char gasification reaction kinetics 24
2.4.1 Pressure influence on gasification reaction kinetics 25
2.4.2 Summary 27
2.5 Char gasification using gasifying agent mixtures 27
2.5.1 Mechanism 29
2.5.2 The role of the inhibition and the catalytic effect 29
2.5.3 Summary 32
2.6 Thermodynamic aspects and the estimation of the reaction rate 32
2.6.1 Background 32
2.6.2 Basic definitions of reaction rate 34
2.6.3 Intrinsic kinetic models 35
2.6.4 Theoretical models 36
2.6.5 Empiric Models 39
2.6.6 Intrinsic kinetic models expressed by CO2 concentration 40
2.6.7 Arrhenius Activation Energy 40
2.6.8 Differentiation of a polynomial fit data (Differential method): 41
2.6.9 Summary 43
3. Experimental Analysis 44
3.1 Thermogravimetry 44
3.2 Testing of the gas volume fraction and the total pressure influence on char gasification 45
3.2.1 Testing of the gas volume fraction influence 45
3.2.2 Testing of system pressure influence on char gasification 56
3.2.3 Discussion 65
3.3 Coal gasification at 40 bar with pure CO2, H2O and their mixtures 65
3.3.1 Gasification with pure CO2 and H2O 66
3.3.2 Coal gasification using CO2 / H2O mixtures at high system pressure 87
3.3.3 Discussion 96
3.4 Pressure influence on coal gasification 100
3.4.1 Coal gasification under different system pressures 100
3.4.2 The effect of increasing pressure on coal morphology 104
3.4.3 Discussion 117
3.5 Influence of the pressure on the char properties during gasification 118
3.5.1 Discussion 129
4. General discussion 134
5. Conclusions 139
5.1 Significance of the findings 143
5.2 Recommendations 144
6. Appendix 146
6.1 Literature and Results 146
6.1.1 Conditions influence on gasification of the (a) temperature, (b) partial pressure 146
6.1.2 TGA-DMT 147
6.1.3 Testing of the gas volume fraction influence on coal gasification 148
6.1.4 Testing of system pressure influence on char gasification 150
6.1.5 Coal gasification at 40 bar with pure CO2, H2O and their mixtures 152
6.1.6 Coal gasification under different pressures 162
6.1.7 Summary of gas mixture gasification studies 167
6.2 Figures Index 169
6.3 Tables Index 175
6.4 References 177
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:90773 |
| Date | 15 April 2024 |
| Creators | Abosteif, Ziad |
| Contributors | Meyer, Bernd, Amro, Moh'd, Technische Universität Bergakademie Freiberg |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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