Performance Evaluation ofCatalytic Gasification of Indonesian Low Rank Coals through the Lab- and Bench-scale Experiments
Performance Evaluation ofCatalytic Gasification of Indonesian Low Rank Coals through the Lab- and Bench-scale Experiments
- 주제(키워드) Catalytic gasification , Low Rank Coal , Gasification Reaction , Gasification Kinetics , Scale-up
- 발행기관 아주대학교
- 지도교수 김형택
- 발행년도 2015
- 학위수여년월 2015. 8
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000020286
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Coal gasification technology is used to convert the carbon and hydrogen components of coal into syngas. The main components are carbon monoxide and hydrogen in gas form. Syngas can be applied in various processes such as the Integrated Gasification Combined Cycle (IGCC) to generate power and Coal to Liquid (CTL) conversion to obtain liquid fuel through the Fischer-Tropsch process. Syngas can also be used as Synthetic Natural Gas (SNG). In general, the liquid substance tar is generated in a fixed-bed gasifier in large quantities contrary to a fluidized-bed gasifier which has the problem of producing only a little tar, and low carbon conversion. Currently, commercial gasifiers use the pulverized coal in the entrained-bed. This has an advantage when processing large capacities under high temperature and it therefore leads to a high carbon conversion and results in high cold gas efficiency. In the application of low rank coals, a high carbon conversion is expected even under low temperatures because of their good reactive characteristics. Moreover, fixed-bed or fluidized-bed reactors are also used when processing low rank coal. Although an entrained gasifier, processes ash in a molten state, it has the disadvantages when processing low rank coal. Various methods are used in the coal gasification technology for increasing the efficiency of low rank coal to the level of high rank coal through catalytic gasification. Therefore, the problems of low rank coal are overcome. The catalyst used in the catalytic gasification process lowers the activation energy required in the coal gasification reaction. As a result it lowers the reaction temperature and increases the selectivity of the reaction. It is used for the purpose of producing particular gasification products. Catalytic gasification is a method that catalyzes the gasification reaction even at a relatively low temperature and changes the composition of the syngas. In general, on the reason that a fluidized-bed gasifier has a relatively short residence time, in order to secure the residence time required for gasification it is used rather than an entrained gasifier. Furthermore, during the gasification reaction, an endothermic reaction, the exothermic methanation reaction and the exothermic water gas shift that occur with the direct method catalytic gasification technology require less energy than the existing gasification method. Catalytic gasification uses steam rather than oxygen as the oxidant and can increase the H2/CO ratio; as a result, water gas shift process is not required. The purpose of this study was to determine the characteristics of the reaction conditions for producing syngas and the characteristics for catalytic gasification performance, while simultaneously presenting the kinetic conditions through a lab-scale experiment using Indonesian low rank coal and a bench-scale catalytic gasifier design. For the design of bench-scale catalytic gasification reactor, the lab-scale reactor was used to obtain the residence time and kinetic data taking into account the similarities, such as volume and Lh/D, to design a bench-scale fluidized-bed catalytic gasification reactor. Among various coals, this study used Indonesian low rank coals (IBC, MSJ, Roto South) characterized by a large deposit volume and low cost. In addition, they are not sensitive to the fluctuations of the price of crude oil. A catalytic gasification reactor was used in the lab and bench-scale experiments to compare the syngas composition and its reaction characteristics. The parameter such the temperature was set at 600℃, 700℃, and 800℃, and the catalyst (K2CO3) injection method (physical mixing and impregnation) was set at 5 wt% and 10 wt% through physical mixing and 10 wt% through impregnation. Furthermore, the experiment was conducted with H2O/C mole ratios of 0, 1, 5, and 10, and the gas velocity was fixed at 1.5 Umf. The optimum experimental conditions for syngas production were derived using lab-scale catalytic gasification. The scale-up of a bench-scale catalytic gasifier was based on the lab-scale results and shared similarities. The syngas composition and its reaction characteristics were investigated through the continuous operation of the bench-scale catalytic gasification. The results of the lab-scale catalytic gasification showed that 70% carbon conversion could be achieved with a shorter reaction time within 6 min. The results indicated that when the catalytic gasification reaction was maximized by applying the K2CO3 catalyst to low rank coal even under a low temperature, a higher hydrogen yield could be produced compared to the conventional gasification process. A bubble fluidized-bed (BFB) was used for the bench-scale catalytic gasification design. It produces syngas with a higher calorific value (1,070 kcal/Nm3) and attains a faster steady-state, better H2 selectivity, and higher carbon conversion than the K2CO3 as catalyst utilized in other studies. In conclusion, catalytic gasification of low rank coal can be used for H2 rich gas production for CTL (H2O/C mole ratio of one, 800℃) and CTL, SNG, fuel cell application, and synthesis gas production for GTL process (H2O/C mole ratio of 10, 800℃).
more목차
Chapter 1. Introduction 1
1.1 Background and Motive 1
1.2 What is Catalytic Gasification? 3
1.3 Scope and Objective 4
Chapter 2. Literature Review 7
2.1 Introduction of Coal Gasification Technology 7
2.2 Characteristics of Gasifier Types 11
2.3 Fluidized-bed 13
2.4 Mechanisms of Catalyst Utilization for Coal Gasification 18
Chapter 3. Experimental Method and Apparatus 23
3.1 Characteristics of Coal Sample 23
3.2 Lab-scale Fluidized-bed Reactor and Accessories for Pyrolysis and Catalytic Gasification Experiment 25
3.3 Method for Scaling-up to Bench-scale 29
3.4 Bench-scale Fluidized-bed Reactor and Accessories for Catalytic Gasification Experiment 30
Chapter 4. Results and Discussion 34
4.1 Results of Pyrolysis 34
4.1.1 Results of Pyrolysis using Thermogravimetric Analyzer (TGA) 34
4.1.2 Results of Pyrolysis using Fluidized-bed Reactor 39
4.2 Results of Catalytic Gasification using Lab-scale Fluidized-bed 48
4.3 Comparison of Pyrolysis and Catalytic Gasification using Lab-scale Fluidized-bed Reactor 83
4.4 Results of Catalytic Gasification using Bench-scale Fluidized-bed 106
4.4.1 Method for Scaling-up Lab-scale Fluidized-bed to Bench-scale 106
4.4.2 Results of Experimental Bench-scale Catalytic Gasification using Indonesian MSJ 113
Chapter 5. Conclusions 118
References 120
Nomenclature 132
Abstract in Korean 134
Appendix 137
