Performance Evaluation ofCatalytic Gasification of Indonesian Low Rank Coals through the Lab- and Bench-scale Experiments

학위논문(박사)--아주대학교 일반대학원 :에너지시스템학과,2015. 8Chapter 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 137DoctoralCoal 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℃)

On the Mechanical Properties and Thermal Stability of Carbon/Kevlar Interply Hybrid Composites

Mechanical and thermal properties of carbon/Kevlar interply hybrid composite materials have been studied. Through hybridization, tensile strength and modulus of the Kevlar reinforced composites were increased by about 25% and 31%, respectively compared with 100% Kevlar composites. In case of interlaminar shear strength, the carbon/Kevlar hybrid composite showed lower value becarse of the mismatch of the thermal expansion coefficient. The stacking sequence and the difference in interlaminar shear strength had and effect on the impact resistance and flexural properties of the hybrid composites. In the impact test, the composites with Kevlar ply at impact side absorbed more energy and showed synergy effect in impact energy absorption. The composites carbon reinforced laminates at both sides showed higher properties in the flexural properties. The static properties of hybrid composites showed inferior to those of carbon composites. However, the hybrid composites showed superior to the two composites of carbon and kevlar in impact property. After repeated heat treatments up to 7 cycles at 2500C the carbon reinforced composites showed the highest flexural strength and interlaminar shear strength. 본 논문은 케블라/탄소 층간 하이브리드 복합 재료의 역학적, 열적 성질에 관한 연구이다. 탄소섬유층과 케블라 섬유층의 두가지 보강섬유로 되어 있는 하이브리드 복합재료의 물성은 케블라 보강 복합 재료의 물성에 비하여 인장 강도가 약 25%, 인장 계수가 약 31% 증가하였다. 층간 전단력에 있어서는 경화 후 상온으로의 냉각과정에서 발생하는 열 수축 불균형으로 인하여 탄소섬유층과 케블라층간의 층간물성이 가장 영향을 받는 것으로 나타났다. 층간 물성의 감소로 인하여, 충격이 가하여진 경우, 층간 분리의 발전이 용이하게 되었으며, 이에따라 케블라섬유층을 표면층에 배치한 하이브리드 복합 재료가 케블라 100%의 경우보다 더 높은 충격 에너지흡수 능력을 보였다. 굽힘 성질에서는 탄소 보강 복합 재료 라미나가 양 바깥쪽에 위치한 경우, 가장 높은 수치를 나타내었다. 정적 물성에 있어서는 하이브리드 복합재료가 중간값을 보였으며, 충격실험에서는 하이브리드 효과가 매우 높음을 보여 주었다. 열처리 후 굽힘 성질 및 층간 전단력 실험에서는 탄소 보강 복합재료가 가장 우수한 성질을 보였다