Performance Evaluation of Potassium Catalyst Recovery Process in the K2CO3-Catalyzed Steam Gasification System
- 주제(키워드) Catalyst Recovery , Catalytic Steam Gasification , Low Rank Coal
- 발행기관 아주대학교
- 지도교수 김형택
- 발행년도 2016
- 학위수여년월 2016. 8
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000022986
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
In this study, the catalyst recovery process (CRP) was investigated utilizing different operating conditions and washing methods. Two different gasified residues, generated through a catalytic steam gasification process (CSGP) in fixed and fluidized bed reactors, were collected and utilized as CRP samples. Firstly, when conducting the CSGP with K2CO3 as a catalyst, H2-rich syngas was obtained under a gasification temperature of 800 °C and catalyst loading amount of 10 wt % (saturation capacity). Based on X-ray diffraction (XRD) analysis results, the potassium compounds in the gasified residues mainly existed in three forms (KAlSiO4, KHCO3, and K2SO4). KAlSiO4 is an insoluble potassium compound, KHCO3 can be transformed from K2CO3 in the presence of H2O and CO2, and K2SO4 is steadily formed through oxidation of K2S when the gasified residue is held without discharging air treatment. Secondly, after conducting lab- and bench-scale CRPs, the following optimal operating parameters were elucidated: pressure of 20 bar, reaction time of 1 h, reaction temperature of 150 °C, water-to-residue (wt %) ratio of 10/1, and three washes using the No.1 combined washing method. Under these parameters the catalyst recovery efficiency (ηK) reached 87.62 %. Based on CRP experiments in the lab-scale reactor, a scaled-up bench reactor was designed and equipped with fast heating and cooling systems, which can accurately control reaction time, and mesh wire was set at the bottom of the reactor, in order to conveniently and readily separate the recovered catalyst from the reactor. Thirdly, Brunauer-Emmett-Teller (BET) analysis shows that the combined washing method can effectively and adequately enlarge surface area, total pore volume, and average pore size, thereby increasing the area in contact with the CRP washing solution, which increases ηK. Fourthly, the recovered catalyst was loaded with raw coal and CSGP was undertaken in order to verify its catalytic activity. Not only were the trends of carbon conversion (XC) similar at each gasification temperature, but there was also no obvious difference in volume percentage of gases produced. When adopting the random pore model (RPM), both reaction rate constant (kRPM) and activation energy (Ea) remained similar whether using fresh K2CO3 or recovered catalyst. Therefore, it can be concluded that the recovered catalyst has the same catalytic activity as fresh K2CO3. Fifthly, a new and advanced system was conceptually designed, including CSGP, CRP, and carbon capture, utilization and storage (CCUS), which will play a significant role in energy utilization in the next few decades. On one hand, the K2CO3 CSGP can produce H2-rich syngas, and the CO2 produced can be captured and used in CRP as a washing atmosphere; on the other hand, the K2CO3 catalyst, utilized in CSGP, can be recovered in CRP and recycled in CSGP to lower the catalyst investment and eliminate the pollution caused by alkali metals in gasified residues.
more목차
Chapter 1. Introduction 1
1.1. Background and Motive 1
1.2. Scope and Objective 5
1.3. Thesis Outline 6
Chapter 2. Literature Review 8
2.1. Introduction to Catalytic Gasification Technology 8
2.1.1. Introduction to Coal Gasification Technology 8
2.1.2. Introduction to Catalytic Coal Gasification Technology 10
2.2. Catalyst Utilization in Coal Gasification Process 16
2.2.1. Types of Catalyst for Coal Gasification Process 16
2.2.2. Catalyst Function in the Coal Gasification Process 19
2.3. Development Status of the Catalyst Recovery Process 21
2.3.1. Exxons Catalyst Recovery Technology 21
2.3.2. GreatPoint Energys Catalyst Recovery Technology 24
2.3.3. Eutectic Catalyst Recovery Technology 25
2.3.4. Chinese ENN Energys Catalyst Recovery Technology 26
Chapter 3. Experimental Method and Apparatus 28
3.1 Introduction 28
3.2. Characteristics of Coal Samples and Catalyst Loading Method 28
3.2.1. Coal Sample Preparation 28
3.2.2. Catalyst and Loading Method 32
3.3. Experimental Methodology of Catalyst Recovery Process 34
3.3.1. Lab-Scale Experimental Apparatus and Operation of K2CO3-Catalyzed Steam Gasification Process 34
3.3.2. Lab-Scale Experimental Apparatus and Operating Parameters of the Catalyst Recovery Process 36
3.3.3. Experimental Methodology of Catalyst Recovery Process 38
3.4. Other Analyses 42
Chapter 4. Results and Discussion 43
4.1. Introduction 43
4.2. Experimental Results on Catalytic Steam Gasification with Different Reactors and Coal Samples 44
4.2.1. Experimental Results on Lab-Scale Catalytic Steam Gasification Process of Lanna Coal in a Fixed Bed Reactor 44
4.2.2. Experimental Results on Bench-Scale Catalytic Steam Gasification Process of MSJ Coal in a Fluidized Bed Reactor 48
4.3. Experimental Results on Potassium Catalyst Recovery Process in Batch Reactor 50
4.3.1. Lab-Scale Catalyst Recovery Process on a Fixed Bed Gasified Residue 50
4.3.2. Scaling up to Bench-Scale Batch Reactor from Lab-Scale Batch Reactor 57
4.3.3. Bench-Scale Catalyst Recovery Process on a Fluidized Bed Gasified Residue 61
4.3.4. SEM, XRD, and BET analyses on recovered samples after conducted CRP 72
4.4. Experimental and Kinetic Results of Recovered Potassium Catalyst-Catalyzed Steam Gasification Process 76
4.4.1. Experimental Results on Recovered Potassium Catalyst-Catalyzed Steam Gasification Process Using the Fixed Bed Reactor 76
4.4.2. Kinetic Investigations of Gasification Reactivity Adopting both Fresh K2CO3 and Recovered Potassium Catalyst 82
4.5. Conceptual Design of a New and Advanced System 88
Chapter 5. Conclusions 91
Reference 93
Terminology: 104
Abbreviations: 105
Curriculum Vitae 107
