Simulation of Two-stage Coal Gasification and Syngas Reforming Process to Produce SNG Using Aspen Plus
- 주제(키워드) coal gasification , two-stage system , Aspen Plus , Fixed bed , Fluidized bed , Syngas , SNG , WGS
- 발행기관 아주대학교
- 지도교수 Hyung-Taek, Kim
- 발행년도 2015
- 학위수여년월 2015. 8
- 학위명 석사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000020167
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
The simulation of the two-stage coal gasification is studied to find out the pyrolysis products evolution trend and char gasification products. A series of other process: coal preparation, water gas shift (WGS), gas cleaning, and syngas reforming process to produce synthetic natural gas (SNG) are also studied in this work. (1) Coal Preparation. Coal is firstly crushed into smaller size. Screen is used to make sure that the coal size is limited to needed value. (2) Simulation of fluidized bed coal pyrolysis using Rstoic Block and inner FORTRAN sentences. Based on the First-order weight loss principle, RStoic and inner FORTRAN code are used to simulate the three staged lignite coal pyrolysis. With heating rate of 1000 k/s, the simulation results shows the final temperature for stage one, two, three is 500 °C, 640 °C and 900 °C respectively with given pyrolysis products composition. The pyrolysis simulation process was further tested by North Dakota lignite coal and later applied to Illinois No.6 bituminous coal. Its shows that to achieve the given amount of pyrolysis products, pyrolysis of bituminous coal needs relatively lower temperature, 500 °C, for the first stage. After the weight loss based pyrolysis, char is broken into its composing components, solid C, small amount of H, N, O and S, in preparation for the next stages. (3) Simulation of fixed bed char gasification using four types of models. With the same temperature, pressure, reactants feeding rate, RGibbs, RPlug, One RCSTR and Ten RCSTR models are used to simulate char gasification. In order to handle the complicated kinetic reaction function, which is not capable to be dealt with by Aspen Plus’s inner kinetic function or inner FORTRAN sentences, external FORTRAN sentences are used to calculate the reaction kinetics in RPlug and RCSTR model. The simulation result is suiting very well with literature data. Carbon conversion in RGibbs reactor (99%) is higher than RPlug model (98.9%). One RCSTR model has the lowest carbon conversion (75.5%). The comparison between experiment results and simulation results shows that RPlug model is more coincident with experiment than other three models. (4) Syngas reforming to produce SNG. The syngas from two-stage char gasification is firstly experiencing a water gas shift (WGS) process, adjusting the mole ratio of H2/CO to 3.4. After WGS process, syngas is purified by removing particles, acid gases H2S and CO2. The clean syngas is then reformed by four adiabatic reactors to generate high concentration of methane (86%).
more목차
Abstract I
Acknowledgements III
Table of Contents V
List of Figures VII
List of Tables VIII
Chapter 1. Introduction 1
Chapter 2. Literature Review 4
2.1. Simulation of Coal Pyrolysis and Char Gasification 4
2.2. Simulation of Syngas Reforming to Produce SNG 6
Chapter 3. Coal Preparation and Fluidized Bed Coal Pyrolysis Process 8
3.1. Coal Preparation 8
3.1.1. Coal Crushing 8
3.1.2. Coal Screen 9
3.2. Description of Two-Stage Coal Gasification 9
3.3. Coal Pyrolysis Simulation Process 14
3.3.1. Model Description 14
3.3.2. Calculation of Coal Pyrolysis Evolution Functions 17
3.4. Results and Discussion 19
3.4.1. Montana Lignite Coal Pyrolysis Simulation Results Analysis 19
3.4.2. Testing of Pyrolysis Simulation Model Using Zap North Dakota Lignite Coal 22
3.4.3. Lignite Coal Pyrolysis Model Applied to Illinois No.6 Bituminous Coal 25
3.5. Conclusions 27
Chapter 4. Fixed Bed Char Gasification 28
4.1. Char Gasification Models Description 28
4.1.1. One RPlug Block Model Simulates Char Gasification 31
4.1.2. One RCSTR Block Model Char Gasification 34
4.1.3. Ten RCSTR Block Model Char Gasification 34
4.1.4. RGibbs Block Model Char Gasification 36
4.2. Chemical Reactions 36
4.3. Results and Discussions 39
4.3.1. Products Gas Evolution Trends 39
4.3.2. Simulated Results Compared with Experiment Data 43
4.4. Conclusion 46
Chapter 5. Syngas Reforming Process to Produce SNG 48
5.1. WGS Process Adjust H2/CO Mole Ratio for Methanation Synthesis 48
5.2. Syngas Cleanning 50
5.3. Clean Syngas Reforming to Produce SNG 51
5.3.1 Methanation Process Development 51
5.3.2 Methanation Result and Discussions 54
5.4. Conclusions 57
Chapter 6. Conclusion 58
Reference 60
