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Simulation of Two-stage Coal Gasification and Syngas Reforming Process to Produce SNG Using Aspen Plus
- Author(s)
- DENG LINGYAN
- Advisor
- Hyung-Taek, Kim
- Department
- 일반대학원 에너지시스템학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2015-08
- Language
- eng
- Keyword
- coal gasification; two-stage system; Aspen Plus; Fixed bed; Fluidized bed; Syngas; SNG; WGS
- Alternative Abstract
- 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%).
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Energy Systems > 3. Theses(Master)
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