1. Statement of Research Interest and Experience
In recent years, coal gasification is the most important direction of new coal chemical
and clean power industry. During my undergraduate studies, some factors, which are
my education background, the vast coal reserves in China and the concern of the CO2
emission throughout the entire world, make me have a strong interest in clean coal
energy. That was why I chose to study coal gasification in energy process lab of Ajou
University. In China, with the increase in the electricity consumption and the CO2
emission, developing an efficient energy technology and reducing the greenhouse gas
emission have become the hot topic and the common wishes for our generation and the
future. Therefore, I hope I can use my small power to do something for our living
environment and next generation. As we know, coal gasification has become the trend
in clean coal energy, and it has a higher energy efficiency and lower greenhouse
emission, so it is the key technology in the coal gasificationpoly-generationtechnology,
IGCC and clean power generation. I hope I can grasp a good skill and make my
contribution for this field.
Since I came to Korea, I began to study in energy field under the guidance of Professor
Hyung-Taek Kim. During these two years, I am committed to the topics of coal drying,
gasification and simulation of coal to SNG.
For my master degree, in the first semester, I learned about the background of clean
coaltechnology and entered into the project of coal drying to assist some seniors’ work.
After I researched some papers and finished some experiments, I got a further
understanding which provided my own opinion in the coal drying mechanism. I think
the coal also have the phenomena of plasmolysis as the plant cell, because coal is
derived from some plant and is formatted under the ground for hundreds years, it also
has the characteristics of a plant. When the concentration difference takes place, the
moisture content will be changed. That is why when we change the temperature of
drying gas, the moisture content of drying gas, the drying pressure and so on; drying
process is easier to happen, only if we can find some driving force to make the
difference between the inner and the outer part of the coal.
In the second semester, I followed one PhD candidate to study the fouling phenomena
of Indonesian lignite using drop tube furnace (DTF), this is related to the IGCC project
in my lab. This experience gave me the knowledge on how to make the coal
gasification happen, and the effect of coal ash composition on the fouling
characteristics. In the experiment, we observed the accumulation characteristics of ash
2. that is produced in entrained-bed reactor in different material surface and reaction
conditions.
From the third semester to now, I am engaged in developing the simulation model of
low rank coal to SNG plant by Aspen plus. The purpose of this work is to develop a
model for the utilization of SNG plant from low rank coal using Aspen plus simulator.
In this simulation model, I simulated five processes based on the previous work and
my limited acquired experience: coal preparation process, gasification process, gas
cleaning process, water gas shift reaction (WGS) process and methanation process.
After this, they were combined to develop a low rank coal to SNG simulation plant. In
order to take into consideration of the energy saving, CO2 emission and SNG purity,
some concepts were introduced for the upgrading of the simulation plant. Even though
the time for studying is short, I have tried my best to make everything go well.
In the future years, I still want to further improve my ability and skill in the field of
clean coal energy.
The following is the outline of my Master’s thesis:
The Performance Evaluation of Low Rank Coal - to - SNG Process with Upgraded
Drying Concepts by Aspen Plus Simulation
Abstract
Natural gas is the fuel of choice worldwide and represents an important pillar of
energy supply in the form of electricity and for covering heat demand. However
consumption and price of natural gas are rising steadily throughout the entire world,
bringing about the need to develop and seek technologies like SNG. Coal-to-SNG
technology is promising for countries with significant proven reserves of coal but
scarce natural gas. Modern coal gasification and methanation technologies constitute
an excellent opportunity to address energy and environmental challenges for
producing SNG in an economically attractive way. The idea of using low rank coal to
produce SNG is mostly due to the abundant of low rank coal reserves. It has low
mining strip ratio and good quality in terms of sulfur and ash content.
The purpose of this work is to develop a model for the utilization of SNG plant from
low rank coal using Aspen plus simulator. This model, which is involved in the Shell
coal gasification process (SCGP) and Haldor Topsoe’s Recycle energy-efficient
methanation process (TREMPTM), is the combination of some advanced technologies
and would be flexible enough for future development. In order to evaluate the effect
3. of low rank coal on this plant, IBC coal (Indonesian lignite) is chosen as the input
feedstock of gasification. IBC coal has lower ash content (2.27%) and sulfur content
(0.06%), but has higher moisture content (34.05%) and oxygen content (19.59%)
compared with high rank coal.
Present investigation focuses on the evaluation of low rank coal to SNG plant, the
comparison of two drying concepts in terms of energy input and the upgrading of the
simulation plant. Firstly, five processes are simulated according to the literatures and
report from the commercial case. The two main parts, which are gasification process
and methanation process, have a good match with the commercial case. Fuel
preparation process and gas cleaning process are the simple simulation model based
on some experimental data, and the water gas shift reaction process has a higher CO
conversion (>98%). These processes have a good performance to support the
establishment of low rank coal to SNG plant. Secondly, after each process is
simulated, they are combined together and IBC coal is fed into the simulation system
for evaluating the performance of low rank coal on the coal to SNG plant. The
parameters for the evaluation are cold gas efficiency (CGE) and carbon conversion
(CC) of gasifier, syngas composition and end-product purity. Sensitivity analysis is
conducted, in order to indicate the effect of oxidant index and steam index on the
evaluating parameters. According to the sensitivity analysis and when the ratio of
oxygen to drycoal is equal to 0.91, which is the value when it has the same
temperature range and heat loss with Illinois #6, CC and CGE of IBC coal reach 99.8%
and 78.6%, respectively (Illinois #6: CC=99.4%, CGE=80.0% when oxygen/dry coal
uses the reference data.). The SNG purity of end-product is 83.5%. Thirdly, two
drying concepts, which are the conventional and recycle syngas drying processes, are
introduced into the drying system. The recycle syngas drying concept, which has a
high temperature and pressure, can reduce the energy consumption compared to the
conventional drying concept, and also saves a lot of fuel for heating up the drying
system. Fourthly, in order to meet the requirement for improving the product purity
and reducing the greenhouse gas emission, the concept of conventional carrier gas is
replaced by carbon dioxide and the optimal concepts from the sensitivity analysis are
used. Finally, based on the developed models, the coal to SNG plant is upgraded into
a low rank coal to SNG plant and the end-product purity is also improved, which
improves the CH4 purity of the end-product from 83.5% to 94%, and the
oxygen/drycoal ratio is decreased to 0.78. The CO2 content (5.2%) in the syngas from
the gasifier is lower than the original case (7.7%) that uses N2 as the carrier gas.
