ENCH 607- Natural Gas Processing Principles
Gas to Liquid Technology from a Canadian Industry Perspective
Project Engineers:
Frederick Seale
10119648
Logan Evans
10119700
Craig Wong
00326767
Landon Lewoniuk 00505003
Joyce Chau
Project Coordinator:
11/30/2012
00902390
Dr. N. Nassar, PhD, P. Eng.
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PROJECT FOCUS
Canada is considered to be the third largest natural gas producer in the world. Its vast quantities of
undiscovered natural gas reserves make Canada a perfect candidate for utilization of unconventional
technologies in today’s oil and gas industry. One of these technologies being introduced into Canada’s oil and
gas industry is Gas-to-Liquid (GTL) technology. The basis of this technology is to convert remote gas reserves
into transportable liquid products, which would reduce environmental concerns such as flaring or reinjection
while being economically viable.
In 2011 the Canadian company Talisman Energy entered a joint operation with an international firm by selling
50% of its working interest in the Montney shale gas resources in British Columbia to Sasol Ltd. The
abundance and remoteness of shale gas reserves in Canada has created an interest for large energy
companies such as Talisman Energy to invest in GTL technology. This gave Sasol the opportunity to apply
their technology in Canada, introducing the first GTL facility in the country. Currently Sasol is also applying
this technology to the Canadian liquids market through a proposed gas-to-liquids operation in Fort
Saskatchewan, Alberta. The plant capacity is ultimately going to be 96,000 barrels a day, making the
technology a sizable contributor and competitor in the market for diesel, naphtha, kerosene and other
valuable gas-to-liquid products.
The paper under review - “The Conversion of Natural Gas to Liquid Fuels using the Sasol Slurry Phase
Distillate Process” by Roy W. Silverman and Cavan R. Hill - describes SASOL’s proprietary “slurry phase
distillate” (SPD) process, and highlights benefits/shortfalls of the technology with respect to alternative
methods currently in use. This critique will focus on identifying the feasibility of the process and the claims
made in the paper, as well as provide a comparative analysis between SPD and alternative gas-to-liquids
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methods. The critique will discuss the implications of this technology in the context of the Canadian
petroleum Industry. The strength and effectiveness of the paper will also be evaluated.
PROCESS BACKGROUND
The discovery of hydrogenating carbon monoxide over iron and nickel catalysts to generate methane was
founded by Paul Sabatier and Jean Sanderens in 1902. Following this, two German Scientists Franz Fischer
and Hans Tropsch were able to produce hydrocarbons over alkalized iron in 1923. Franz Fischer and Hans
Tropsch used a catalytic conversion of carbon monoxide and hydrogen to generate synthesis gas. The process
to convert natural gas into synthetic fuels and chemical feed stocks was initially driven by economic sanctions
and embargoes, for countries that were unable to meet internal market demands for fuel by importing and
refining crude oil. In 1930 the Fischer-Tropsch (F-T) process was recognized as a commercially viable
technology. Although there are a multitude of reactions within the F-T group, the most critical and desirable
are as follows:
Synthesis gas generation
Water-gas shift reaction:
Steam reforming:
H2O + CO → H2 + CO2
H2O + CH4 → CO + 3 H2
Fischer-Tropsch reaction
Alkane production via F-T reaction:
(2n + 1) H2 + n CO → CnH(2n+2) + n H2O
Current GTL technology employs various forms of Fischer-Tropsch processes. The common result is
conversion of natural gas into synthetic hydrocarbon molecules, which can be manipulated into various fuels
and hydrocarbon-based products. In other words, GTL processes manipulate the natural gas molecules by
reassembling them into longer chain molecules.
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Figure 1: GTL Process (4)
Since formation in 1950, Sasol has become one of the llargest industrial
trial companies in South Africa, and as a
result the firm has developed several auto thermal process designs for optimization of the Fischer-Tropsch
synthesis reaction. Sasol has commercialized four reactor technologies, with the slurry phase distillate (SPD)
process being the most recent.. These four designs can be categorized into two groups:: High Temperature
Fischer-Tropsch Reactor, and
d Low Temperature Fischer-Tropsch Reactor. The SPD process falls under the
“Low Temperature Fischer-Tropsch Reactor” category, and ffor the purpose of this paper critique, this design
will be the focus.
occupied with a synthetic wax liquid phase containing a catalytic
The slurry phase reactor uses a vessel that is occupi
mixture.. The suspended solid catalyst particles provide a surface on which the synthesis gas has an affinity to
react with the wax phase to produce a variety of hydrocarbon molecules
molecules.
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Figure 2: Slurry Phase Reactor (4)
As shown in Figure 2 above, the synthesis gas migrates through the slurry bed wher
where
e heat is being generated
via the net-exothermic F-T reactionss. Heat is removed from the slurry via a cooling coilil located
locate inside the
vessel, through which BFW is vaporized to steam. Light hydrocarbons will evolve from the slurry where it will
occupy the free space at the top of the vessel and be removed. The heavier liquid hydrocarbons are mixed
into the slurry from which they
hey must be removed by means of a Solid Separation Process. The type of catalyst
is critical for this design as it needs to be strong enough to prevent breakup in the slurry,
slurry and allow
downstream liquid-solid separation and catalyst regeneration and reuse
reuse. The main benefit of the SPD reactor
is that it is well mixed and can operate virtually isothermally.
EFFECTIVENESS OF SUPPORTING LITERATURE
Throughout the paper, the
he authors highlight some of the potential applications for GTL
GT technology and
suggest reasons
easons why companies would ad
adopt this process into their operations.
Overall, the article provides a reasonable amount of information regarding GTL technology.
technology However, the
authors expressed the SPD process as a fool proof technology and only highlight its
it benefits. Any
disadvantages associated with the process are excluded. Furthermore, The only sources cited in the article
are the findings of Sastech, to which one of the authors is affiliated. This poses an obvious difficulty in
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evaluating the credibility of the literature supporting the authors’ argument. However in lieu of this, the
below criteria will be employed to identify the strength and effectiveness of delivery of the paper’s main
arguments:
Clarity of the authors’ writing
Effectiveness and compassion behind the authors’ argument
Bias behind the argument
How convincing the authors’ arguments are
The authors’ writing is clear in terms of enforcing their argument by providing reasoning as to why the
process should be employed. They clearly mentioned that LNG plants are expensive and that the market for
methanol is limited (1). As a result of these issues the authors continued to remark in confidence that
“clearly, there is a need for an alternative that produces high quality fuels […] the Sasol Slurry Phase Distillate
Process will fulfill this need” (1). Another major highlight that clearly presented the authors’ argument was
the emphasis on environmental benefits such as reductions in particulates, NOx, CO and hydrocarbon
emissions when burning GTL fuels (1). Additionally, irrelevant information was included by the authors to the
effect of weakening their argument. For example, the excessive detail regarding the pilot Fischer-Tropsch
reactor and evaluation of the pilot reactor diameters.
This article suggests that the SPD process is a great way to utilize remote natural gas because no
disadvantages associated with the technology are presented. The main areas within the article that express
the authors’ evident compassion towards GTL technology is where they suggest that “the Sasol Slurry Phase
Distillate Process will fulfill this need” (1) of higher quality fuel demand. To enforce their argument, the
authors discuss several main points about the GTL process. These were the product refining and process
economics sections. Outside of this, the authors emphasized excessive background and process descriptions
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rather than concentrating on promoting their argument. This took away from the overall effectiveness of
their argument and may also cause the reader to lose interest in the article. Instead of providing lengthy
descriptions the authors could have simply made a diagram of Sasol’s main process with all the major steps;
this could effectively explain to the reader the concept of the SPD process and why it is beneficial. Several key
factors such as putting emphasis on applications around the world and mentioning existing facility examples
like capacity and marginal costs of commodities would have helped promote the authors’ argument.
This article clearly exhibits bias in the authors’ argument because no pitfalls or disadvantages are mentioned.
Rather than highlighting the main concerns, such as construction costs and uncertainties of gas prices, the
authors described the process’ benefits and completely ignored its disadvantages. In terms of the
environmental benefits of GTL fuels, the authors suggest that lower emissions are a direct result. In
contradiction to this, one can claim that the authors convey a bias since large amounts electricity and heat
are needed to produce the synthesis gas and operate the F-T process. The energy consumed in this process
generates emissions. These produced emissions would then reduce the effectiveness of any environmental
benefits yielded from using a large scale GTL process over an alternative.
From an environmental, energy integration and economic standpoint, the authors could have provided more
information in these critical areas. Greater emphasis in these areas would have also helped promote the
authors’ argument.
This author clearly suggests that the SPD process is an applicable GTL technology that can be widely used in
industry given certain favorable conditions by recognizing advantages such as low emissions and reasonable
investment returns can be achieved. The authors bias is clearly evident throughout the article, which greatly
reduces the effectiveness of their argument.
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EFFECTIVENESS OF RESEARCH STUDY
Aside from the demand for production of diesel-type fuels, the main issue Sasol’s GTL technology attempts to
address is the difficulty and inefficiency of transporting energy in the form of natural gas long distances from
source to market. The root of this problem is the low energy-density of natural gas. Higher pumping and
piping costs per unit of usable energy than higher energy-density fuels are observed. As a solution, Sasol
technology converts natural gas into higher value hydrocarbon fuels to minimize these transportation costs.
Although the main subject of research in this article is the GTL process, a number of alternative methods for
reducing transportation costs are available, and were somewhat overlooked as part of the research shared in
this article.
Liquefied Natural Gas (LNG) technology has been available for nearly a century and has been successfully
implemented globally for the purpose of reducing transportation costs from remote reserves (5). In recent
years, Australia, Alaska and the Gulf states have employed this technology successfully by opening avenues
from remote reservoirs to global natural gas markets. The subject article does address this technology briefly
by stating the drawbacks of LNG processing plants:
Process plants for LNG production are costly;
Require ‘economies of scale’ to be profitable;
Require dedicated shipping infrastructure; and
Suffer from a limited market in only a few countries.
Although these points can be justified, when compared to GTL technology it is evident there are similarities
which negate the value of these statements. Firstly, the TIC (total installed cost) of a typical 90 MMscfd GTL
processing plant is indicated in the article as roughly $300 million. This is comparable to that of an equal
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throughput NGL processing plant at $167 million using a benchmark cost of $200/tpa which was observed
during the 2000’s (6). Additionally, there is a large market for LNG developing globally where natural gas
reserves are scarce. The below chart from BP illustrates the fast increasing demand of LNG particularly in
Asian and European markets.
Figure 3: Growth of LNG Demand (5)
In addition to NGL, the author mentions methanol as a potential conversion product of remote natural gas
reserves. Silverman & Hill briefly describe the market for petrochemical feedstock methanol as limited, and
point
int out the required downstream processing for final use of this methanol in the form of methyl tertiary
butyl ether (MTBE) oxidizer. Although there is no source indicated for these statements, as per a research
paper published by China Markets Research R
Reports
eports these are valid points. Global demand for MTBE has
decreased significantly from 19.33 million tons in 2000 to 12.1 million tons in 2011 (7).. The driving factor for
this decrease is primarily bans on use of the product as a gasoline supplement withi
within
n the US and Canada.
The compound is an oxidizer which when blended with gasoline (10% to 15% vol.) and burned, reduces to
oxygen which leads to cleaner burning of the primary fuel. However, this compound has been found to be
carcinogenic and as such has limited use in many countries (8).. Although little research was sourced by
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Silverman & Hill in the article, the points raised regarding this potential use for remote natural gas are valid
and show an understanding of this alternative.
Putting alternative technologies aside, the article also briefly discusses the necessary preliminary syngas
generation reaction, however does not disclose the importance of this step in ensuring the GTL process is
economical in its entirety. ConocoPhillips has done extensive research into syngas generation technologies
and claims this process can be up to 60% of the total GTL capital cost (9). Leaving this information out of the
article seems to mislead the reader by directing attention towards the Fischer-Tropsch process and ignoring
the more costly syngas generation.
Lastly, Silverman & Hill state that Sasol Advanced Synthol reactor (an improved fluid bed design) produces
similar range of products to the circulating fluid bed reactor, more efficiently and at a substantially lower unit
production cost. The Slurry Phase Distillate (SPD) process is proprietary to Sasol and is referred to in the
article as the driving technology which allows an efficient Fischer-Tropsch reaction to occur. It is evident that
significant research and understanding of this process has been incorporated by the authors into the article,
as is expected considering the authors are members of the Sasol group (Sastech). However, the article lacks
adequate evaluation of the alternative fluidized bed systems available, and a convincing comparison to these
alternatives. This dilutes the authors’ argument for use of the SPD process, and indicates either a lack of
research into alternative reactor technology, or an unwillingness to address any comparative fallbacks to
employing the SPD process.
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CONCLUSIONS AND RECOMMENDATIONS
In conclusion, there is an evident need to increase the efficiency of natural gas transportation over long
distances from source to market. Sasol’s SPD process appears to be an attractive solution to this problem.
The conversion of low energy density to high energy density products can reduce the overall costs associated
with transportation.
Although the report makes several claims the SPD process is the favourable choice it is evident that options
such as LNG have been overlooked– specifically from an economic standpoint. LNG technology is mature and
economically viable as shown by the growing global LNG demand.
This paper stressed the importance of making the process economics and energy self-sufficient. This was
especially critical for the GTL process to be successful as this was a valued added process. The return on
investment of this operation had to be higher than selling the raw materials directly. The paper spent two
paragraphs to elaborate the energy integration of the process and did a thorough economics analysis. The
author has done a good job to solve the problem raised in the introduction.
The overall effectiveness of the argument could have been improved by providing more information
associate of Sasol’s main process and supporting data to compare its technology among the peers. More
alternatives methods and investigations along the processing steps and environmental concerns could have
been provided to enhance the strength of the arguments. It is evident the authors of this paper are biased
toward the process seeing as very few drawbacks are mentioned.
With current global trends it does not appear GTL will be a valuable technology from a Canadian industry
perspective.
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REFERENCES
1) Silverman, R. W.; Cavan, R. H. Proceedings of the 76th GPA Annual Convention: Technology
Improvements, 1997, 39, 239-241.
2) Sasol in Canada.
http://www.sasol.com/sasol_internet/frontend/navigation.jsp?pnav=country%20profile&countryId=
2000004&navid=2&cnav=canada&rootid=2 (accessed 10/15/12).
3) Energy. http://www.canadainternational.gc.ca/chinachine/bilateral_relations_bilaterales/Energy.aspx?view=d Government of Canada Website. (accessed
10/16/12).
4) Al-Shalchi, W. Gas to Liquids Technology (GTL) http://www.scribd.com/doc/3825160/Gas-to-LiquidsGTL-Technology (accessed 10/06/12).
5) Brief History of LNG http://www.beg.utexas.edu/energyecon/lng/LNG_introduction_06.php Center
for Energy Economics. (accessed 10/18/12).
6) A Liquid Market- Thanks to LNG, spare gas can now be sold the world over.
http://www.economist.com/node/21558456 The Economist. (accessed 10/22/12).
7) Methyl Tertiary Butyl Ether (MTBE) Global Markets 2020. http://www.prnewswire.com/newsreleases/methyl-tertiary-butyl-ether-mtbe-global-markets-to-2020---china-dominates-global-mtbedemand-while-developed-regions-look-to-etbe-and-ethanol-as-replacement-options-china-marketresearch-reports-169600096.html PR Newsire. (accessed 10/19/12)
8) MTBE and Underground Storage Tanks. http://www.epa.gov/swerust1/mtbe/ EPA Website.
(accessed 10/15/12).
9) Wright, H. A.; Allison J. D.; Jack D. S.; Lewis G. H.; Landis S. R.; ConocoPhillips GTL Technology: The
COPox™ Process as the SynGas Generator. Am. Chem. Soc. 2003, 48(2), 791-792.