You might remember in a couple of different
blog posts over the past few months, we discussed two ongoing projects for
clients building plants that will generate fuels – from solid waste and from
natural gas. The environmental engineering work we do for these clients is – we
believe – exceptionally important both to the growth prospects of our company
and to our overarching company goal of helping foster a sustainable future for
the world. We also believe that as part of our role as environmental stewards,
it’s important to promote education in the areas of science, technology, and
environmental engineering. For that reason, today we want to discuss one of the
areas relevant to this work– the process of conversion of natural gas into usable
fuels.
A
bit of Chemistry
In theory it is possible to convert any
run-of-the-mill hydrocarbon, such as methane, which makes up about 85% of
natural gas, into almost any other hydrocarbon.
In fact, nature does this sort of thing all the time. Plants, comprised of many complex
hydrocarbons, are converted through time, heat and pressure into crude oil,
coal and natural gas. Plants themselves
are chemical factories in miniature.
Through photosynthesis, plants convert sunlight and carbon dioxide into complex
sugars, cellulose and myriad other complex hydrocarbons with myriad physical
and chemical properties. By adding in
some nitrogen, oxygen and few other ingredients from the soil, plants can make
proteins, oils, sugars, and in some cases, such as the nightshade plant,
alkaloid poisons. Plants create
chemicals that mankind refines into medicines and drugs. For example, morphine, nicotine, aspirin and
caffeine are four plant supplied chemicals that directly impact man’s
wellbeing, for better or worse. The
conversion of natural gas into liquid fuels in our client projects is not
nearly as complex as what is going on in that oak tree growing in your back
yard.
In brief, the process goes something like
this: methane from natural gas is
partially oxidized, that is partially burned in a low oxygen environment to
form carbon monoxide (CO) and hydrogen (H2). Water vapor is added as a source of
additional hydrogen. Some of the CO
reacts with the water vapor (the “water gas shift reaction”) to form hydrogen
(H2) and carbon dioxide (CO2). The CO2 formed in the reaction is
then stripped from the gas mixture. In
some designs, direct steam reforming is used where water vapor is directly
reacted at high temperature, with methane to form CO and H2. The CO and H2 are then pushed
through a catalyst, which converts the two simple chemicals into larger
molecules, typically alkanes, which are saturated hydrocarbons like methane or
propane. The catalyst selected controls
whether synthetic gasoline, diesel, jet fuel or paraffin waxes is produced.
A
bit of History
Perhaps because we don’t see natural gas
conversion plants on every street corner, we tend to think of the technology as
something new, at bit cutting edge. But
the truth is that the process was developed in 1925 by two German chemists,
Franz Fischer and Hans Tropsch. Today we
call the process the Fischer-Tropsch process or “F-T” for short, I imagine to
avoid having to learn how to pronounce Tropsch (usually pronounced Trope, with
a long “o”). Germany made great use of
the process in World War II - having relatively small native oil reserves,
Germany was able to fuel their war machine using the Fischer-Tropsch process by
converting coal into liquid fuels. The
WWII German synthetic fuels industry was able to produce 3.7 million barrels
per month by early 1944, utilizing 25 F-T plants scattered across Germany and
the occupied lands. The Pölitz plant
alone was able to produce 575,000 tons of fuel in 1943. A documentary on the topic can be viewed at https://www.youtube.com/watch?v=jwHypKFYzGg.
A
bit of Technology
The F-T process uses a specialized catalyst
to facilitate the conversion of CO into heavier molecules, mostly alkanes. An alkane is a class or family of chemicals
that all share the general formula CnH2n+2. Don’t let the
symbols throw you. The formula just says
that for every (n) number of carbon atoms there are (2n+2) hydrogen atoms, for
example C3H8 or C6H14. The family
includes many useful compounds whose names are in general use by the public, such
as methane, butane, propane, and octane, to name a few. As the number of carbon atoms in each
molecule increases, the higher the compound’s boiling point becomes. Methane with one carbon is a gas, even at the
North Pole in January. Propane with
three carbons is a gas at room temperature but can be compressed to form a
liquid for use in gas grills, and home heating as well as other uses. Octane, with eight carbons, is a liquid with
about the same boiling point as gasoline.
Paraffin wax is an alkane with 20 to 30 carbon atoms and is a solid at
room temperature but is still flammable if given enough encouragement. The F-T process produces a mixture of alkanes
from methane (one carbon) to paraffin wax (30 or more carbon atoms).
The percentage of each alkane produced is
controlled by the selection of catalyst and the operating conditions in the F-T
catalytic converter. The most commonly
used catalysts include those made from transition metals like cobalt, iron and
ruthenium. For natural gas F-T processes, cobalt is the most commonly
used. Unfortunately, it is impossible to
have the process produce only the alkane desired. Mixtures of different alkanes are inevitable. So,
the F-T unit is often followed by a catalytic cracker where the heavier alkanes
can be thermally “cracked” to reform lighter, often more desirable liquid
fuels. The process produces very pure
liquid fuels, such as ultra-low sulfur synthetic diesel and high purity jet
fuel.
Technology has surged forward since WWII
and modern materials science has created new catalysts that are significantly
more efficient at converting CO into alkanes and allowing simpler upstream
gasification steps. The newer catalysts
also help narrow the range of alkanes produced, making refining the final
products easier and more cost effective. It is now possible to produce ultra-low sulfur
diesel at prices less than the current retail
price of petroleum sourced ultra-low sulfur diesel. Modern designs also include
secondary processes to capture and make use of what were once waste materials,
such as carbon dioxide, extra hydrogen and organic chemicals that were formed
as byproducts.
A
bit of Economics
So, if the technology is mature and the raw
materials to feed the process are plentiful, why don’t we see F-T conversion
plants on every street corner? The simplest
answer is we don’t need to. The graph
below, taken from the US Government website https://www.energy.gov shows that the
United States started to produce more oil than it imported in early 2014, and it’s
simply more cost-efficient for us to procure oil the old-fashioned way.
It remains much less expensive to drill, pump and refine crude oil than to create synthetic fuels from other hydrocarbons. As long as the price of crude oil is below some undefined trigger point, synthetic fuel plants will be rare. Note that we mentioned that we could produce F-T ultra-low sulfur diesel fuel at less than the retail price of petroleum based ultra-low sulfur diesel. However, to be competitive, the production price needs to be competitive with the wholesale, raw production price of the petroleum-based products.
Occasionally, the undefined trigger point is reached and excitement builds in the synthetic fuels industry. Each time world events create political unrest and the price of crude oil goes up, the number of proposed or planned synthetic fuel plants escalates. However, by the time the planning, design, and permitting of a new plant is completed, the crisis is over, and the price of oil falls back making the new plants economically unsound.
There are other reasons we don’t have F-T conversion
plants across the country. One, the capital
and infrastructure invested in traditional petroleum refining is staggering and
not easily abandoned. The mega-companies
that make up the oil industry are resistant to new perhaps, dare I say it,
disruptive approaches. And, small
companies don’t have the economies of scale to easily compete in that
market. Another reason is the history of
the F-T process itself, being used so effectively by the Nazis in WWII. It was not, of course, the fault of the
process that its first great accomplishment was to fuel what is generally
considered the most evil regime in the history of the planet. Nevertheless, the stain of the Nazis remains
and is perpetuated unintentionally by every professor who has ever taught about
the F-T process, who dwell on the history and first large-scale use of the
technology.
Of course, there will come a day when the
world’s oil reserves will be expended, and other sources of energy will need to
be developed and exploited. Perhaps
there is some comfort in the knowledge that as that day approaches, there
already exists a technology that can convert less useful hydrocarbons into more
useful forms; trash into treasure in a sense.
BLEST is already involved with a project to convert municipal solid
waste into F-T fuels with the expectation that 1,000 tons of high-grade
synthetic fuels will be produced daily, consuming materials that would
otherwise go to the local landfill. Trash
into treasure, indeed.
In theory, if all our fuel came from F-T
conversion plants, we would have overall better environmental outcomes from our
fuel production because of the absence of drilling, fracking, and refining of
crude oil and the environmental outcomes associated with them. BLEST is
therefore proud to be a part of these projects and hopes to assist industry
leaders in fostering this type of process and technology throughout the future.
By Randall
Moore
President, BioLargo Engineering, Science &
Technologies (BLEST)
Mr. Moore is an engineer/executive with more
than 30 years of industrial commercial experience. Most recently he served as
Manager of Operations for Consulting and Engineering for the Knoxville,
Tennessee office of CB&I Environmental & Infrastructure, Inc. Prior to
that, from February 2013 – May 2017, he was the Manager of Operations at
Integrated Environmental Solutions a Consulting and Engineering group within
CB&I, Environmental and Infrastructure, Inc.
