Fischer–Tropsch
Kimmo Klemola
17.04.2006
updated 24.11.2006
Have you thought of combining H2 made of water and coal (or whatever C containing material) into C in gigantic plants? The product is gasoline and the raw material will be there for hundreds of years to come. The process already exists since 1920s–1930s and it is called Fischer–Tropsch synthesis. The infrastructure is already there and the process is profitable even today.
The technology was invented in 1920s by two German chemists Franz Fischer and Hans Tropsch. In the Second World War, German warfare was in part fueled by Fischer–Tropsch liquids from coal. Most of Nazi Germany’s synthetic fuels were produced by direct coal liquefaction using the process developed by German chemist Friedrich Bergius (Nobel laureate in 1931). During the isolation period because of its apartheid policy, South Africa produced fuels from coal using the Fischer–Tropsch technology.
At first the raw material is converted to synthesis gas (CO + H2) and then using proprietary Fischer–Tropsch catalysts (cobalt) the synthesis gas is converted mostly to sulfur-free high-quality diesel and chemicals.
Fuel synthesis is a proven technology since World War 2. In Hydrocarbon Processing there was a piece of news that Chinese can produce synfuel that is economic even with US$15 oil barrel (coal to liquids, CTL).
Shell and Sasol in particular have a lot of interests in gas-to-liquids (GTL) from natural gas. Shell already has a commercial GTL plant in Malaysia and new GTL plants will be commissioned in Qatar and Nigeria. The most interesting in long term, however, is the BTL (biomass to liquids) development (google: Choren, sundiesel, sunfuel, synfuel, Volkswagen, BTL).
In ambient conditions fuel should preferably be liquid. Fischer–Tropsch diesel is low-sulfur fuel. Because of its high quality, Fischer-Tropsch diesel has a price advantage of about US$8 a barrel. See below gasoline and hydrogen vehicle, when fuel is at ambient conditions:
Various sources can be used to
produce synthesis gas, and various products can be made from synthesis gas.
Fischer–Tropsch products: diesel, gasoline and chemicals, are
just one choice. See the chart below:
Fischer–Tropsch biodiesel and cellulosic ethanol have fairly good fossil energy balance and they do not compete directly with food production.
There are three routes to manufacture biodiesel: 1) from vegetable or waste food oils and some alcohol to produce ester (biodiesel), 2) from vegetable or waste food oils or animal fats and hydrogen to produce high-cetane biodiesel (Neste's NExBTL) and 3) from biomass via synthesis gas and Fischer-Tropsch to produce more dinodiesel-like biodiesel, but sulfur free. The latter involves the manufacture of H2 from biomass, and one alternative is to stop there and purify the hydrogen and use it as a fuel (see the chart).
Gas to liquids (e.g. stranded natural gas fields), coal to liquids and biomass to liquids using Fischer–Tropsch technology may be the answer for at least some decades after the oil era – or in the near future after the peak oil.
The abundance of coal and the simple product, diesel/gasoline, make it possible to use the same engines and infrastructure as today. It may be a good enough reason to choose coal to oil rather than hydrogen.
The drawback of coal to oil Fischer–Tropsh is higher CO2 emissions per MJ output. The F–T products are also more expensive than petroleum based gasoline and diesel. In short term (10 to 20 years), not enough Fischer–Tropsch capacity can be built in case the consumption increase will be as big as predicted and the oil production cannot meet the demand. We may already have reached peak oil (read about the peak oil math by Kenneth S. Deffeyes) or we will soon reach peak oil. The coming crisis is about the shortage of liquid fuels. You better prepare for three-digit crude prices for one barrel.
Sasol's break-even price is about US$22 (crude market price) for coal to liquids using Fischer-Tropsch. It may be low, because they have the best and proven F-T technology with very low cost coal.
Natural gas is very suitable for the syngas production because of its purity and good C to H ratio. Coal has a lot of impurities, sulfur etc. There is lack of natural gas in some decades and that is why coal should be chosen for Fischer–Tropsch. However, Fischer–Tropsch could be the best choice for stranded gas, where pipelines and LNG infrastucture are uneconomic.
The main raw material for the U.S. chemical industry is natural gas and in order to maintain this situation natural gas reserves should not be used in energy generation (heat, electricity, gasoline, hydrogen).
There are newer statistics, but I had the book of Weissermel and Arpe (Industrial Organic Chemistry) from 1993 on my reach. It says about the fossil reserves:
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Natural gas 60–70 years (proven)
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Coal. "A study by the Leningrad Geological Institute reached a similar conclusion: even at the current rate of growth, the minable hard and brown coal reserves would be adequate for at least 5000 years."
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Oil 40 years (proven)
Supplementary reading:
Biodiesel
–
Fischer–Tropsch
(in Finnish)