The Fischer Tropsch process: synthetic fuel
Key words: fisher, tropsh, process, liquefaction, fuel, solid, liquid, coal, carbon, biomass, syncrude, syngas, synthesis, fuel, biofuel, agrofuels.
The Fischer Tropsch process is a fairly complex liquefaction process for solid or gaseous fuel. In other words, it makes it possible to obtain a liquid fuel from a solid fuel or gas.
The interest of the liquefaction process is obvious, here are its 2 main arguments:
- a liquid fuel generally has a calorific value more interesting, that is to say that the same potential chemical energy will take a much smaller volume when the fuel is in liquid form than in solid form and even more for gas. This allows for easier storage and transport.
Example: for the same stored energy, wood pellets take about 3,5 times more volume than fuel oil.
- a liquid fuel is generally much more easily "ignitable" and allows a much easier regulation of the power. This can be a fundamental criterion in some energy fields such as transport, for example.
The Fischer-Tropsch process (according to Wikipedia)
The Fischer-Tropsch process is a chemical reaction that catalyzes carbon monoxide and hydrogen in order to convert them into hydrocarbons. The most common catalysts are iron or cobalt.
The interest of the conversion being to produce synthetic liquid fuel, Syncrude, from coal, wood or gas. The Fischer-Tropsch conversion is a very efficient process in terms of yield, but which requires very heavy investments, which makes it economically vulnerable to downward fluctuations in the price of a barrel of oil. Furthermore, the step of producing synthesis gas (the mixture of H2 and CO) exhibits a fairly poor yield, which penalizes the overall yield of the process.
The Fischer-Tropsch process as discovered by its two inventors is as follows:
CH4 + 1 / 2O2 -> 2H2 + CO
(2n + 1) H2 + nCO -> CnH (2n + 2) + nH2O
The mixture of carbon monoxide and hydrogen is called syngas or syngas. The resulting production (synthetic crude or syncrude) is refined to obtain the desired synthetic fuel.
Origin and history of this process (according to Wikipedia)
The invention of the Fischer Tropsch process dates from 1925 and is attributed to two German researchers, Franz Fischer and Hans Tropsch, working for the Kaiser Wilhelm Institut (Germany). This process is based on the catalytic reduction of carbon oxides by hydrogen in order to convert them into hydrocarbon. Its interest is to produce, from coal or gas, a synthetic petroleum (syncrude) which is then refined in order to provide synthetic liquid fuel (synfuel).
German origin: 124 synthetic barrels per day in 000 ...
This process was developed and exploited by Germany, poor in petroleum and oil colonies, but rich in coal to produce liquid fuel, which was used extensively by the Germans and the Japanese during World War II. Thus was set up the first pilot plant by Ruhrchemie AGS in 1934 and industrialized in 1936.
At the start of 1944, the Reich was producing some 124 barrels / day of fuel from coal, which represented more than 000% of its aviation fuel needs and more than 90% of the country's total fuel requirement.
The fuel obtained was still of lower quality (and especially consistency) than fuel of petroleum origin, the engineers therefore resorted to water injection in order to compensate for fairly low octane numbers. Find out more: water injection into the Messerschmitt.
This production came from 18 direct liquefaction plants but also 9 small FT plants, which produced some 14 000 barrels / day.
... but also in Japan
Japan has also tried to produce fuels from coal, the production was mainly through low-temperature carbonization, a process that is not very efficient but simple.
However, the Mitsui company bought a license of the Fischer Tropsch process from Ruhrchemie to build three factories in Miike, Amagasaki and Takikawa, which never reached their nominal capacities due to design problems.
In the 1944s Japan produced 114 tonnes of fuel from coal, but only 000 of these were made using the FT process. Between 18.000 and 1944 German and Japanese factories were badly damaged by Allied bombing, and the majority were dismantled after the war.
Abandonment of technology after the war except in South Africa
The German scientists who had developed the FT process were captured by the Americans and seven of them sent to the United States as part of Operation Paperclip. However after structuring of the oil market, and the sharp drop in prices, the United States abandoned research and the Fischer-Tropsch process fell into disuse.
During the 1950s, however, it regained interest in South Africa: this country, with abundant coal resources, built highly mechanized mines (Sasol) which supply CTL units, whose production is based on two distinct Fischer Tropsch syntheses:
- Arge process (developed by Ruhrchemie-Lurgi) for the production of high-boiling hydrocarbons, such as gas oil and waxes.
- Synthol process for the production of hydrocarbons with lower boiling points, such as gasoline, acetone and alcohols.
Production was sufficient for its supply of road fuels.
Always used today
In 2006, these units covered around a third of South African needs, and the Sasol company has become one of the world specialists in this field.
After the first oil shock of 1973, which caused the rise in the price of crude oil, several companies and researchers tried to improve the basic process of Fischer-Tropsch, which gave birth to a wide variety of similar processes , grouped under the Fischer-Tropsch synthesis or Fischer-Tropsch chemistry component.
A B-52 that flies in the USA
Since the 2000s, the process has therefore regained economic interest. Thus the American Department of Defense recommended in September 2005 the development of an oil industry based on the exploitation of the energy resources of the United States in coal in order to produce fuel by the Fischer-Tropsch process and thus not be dependent on external natural resources for its own needs.
Since 2006, a US Air Force B52 has been carrying out tests with Fischer-Tropsch fuel, mixed at 50% or pure. For now, it is a success that will allow the American army to regain strategic independence for its military fuel.
Econological and sustainable applications
The fact of liquefying coal or gas does not change anything, or not much, to the greenhouse effect and to the depletion of fossil resources, indeed; sooner or later carbon will be released into the atmosphere and the natural resource used is not renewable.
It is quite different using the Fischer-Tropsch process from biomass, biogas or even organic industrial waste.
Thus the general principle of the Fischer-Tropsch reaction has diversified a lot since the beginning, and has given rise to more generic processes and names, such as CtL (Coal to Liquids), GtL (Gas to Liquids) but above all BtL (Biomass to Liquids). It is this last sector which is of particular interest to econology.
Many organizations, including CEA, are currently working to improve conversion processes, as the overall energy efficiency of this technology is also a weak point.
Example, liquefaction of industrial waste by a German company (broadcast in Autoplus in November 2005):