Page 33 - Synthetic Fuels Handbook

FUEL SOURCES 21

of carbon monoxide in a proprietary solvent containing cuprous aluminum chloride
(CuAlCl ) dissolved in an organic liquid such as toluene. The purified carbon monoxide
4
can have purity greater than 99 percent. The reject gas from the process can contain carbon
dioxide, nitrogen, methane, ethane, and hydrogen. The reject gas can be further processed
on a pressure swing absorption system to remove hydrogen and the hydrogen and carbon
dioxide recombined in the proper ratio for methanol production, Fischer-Tropsch diesel,
and so on.
The process of producing synfuels is often referred to as coal-to-liquids (CTL), gas-to-
liquids (GTL), or biomass-to-liquids (BTL), depending on the initial feedstock.
Gas-to-liquids is a process for conversion of natural gas into longer-chain hydrocar-
bons. Thus, methane-rich gases are converted into liquid fuels either via direct conver-
sion or via syngas as an intermediate, for example, using the Fischer-Tropsch process.
Using such processes, refineries can convert some of their gaseous waste products into
valuable fuel oils, which can be sold as or blended only with diesel fuel. The process
may also be used for the economic extraction of gas deposits in locations where it is not
economic to build a pipeline. This process will be increasingly significant as crude oil
resources are depleted, while natural gas supplies are projected to last into the twenty-
second century.
The best known synthesis process is the Fischer-Tropsch synthesis which was used on
a large scale in Germany during World War II. Other processes include the Bergius pro-
cess, the Mobil process, and the Karrick process. An intermediate step in the production of
synthetic fuel is often syngas, a stoichiometric mixture of carbon monoxide and hydrogen,
which is sometimes directly used as an industrial fuel.
The leading company in the commercialization of synthetic fuel is Sasol, a company
based in South Africa. Sasol currently operates the world’s only commercial coal-to-liquids
facility at Secunda, with a capacity of 150,000 bbl/day.
The U. S. Department of Energy has projected that domestic consumption of synthetic
fuel made from coal and natural gas could rise to almost 4.0 million barrels per day in
2030 based on a price of $57 per barrel of high sulfur crude (Annual Energy Outlook
2006, Table 14, page 52). However, depending on price scenarios, synthetic fuels require a
relatively high price of crude oil as well as a relatively low price for production (i.e., crude
oil price is not the only parameter), in order to be competitive with petroleum-based fuels
without subsidies. However, synthetic fuels do offer the potential to supplement or replace
petroleum-based fuels if oil prices continue to rise.
Several factors do make synthetic fuels attractive relative to conventional petroleum-
based fuels:
1. The raw material (coal and tar sand) is available in quantities sufficient to meet current
demand for centuries.
2. Many of the raw materials can produce gasoline, diesel, or kerosene directly without the
need for additional refining steps such as reforming or cracking.
3. In some cases, there is no need to convert vehicle engines to use a different fuel.
4. The distribution network is already in place.
However, with higher costs of production and higher risks, companies may be well
inclined to seek tax credits for the production of synthetic fuels from nonconventional
sources. In allowing these credits, governments will be well advised to consider the value
of a measure of energy independence. Canada asked this question in the 1970s with respect
to the development of the Athabasca oil sands (tar sands) located in north-eastern Alberta.
As a result, production is now almost 1,000,000 bbl/day of synthetic crude oil which makes
a considerable difference to Canada’s imports of nondomestic crude oil.