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At a glance: The history of gas to liquids technology
Petroleum News Alaska Staff
Despite beliefs to the contrary, gas-to-liquids technology is not new nor is it untested. The enabling process dates back some 70 years and has been used commercially for 45 years.
At the heart of any gas-to-liquids technology is a process called Fischer-Tropsch, says Richard Peterson, president of Alaska Natural Gas to Liquids Co. Named after the two German scientists who discovered the process in the 1920s, the Fischer-Tropsch process converts synthesis gas to liquid hydrocarbons and, depending on a variety of controllable factors (temperature, catalyst, pressure, gas composition), the resulting products can range from gasoline to waxes to plastics.
As early as World War II, the Germans used the process and produced about 180,000 barrels per day of diesel to support their war efforts, Peterson said.
After the war, he said that the Kellogg company brought the process to the United States and established a GTL demonstration facility in Texas. The process generated little interest in this country because of Texas then ample oil reserves. However, South Africa in 1950 had no oil of their own, relying instead entirely on imports. But they did have coal and since the process works with either coal or natural gas they saw an opportunity to reduce their dependence on foreign oil.
South Africa brought the process to their country, formed the South African Oil Co. (called Sasol an Afrikaans acronym), and opened their first plant in 1954. That first plant converted coal to gas and then, through the Fischer-Tropsch process, converted the gas to gas liquids or syncrude. Peterson said that Sasol has continuously refined their GTL technology and in 1993, began using what the company calls the slurry phase distillate process. The slurry phase distillate process in brief Using conventional technology, the slurry phase distillate process consists of three major steps:
The first step, called natural gas reforming, uses a process called auto thermal reforming (there are alternatives, but Sasol decided this was best for them) that treats the natural gas to make it reactant. Peterson said that this step is the most expensive in the GTL process, making up about 60 percent of the operational costs.
In the second step, syngas (the product of the first step) is converted to a waxy syncrude through the Fischer-Tropsch process and then passed to the third step.
The third step, product development, is essentially a typical refinery type of operation where the final products are made, Peterson said.
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