Exxon's gas-to-liquids technology is called AGC-21. The text below is public domain information from the Exxon "Lamp" publication from last summer, and is available on their web site (search for words "gas conversion"). As discussed in text, AGC-21 is based on Fischer-Tropsch process. Enhancements made by Exxon related to catalysts and operating parameters to improve viability are likely proprietary.
*******************
From "The Lamp"
You might own the largest natural gas field in the world. However, if you can't get the gas to market at a reasonable cost and at a competitive price, it may be worthless.
While crude oil is relatively easy to transport to markets from remote locations, natural gas isn't. Exxon scientists have worked on the problem for almost 20 years.
Building on an earlier process designed to produce liquids from coal, they have found an economical way to turn natural gas into a crystal-clear product that some call "white crude."
This high-quality liquid is easy to move by conventional oil pipelines, ships, railcars or trucks – and is so clean that it can justify a premium price.
The new product is very different from liquefied natural gas (LNG), which must be kept extremely cold and transported in special tankers.
Industry leader
"Only a few companies are active in developing gas-to-liquids technology, but many others are trying to get in," says Ben Eisenberg, technical project manager, Exxon Research and Engineering Company (ER&E). "The advanced, fully integrated three-step process we developed early on makes Exxon clearly the industry leader."
The company's technology evolved from a process that German scientists Franz Fischer and Hans Tropsch developed in the early 1920s. During World War II, Germany used an early version of this process to make synthetic diesel fuel from coal.
Since 1981 Exxon has spent some $300 million on research to improve on these processes and holds more than 1,500 gas-to-liquids patents worldwide. Today, there's no question about the technical readiness of Exxon's technology. Multiple improvements to catalysts and reactor designs have significantly reduced the company's cost of converting gas into liquids, down to a level that is economic in the right settings.
Exxon's proprietary process is known as Advanced Gas Conversion for the 21st Century (AGC-21). Research continues at ER&E in New Jersey and at Exxon Research and Development Laboratories in Baton Rouge, Louisiana, with the near-term goal of reducing the cost another 30 percent.
Baton Rouge is also the home of the company's 200-barrel-a-day process-demonstration plant.
"People once thought that making liquids from gas could never be economically viable," says Dick Bauman, manager of gas-conversion research in Baton Rouge. "Many companies even quit trying. But in the last 10 years, research has cut the cost significantly. That's why everyone is looking at the technology again."
Although several companies have some form of gas-to-liquids technology, Exxon's proprietary process costs less per barrel than that of the closest competitor.
"The efficiency of our catalysts, reactors and processes remains the central focus of our patent work in gas-to-liquids technology," says Bauman.
The products
Liquids made from natural gas are important for two reasons.
First, gas too distant from markets to transport economically can be shipped cheaper as a liquid, opening many remote fields to development. By some estimates, that includes half the world's 5,100 trillion cubic feet of discovered natural gas.
Second, the liquids themselves are very pure. "They look and feel like baby oil," says Eisenberg, "and they're free of contaminants, such as sulfur and heavy metals that are expensive to remove from ordinary crude oil."
Exxon's AGC-21 technology is highly versatile. It can make a wide range of products. For example, the second step of the three-step conversion process (see process illustration) produces a premium-quality wax. This wax can be used in candles, wax coatings on milk cartons, adhesives and a wide variety of other products.
The third step converts the wax into high-quality refinery or chemical feedstocks for making specialty products, such as lubricants or plastics. It can also produce a superior grade of diesel fuel that burns cleaner and more efficiently than conventional diesel.
Still another bonus: process heat from gas conversion can produce enough electricity to run the conversion plant, plus have some left over for sale to electric power companies.
"This heat could also be used to desalinate seawater," Eisenberg adds. "A 100,000-barrel-a-day gas-conversion plant can make more than 20 million gallons of fresh, drinkable water a day. This could be significant in arid regions.
Lower cost
Exxon's AGC-21 technology is for use in the smallest to the largest of plants, a flexibility competing technologies don't have.
Scott Nauman, Business Development advisor, Exxon Company, International Gas Department, says this competitive advantage will be particularly important in developing large gas fields that are far from markets.
"For example, we are negotiating to build a gas-to-liquids plant in the Middle East that will produce 80,000 to 100,000 barrels a day," he says. "That's more capacity than all the other gas-to-liquids plants in the world combined.
"The size of our proposed plant puts us in a strong position commercially because scaling up any chemical or refining process lowers the cost per barrel.
While many of these plants will likely come onstream in the future, they will not come close to competing with conventional oil refineries in satisfying the world's appetite for energy products. World demand for oil is now about 74 million barrels a day.
Exxon proved the readiness of its gas-to-liquids technology at this process-demonstration plant in Baton Rouge, Louisiana.
"Even 10 large-scale plants would meet only about 1 percent of that need," Nauman explains.
Likely locations
The economics of gas-to-liquids technology vary for different geographic locations and are affected by many factors, from the size of the reserves and construction costs, to the local tax structure and the prices received for the products.
Among the most likely locations for gas-conversion plants over the next decade are the Middle East, including Qatar; the North Slope in Alaska; Venezuela and West Africa.
Qatar is especially attractive because it is so distant from consumers and has the world's largest natural gas field. It could support a large conversion plant for many years, in addition to offering the potential for expansion.
A gas-conversion plant on the North Slope of Alaska would produce liquids that could be sent to markets down the 800-mile trans-Alaska pipeline.
"The Prudhoe Bay field contains a significant gas resource," says Mark Albers, Alaska Interest Organization manager, Exxon Company, U.S.A. "Indeed, the gas, which is reinjected into the field, has helped boost oil recovery and prolong the life of North America's largest oil field. But as oil production declines, converting the gas into liquids provides an opportunity to ship the product to market through the existing oil pipeline system."
Exxon recently announced major oil discoveries in deep waters off Angola in West Africa. With no nearby market for the associated gas, it must be reinjected. Converted into a liquid by small gas-conversion units on offshore platforms, it could be shipped to market by tankers.
Fritz Voigt, vice president, Exxon Company, International Gas, says the development of gas conversion will be driven by its economic fit in the market and by the degree of cooperation from the host government of each country where it is produced.
"Gas conversion has an important role to play," says Voigt, "but there are many variables."
However, merely having the technology available gives Exxon more options for developing new fields.
"Our leadership role in gas-to-liquids technology is a strategic advantage," Voigt says. "Natural gas is an excellent resource, and this is a smart way to use it."
How we do it
Gas-to-liquids technology
[simplified flow diagram of process exists on Exxon web page]
Clean-air pluses from AGC-21
Opening remote gas fields to markets isn't the only attraction of Exxon's AGC-21 gas-to-liquids technology. It produces a clear and nearly odorless diesel fuel free of sulfur and some of the other components that cause emissions. Laboratory tests have shown a reduction in engine emissions ranging from 10 to 50 percent. The fuel by far exceeds the quality that is in the market today. Even when blended with conventional fuels, it retains its emissions-reduction characteristics. |
