By Gwen Bristol

While there are about seven coal gasification technologies developed or developing in the nation right now, the technology at the Great Plains Synfuels plant is the only one proven to work with consistently North Dakota lignite coal, according to Daryl Hill, media relations supervisor with Basin Electric Power Cooperative.

The process used at the gasification plant is called the Lurgi process. In this system, coal gasification occurs in tall, cylindrical vessels.

“Coal is fed into those vessels and at one point there is a bed of coal, and it’s burning,” Hill said. “In my mind it’s burning the equivalent of what you would see in a charcoal grill.”

Pure oxygen and steam are fed through the bottom of the fourteen gasifiers. As the heat rises through the coal, a raw gas is produced. The gas is captured at the top of the vessels, taken out of the gasifiers and further refined into natural gas.

The process creates a host of other byproducts, as well. Some of them, including carbon dioxide and the fertilizer ammonium sulphate, are sold in addition to the methane.

The gasification process uses pieces of coal at least two inches in diameter.

It basically is taking the coal and breaking it down into its hydrocarbon components,” said Floyd Robb, vice president of communications and marketing support at Basin Electric.

Hill said if the company ever builds a new gasification plant it might not use the Lurgi process. Instead the company might consider using a newer technology that produces less liquid byproducts.

“Newer technologies are being developed all the time,” Hill said.

Basin Electric doesn’t currently have any plans to build new gasification facilities in the foreseeable future.