Researchers at Purdue University’s Calumet campus in Hammond, Indiana created a new less-expensive process for producing coke, a derivative of coal used in the making of steel, and received a U.S. patent for their discovery. Patent number 8,287,696 was awarded by the U.S. Patent and Trademark Office in October to Purdue-Calumet physics professor Robert Kramer and four other inventors.
Steel is an alloy of iron and carbon, with coke providing the purified carbon needed in the steel-making process. Coke is made from coal with a pyrolysis technique, melting the coal in ovens under intense heat without oxygen, that produces the hard, porous material then mixed with iron ore in a blast furnace to make steel.
Indiana, says the patent, produces 22 percent of the steel in the U.S., requiring 8 million tons of coal each year for coke production. In addition, the U.S. does not produce enough of its own coke to meet current steel-production needs, requiring imports of 5.5 million tons of coke each year.
Currently, most of the coal needed by Indiana steel mills comes from Kentucky, West Virginia and Virginia, but the Purdue-Calumet process aims to make coal from mines in Indiana and nearby Illinois better suited for coke. Kramer and colleagues designed a coke oven that could be sited at a coal mine or existing coke plant. The oven uses a new process that makes it possible to blend lower-cost coal from the Indiana/Illinois basin with conventional metallurgical coals.
The Purdue-Calumet process uses enhanced blending techniques that meet coke quality requirements and also generate gas from the pyrolysis stage in the process with other potential economic benefits. “By using lower cost Indiana/Illinois Basin coal, net coal coke costs can be reduced,” says Kramer, who is also director of the university’s Energy Efficiency and Reliability Center. Kramer calculates, “producing coke with a blend that includes 20 to 40 percent of Indiana/Illinois coal would reduce overall production costs significantly.”
The gas from the pyrolysis stage, says the patent, can be extracted for conversion to liquid transportation fuels, fertilizer, hydrogen, and electricity. The patent outlines several scenarios for converting the gas, including cogeneration of electric power at the coking plant for sale into the local electricity market.
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