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The blast furnaces used today in the U.S. are similar in form and function to those built about 260 years ago, but the energy efficiency is incomparably better. Through steady engineering improvements, the smelting process has become nearly 20 times more energy-efficient since the mid-1700s.[I] The challenge now is to better understand how to use alternative fuel sources in order to continue to decrease the carbon intensity of blast-furnace ironmaking.
Chris Pistorius joins us to talk about his research to improve energy efficiency in blastfurnace ironmaking.
What is the current focus of your blast-furnace research?
In ironmaking, there is an immovable baseline of energy that will always need to be supplied for the process to work. To make the process more energy-efficient, we are up against the laws of nature - a hard battle to win. By focusing on introducing a lower-cost, lower-carbon fuel such as natural gas into the process, however, we can prevent the creation of billions of tons of carbon emissions a year. Natural gas contains about 15% less carbon by mass than coke, the traditional fuel for blast furnaces.
My group is focused on studying how best to introduce natural gas into the blast-furnace ironmaking process, comparing coke replacement ratios, carbon intensity and furnace productivity. Just this past fall, we uncovered new data around the best natural gas utilization methods. We now have better estimates of how much natural gas can be injected through the tuyères. This is upward of 150 kg of natural gas per metric ton of hot metal, which is more than one-third of the total fuel requirement of blast-furnace ironmaking. The most effective use of natural gas to displace coke, though, would be to use the gas to reduce the iron ore to metallic iron in a separate shaftfurnace. Use of metallic iron in a blast furnace increases productivity and gives a large decrease in coke rate - effectively saving around...