Variable Frequency Drives at Steel Mill

Steel is the backbone of industrial and developing nations, but often its production is more energy intensive than necessary. Bethlehem Steel Corporation (BSC), the second largest producer of steel in the United States, knew that to remain competitive it needed to reduce its energy costs. Its Burns Habor Facility, located on about 1,700 acres (6.9 km²) on the shore of Lake Michigan, employs 600 people and is capable of annually producing 5.3 million tons (5.4 million metric tons) of hot-rolled sheet, cold-rolled sheet, and steel plates. BSC identified one of the facility's basic oxygen furnaces (BOFs) as a prime candidate for energy conservation measures. Each of the facility's three BOFs can make approximately 300 tons (305 metric tons) of molten steel in 30 minutes and consumes approximately 31,000 MWh a year. By installing a variable frequency drive (VFD) and making equipment modifications to the induced draft fans that remove gases from this BOF, BSC was able to better match the fan's speeds to the BOF's varying requirements, saving energy, reducing operation costs, and decreasing system maintenance expenses. The energy use of the BOF was cut about 50% to 15,500 MWh annually, and total operating savings were more than $620,100 (USD) annually. With a total capital cost of $1,225,000 (USD), the project's simple payback was just under two years. The U.S. Department of Energy's Motor Challenge Program verified energy savings, and Meade Industrial Services, Inc., a Motor Challenge Partner, performed motor and electrical installation.

Technical Data

An important part of the steel-making process involves blowing gaseous oxygen in the BOF, generating high temperatures and chemical reactions that oxidize impurities in the metal and convert iron into steel. The fans used to remove gas produced in this process operated at a continuous 1,200 RPM, though analysis showed that maximum was only needed during one-third of the BOF's 45-minute cycle. In addition, the fans only needed to run at a maximum rate of 1075 RPM. Controlling the flow by modulating the inlet dampers on the induced draft fans caused unnecessary pressure drop in the system. Therefore, a VFD was installed to modulate the flow.

Energy Data

The average monthly energy consumption of the BOF fell nearly 50% from 2,602 MWh a month to 1,310 MWh. Over a year, that translates to energy savings of about 15,500 MWh.

Economic Data

The project produced savings of $620,100 (USD) a year. Total project cost was $1,225,000 (USD), creating a simple payback of about two years.

Environmental Data

The project reduction the production of 36,600,000 lbs (1,6601,000 kg) of CO₂, 115,000 lbs (52,163 kg) of SO₂, and 143,000 lbs (64,863 kg)of NO_X.

Contacts:

Bethlehem Steel Corporation Rick Anderson 1170 Eight Ave. Bethlehem, PA 18016-7699 610-694-2424 610-694-5743 (Fax) http://www.bethsteel.com	Meade Industrial Services Inc. Earl Horecky 1825 Summer Street Hammond, IN 46320 219-932-2100 219-933-1606 (Fax)
DOE Motor Challenge Mitch Olszewski Oak Ridge National Laboratory P.O. Box 2008 Oak Ridge, TN 37831 865-574-0770 http://www.ornl.gov/sci/engineering_science_technology/industrial%20energy.htm

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