Nucor Steel manufactures low carbon and high strength low alloy structural steel. Scrap metal is melted, alloyed and refined in electric arc furnaces. A continuous casting machine casts the molten metal into billets which are rolled into the final product - angles, flat bars, channels and rounds.
Various types of hydraulic equipment are used in our manufacturing process. For several years Nucor has used a water glycol mixture as a hydraulic fluid in the operation of the equipment. The primary component of the water glycol mixture was ethylene glycol (CAS No. 107-21-1). Ethylene glycol is a section 313 toxic chemical and subject to section 313 reporting requirements. Our usage rate for the years 1988 through 1990 was approximately 200,000 lbs. per year. A portion of this material was released through leaks into our contact water system. Water is required at numerous points in the manufacturing process for cooling hot billets and cooling of rolls during the rolling process and for flushing of mill scale. The water system is a closed loop system. Water is pumped from a concrete lined reservoir to the various points in the mill for cooling or flushing purposes and returned to the reservoir. Periodically the water is blown down by pumping to an earthen settling pond. As needed, the water is returned from the settling pond to the concrete lined reservoir for use in the manufacturing process. The majority of the ethylene glycol entering the contact water was flashed or thermally reduced to non-toxic products as the water came in contact with hot metal in excess of 2300 degrees F. However, this waste treatment process did not entirely rule out the possibility of some environmental contamination through evaporation.
Because of environmental concerns regarding the use of ethylene glycol, our vendor, E. F. Houghton & Co. of Valley Forge, Pa., supplied us, for trial purposes, in late 1990 with a shipment of water glycol using diethylene glycol as the primary ingredient. Diethylene glycol (CAS No.111-46-6) is not a section 313 toxic chemical. This trial run proved very successful with no detrimental effects from a production view point. Since mid-1991 we have been using the nonhazardous water glycol.
However, the environmental impact has been significant since the potential for environmental contamination from ethylene glycol has been totally eliminated.
Details of Reductions
Additional Information :
The economic impact from switching to diethylene glycol has been minimal since the cost of the new product is approximately the same.