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ZERO WASTE ELECTRIC ARC FURNACE (EAF) STEELMAKING

CHAPARRAL STEEL COMPANY TARGET

Libor F. Rostik

ChaparraI Steel Company Midlothian Texas

EPA Region III Waste Minimization/Pollution Prevention

Technical Conference

Sponsored by:EPA Region III

February 4-7, 1996Wyndham Franklin Hotel

Philadelphia, PA

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ZERO WASTE ELECTRIC ARC FURNACE (EAF) STEELMAKING

CHAPARRAL STEEL COMPANY TARGET

Libor F. RostikChaparral Steel Company

Midlothian, Texas

Chaparral Steel Company is a market mill located approximately 35 miles south of the Dallas/Fort

Worth International Airport in Midlothian, Texas. Chaparrals facilities and operating philosophy

reflect the latest worldwide advancements in steelmaking. The company is committed to the

incorporation of new technologies intended to provide the best quality products at internationally

competitive prices. Chaparrals current employment is 960 people. Its initial production of 228,000tons in 1976 has grown to 1.6 million tons in 1994.

Chaparral owns and operates one of the biggest car shredding facilities in the world which is located

on its site. More than 80% of Chaparrals stock is owned by Texas Industries (TXI) which owns

and operates a cement plant located adjacent to Chaparral.

STEEL MELTING

Chaparral Steels production is 100% scrap based. Chaparrals automobile shredder supplies

approximately 600,000 tons per year. The rest of the scrap is purchased. Scrap is melted by two

computer-assisted Ultra High Powered Electric Arc Furnaces (EAF). Molten steel is refined andis continuously cast in different pre-forms which are hot rolled in the finish products.

Chaparrals product range includes bars, rounds, structural shapes, flats and beams. Chaparral Steel

grades are produced for applications ranging from automotive and forging applications to

construction and structural ones.

Chaparral Steel considers itself to be an efficient recycling facility: steel is produced using the most

stringent environmental controls and Chaparral seeks to be at the leading edge of environmental

technology.

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Steel is the most recycled material in the world. Steel produced by electric arc furnaces uses

recycled material as prime input and the product is totally recyclable. Chaparral is one of the largestEAF mills in the United States and represents a major recycling facility. As shown in Figure 1, the

industry does not produce only steel products. The challenge that Chaparral is addressing is to

reduce the generation of by-products, co-products and wastes and to find valuable uses for themthrough the combined application of technology and economics.

Figure 1.

I U.S. EAF Steelmaking Industry 1994 (1,2)

Product

Raw Steel

Slag

Scale

Dust

U. S. Annual

Tons

38,500,000

4,466,OOO

1,078,000

616,000

Chaparral 1994

% of Raw Steel Production % of Raw Steel

Tons Tons Tons

100% 1,600,OOO 100%

11.60%2 170,000 10.95%

2.8%2 30,400 1.9%

1.6%2 18,000 1.15%

THE STAR PROJECT

To organize environmental efforts effectively, Chaparral and TXI initiated a project called STAR

(acronym for Systems and Technology for Advanced Recycling). The mission of the STAR

project is to develop synergies between the steel and cement manufacturing processes and the

automobile shredding facility to generate new products, conserve energy and improve theenvironment. The STAR project will result in reduction of process wastes, conservation of natural

resources and pollution prevention through the environmentally and economically sound recycling

of waste materials generated by the steel and cement manufacturing processes.

The ultimate goal of the project is to achieve zero waste from the complex through better

understanding of the process requirements and the application of innovative technology and sound

economics.

Hatch Associates Ltd. is a consulting firm to the metallurgical industry worldwide. It has a long

standing relationship with Chaparral Steel. It is associated with Chaparral Steel and Texas

Industries in this project, providing process expertise and technological know how.

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FlGURE3. MASS BALANCE

POWER

AUTO BODIES

OTHER SCRAP

AUTO SHREDDER RESIDUE

NON FERROUS

PARTICULATE

STEEL

ALLOYS

REFRACTORIES

POWER

GASES:

NATURAL GAS

OXYGEN

NITROGEN

ARGON

STEEL PRODUCTS

BAGHOUSE DUST

SPENT REFRACTORIES

PARTICULATE

CO

RECOVERABLE ENERGY

POWERNATURAL GAS

REFRACTORIES

MILL SCALESPENT REFRACTORIES

PARTICULATE

c o

NOX

SO2

VOC

RECOVERABLE

ENERGY

TECHNOLOGICAL CHALLENGES AND OPPORTUNITIES

Chaparral and TXI have addressed a number of technological issues to reduce or eliminate the

production of hazardous wastes, to upgrade the value of by-products and to reduce consumption ofresources.

Baghouse dust is characterized as hazardous waste and disposal costs are currently $25O/ton. Duringthe period 1990-93, Chaparral has reduced considerably the volume of dust going to disposal whichno represents 1.15% of steel production compared to an industry average of 1.6% (Figure 4).

Changes to the lime delivery system reduced the lime content of the dust from 30% to less than 4%.

A portion of the dust is recycled to the furnaces. The remaining enriched dust is shipped for metal

recovery at a lower overall cost. There is thus an incentive to seek on-site recovery of the iron, zinc

and other metals in the dust with the metal-rich residues sold to downstream processors.

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FIGURE4 BAGHOUSE DUST GENERATION- per ton of steel production -

Refractories

The refractories used in the steelmaking process are a mix of alumina and magnesitic materials. No

comprehensive solution has yet been found to recycle the remaining refractory after use int he

process, with one significant exception. Magnesitic refractories are separated, crushed and returned

to the melting furnace as a flux component to help maintain the slag properties required by the

process. The further development of this technology will not only eliminate the present practice oflandfilling of the used refractories but will also minimize the use of virgin materials.

Solvents used in mill cleaning ark generally classified in three groups: non-organic caustic,

halogenated organic, and ignitable organic. The first two groups are considered to be hazardous and

subject to control. The target at Chaparral has been to eliminate the use of hazardous materials and

to minimize the use of the third group. Figure 4 tracks the attainment of this goal over the last seven

years. The elimination of hazardous materials and the overall reduction in material use has resulted

in a significant reduction of expenditure for this family of products.

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FIGURE5. USE OF SOLVENTS AT CHAPARRAL

TONS - historical annual usage6 0 0

5 0 0

4 0 0

3 0 0

2 0 0

1 0 0

01 9 8 8 1 9 8 9 1 9 9 0 1 9 9 1 1 9 9 2 1 9 9 3 1 9 9 4

EAF Slag

Molten slag is collected in iron slag pots during the melting of raw materials in the electric arc

furnace. Slag is cooled by pouring it in the designated area.

Slag contains significant amounts of iron units and, in 1993, Chaparral upgraded the crushing andprocessing of the slag in order to recover lower grade metallics and recycle them back to the

furnace. This also created synergy with the TXI cement plant.

TXI developed and patented a method which allows this EAF slag to be used in the manufacture ofhigh quality cement. Such use of slag conserves resources and reduces energy requirements as

compared with typical cement manufacturing.

Mill scale is generated at the continuous casting and rolling process. It represents approximately

1.9% of steel produced. Chaparral follows the common practice of supplying it as feed stock tocement plants which use it for a production of Portland cement. Since mill scale is approximately

70% Fe (by weight), future developments will aim at recovery of the iron units which will result in

higher financial rewards.

Energy

Chaparral is highly energy conscious. Most of the steps taken to date have had a positive impact on

energy efficiency (energy requirement/unit output). Every process improvement will continue to

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be assessed in terms of energy efficiency. Other directions for the future lie in reducing or re-using

what is now waste heat. Improved furnace design and scrap pre-heating are some of the measures

being considered, as well as the opportunity of utilizing the energy of the liquid slag.

Water

Chaparral was designed from the start as a closed loop water system with total recirculation. Make-

up water is required to compensate for evaporation losses. By modifying operating procedures,

aquifer pumping has been reduced in half from 450 to 229 million gallons per year. This action has

resulted in significant savings in energy and maintenance costs as well as conservation of a valuable

resource.

Other Activities

The STAB project also involves activities at the cement plant and shredder facility towards the zero

waste target.

TXI now landfills kiln dust that is too fine to be captured into cement. That dust contains

a large amount of lime which might be used in the EAF for slag making, a recycling

operation that would be of benefit to both the cement plant and the steel mill.

Automobile shredding is an integral part of Chaparral operations. Up to 600,000 obsolete

cars are shredded every year providing approximately 30% of the raw material input and asignificant competitive advantage.

Automobile shredding is a multistage operation. The ferrous metals are separated first. The non-

ferrous materials are separated in several steps involving air separation, the Van-Over process and

magnetic separation technologies. In this manner, the auto shredding operation minimizes theresidue sent to landfill while optimizing the degree of metals recovery.

ECONOMIC BENEFITS TO DATE

Every step that has been taken so far has been designed to be profitable.

The new lime feed system has reduced the use of lime from 89,500 to 59,700 tons per year.

As a result, the carry-over of lime fines in the baghouse has also been reduced, resulting inan additional savings.

In 1994, recycling 5,950 tons of EAF dust to the furnace produced a significant savings.

The use of slag in lieu of raw material in cement making has raised the value of the product

and has also achieved significant energy savings.

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The replacement of solvents by non-hazardous products and the reduction in their use to

approximately 160 tons per year represents a savings as well.

The next steps to be taken will maintain the same target of combining technological progress with

economic efficiency.

FUTURE PROSPECTS

The continued emphasis on recycling and stewardship will inevitably lead to the development ofnew technologies and further progress for the industry.

Development work is proceeding on a number of fronts, integrating the managerial, technological

and economic goals. The recovery of iron from slag, dust and scale would constitute a major

advance. The value of iron to the furnace would be of the order of $180/ton and the low iron slagcould be of increased benefit to the cement plant. Work on this subject is proceeding from the

conceptual to the testing stage. Such a step could lead to combined processing of slag scale and dust

together on-site.

In terms of energy efficiency, improved steelmaking processes that could recover iron units from

molten slag would mean significant energy improvement as would other means to recover wasted

energy (furnace design modifications, scrap pre-heating, new scrap melting technologies).

CONCLUSIONS

Though the ultimate target still lies ahead, a number of conclusions can be reached form progressso far.

This initiative combines aggressive business objectives with challenging environmental

goals.

Progress towards the target comes in realistic, incremental steps each of which brings added

value to the business.

It is no longer possible for steelmakers to be concerned with only the production of steel.

They have to accept responsibility for by-products and waste streams. That responsibility

becomes an incentive for innovation and progress.

The proximity of the other businesses has provided Chaparral with many opportunities for

synergy. Other circumstances may create different synergies.

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