Materials Characterization Paper In Support of the Final Rulemaking:

Identification of Nonhazardous Seco ndary Materials That Are Solid Waste Blast Furnace Slag - Used as ingr edient in clinker manufacture

February 3, 2011

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1. Definition of BFS

Blast furnace slag (BFS) is a nonmetallic byproduc t of the manufacture of pig iron in a blast furnace. BFS consists primarily of silicates, aluminosilicates, a nd calcium-alumina-silicates. BFS forms when slagging agents (e.g., iron ore, coke ash, and limestone ) are added to the iron ore to remove impurities. In the process of reducin g iron ore to iron, a molte n slag forms as a nonmetallic liquid (consisting primarily of silicates and aluminosilicates of calcium and other bases) that floats on top of the molten iron. The molten slag is then separated from the liquid metal and cooled. Different forms of slag product are produced depending on the method used to cool the molten slag and subsequent processing: (1) gran ulated blast furnace slag (GBFS) is produced by quickly quenching (chilling) molten slag to pro duce a glassy, granular product; (2) GBFS can further be ground to a specified fineness, yielding ground granulated blast furnace slag (GGBFS); (3) blast furnace slag aggregate (BFSA) is produced by allowing the molten slag to cool and solidify slowly under ambient (atmosph eric) conditions. BFSA a nd GBFS are used in clinker manufacture (EPA 2008).

2. Annual Quantities of BFS Generated and Used

(1) Sectors that generate BFS:

• Blast furnace slag is generated by NA ICS industry sector 331111, Iron and Steel

Mills

.

(2) Quantities and prices of BFS generated:

• In 2004, between 13 and 15 million short tons of blast furnace slag were generated in the U.S (van Oss 2004). 1 This is reasonably consistent with U.S. sales (as opposed to generation) of bl ast furnace slag. According to public comments received by EPA in response to the Advanced Notice of Proposed Rulemaking (ANPRM), the U.S. consum ed approximately 21 million tons of domestic iron and steel slag in 2005, 60 percent of which (or 12.6 million tons) was blast furnace slag (Wittenborn 2009).

• Approximately one million short tons of bl ast-furnace slag were imported into the United States in 2005 (van Oss 2004). Similarly, citing Census Bureau data summarized by USGS, a public comment submitted to EPA in response to the ANPRM indicates that the corresponding fi gure for ferrous slags in general in 2006 was approximately 1.3 million metric tons (or 1.5 short tons) (Kiggins 2009).

1 The USGS estimates that the quan tity of blast-furnace slag produced is equivalent to 25 percent to 30 percent of crude iron (i.e., pig iron) production (EPA 2008).Blast Furnace Slag

2 • In 2004, average sales prices for GBFS we re $55.79 per short ton, with a reported range of $20.00 per ton for un-ground GBFS to $64.99 per ton for GGBFS (EPA 2008). 2

• In 2004, average sales prices of BFSA we re $5.90 per short ton, with a range of $1.40 to $15.74 per short ton (EPA 2008). 3

(3) Trends in generation of BFS:

• The generally declining trend in the U.S. output of iron and steel implies future overall supply constraints from domestic sources, especially as existing stockpiles get drawn down. This is especially true fo r the long-term availabi lity of air-cooled slag, given the continuing decline in th e number of operating blast furnaces (van Oss 2006).

• The supply of GBFS from domestic blast fu rnaces is constrained by the fact that granulation cooling is currently installed at only five blast f urnaces in the United States, and one of these has been idle since mid- 2005, with no assurance of restarting. Retro fi tting other blast furnaces with granulators is possible and a handful of new slag grinders are being c onstructed in the U.S., which will likely increase GGBFS supply in coming years (EPA 2008).

3. Uses of BFS

(1) Ingredient uses of BFS:

• Both BFSA and GBFS can be added to the raw material feed in clinker manufacturing to contribute specific requi red elements, such as silica, alumina, calcium, and magnesium in the final cement composition. The primary virgin

material used in clinker ma nufacture is limestone, with smaller quantities of sand, clay, and shale to achieve the correct mineral composition. Thus, BFS partially offsets these virgin raw feed materials.

• Public comments submitted to EPA follo wing the release of the ANPRM suggest that cement kilns primarily use iron and steel slag as a raw material source for silica, alumina, calcium, and magnesium, elements needed for the final cement product. Slag is also used as a substitute for virgin aggregate in road base, concrete, asphalt concrete, ra il ballast, roofing, shingl es, mineral wool, and glass making. At some facilities, steelmaking slag is also returned to the furnace as ferrous and flux feed (Wittenborn 2009).

• Cement kilns are represented by NAICS industry sector 327310, Cement Manufacturing, which included 247 facilit ies in 2002 (U.S. Census Bureau, 2002). EPA reports that this sector in cluded 144 facilities in 2006 (EPA 2006).

(2) Non-combustion uses of BFS:

• Blast furnace slag aggregate is used as a substitute for virgin aggregate in road base, concrete, asphalt concrete, rail balla st, roofing, shingles, mineral wool, and glass making.

2 This range does not include old, weathered GBFS from existing stockpiles that is sold as fine aggregate for a few dollars per metric ton (EPA 2008). Prices we re converted from a metric ton to short ton basis.

3 Prices were converted from a metric ton to short ton basis.Blast Furnace Slag

3 • GGBFS can be used as a supplementary cementitious material either by premixing the slag with portland cement or hydrated lime to produce a blended cement (during the cement production proces s) or by adding the slag to portland

cement concrete as a mineral admixture.

• Public comments submitted in response to the ANPRM also state that steel furnace slag can be used within the agricultural industry or as water filter media for acid mine drainage and po llution control (Kiggins 2009).

(3) Quantities of BFS landfilled:

• No data exist on the disposal or landfilling of blast-furnace slag, but it is likely

that the utilization of blas t furnace slag is nearly 100 percent of U.S. production, reflecting the high value of these materials as cementitious materials, aggregates, or components of blended cements (EPA 2008).

(4) Quantities of BFS stockpiled/stored:

• A preliminary sampling of three blast fu rnace slag processors in the U.S. has identified approximately 100 million metric tons of stockpiled slag as of 2006 (Connor, Martin, and Wolanske 2006). The to tal quantity of stockpiled slag in the U.S. is likely significantly higher, but a dditional slag processors have not been surveyed to obtain an estimate.

• Public comments from the National Slag Association in resp onse to the ANPRM note that while the majority of stockpile d slag is a byproduct of production, some of this stockpiled material is mined from slag piles at closed iron and steel plants (Kiggins 2009).

• It is unclear what percentage of the k nown 100 million metric tons of stockpiled slag is suitable for use in clinker manufacture.

Exhibit 1: Overview of Generation and Use of BFS in 2004

Commodity Annual Quantity

Generated Annual Quantity Used as Ingredient Annual Quantity

Landfilled Annual Quantity in

Other Uses Total Quantity Stockpiled as

of 2006 Cement

Kilns Other

-------------------- Short Tons --------------------

Blast Furnace Slag 12.0-14.0 million 0.25 million 0 0 11.58 million >100 million a

Sources : Unless otherwise noted, data is from U.S. EPA, April 28, 2008, Study on Increasing the Usage of Recovered Mineral Components in Federally Funded Projects Involving Procurement of Cement or Concrete to Address the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users

. Notes : a. Personal communication with Jamie Connor, Tube City IMS Corporation, Chuck Martin, Beaver Valley Slag,

Inc., and Max Wolanske, Lafarge NA, D ecember 5, 2006 and December 6, 2006.Blast Furnace Slag

4 4. Management and Combustion processes for BFS

(1) Types of units using BFS

• Blast furnace slag is added to cemen t kilns during the cl inker manufacturing

process.

(2) Sourcing of BFS

• Cement manufacturing facilities purchase blast furnace slag directly from iron mills or from a slag processing/grinding facility.

(3) Processing of BFS:

• Once molten slag has been cooled into either BFSA or GBFS, no further processing is required for use as a ra w material in clinker manufacture.

• According to public comments received by EPA in resp onse to the ANPRM, previously generated blast furnace slag is often removed from slag mineral reserve sites by ripping a nd digging. The material then undergoes magnetic separation, crushing, further magnetic sepa ration, and screening (Kiggins 2009).

(4) State status of BFS use as ingredient:

• At this stage, we have not identified any states that have specifically granted beneficial use designation to the use of blast furnace slag in clinker manufacture, but we have not performed an exhaustiv e investigation of state activities and regulations.

5. BFS Composition and Impacts

(1) Composition of BFS:

• The chemical composition of BFS includes: calcium oxide (CaO ), silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), magnesium oxide (MgO), iron (FeO or Fe 2 O 3 ), manganese oxide (MnO), and sulfur (S ) (Turner-Fairbank Highway Research Center) The chemical composition of BF S varies, but Exhibit 2 presents the average concentration of the constituents outlined above and the typical range of

concentrations.

• When heated to high temperatures (1,450 de grees Celsius) in a cement kiln, some of the chemical constituents of slag may be volatized.Blast Furnace Slag

5 Exhibit 2: Typical Composit ion of Blast Furnace Slag

Constituent

(Percent) Average (mean)

Concentration Range

percent by wight

Calcium Oxide 39 34 – 43

Silicon Dioxide 36 27 – 38

Aluminum Oxide 10 7 - 12 Magnesium Oxide 12 7 – 15 Iron (FeO or Fe 2 O 3 ) 0.5 0.2 – 1.6 Manganese Oxide 0.44 0.15 – 0.76

Sulfur 1.4 1.0 – 1.9 Source: Turner-Fairbank Highway Research Center, National Slag Association data: 1949 (22 sources) 1957 (29 sources), 1968 (30 sources), 1985 (18 sources)

(2) Impacts of BFS use:

• In clinker manufacture, blast furnace slag partially offsets the need for virgin materials such as limestone, sand, clay, and shale. Substitution of slags for natural raw materials to make clinker can reduce the unit consumption of fuel and limestone in the kiln, which may then reduce the emissions of certain pollutants (van Oss 2006).

• The specific lifecycle impacts of BFS use as a raw material in clinker production

are not evaluated here because of uncertain ties in lifecycle scenario development. For example, it is difficult to determin e the replacement ratio between BFS and other raw feed materials in clinker pr oduction. Thus, the correct quantity of

material to be modeled is unclear. In a ddition, BFS may substitute for a variety of virgin raw materials as well as other s econdary materials (e .g., cement kiln dust, CCPs, foundry sand, etc.); the choice of material often depends on locationspecific factors such as the proximity of material sources to the cement kiln and relative availability of different mate rials. Avoided upstream impacts depend heavily on the specific material being displaced in the lifecycle scenario.Blast Furnace Slag

6 References

Kiggins, Karen, public comment public comment in resp onse to EPA’s Advanced Notice of Proposed Rulemaking

for Identification of Non-Hazardou s Materials That Are Solid Wast e, EPA docket EPA-HQ-RCRA-2008- 0329, submitted on behalf of National Slag Association, February 2, 2009.

Personal communication with Jamie Connor, Tube City IMS Corporation, Chuck Martin, Beaver Valley Slag, Inc., and Max Wolanske, Lafarge NA, Decembe r 5, 2006 and December 6, 2006.

Turner Fairbank Highway Research Center and the Federal Highway Administration. User Guidelines for Waste and Byproduct Materials in Pavement Construction , accessed at: http://www.tfhrc.gov/hnr20/recycle/waste/begin.htm

.

Turner-Fairbank Highway Research Center and the Federal Highway Administration. Blast Furnace Slag Material Description , accessed at: http://www.tfhrc.gov/hnr20/recycle/waste/bfs1.htm

United States Census Bureau. 2002 Economic Census, Indu stry Snapshots for Cement Manufacturing, accessed on August 18, 2008 at: http://quarterhorse.dsd.census.gov/TheDataWeb_HotReport/servlet/HotReportEngineServlet?emailname=b h@boc&filename=mfg1.hrml&20071204152004.Var.NAICS2002=327310&forward=20071204152004.V

ar.NAICS2002.

United States Environmental Pr otection Agency (EPA). 2006, Sector Strategies Performance Report: Cement

, accessed at: http://www.epa.gov/ispd/pdf/2006/cement.pdf

.

United States Environmental Protectio n Agency (EPA). June 3, 2008, Study on Increasing the Usage of Recovered Mineral Components in Federally Funded Projects Involving Procurement of Cement or Concrete to Address the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users , pgs 2-5

and 2-8.

United States Geological Surv ey (USGS). January 2006, Mineral Commodity Summaries: Iron and Steel Slag

, accessed at: http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/feslamcs06.pdf

.

van Oss, H.G. 2003, USGS 2003 Minerals Yearbook: Slag-Iron and Steel , accessed August 21, 2008 at: http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/islagmyb03.pdf

.

van Oss, H.G. 2004, USGS 2004 Minerals Yearbook: Volume II--Metals and Minerals: Slag-Iron and Steel

, accessed October 2, 2006, at: http ://minerals.usgs.gov/minerals/pubs/ commodity/cement/ cemenmyb04.pdf.

van Oss, H.G. 2006, USGS 2006 Minerals Yearbook: Slag-Iron and Steel , accessed August 21, 2008 at: http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/myb1-2006-fesla.pdf

.

Wittenborn, John L., public comment public comment in response to EPA’s Advanced Notice of Proposed Rulemaking for Identification of Non-Hazardous Mate rials That Are Solid Waste, EPA docket EPA-HQRCRA-2008-0329, submitted on behalf of Steel Manufactu rers Association, Specialty Steel Industry of North America, and American Iron & Steel Institute, February 2, 2009.