Materials Characterization Paper

In Support of the

Advanced Notice of Proposed Rulemaking –

Identification of Nonhazardous Materials That Are Solid Waste

Blast Furnace Slag - Used as ingredient in clinker manufacture

December 16, 2008

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1.	Definition of BFS  

Blast furnace slag (BFS) is a nonmetallic byproduct of the manufacture
of pig iron in a blast furnace. BFS consists primarily of silicates,
aluminosilicates, and 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 reducing iron ore to iron, a
molten slag forms as a non-metallic 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) granulated blast furnace slag (GBFS) is produced by
quickly quenching (chilling) molten slag to produce 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 (atmospheric) conditions. BFSA and
GBFS are used in clinker manufacture (EPA 2008).

2.	Annual Quantities of BFS Generated and Used

Sectors that generate BFS: 

Blast furnace slag is generated by NAICS industry sector 331111, Iron
and Steel Mills.

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). 

In addition, approximately one million short tons of blast-furnace slag
were imported into the United States in 2005.

In 2004, average sales prices for GBFS were $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).

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

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 for the long-term availability of air-cooled slag, given the
continuing decline in the number of operating blast furnaces (van Oss
2006).

2005, with no assurance of restarting. Retroﬁtting other blast
furnaces with granulators is possible and a handful of new slag grinders
are being constructed in the U.S., which will likely increase GGBFS
supply in coming years (EPA 2008). 

3.	Uses of BFS

Ingredient uses of BFS:  

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

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

Non-combustion uses of BFS:

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

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 process) or by adding the
slag to portland cement concrete as a mineral admixture.

Quantities of BFS landfilled: 

No data exist on the disposal or landfilling of blast-furnace slag, but
it is likely that the utilization of blast 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).

Quantities of BFS stockpiled/stored:

A preliminary sampling of three blast furnace 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 total quantity
of stockpiled slag in the U.S. is likely significantly higher, but
additional slag processors have not been surveyed to obtain an estimate.


It is unclear what percentage of the known 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 milliona



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,
December 5, 2006 and December 6, 2006.



4.	Management and Combustion processes for BFS

Types of units using BFS

Blast furnace slag is added to cement kilns during the clinker
manufacturing process.

Sourcing of BFS

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

Processing of BFS:  

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

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 exhaustive
investigation of state activities and regulations.

5.	BFS Composition and Impacts

Composition of BFS:

The chemical composition of BFS includes: calcium oxide (CaO), silicon
dioxide (SiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), iron (FeO
or Fe2O3), manganese oxide (MnO), and sulfur (S) (Turner-Fairbank
Highway Research Center).

When heated to high temperatures (1450 degrees Celsius) in a cement
kiln, some of the chemical constituents of slag may be volatized.

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 uncertainties in lifecycle
scenario development. For example, it is difficult to determine the
replacement ratio between BFS and other raw feed materials in clinker
production. Thus, the correct quantity of material to be modeled is
unclear. In addition, BFS may substitute for a variety of virgin raw
materials as well as other secondary materials (e.g., cement kiln dust,
CCPs, foundry sand, etc.); the choice of material often depends on
location-specific factors such as the proximity of material sources to
the cement kiln and relative availability of different materials.
Avoided upstream impacts depend heavily on the specific material being
displaced in the lifecycle scenario.

References

Personal communication with Jamie Connor, Tube City IMS Corporation,
Chuck Martin, Beaver Valley Slag, Inc., and Max Wolanske, Lafarge NA,
December 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:   HYPERLINK
"http://www.tfhrc.gov/hnr20/recycle/waste/begin.htm" 
http://www.tfhrc.gov/hnr20/recycle/waste/begin.htm .

United States Census Bureau. 2002 Economic Census, Industry Snapshots
for Cement Manufacturing, accessed on August 18, 2008 at:   HYPERLINK
"http://quarterhorse.dsd.census.gov/TheDataWeb_HotReport/servlet/HotRepo
rtEngineServlet?emailname=bh@boc&filename=mfg1.hrml&20071204152004.Var.N
AICS2002=327310&forward=20071204152004.Var.NAICS2002" 
http://quarterhorse.dsd.census.gov/TheDataWeb_HotReport/servlet/HotRepor
tEngineServlet?emailname=bh@boc&filename=mfg1.hrml&20071204152004.Var.NA
ICS2002=327310&forward=20071204152004.Var.NAICS2002 . 

United States Environmental Protection Agency (EPA). 2006, Sector
Strategies Performance Report: Cement, accessed at:    HYPERLINK
"http://www.epa.gov/ispd/pdf/2006/cement.pdf" 
http://www.epa.gov/ispd/pdf/2006/cement.pdf . 

United States Environmental Protection Agency (EPA). 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 Survey (USGS). January 2006, Mineral Commodity
Summaries: Iron and Steel Slag, pg 2, accessed at:   HYPERLINK
"http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/fesl
amcs06.pdf" 
http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/fesla
mcs06.pdf . 

van Oss, H.G. 2003, USGS 2003 Minerals Yearbook: Slag-Iron and Steel,
accessed August 21, 2008 at:   HYPERLINK
"http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/isla
gmyb03.pdf" 
http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/islag
myb03.pdf . 

van Oss, H.G. 2004, USGS 2004 Minerals Yearbook: Volume II--Metals and
Minerals: Slag-Iron and Steel, accessed October 2, 2006, at:   HYPERLINK
"http://minerals.usgs.gov/minerals/pubs/commodity/cement/cemenmyb04.pdf"
 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:   HYPERLINK
"http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/myb1
-2006-fesla.pdf" 
http://minerals.usgs.gov/minerals/pubs/commodity/iron_&_steel_slag/myb1-
2006-fesla.pdf . 

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

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ᔀ硨陭ᘀ䙨鹃唀Ĉ∀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 were converted from a metric
ton to short ton basis.

 Prices were converted from a metric ton to short ton basis.

Blast Furnace Slag

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