Materials Characterization Paper

In Support of the

Advanced Notice of Proposed Rulemaking –

Identification of Nonhazardous Materials That Are Solid Waste

Foundry Sand - Used as ingredient in clinker manufacture

December 16, 2008

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1.	Definition of Foundry Sand

Foundry sand is an industrial material generated by the metal-casting
industry, which uses the sand to form a physical mold used in the
production of metal products.  Two general types of sand are used in
metal casting: clay-bonded sand (green sand); and chemically-bonded
sand:

Green sand is composed of naturally occurring materials that are blended
together: high quality silica sand; bentonite clay as a binder; a
carbonaceous additive to improve the casting surface finish; and water. 
Due to the carbon content, green sand is actually black in color and
adheres together due to the clay and water content.  Green sand molds
comprise about 90 percent of the casting volume in the United States.

Chemically-bonded sand does not employ  SEQ CHAPTER \h \r 1  a clay
binder. Instead, chemical binders are used to cause the sand to hold its
shape during the introduction of the molten metal into the mold and the
cooling of the casting. Chemically-bonded sand is generally light in
color and coarser in texture than clay bonded sand, and accounts for
only 10 percent of casting volume in the United States.  Foundries use
chemically-bonded sand in coremaking, where high strengths are necessary
to withstand the heat of the molten metal (FIRSTb).

After multiple uses in castings, the sand becomes unsuitable for
castings and is either disposed of in landfills or beneficially used in
other applications, including use as an ingredient in the manufacture of
portland cement.  

2.	Annual Quantities of Foundry Sand Generated and Trends in Generation

Sectors that generate foundry sand: 

The metal-casting industry, represented by NAICS code 3115, is the sole
generator of spent foundry sand.

Quantities and prices of foundry sand generated:   

According to the American Foundry Society (AFS), a metal casting
industry group, the metal-casting process generates 9.4 million tons of
foundry sand annually (AFS 2007).

Trends in generation of foundry sand:  

The generation of foundry sand generally tracks with the manufacture of
cast metal products. Despite increased foreign competition, the metal
casting industry expects modest growth to continue. Sales of metal
castings are expected to grow 14 percent over the next three years from
$33 billion in 2005 to $37.7 billion in 2008 (Industrial Metalcasting).

3.	Uses of Foundry Sand

Ingredient uses of foundry sand:  

Spent foundry sand can be used in the manufacture of portland cement
clinker.  Most foundry sands are high in silica content and can serve as
a potential alternative silica source in portland cement clinker
production. In addition, portland cement clinker production requires
certain minerals, such as iron and aluminum oxides, both of which are
found in many spent foundry sands.  Brass foundries create sands that
can be hazardous under RCRA (if disposed of) due to metals content and,
therefore, are outside the scope of this report.

According to the portland cement industry, foundry sand can be
beneficially reused in the manufacturing of portland cement when it
possesses the following properties: silica content of 80 percent, low
alkali levels, and uniform particle size. In addition, large quantities
of foundry sands must be available for it to be used by Portland cement
manufacturers (FIRST).

Non-combustion uses of foundry sand:

Spent foundry sand can be used as a substitute for virgin sand in road
base, structural fill, flowable fill, soil amendment, or as the fine
aggregate portion of concrete or hot-mix asphalt.  In addition, some
sand can be used as a high-end additive to industrial materials, such as
plastics, to provide specific textures and colors.  

Quantities of foundry sand landfilled: 

AFS estimates that in 2006, 6.8 million tons of foundry sand were
disposed in landfills. This quantity includes sand used as a landfill
daily cover.

Quantities of foundry sand stockpiled/stored:

The sources consulted for this paper did not provide available
information concerning whether significant quantities of foundry sand
are stockpiled or stored.  

Exhibit 1:  Overview of Generation and Use of Foundry Sand in 2007

Commodity	Annual Quantity Generated 	Annual Quantity Used as Ingredient
Annual Quantity Landfilled	Annual Quantity in Other Uses	Total Quantity
Stockpiled 



Cement Kilns	Other





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

Foundry sand	9.4 million	Undetermined	None	6.8 million	2.6 million
Undetermined



Sources:

Oman, Alicia. American Foundry Society (AFS), personal communication,
12/21/07, and Foundry Industry Benchmarking Survey, August 2007,
accessed at:   HYPERLINK
"http://www.strategicgoals.org/benchmarking/foundryresults8-7.pdf" 
http://www.strategicgoals.org/benchmarking/foundryresults8-7.pdf . 

Notes:

Detailed quantitative data on the various beneficial use applications of
foundry sand have not been well documented in the past.  In an attempt
to address this issue, AFS recently conducted a benchmark survey to
collect information from the foundry industry on the specific quantities
of spent foundry sand being beneficially used in different applications.
The survey results indicate that none of the respondents are currently
using foundry sand in clinker manufacture. According to the Portland
Cement Association, however, foundry sand is being used by a number of
North American cement kilns (FIRSTb).



4.	Management and Combustion processes for Foundry Sand

Types of units using foundry sand:

When used in clinker manufacture, foundry sand is fed into cement kilns
with other raw material feed.  No other combustion applications appear
to use significant quantities of foundry sand as an input.

Sourcing of foundry sand:

In some cases, cement manufacturers obtain foundry sand through direct
agreements with foundries, most of which are located in certain states,
including Illinois, Wisconsin, Michigan, Ohio, and Pennsylvania. Some
foundries market their spent sand through a third-party or a cooperative
instead of selling directly to the end-user. The majority of foundries
are small businesses that generate small quantities of spent foundry
sand. Through arrangements with multiple foundries, cooperative
brokers/third party processors may be able to provide sufficient and
consistent amounts of spent foundry sand to support the need of cement
kilns.  If a cement kiln uses a third party broker, the broker will pay
the foundry for the foundry sand, but in some cases the kiln purchases
the sand directly from the foundry.

Processing of foundry sand:  

Foundry sand used in portland cement manufacturing must be separated
from other foundry by-products through a series of screens (FIRST). The
oversized material that does not pass the screens is termed "raw core
butt" and consists of chunks and grains of coarse sand and scrap metal.
Most portland cement plants also require that core butts be ground to a
uniform grain size. Vibrating screens and a ball mill are used to
further separate the components of this stream and to crush the
oversized chunks of sand. Through use of a magnetic separator, metal in
the stream is removed.

State status of foundry sand use as ingredient:  

At this stage, we have not identified any states that have specifically
given beneficial use designation to the use of foundry sand in clinker
manufacture, or that prohibit use of foundry sand in clinker, but we
have not performed an exhaustive investigation of state activities and
regulations.

5.	Foundry Sand Composition and Impacts

Composition of foundry sand:

Spent foundry sand consists primarily of silica sand, coated with a thin
film of burnt carbon, residual binder (bentonite, sea coal, resins) and
dust (Turner Fairbank Highway Research Center).  Spent foundry sand may
also contain heavy metals and phenols that are absorbed by the sand
during the molding process and casting operations. Phenols are formed
through high-temperature thermal decomposition and rearrangement of
organic binders during the metal pouring process. The presence of heavy
metals is greater in foundry sands generated from nonferrous foundries.
Spent foundry sand from brass or bronze foundries, in particular, may
contain high concentrations of cadmium, lead, copper, nickel, and zinc
(Turner Fairbank Highway Research Center).

Impacts of foundry sand use:

In clinker manufacture, foundry sand partially offsets the need for
virgin silica, iron, and alumina sources. Thus, using foundry sand in
the cement kiln can reduce the unit consumption of virgin feed stock
materials and related emissions.

The specific lifecycle impacts of foundry sand 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 foundry sand and other raw feed
materials in clinker production. Thus, the correct quantity of material
to be modeled is unclear. In addition, foundry sand may substitute for a
variety of virgin raw materials as well as other secondary materials
(e.g., blast furnace slag, CCPs, cement kiln dust, 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

American Foundry Society (AFS), About Metal Casting, accessed at:  
HYPERLINK "http://www.afsinc.org/content/view/62/122/" 
http://www.afsinc.org/content/view/62/122/ .

American Foundry Society (AFS). August 2007. “Foundry Industry
Benchmarking Survey: Industry Practices Regarding the Disposal and
Beneficial Reuse of Foundry Sand – Results and Analysis.” Accessed
at:   HYPERLINK
"http://www.strategicgoals.org/benchmarking/foundry.html" 
http://www.strategicgoals.org/benchmarking/foundry.html .

Foundry Industry Recycling Stars Today (FIRSTa), Foundry Sand in
Portland Cement Manufacturing, accessed at:   HYPERLINK
"http://www.foundryrecycling.org/TechnicalApplications/ManufacturedProdu
cts/PortlandCement/tabid/173/Default.aspx" 
http://www.foundryrecycling.org/TechnicalApplications/ManufacturedProduc
ts/PortlandCement/tabid/173/Default.aspx . 

Foundry Industry Recycling Stars Today (FIRSTb), What is Recycled
Foundry Sand?, accessed at:   HYPERLINK
"http://www.foundryrecycling.org/Home/WhatisRecycledFoundrySand/tabid/29
4/Default.aspx" 
http://www.foundryrecycling.org/Home/WhatisRecycledFoundrySand/tabid/294
/Default.aspx . 

Industrial Metal Casting, “Casting Industry,” accessed at:  
HYPERLINK "http://www.industrialmetalcasting.com/casting-industry.html" 
http://www.industrialmetalcasting.com/casting-industry.html . 

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 .

		

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