Adopt processing standards for your best beneficial reuse options.

If you want to reap the benefits of beneficial reuse, you must start treating your spent foundry byproducts as end-users see them - a marketable, clean alternative to new materials.

Successful recycling programs involve establishing reliable, quality-controlled sources of raw materials that provide a performance and/or economic advantage to the end-user. Foundry owners and operators understand the importance of quality control in their incoming raw material streams and certainly in the quality of the castings they ship. Yet many attempts at recycling foundry byproducts fail because foundries do , not meet market specifications.

Reuse Opportunities

Foundries that want their byproduct materials to be recycled or beneficially reused must understand that they must make investments to produce a quality reuse product. Investments may take the form of dedicated staff time, education, research, material testing, pilot projects and capital equipment. For most foundries setting a goal of zero waste, all of these are necessary.

With very few exceptions, spent foundry sand must be contaminant-free and screened to a given size distribution in order to be marketable. Foundries have two options to deliver high-quality material: either segregate byproduct streams internally and process them for market, or commingle them and process later. Foundries must do an economic analysis to see which option will meet the local market needs. Compare the cost of internal handling and storage to the cost of paying for processing of commingled materials. Both must be compared against the lifetime cost of continuing to landfill material, including hauling costs.

Most foundries will need to invest in screening, crushing and magnetic separation themselves or form a business partnership with someone who can provide that service for them. Exceptions are those foundries who have good internal quality control and already segregate their waste streams.

Some foundries do not consider processing equipment because they perceive that capital costs are high. However, used equipment can be a viable option. Fixed and mobile screens, conveyors, crushers, magnetic separators and stackers are available from used equipment brokers.

Suiting Different Needs

Processing requirements ultimately will be determined by the local end-use markets for foundry byproducts, but there are three basic steps common to all markets:

* removal of general refuse, wood and other contaminants;

* removal of metals;

* crushing, screening and sizing to produce a uniform, consistent product.

For larger foundries, one of the advantages of segregating core sand streams from molding sand streams is that the two types of sands are better suited for different markets. Green sands are dark in color and typically have high fines contents and higher moisture contents. These properties are advantages in geotechnical and manufactured soil markets. However, green sands may have limited usage in concrete and masonry products, in which its color and fines are a detriment. Lighter color core sands often are easier to introduce into concrete-related products.

"Pure" green sand streams that are free of core pieces, metals and general refuse are usable in geotechnical applications because their moisture and clay contents provide excellent compaction. In states that permit this use, foundries may be able to work with local contractors to provide spent foundry sand at little or no cost to the contractor.

Core sands and core butts generally need crushing, screening and magnetic separation. Cores from nonferrous foundries are subjected to lower temperatures than ferrous cores and may be broken up with a screened shaker table or trommel and screening system. Ferrous cores and core butts require processing through a stationary or mobile crusher, a common piece of equipment at quarries and at concrete recycling companies.

Smaller foundries may be able to commingle their various molding, core and shakeout sand streams, as long as the combined material is screened, magnetically separated and cores are crushed.

Fines and Slag

Fines content is of particular concern when evaluating materials for use in concrete and asphalt products. Hot asphalt mix designs limit the amount of material passing 200 sieve to 4-5%. Processors of virgin materials screen out the fines prior to use in these applications. Foundry sands containing a large percentage of fines must be processed to meet concrete and asphalt mix design requirements. However, the fines content may not be a problem if the sands are destined for use in flowable fill, a low-strength application in which foundry sand can substitute for new construction sand.

According to Pat Peterson, division manager for Rochester Sand and Gravel (Mathy Construction), Rochester, Minnesota, most aggregate producers have equipment on hand that will satisfactorily process foundry sands and slag for use as aggregates in asphalt. The fines portion may be an operational problem - the material is so light it may blow off the conveyors. In most states, fines and dust emissions are regulated and must be controlled.

Quenched slag often can pass through a simpler screening process, in contrast to air-cooled slag, which tends to need substantial crashing equipment, such as that used to reclaim concrete. In both cases, metals must be removed from the slag, either through magnetic separation systems or by hand picking. Large chunks of metal can damage even heavy-duty crushers. Most state transportation departments' specifications for road base aggregates set a cap of 5% or less of foreign material.

A processing option generally overlooked is running molding and core sands through a mechanical or thermal reclamation system that reduces the material to grain size. Sand processed through a reclaimer is typically user-ready, especially if the fines have been removed in the reclamation process. DePere Foundry, DePere, Wisconsin, installed a tank with a vibratory mill to process its chemically bonded sands. The unit breaks up the cores, and the material is conveyed out to a silo in a load-out area.

For many small- to medium-size foundries, the capital costs and expertise required for entry into beneficial reuse markets have been prohibitive. So, for many foundries, co-processing of byproduct streams from multiple foundries represents a cost-effective way to participate in beneficial reuse markets.

PROCESSING PROFILES

Grede-Reedsburg

One foundry that has chosen to invest in processing equipment in Wisconsin's Grede Foundry-Reedsburg. This foundry's success can be attributed keeping its product streams separated within the operation. The amount of processing required is reduced drastically and the processing required is focused on fine-tuning the goal of achieving zero waste. Environmental Technician Dave Williamson said, "It cost the foundry virtually nothing in capital investments. The byproduct streams are naturally separated within the general foundry process. Our foundry isn't unique from foundries in that standpoint. It's just a matter of education for our workers to understand that pop cans, cigarettes and other garbage can't be placed into the hoppers - this material is a product."

The Reedsburg plant produces two sand steams: sand from the molding lines, which has no cores or iron, and sand that has some core butts, scrap cores and iron in it. The foundry has invested in a magnetic separator outside of its sand storage building. In its metallic-free state, the sand is clean enough to be used as general fill by local contractors; job site compaction breaks down the remaining core fragments.

According to Williamson, Grede's next step would be to put in a rotary screen and small conveyor to further clean up its core sand.

Grede also has an automated slag handling system that conveys its cupola slag to a lined pit area full of water, which initially fractures the slag. The quenched slag is moved on a vibratory conveyor that further fractures the material into a 0.25-0.5 in. size. Slag is piled on-site and, as it is needed, used to improve poor soil subgrade conditions on local road base projects. "We build up the pile, but at some point every year we run out," Williamson said.

Grede is working with an asphalt contractor on several pilot projects this summer to supplement its geotechnical markets.

Process Recovery Corp.

One of the pioneers in processing commingled foundry residuals is Process Recovery Corp. (PRC) of Sinking Spring, Pennsylvania, a suburb of Reading. PRC was established in 1985 by a consortium of 33 iron, brass and steel foundries in southeastern Pennsylvania and the Pennsylvania Foundrymen's Assn. In 1989, PRC received a permit from the state to operate a lined residual waste monofill for member foundries.

PRC accepts only non-hazardous foundry sand, slag, refractories and dust from foundries within 100 miles of its landfill. For the first 4 years of operation, the incoming materials were simply trucked from the participating foundries and deposited in the monofill. From 1990-98, more than 1.1 million tons of material were brought to PRC's site. Participating foundries are charged a fee for each load, which is considerably lower than the average statewide tipping fee of $35. PRC President Tom Hartman estimates that member foundries have saved more than $15 million in tipping fees since the monofill began operation in 1990.

Beginning in 1993, PRC started processing foundry residuals for resale. Using its fleet of trucks and rolloff containers to bring material back to a site colocated with the monofill, PRC accepts both segregated and commingled materials. Most of PRC's larger foundries, with outputs of 20 tons or more/day, find it economically feasible to segregate their materials into three different streams: commingled sand streams and cores; slag and used refractories; and dusts. Smaller foundries commingle these byproduct streams in a single rolloff. Approximately 80% of incoming material is segregated into these three categories.

At its central processing site, PRC runs the sand streams through a mechanical sizing operation. The processing line is equipped with magnetic separators for ferrous recovery; nonferrous and stainless steel metals are hand-picked off the conveyors. The resulting fine aggregate, passing a 0.25-in. screen, is stockpiled for resale as a fine aggregate for use in hot mix asphalt. PRC aggregate has its own state Dept. of Transportation specification, and some PRC material is sold into the landfill construction market.

In its first year of full operation, PRC processed and sold 10,000 tons of foundry aggregates. In 1998, PRC sold more than 80,000 tons of aggregate, and it is well on its way to surpassing the 100,000-ton mark this year. Forty foundries pouring iron, steel, aluminum and brass are serviced by PRC. The largest of these foundries generates 450 tons of usable byproduct per week; the smallest, 20 tons.

RRC of West Michigan

Resource Recovery Corp. of West Michigan (RRC) was formed in 1990 as a for-profit stock corporation, with shares purchased by member foundries. RRC serves 20 western Michigan foundries, half of which are stockholders. Participating foundries segregate their non-hazardous residual waste streams into 20- or 26-cubic-yard rolloff boxes supplied by RRC. Sand molds and cores are segregated into one box for processing, slag suitable for crushing is segregated into a second, and other process residuals are placed into a third.

RRC's central collection and processing site is located on leased land at a regional landfill. Uncontaminated sand is hauled either to the processing site or to globally positioned storage in a separate cell where materials are stored for later processing. Contaminated loads are sent to the landfill cell for disposal. Process residuals for disposal are hauled to the working landfill cell.

At the processing site, materials are fed through a vibratory feeder into a rotary attrition lump crusher with a gas burner for drying the aggregate. Material is screened to a 0.125 in. size, discharging oversize material (metal and tough core butts). A dust collection system pulls off the fines (material passing a 200 screen), which are not marketed by RRC. Metals, including shot-size spheres and metallic fines, are removed via magnetic separation. The sand - now particle size - enters a radial stacker in the finished product side of the processing site.

Although ferrous and nonferrous materials are processed separately to achieve higher throughput, RRC's finished product is a blend of ferrous and nonferrous sands for consistent product quality. RRC's process converts 99.5% of the incoming sand streams to finished grainsize fine aggragate. The largest proportion of RRC's sand products are sold to a nearby asphalt plant where selected mix designs meet Michigan Dept. of Transportation specifications. The remainder of RRC's sand product is sold as liner cover in the construction of landfill leachate collection systems.

Slag is accumulated at a separate site, and a mobile concrete crusher is brought on-site several times a year. Most of the RRC's crushed slag is sold to asphalt plants in Muskegon; larger oversized material is sold for landfill construction.

Kurtz Bros.

Kurtz Bros., Inc., Cleveland, processes and beneficially uses more than 400,000 tons of spent foundry sand annually. Although best known as the sand processor for the Ford Cleveland Casting Plant, the firm now provides recycling services for more than 25 foundries in northern Ohio and neighboring regions. Processing is an integral part of the service Kurtz provides. Says Mike Lenahan, industrial services manager, "In a perfect world, these sands would come to us clean, free of debris, segregated and crushed to grain size. The fact of the matter is that in the real world this isn't the case all of the time."

Kurtz processes material differently depending on the market for which it is destined. The Ford plant produces several different sand streams. Green sands with high moisture contents are targeted for geotechnical projects and generally do not need screening because of Ford's attention to quality control and cleanliness on the shop floor. Ford's core scrap is primarily being used in flowable fill (low-strength concrete) applications, where the material must be uniform. This sand stream is processed by crushing the cores and then screening material through an Erin screen with several different types of magnetic recovery. Core scrap is typically reduced to 0.375 in. size for use in flowable fill.

As a rule of thumb, incoming materials are separated into piles with similar physical characteristics. Commingled green sands are screened and passed through magnetics for metal recovery. Brown nobake sands are usually crushed and screened. Refractories are processed through crushing, sizing and magnetic separation. For larger materials, a crusher reduces the size to 6 in., and then a series of screen decks further size material to 12 in., depending on the end market. Crushed and sized refractories are typically used in road base applications.

Eliminating processing steps can have a tremendous impact on cost, Lenahan said. For this reason, sand from aluminum foundries using sodium silicate binder systems is separated from commingled green sands. The crusher is not needed because lumps in the material can be broken down by turning them over with a loader.

Foundry sand is blended with other materials to create manufactured soil products for many markets, ranging from topsoil to golf course construction. From a processing standpoint, sands to be used in soil amendments must be processed to a high degree of consistency, so they are typically screened. A significant issue with respect to the manufactured soils markets is regulatory approval. As Lenahan puts it, "only the cleanest of the clean make it to this application." Materials must be tested for environmental compliance and adhere to each state's regulatory requirements.