Assessing the bottom - line sand reclamation economics.

By looking at the sand reclamation costs and financial benefits at four different foundries, you can begin to explore how reclamation may fit into your operation.

There is plenty of information available on the technical aspects of sand reclamation, but its costs and financial benefits are rarely explored in depth.

Why is there a lack of financial/economic information? The answer is twofold. Most, if not all, people involved in a reclamation team come from a production/process/engineering background and not from a financial or business history. As a result, they are generally more comfortable in dealing with the myriad of technical details surrounding sand reclamation than the strange art of financial analysis.

Second, the financial analyses that must be performed can be as complicated as the technical aspects. A professional, responsible investment analysis cannot be just a simple "plug-and-chug" computation. Every foundry calculates its costs and benefits differently, and a certain methodology applicable to one foundry will not be appropriate for another.

Local economic conditions facing the foundry most often impact whether sand reclamation systems can show a positive return on investment. If sand reclamation doesn't make sense today, it probably will tomorrow. Over the past 20 years in the U.S., the prices of sand, transportation and disposal have increased substantially. If you are not reclaiming today, take the time to do a quick pro forma statement after reading this article - based on the results, you may decide to delve deeper into sand reclamation.

This article highlights the actual costs and investments of four foundries that decided to make the plunge into sand reclamation. It's important to note that the specific numbers presented in the following economic analyses are not as important as the thought process and financial analysis techniques presented.

Green Sand to Green Sand

One of the most cost-effective reclamation systems is one that reclaims green sand back into a green sand system. While green sand is highly recyclable, there comes a point where contamination of agglomerates, fines, oolitics, dead clay, coked carbons and ash becomes a problem and the sand system must be "refreshed."

Table 1. Economics of a Green Sand to Green Sand Reclamation System

GENERAL DESCRIPTION

Foundry Type                        Green Sand Steel
Product Type                        Railroad
Production Rate                     22 tons of castings/shift
Typical Sand-to-Metal Ratio         2.5:1
Sand System Size                    800 tons
Sand Type                           Round Grain Silica, 85 AFS GFN
Sand Usage                          15.3 tons/hr

Year Started                        1976
Capacity                            8 tph; 32,000 tpy
Actual Production                   4 tph; 16,000 tpy
Yield                               85%
New Sand:Reclaimed Sand             0:100
Disposal                            15%

Description of Reclamation System   Pneumatic reclaimer, feed
Purchased During Project:           hopper, cyclone, dust collection
                                    and installation.

ECONOMIC EVALUATION

Sand Usage Savings (tpd)                  27.31
Bentonite Savings (tpd)                    2.16
Cost of New Sand (per ton)               $38.00
Cost of Disposal (per ton)               $40.00
Total Cost of Sand (per ton)             $78.00
Cost of Bentonite (per ton)              $95.00
Initial Investment                  $210,000.00

Cost of Operation (S/day):

Direct Labor and Fringes                 $58.80
Electrical                              $161.14
Total Direct                            $219.94

Maintenance                              $37.28
Additional Lab Analysis                  $58.80

New Sand Cost Reduction               -$1037.78
Disposal Cost Reduction               -$1092.40
Bentonite Cost Reduction               -$205.20
Total Operating Cost                  -$2019.36
Depreciation                             $84.00
Interest                                 $67.20

Total Daily Savings                   $1,868.16

Traditionally, this has been accomplished by making a continuous new sand addition to the system. A typical rule of thumb adds 200-300 lb of sand/ton of metal poured (for ferrous foundries), subject to corrections to compensate for core sand dilution. Whatever the actual amount of new sand added, most foundries must make new sand additions to keep their system in balance.

If a foundry is removing a percentage of green sand every day and adding raw sand, it is a prime candidate for green sand reclamation. By pneumatically reclaiming some return green sand, the troublesome elements can be removed from the sand while the majority of valuable components can be saved, including the sand itself, live clay and carbons. In addition, the potential savings can be substantial.

Sand is more expensive than the delivered purchase price - it must be off-loaded, stored and then distributed within the foundry, and when that sand has reached the end of its productive life, it must be segregated and collected, loaded, transported and dumped. Sometimes the disposed sand must be treated before final disposal or for beneficial reuse. This all costs money.

Cost savings also can be achieved by returning live bentonite to the sand system rather than indiscriminately throwing it out with the discarded sand. Savings include not only the live clay saved but also the energy used to activate it. Any new sand would require additional clay to be added to the system (at additional cost).

The foundry in the first example reclaims green sand back into its green sand system. A simplified mass flow diagram of the system after reclamation is shown in Fig. 1. Before installing a pneumatic reclaimer, the foundry was adding an additional 25 tons of sand/day to the system in the form of facing sand and was removing an equal amount to keep the system in balance. New sand used for facing suffers from a lack of pre-activated clay and displays weaker mechanical properties, which could in turn lead to sand-related defects. Along with sand, the foundry was removing valuable clay from its system.

Today, reclaimed sand is used as facing sand. Table 1 highlights the economic analysis of this installation. By foregoing the dumping, the savings were significant, even considering the depreciation and interest costs associated with the new equipment. Payback was less than 6 months, and the project had a simplified internal rate of return (IRR) of 212%.

Table 2. Economics of Nobake to Nobake Reclamation System

GENERAL DESCRIPTION

Foundry Type                        Nobake aluminum
Product Type                        Precision parts for aerospace,
                                    motorcycle, industrial
Production Rate                     1 ton of castings/shift
Typical Sand-to-Metal Ratio         13:1
Sand System Size                    150 tons
Sand Type                           Silica, 60AFS GRN
Sand Usage                          2.57 tons/hr

Year Started                        1987
Capacity                            2.5 tph; 10,000 tpy
Actual Production                   2.0 tph; 7000 tpy
Yield                               90%
New Sand:Reclaimed Sand             30:70
Disposal                            10%

Description of Reclamation System   Shakeout, inclined conveyor,
Purchased During Project:           lumpbreaker,  pneumatic
                                    reclaimer, dust collection,
                                    distribution panel and
                                    installation.

ECONOMIC EVALUATION

Before Reclamation:

Cost of New Sand (per ton)                $18.00
Cost of Disposal (per ton)                $21.00
Total Cost of Sand (per ton)              $39.00
Total Cost of Sand (per hr)              $100.23

After Installation:

Initial Investment                   $250,000.00

Cost of Operation ($/hr):

Direct Labor and Fringes                  $17.29
Electrical                                 $9.50
Total Direct                              $26.79
Maintenance                                $2.40
New Sand Costs                            $14.22
Disposal Costs                            $16.59
Total Operating Cost                      $60.00

Depreciation                               $6.25
Interest                                   $5.00

Total Daily Cost                          $71.25/hr or $27.72/ton

Nobake to Nobake

Another reclamation plan is to return nobake molding sands to like new" quality. Often, only a pneumatic attrition-type scrubber is needed to reclaim these sands. The list of nobake sands that have been successfully reclaimed using this strategy includes furan, phenolic urethane, sodium silicate, ester-cured phenolics and polyol urethane.

Complications can arise when cores of a different incompatible binder type are used. This might lead to either a thermal-pneumatic attrition system or a change of core binder systems. Also, certain binder systems demand a thermal pneumatic attrition-type process, especially shell sand cores.

Besides minimizing new sand purchases, reclamation can reduce the demand for binder, allowing even greater savings. As sand is rebonded, indentations in the sand grains become filled, and as sand goes through the reclamation process, corners are removed from the sand. Both phenomena can reduce binder requirements, providing substantial savings.

In an aluminum nobake foundry that produces precision parts for the aerospace and motorcycle industries, pneumatic attrition scrubbers were installed to minimize new sand purchases and waste volumes and to avoid ever-increasing disposal costs. Figure 2 highlights the resultant mass flow balance of molding sand. The reclamation system has a 90% yield rate, and new sand is added at a ratio of 30:70 to reclaimed sand. Table 2 gives the relevant financial data.

Costs and benefits have been calculated on a dollar per hour basis as well as a more traditional dollar per ton basis. This was done because much of the cost data was easier to define on an hourly basis vs. a per ton basis. The conversion between the two can be made by factoring in sand usage on an hourly basis.

Before reclamation, the foundry was disposing all of its molding sand. Therefore, the installed system included equipment from the shakeout through ancillary utilities. Many foundries may already have such equipment in place, and therefore, the investment and operating costs assigned to the reclamation system may be reduced.

Table 3. Economics of Core Sand to Core Sand Reclamation System

GENERAL DESCRIPTION

Foundry Type                        Semi-permanent mold aluminum
Product Type                        Cylinder heads and intake
                                    manifolds
Sand Type                           Silica, 43 and 52 AFS GRN
Sand Usage                          165 tons/hr

Year Started                        1986
Capacity                            8.8 tph; 50,000 tpy
Actual Production                   7.0 tph; 40,000 tpy
Yield                               92%
Disposal                            8%

Description of Reclamation System   Lumpbreakers, calciners,
Purchased During Project:           fluidized cooler beds,
                                    recuperator, dust collection,
                                    sand sitters, pneumatic
                                    transport, controls,
                                    installation and spares.

ECONOMIC EVALUATION

Before Reclamation:

Cost of New Sand (per ton)                 $51.92
Cost of Disposal (per ton)                 $40.60
Total Cost of Sand (per ton)               $92.52

After Installation:

Initial Investment                  $3,132,200.00

Cost of Operation (S/ton):

Direct Labor and Fringes                    $7.27
Electrical                                  $0.69
Gas                                         $5.10
Maintenance                                 $6.74
Fixed                                      $19.66
Energy Savings                              $6.50
Resin Savings                               $3.30
New Sand Cost                               $5.01
Disposal Cost                               $1.89
Total Operating Cost                       $36.56

Depreciation                                $7.83
Interest                                    $6.26

Total Cost                                 $50.65

The foundry purchased all goods and services related to this project with cash, therefore it did not have any interest costs associated with the investment. However, for comparison purposes, a financial cost for using the capital was calculated. Regardless if a foundry borrows money for a project, there should be some provision in an economic evaluation to cover the cost of capital. This will then cover the "opportunity costs" that have been foregone because the money was invested in reclamation.

Payback for this project was approximately 2.1 years. A simplified IRR yields 47%. For many foundries, this would represent an attractive investment.

While this foundry was unable to reduce resin consumption for a variety of reasons, other nobake foundries have increased their returns by doing so. But, each foundry is different, and only after an initial testing program during the project evaluation phase should such benefits be projected in the project's pro forma statements.

Core Sand to Core Sand Reclamation

Another possible route to reclaiming nobake or coldbox sands is to use thermal reclamation, which may or may not be followed by a pneumatic attrition step. Some foundries feel they need the type of cleaning this process flow provides, albeit at increased investment and operating costs.

The semi-permanent mold foundry highlighted in Table 3 produces aluminum automotive parts. All shakeout sand is thermally reclaimed before reuse. New sand is added only to compensate for reconditioning losses.

Economics are further enhanced by reduced binder usage and heat recuperation. Gas costs also are reduced because of the thermal contribution to the calcining process of the residual binder found in the incoming sands. For this foundry, the system paid back in 1.7 years and had an IRR of 60%.

While the foundry did not perform any post-calcining scrubbing, foundries may find some type of scrubbing is necessary in order to remove inorganic, non-combustible contaminants. As an example, many foundry sands contain alkaline materials such as limestone and shells. When these materials are calcined, calcium carbonate is converted to calcium oxide, which can significantly increase the acid demand value of the calcined sand. If the inorganics are not removed via pneumatic scrubbing, this elevated property could introduce new problems in making cores from this sand.

Green Sand to Core Sand System

One of the most fruitful areas for green sand to core sand reclamation is in copper-base foundries, especially those foundries that pour lead- or cadmium-containing alloys. Disposal costs for lead-contaminated sands have soared over the last decade. Often these sands must be treated with chemicals in an effort to "tie-up" the lead and any leachable metals. These treatments further increase the cost of disposal. The cost of properly disposing lead-contaminated sands and the cost of complying with other lead-related regulations has resulted in foundries, which previously poured such alloys, to stop producing castings of this metallurgy.

However for many foundries, the lead-containing alloys they pour have few suitable substitutes and are vital to the products produced.

The brass foundry described in Fig. 3 and Table 4 is one such example. Reclamation was required to minimize waste volumes and reduce the ever-increasing costs of disposal. After an evaluation program, calcining followed by pneumatic attrition was chosen as the process flow of choice. Payback for the project was 2.1 years with an IRR of 47%.

Table 4. Economics of Green Sand to Core Sand Reclamation System

GENERAL DESCRIPTION

Foundry Type                        Copper-base green sand
Product Type                        Plumbing goods
Production Rate                     10 tons of castings/shift
Typical Sand-to-Metal               Ratio 15:1
Sand System Size                    250 tons
Sand Type                           Sub Angular, 85 AFS GFN
Sand Usage                          38 tons/hr

Year Started                        1989
Capacity                            0.67 tph; 4000 tpy
Actual Production                   2640 tpy
Yield                               75%
New Sand:Reclaimed Sand             25:75
Beneficial Reuse                    5%
Disposal                            20%

Description of Reclamation System   Sand crusher, thermal calciner,
Purchased During Project:           pneumatic scrubber, dust
                                    collection, material handling.

ECONOMIC EVALUATION

Before Reclamation:

Cost of New Sand (per ton)               $20.80
Cost of Disposal (per ton)              $252.00
Total Cost of Sand (per ton)            $272.80

After Installation:

Initial Investment                  $900,000.00

Cost of Operation ($/ton):

Total Direct                             $12.30
Maintenance                              $21.33
Misc. Fixed                               $0.84
New Sand Costs                            $5.20
Disposal Costs                           $50.40
Metal Recovery                           -$9.47
Total Operating Cost                     $80.60

Depreciation                             $34.09
Interest                                 $27.27

Total Cost                              $141.96

Thermal/attrition systems able to bring green sand to core sand quality are not limited to copper-base foundries. One U.S. steel foundry utilizes a 6 tons/hr calciner to reclaim mixed incoming sand (green and chemically bonded) into products used for the production of alkyd oil urethane and furan molds/cores. This 16,500-tons/year shop has been able to show a payback of less than 3 years.

This article was adapted from a paper presented at the 1994 AFS International Sand "Reduce, Reuse, Reclaim" Conference. Proceedings are available from AFS Publications at 800/537-4237.

RELATED ARTICLE: One View on Reclamation Choices

In addition to examining the economics behind reclamation systems, it's important to purchase a system that is the right fit for your foundry.

Reclaiming green sand for use in a green sand system, in lieu of new sand, should always be done without high thermal impact. In this process, the objective is to retain not only the sand, but also as much of the additives (clay, seacoal, etc.) as possible. The most appropriate approach is an intensive attrition process, combined with air classification. Attrition is necessary to destroy any existing agglomerate that would coarsen the sand. Drying below 200F (93C) may be needed if high return sand moisture exists, because the processed sand must be screened at fine mesh (20-30-mesh U.S. sieve) without screen blinding. For more information, see AFS Transactions, 1984, p. 1, and 1988, p. 13.

Reclaiming chemically bonded sand for use in a chemically bonded system will, in most cases, require an intensive attrition system. The newer "grinding"type systems are more effective than "impact"-type systems. Careful de-dusting (air-wash) is imperative.

Thermal processing may become necessary if incompatible binder systems are used, such as an acid-cured furan and an alkaline phenolic urethane. However, processing at temperatures greater than 1000F (538C) can be detrimental if inorganic contaminants are present. For example, the raw sand contains substances that are chemically changed as a result of the high temperature. Calcium carbonate, common in lake sands, may be reduced to highly reactive calcium oxide, which would negatively affect use in both an acid and an alkaline-cured system. Or inorganic components in the sand may be fused onto the sand grains, grossly changing the bonding behavior, as in the case of phosphorus from the acid in a slow furan system or potassium from an inhibitor when pouring magnesium. Many other such reactions are known. For more information, see the Industrial Pollution Prevention Handbook, McGraw-Hill, 1994, p. 667-684.

Reclaimed chemically bonded sand in a green sand system is a standard occurrence in all foundries running cored jobs in which collapsed cores automatically flow into the green sand. In most cases, no special equipment is needed, however, attention must be paid to gross fluctuations, such as from uncored jobs to more than 1000 lb of cores/ton of metal poured. In these cases, some attrition processing may be required, similar to the case in which green sand is to be used in lieu of new make-up sand.

Reclaiming green sand for use in chemically bonded systems requires thermal processing in all cases. Many differing opinions exist as to the necessary degree of processing (temperature, time, etc.). For more information, see AFS Transactions, 1994, p. 443.

It is absolutely imperative that all investigations into sand reclamation pay attention to the complete system, not just the reclaimer. The major components of a system are:

* sand storage and handling (shakeout never supplies sand at a consistent rate required by a reclaimer);

* the reclaimer itself;

* dust collection, preferably dedicated to the reclamation system for ease of balancing, to permit efficient removal of fines;

* the cooler, to deliver reclaimed sand at the required temperature for rebonding;

* the process control system, which is of utmost importance because standard laboratory tests do not suffice to effectively control a sand reclamation system. For more information, see Foundry Trade Journal (U.K.), October 1994, p. 490.

It is vital to become familiar with all of details of sand reclamation before deciding on the appropriate system.

- Dieter Leidel, Tanoak, Inc., Ontario, Canada