Recovering and refining precious metals from spent catalysts

In addition to obtaining the most effective expertise in precious metal recovery, serious consideration must be given to financial and legal issues that could arise when partnering with a precious metals refiner

Kevin M Beirne Sabin Metal Corp, East Hampton, NY, USA

Figure 1 Typical melt sampling process

 

Many hydrocarbon and petrochemical processes use precious metal-bearing catalysts to facilitate and/or speed up chemical reactions. These catalysts are also used for end-of-pipe pollution abatement applications, mainly to eliminate the emission of volatile organic compounds (VOCs) and other pollutants into the atmosphere. Most catalysts used for hydrocarbon processing applications are composed of platinum group metals (PGMs), including platinum, palladium and rhodium. In some catalyst applications, these metals are utilised in combination and can include gold. A variety of carriers are employed, depending upon the application, including catalyst supports such as soluble or insoluble alumina, silica/alumina or zeolites.

However, whatever precious metalbearing catalyst is employed, their users share a common goal: recovering as much value as possible from the precious metals in their spent catalysts, while minimising environmental liability.

Values for PGMs, particularly platinum and palladium, have fluctuated wildly during the past few years. For example, at one point in 2001, palladium prices rose as high as US$1100 an ounce, and platinum prices reached $650 an ounce. While nowhere near those prices today, the high value of PGMs demands that an efficient way (with maximum returns and fast processing turnaround) of recovering these metals be found, which is why more industrial processors are turning to precious metal refiners. However, there are legal implications to be aware of when working with a precious metals refiner. These concern possible effluent or atmospheric discharges from the refiner’s facility and any consequential environmental violations. Choosing the wrong refiner could end up being a costly mistake. There are many criteria to take into account when selecting a precious metals refiner. But first consider the various methods used to help maximise the returns from spent precious metals catalysts. There are three critical factors that the refiner can control, which apply to almost all precious metal-bearing materials: sampling, assaying and processing turnaround time.

Sampling

Three sampling techniques are used to accurately determine the amount of precious metals present in materials for recovery, including melt sampling, solution sampling and dry sampling. Each of these techniques offers specific advantages. Determining the most appropriate method depends upon the type of material being processed as well as its estimated precious metals content.

Fundamentally, the principle of sampling involves “reducing” large quantities of precious metal-bearing material (as much as many tons) into small quantities (as little as a few grams). Samples are then extracted for analysis from different fractions and/or different stages of the resultant sub-lot. The sampling procedure begins by converting precious metal-bearing scrap into a homogeneous mass so that molecules of precious metals and other constituents are evenly distributed. Results of sampling the homogeneous mass thus represent an accurate ratio of the precious metals content in the overall matrix.

In melt sampling (Figure 1), a carrier metal such as copper is melted along with the precious metal-bearing material. The resultant molten metal is poured into ingots, which are sampled at the beginning, middle and end of the pour. Subsequent processing steps yield an extremely high degree of accuracy, with tolerance as close as ± 0.1 per cent between samples.

For precious metal-bearing solutions, solution sampling (Figure 2) is both cost-effective and extremely accurate in determining precious metals content. This technique also involves achieving a homogeneous dispersion of precious metals and other constituents at the molecular level, with precision comparable to melt sampling. Multiple samples are taken from different parts of the solution as well for further analysis.

Figure 2 Typical solution sampling process

 

Dry sampling (Figure 3) is used whenever materials cannot be dissolved in solution or are inappropriate to melt, either because of their structure or due to the cost associated with melting set against the possible return. Since it is difficult to achieve homogeneity, dry sampling is more complex and potentially less precise than melt or solution sampling. In fact, this method requires more judgmental skills than the others. Materials for dry sampling are homogenised generally by grinding large pieces into smaller and ever finer particles. The material is allowed to freefall in a stream and into a crosscut, timed automatic sampler. Representative samples are also taken periodically and sampling accuracy is typically ± 2 per cent. Precious metal-bearing catalysts are usually sampled using this technique.

Some precious metal-bearing materials can be sampled only by one of the three methods previously described. However, others may be processed by more than one, depending upon variables such as the estimated value of their precious metals content, cost-effectiveness of using one method over another for highest possible returns, and practicality (ie, a function of refining costs, materials value, and other factors). Since precious metal-bearing catalysts are made in many sizes and configurations (for example, pellets, beads, monolithic structures and extrudates), determining the best sampling technique is crucial to recovering the greatest possible value from spent catalyst.

Assaying

Accurate and repeatable assaying procedures, on the other hand, are dependent upon sophisticated instrumentation used for measuring the precious metals content of materials being reclaimed. A well-equipped analytical laboratory utilises advanced Xray fluorescence equipment, atomic absorption (AA) and inductively coupled plasma (ICP) emission spectroscopy. It also incorporates classic volumetric, gravimetric and fire assay techniques. When all methods are used together, they provide the most thorough and precise approach for determining precious metals content in spent catalyst materials, thus assuring the highest possible returns. In general, the types of materials being processed determine the specific techniques used for assaying.

Bottom line

Figure 3 Typical dry sampling process

 

The speed at which catalysts are processed and their precious metal recovered (ie, reclamation turnaround time) is the third key factor of the “maximum return” equation. Logically, faster processing turnaround minimises interest charges a user accrues for leasing replacement precious metals to eliminate process downtime. It also avoids the necessity of purchasing PGMs on a volatile spot market for use in the timely manufacture of catalysts, allowing uninterrupted processing or production.

Leasing and pool accounts

Typically, precious metals used in catalytic processes, especially platinum and palladium, are not purchased on an outright basis by their users. Instead, they are held in a “pool account” at one of a number of physical locations where the metal is commingled with other owners’ or lessees’ metal. Owners or lessees of these metals “draw” on this material on an “as needed” basis or are provided with credit from a pool account from which to draw. From this pool, users can request delivery of metals for incorporation into catalyst products.

Leasing PGMs for catalyst production is strictly a financial transaction, where the user has no desire to purchase the metal but rather “borrows” it, the same as borrowing money from a bank. In the precious metals industry, the practice is known as “leasing metal” and is strictly a financial mechanism, with widely varying lease rates depending upon supply and demand. In fact, the rate fluctuation is substantially greater than borrowing money from a bank at a fixed rate, which is generally fairly constant and much more predictable. Most businesses can usually borrow money from lending institutions at one or two points above prime. On the other hand, metal leasing rates have been as low as 3 per cent per annum and as high as 200 per cent. That incredible difference is merely caused by supply and demand.

In addition to leasing precious metals, there is another practice in the precious metals industry commonly referred to as “banking”. This is where owners of metals will “lend” their metals to institutions or other businesses, which pay interest charges to the owners, just as a bank would pay interest on dollar deposits. These institutions, in turn, lease out these metals to users as a method of generating profits. This practice does not appear to be too common with regard to PGMs employed by catalyst users, but is more closely associated with metals speculating or accumulation for future consumption. For example, a speculator or consumer may purchase metal today, but not require it physically for six or 12 months in the future. In order to defray some of the financing costs, they might “lend” this metal back to the market.

As to when to lease and when to buy precious metals, most users make that decision based upon their perception of prevailing lease rates and their trends over extended time periods. Also, many catalyst users prefer not to “own” precious metals, since they don’t want their costs to appear on their balance sheet as inventory or as a fixed asset. Consequently, they are willing to incur added expense by leasing. Typically, those who are leasing precious metals are not consuming them, but are instead using them to produce their products or having others fabricate them into catalysts. Since the majority of precious metals in catalysts are recoverable, users get their metal back after the recovery and refining process.

As a result of these operating practices, it is in the best interests of precious metal catalyst users to obtain the highest possible per cent recovery for their precious metals. They also need to work with a refiner that offers the fastest possible processing turnaround time so as to minimise lease charges.

Recovery processing time

Typically, it could take as long as three months to have a new catalyst fabricated and just as long to have the spent catalyst reclaimed – a period of six months during which new metals may have to be financed. To illustrate this point, take a 40 000lb shipment of 0.6 per cent palladium catalyst valued at $700 per ounce, at a lease rate of 10 per cent. Leasing the metal contained in this material would cost about $5000 per week. As a result, if one refiner has a sixweek turnaround and another a 12-week turnaround, the additional six weeks would cost $30 000 more in lease charges.

Variations in lease rates are governed by worldwide production for primary (mine production) sources and the immediate, local availability of physical metal. For the catalyst user, PGM lease rates usually represent a significant cost, since “new” precious metals are often financed while spent catalysts are being recovered and refined. By providing faster spent catalyst reclamation turnaround times, substantial cost savings may be realised, in many cases translating into thousands or hundreds of thousands of dollars each year. These are serious numbers, and because of this there is a trend in the industry to establish independent asset-recovery programs (or departments), functioning as profit centres for the recovery of precious metals within an organisation.

Environmental/legal issues

It is also important to consider some of the legal implications associated with processing procedures with a contracted precious metals refiner. In addition to possibly choosing the wrong refiner with regard to maximum recovery and fastest possible turnaround, selecting the wrong refiner with regard to possible effluent or atmospheric discharges could become even more costly.

Avoiding problems
The precious metals refining industry does not enjoy a sterling reputation with regard to environmental responsibility. When selecting a refiner, you must not only be aware of how your materials will be processed, but also the materials of other customers. It is your responsibility to determine how any solid, liquid or gaseous by-product is handled at the processing facility.

Ideally, no hazardous waste materials should be shipped from a precious metals processing facility. Some plants will ship them under approved procedures and conditions; you should learn the difference. In addition, no pollutants should be emitted before, during or after refining. Exhaust air quality must be managed by state-of-the art pollution control systems, and the process water evaporation procedure should eliminate all causes of pollution. While each of these functions is fundamental, there are many hidden pitfalls surrounding them with regard to environmental compliance.

As an example of what can go wrong, consider the following case. While not directly related to reclaiming precious metals, note the comments made by an Environmental Protection Agency (EPA) administrator at a major news conference with regard to environmental contamination: “You pollute, you pay.” The news conference from January 2000 focused on a record $35 million fine and associated penalty against a US-based oil company, concerning two lawsuits involving more than 300 oil spills from the company’s pipelines and oil facilities in six states. The oil was discharged into 16 lakes and streams. Based on the outcome of this case, which was settled by the company and EPA, it is obvious that the government means business with regard to pollution control and environmental damage.

Request full documentation
Requesting detailed documentation on environmental law compliance may also help make sure that your chosen refiner does not violate any applicable law or regulation. In the US, the Superfund Act addresses the direct responsibility of customer and refiner. This law mandates that both the company that is the source of the materials for precious metals recovery and the precious metals refiner share “cradle-to-grave” responsibility, as well as future liability for the proper treatment and/or disposal of any materials. Request that the refiner supplies copies of all detailed documentation relative to legal compliance. Essentially, the environment must be protected to avoid serious financial and legal consequences, and the refiner’s violation of environmental laws or regulations could result in heavy fines and legal costs.

One way to determine if a refiner meets these criteria is to check its use of appropriate pollution abatement technology, such as afterburners, bag houses, wet scrubbers and liquid effluent-neutralising equipment. Also, evaluate the refiner’s approval status with all applicable agencies at local, state and federal levels. Most precious metals refiners will be pleased to provide copies of all required documentation, which could include permits under the Clean Air and Water Acts and prove that the company qualifies as a bona fide precious metals refiner as specified in the preamble to the Boiler and Industrial Furnace (BIF) Rule and its amendments.

Summary

There are many variables associated with the recovery and refining of precious metals from spent catalysts. While some of them may be more or less important to your particular application, keep in mind that they are generally interrelated so as to help paint an overall performance picture of a selected precious metals refiner. Above all, don’t lose sight of the full compliance issues concerning environmental regulations. All else being equal (ie, highest possible returns and fastest possible turnaround times), the environmental issue can come back to bite you if your refiner is involved with a serious violation. Remember, whether we like it or not, we are all “partners” with government regulatory agencies as far as precious metals recovery and refining are concerned. Your relationship with a precious metals refiner is essentially a partnership. To that end, it must be mutually profitable and based upon trust and fair treatment. To achieve – and maintain this kind of relationship – consider all of the issues discussed here when selecting a precious metals refiner.

Kevin M Beirne is vice president, sales and marketing, for Sabin Metal Corporation. He has worked in this industry for nearly four decades, at times managing the laboratories, refining and manufacturing operations. Beirne studied at Farleigh Dickinson University. He is a member of the American Electroplaters Society, Investment Recovery Association and treasurer of the International Precious Metals Institute. E-mail: kbeirne@sabinmetal.com