Seven decades of precious metals refining with response and responsibility

Methods to evaluate. . .

methods to evaluate - sabin metal corporation

Methods to evaluate, select, and work with a precious metals refiner

Obtaining maximum value for remaining PGMs from spent hydrocarbon processing catalysts is a worthwhile goal that requires due diligence. It is essential to choose one’s precious metals refiner carefully as the relationship is one that can be compared to a partnership. This article proposes to show how to choose and effectively complement a precious metals refiner.

   

American author and humorist. Mark Twain, is known for his often quoted axiom: "The difference between the right word and the almost right word is like the difference between lightning and the lightning bug." This observation can easily be applied to evaluating, selecting, and working with a precious metals refiner to recover the valuable metals that remain in spent hydrocarbon processing catalysts. In fact, if you could ask him, Twain might say that, "The difference between the right precious metals refiner and the almost right precious metals refiner is the same as the difference between lightning and the lightning bug!

Methods to evaluate

If you use precious metal-bearing catalysts in your processes and products for facilitating and/or speeding chemical reactions, or for end-of-pipe pollution abatement applications, you should be well aware of the escalating values of the PGMs (platinum, palladium, ruthenium, and rhodium) these catalysts contain. Typically, platinum-bearing catalysts are used to refine crude oil and to produce aromatic compounds. Precious metal-bearing catalysts are also employed in many hydrocarbon processing applications. Unfortunately catalysts don’t last forever; they deactivate over time due to their harsh processing environment which contaminates them with carbon, sulfur, volatile organics, moisture, or other substances that reduce their efficacy to the point where they must be replaced.

However, almost all of their precious metals content still remain and thus must be recovered and subsequently refined. Consequently, because of their high values—as well as supply/demand price fluctuations year-to-year or even month-to-month— their users wisely view precious metals leasing, purchasing, and recovery management programs with key emphasis on costs and returns.

As precious metal-bearing catalysts are expensive, they must be processed in a manner that helps assure maximum recovery while also protecting their users from possible environmental consequences arising from their refiner’s recovery and refining procedures. Values of their remaining precious metals are high (for example, current platinum value is $1247 tr. oz., and palladium is approximately $340 tr. oz. Rhenium (not considered a PGM but nevertheless present in most spent catalysts) is valued at about $3500 per pound; many precious metals refiners are now able to recover a significantly high percentage of this metal.

With this knowledge, selecting and working with an established, reliable, and reputable, precious metals refiner has become increasingly important for these key reasons:

Methods to evaluate
  • You must assure maximum returns of remaining precious metals from your process or product.
  • The speed (turnaround time) which your precious metal-bearing materials are processed will affect your costs.
  • Your precious metals refiner must adhere to strict environmental code compliance with regard to atmospheric emissions and effluent discharge/ disposal – at all levels, and at all times. Consequently, your relationship with a refiner should consider all possible legal implications associated with violations of environmental laws – including those affecting transportation of hazardous materials.
  • Most important, you must work with a refiner whom you trust, since you are essentially forming a "partnership" with the refiner when your materials are being processed.

methods to evaluate - sabin metal corporationA precious-metals refiner should use advanced pollution-control equipment, such as this baghouse/scrubber system to prevent discharge of toxic emissions and annoying odors. Essentially, your organization, and your refiner, must establish a "partnership" based upon many circumstances that are beyond your control, and the refiner’s as well (in particular, the multitude of environmental regulations at all levels that must be observed by the refiner not only to protect the refiner’s interest but yours as well). Selecting a refining partner for reclaiming PGMs requires diligence on your part with regard to the refiner’s standards that result in high performance levels and environmentally responsible results.


Contaminant Removal Prior to Sampling

As previously mentioned, a critical step in the PGM refining/recovery process is the removal of process contaminants from spent catalyst materials. The most cost-effective way to do this is to "pre-burn" the spent catalysts in an indirectly fired rotary kiln; occasionally other methods are used such as fluidized beds or multiple hearth furnaces. This first step is important for accurate sampling since PGM-bearing catalysts usually exhibit high loss on ignition (L0I) as their contaminants are removed. The LOI data generated after pre-burning helps assure accurate sampling by accounting for overall weight changes in the spent catalyst materials.

methods to evaluate - sabin metal corporation

Figure 1. This indirectly fired rotary kiln removes contaminants from spent catalysts typically up to 25% sulfur, or 40% carbon at a rate of 300-1000 lb/hr.

Most refiners do, in fact, pre-burn these spent catalysts, but many do not have in-house capability for this process. Instead, the spent catalyst materials must be trans-shipped to an outside third-party which adds direct costs and delays, both of which translate into ultimately higher costs to the catalyst owner, who must purchase and /or lease new precious metals to continue its process.

Another factor to consider when the refiner sends these materials outside is the possibility that other users’ materials may be mixed in with the refiner’s materials; if that happens it virtually eliminates the possibility of eventually generating accurate and realistic samples.


Sampling After Pre-Burning

With regard to sampling (the next step), most hydrocarbon processing catalysts are sampled by dry sampling methods since they cannot be dissolved in solution nor melted because of their composition. Dry sampling (as opposed to solution or melt sampling which has been discussed in previous articles in this publication) is the most complex of the sampling methods since it requires an ultimate result of a virtually homogenous mix from which individual samples are removed for laboratory analysis. In essence, this technique requires the most experience – and with it skill and judgment.

methods to evaluate - sabin metal corporationAfter sampling, the refiner must assay its results using a wide variety of sophisticated laboratory instruments to measure the precious metals content in a group of samples. Typical analyses would result in precision of ±1 % at analyte levels of approximately 0.1%.

To achieve this level of accuracy, typical assaying equipment and techniques would include atomic absorption spectroscopy and inductively coupled plasma (ICP) emission spectroscopy, X-ray fluorescence, and volumetric, gravimetric, and fire assay techniques. Which combination of equipment and techniques to be used is a determination the refiner makes depending upon the types of materials. For example, this substance of the sampled materials along with its specific mix of analytes must be considered when determining the best approach for assaying.

X-ray fluorescence spectroscopy can produce a semi-quantitive analysis of over 80 elements within a few minutes per sample. These analyses are used to determine the most appropriate quantitative method to be used, or to guide the process during refining.

The final step in the refining process involves smelting the materials mix which – at this point – are a blend of spent catalysts, flux, and a carrier metal such as iron or copper. The refiner makes a determination of materials in the mix depending upon the recoverable precious metals in the spent catalyst lot.

The mix (typically referred to as the charge mix) is then smelted in an electric arc furnace or an induction furnace – depending upon its composition. When the charge is melted, it forms two layers (slag floats on top of a molten metal layer). This slag, which contains trace amount of precious metals, is poured into slag pots and then refined further to extract additional PGMs. The molten metal bouillon from the electric arc furnace is then poured into pre-heated molds. After cooling the metal is removed from the mold and stored in a vault.

In summary, the key to selecting, and working with, a precious metals refining organization hinges upon due diligence on your part with regard to determining all of its policies and procedures from start to finish – including point-to-point transportation services which will also reduce costs and speed processing and thus return your materials values quickly. Key emphasis must be placed on the refiner’s environmental policies and procedures, since you essentially are establishing a "partnership" with the refiner which might ultimately affect you if it violates laws associated with its recovery and refining operations.

This publication thanks Mr. Kevin M. Beirne, Vice President, Sales and Marketing, Sabin Metal Corp. for providing this article.

Mr. Beirne has been in the precious metals industry, for over four decades. In addition to his sales and marketing background, Mr. Beirne has managed analytical, instrumentation, and fire assay laboratories as well as precious metal refining and manufacturing organizations, He attended Fairleigh Dickinson University and also completed many specialty courses for instrument analysis and marketing. Beirne was a member of the American Electroplaters Society (AES), Investment Recovery Association (IRA), and is past president of the International Precious Metal Institute (IPMI).