Three sampling procedures

December 12th, 2009 | admin | forex educational

In the previous article, three sampling techniques were discussed: dry, melt and solution sampling. Each of these incorporates a number of specific methods and equipment, and also offers specific advantages. Determining the most appropriate sampling method depends upon the type of material being processed, as well as its estimated precious metals content. Because of their composition and chemistry, precious metals bearing catalysts are usually sampled with dry sampling processes. Dry sampling is used when materials cannot be dissolved in a solution, or are inappropriate to melt, either because of their structure, or because of the cost associated with melting vs the possible return. As it is difficult to achieve homogeneity, dry sampling is more complex, and potentially less precise, than melt or solution sampling; in fact, this method generally requires better judgment than the others. An ideal dry sampling system is capable of drawing representative samples from free flowing catalyst according to the principles of Pitard2 and Gy3 and the practices of Merks4 at a rate of 2000 - 3000 lb/hr.

As sampling is considered the most important procedure in the precious metals recovery and refining process, it must be viewed from the perspective of the refiner as well as the refiner’s customer. Clearly, the customer’s goal is to receive the maximum possible value for the remaining precious metals in their spent catalyst materials. The refiner, on the other hand, must not only consistently meet that goal for its customer; it must also provide the customer with detailed documentation of how this value was determined. The refiner and customer each have responsibilities that must be addressed in order to ensure a mutually rewarding relationship based on fair, straightforward business practices. Without this, there is no possibility that a precious metals refiner can retain its existing customer base; little possibility that it can continue to attract new customers; and not much probability that it can remain in business over the long term.
As previously mentioned, dry sampling procedures begin by converting large lots of spent catalysts materials (as much as many t) to as little as a few g, in a homogenous mass, to distribute molecules of precious metals and other constituents evenly. In essence, when the material cannot be broken down any further, the results of sampling (or reducing) the homogenous mass represent an accurate ratio of the precious metal content in the overall matrix.

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