Recovering precious metals from processing catalysts
In round numbers, there are over 100 Gulf-region hydrocarbon refiners. These organisations are state owned, joint ventures, original concessions, or independent, foreign owned businesses.
Kevin M Beirne
Sabin Metal Corporation
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Mideast refineries convert more than eleven billion barrels per year of crude oil into commercially marketable products. While they compete against each other in one form or another, they also share a common trait: that is, the consumption of thousands of tons of precious metal-bearing catalysts used to facilitate and/or speed hydrogenation during the refining process, and also for controlling end-of-pipe process discharges to comply with pollution abatement regulations. The precious metals in these catalysts are known as PGMs, or Platinum Group Metals that include platinum, palladium, rhodium, and ruthenium; rhenium, while not considered a PGM, is also a valuable precious metal and is often present in hydrocarbon processing catalysts along with gold or silver. PGM-bearing catalysts are typically employed on substrates (carriers) such as soluble and insoluble alumina, silica alumina, zeolite, or carbon supports (Figure 1).
Whatever their composition, eventually, due to the harsh environments which contaminate them with carbon, sulphur, volatile organics, moisture, or other impurities, the catalysts lose their efficacy and thus the ability to function. When that occurs, their valuable precious metals must be recovered and refined, and new precious metal-bearing catalysts must be installed during a process “change out” to minimise production downtime. To recover the value of PGMs that remain in spent process catalysts, hydrocarbon refiners typically work through their Asset Recovery departments in cooperation with well established, highly specialised precious metals refiners.
On another subject concerning profitability, it’s not news that over the past few years many Middle Eastern hydrocarbon producers have felt the economic squeeze caused by volatile feedstock prices, geopolitical instability, increased competition, and reduced fossil fuel consumption. While many Mideast producers have moved towards increased production of non-fossil fuel products such as fine and speciality chemicals (as well as a variety of other petrochemical end products), all of them must deal with the prospect of obtaining maximum value from the precious metals that remain in their spent catalysts.
To further cut into the profit squeeze, Gulf States refiners also face the prospect of China developing its massive shale gas resources, which could have major negative impact on Gulf region hydrocarbon producers. In fact, there have already been major mergers between Middle Eastern refining consortiums and Chinese companies that are now constructing huge hydrocracking facilities in China.
Asset recovery includes catalysts’ precious metals
As an operator, how does all this news affect you? It’s simple, really: It is in the best interest of any hydrocarbon refining organisation to look carefully at its asset recovery program with regard to acquiring highest possible value for remaining precious metals in spent process catalysts. Consider this typical example: A spent catalyst lot from a major refiner (which could weigh a half-million pounds) could easily contain $3 million in recoverable platinum. At today’s platinum price of about $1,600 tr. oz, clearly this represents a significant contribution to any organisation’s profit picture.
Environmental concerns and legal implications
Because environmental protection has become an important concern (with possible serious legal implications for violators), processing procedures at your refiner’s must also be thoroughly evaluated. If your refiner violates an environmental law—and there are plenty of them (go to www.sabinmetal.com/Environmental.html, then scroll down to Environmental Codes & Standards) — not only is your refiner subject to legal action (most likely by more than one authority), but you — as the catalyst owner — may also be held responsible.
How to handle this? When selecting a refiner, you should not only be aware of how your materials will be processed, but also how spent catalysts from the refiner’s other customers are processed. It ultimately is your responsibility to determine how any solid, liquid, or gaseous byproduct is handled at the refiner’s facility. Exhaust air quality should be managed with state-of-the-art pollution control systems; and hazardous waste shipped from a precious metals processing facility must be documented and traceable. Legally, a refiner must ship hazardous waste materials under approved procedures and conditions — and you must be aware of these procedures.
In-house moisture and contaminant removal
To provide an accurate determination of remaining precious metals in spent catalyst lots, representative samples of these catalysts must be obtained under accurate and repeatable conditions. Over time, process catalyst become contaminated by sulphur, carbon, volatile organics, moisture, and other unwanted elements. As a result, when the catalyst is removed from the process, it is usually moist and sticky, and it will not flow freely through automatic sampling equipment.
Contaminants in the catalysts must first be removed to assure accurate sampling and analysis of the remaining precious metals. This process is accomplished with an indirectly fired rotary kiln which not only greatly enhances sampling accuracy to help assure maximum recovery value of remaining precious metals; it can also significantly reduce overall refining costs when it is handled directly at the refiner’s facility. This is a key issue with regard to the total cost of recovery and refining and, by inference, the overall return of your precious metals. The typical rotary kiln will remove up to 25% of the materials’ sulphur content and up to 40% carbon content, usually at a rate of 300 to 1000 lbs per hour. Most contaminants associated with spent precious metal bearing catalysts typically exhibit high loss on ignition (LOI) characteristics, in addition to the other contaminants previously mentioned.
Removal of moisture is also critical to the down stream sampling process. The reason for this, is that the materials must be free flowing (with low LOI) initially to arrive at a final evaluation sample that is at least accurate to ± 2% relative. It is here that pre-burning can make a key difference; if the high moisture content and other contaminants are not removed, a suitably accurate sample cannot be obtained by the refiner, thus eliminating the possibility of providing a fair and true return value to the catalyst owner.
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