Impact of Mercury on Crude Oil Quality

Wilhelm, S. M., "Impact of Mercury in Crude Oil on Refining", World Refining, Jan./Feb. 2003.

ABSTRACT

The trace amounts of mercury in crude oils affect their quality and price. Measuring the concentrations of critical mercury species in oil requires rigorous analytical methods. Predicting the expected amounts in products requires information on how mercury compounds distribute in refining processes.

Mercury in crude oil above certain limits can be problematic to refining operations. Mercury poisons catalysts and reduces the quality of refined products. Environmental impacts are also important because running mercury-laden crudes can produce wastewater and solid waste streams having mercury concentrations that exceed regulatory limits. Refiners have the need to know exactly how much mercury is in the refinery crude diet to allow blending to acceptable limits or to develop contingencies. Attaching a certain range to the concentration of mercury in a purchased crude oil is not an easy task and significant errors can be encountered that can produce negative impacts on refinery operations and profitability.

In the past, special efforts were required to measure mercury concentrations in crude oil accurately and it was seldom included in the list of metals known to be specifically harmful to refining. The specialized equipment and expertise necessary to perform accurate determinations of the concentration of mercury in crude oil often were not readily available. Previously it was not well known that crude oil samples in metal cans lose mercury due to amalgamation with the can's tin plating thus yielding lower than actual amounts when the oil was analyzed. Analytical methods and sampling techniques have now improved thus providing better data and a more complete understanding of how mercury in crude oil distributes in production, transportation and processing systems. Because mercury's negative impact on catalysts and refined products has become more apparent, refiners now scrutinize mercury content of purchased crude oils more closely.



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