Mercury in Crude Oil
Two new ASTM International standards provide the means to quantitatively determine the trace amounts of mercury in crude oils. D7622, Test Method for Total Mercury in Crude Oil Using Combustion and Direct Cold Vapor Atomic Absorption Method with Zeeman Background Correction, and D7623, Test Method for Total Mercury in Crude Oil Using Combustion-Gold Amalgamation and Cold Vapor Atomic Absorption Method, were developed by Subcommittee D02.03 on Elemental Analysis, part of ASTM International Committee D02 on Petroleum Products and Lubricants.
“Mercury is a contaminant in fossil fuels — both coal and crude oil — and has harmful toxicological effects on both human and marine life,” says Kishore Nadkarni, chairman of D02.03. “Emission of mercury during crude oil refining or coal burning during power generation may contaminate refined products as well as the ecosphere.”
Nadkarni notes that there are additional ASTM International standards for determining mercury in other fossil fuels such as natural gas and coal, including the following:
However, this is the first time standards have been developed for the determination of mercury in crude oils.
“The methods standardized in D7622 and D7623 are being used in the oil industry laboratories for analysis but were not standardized throughout the industry until now,” says David Hwang, Chevron Energy Technology Co., and vice chairman of D02.03. “This standardization should bring uniformity in testing across the industry and facilitate decisions in commerce and regulatory compliance.”
In D7622, controlled heating following thermal decomposition of the crude oil sample in air is used to liberate mercury. Mercury and all other decomposition products are then atomized at about 750°C and are viewed through a cold vapor Zeeman atomic absorption spectrometer.
In D7623, a crude oil sample is subjected to heating to about 700°C, and the decomposition products are carried into a gold amalgamator that selectively traps mercury. Later the amalgam is rapidly heated to about 600°C, releasing mercury vapor that is viewed by a cold vapor atomic absorption spectrometer.
Technical Information: Kishore Nadkarni, Millennium Analytics Inc., East Brunswick, N.J.
David Hwang, Chevron Energy Technology Co., Richmond, Calif.
ASTM Staff: David Bradley