Mercury is a highly toxic element that can enter the environment through industrial pathways including coal-fired utility plants, the oil and gas industry, steel scrap processing facilities, gold production, and waste incineration. Mercury is a naturally occurring element, present in virtually all oil and gas. Mercury levels in crude oil and gas can vary widely, both between and within reservoirs and geographical areas. Concentrations vary from low ppb (parts per billion) to low ppm (parts per million) levels. Mercury compounds in crude are largely elemental and inorganic compounds such as mercuric sulfide.
As hydrocarbon exploration expands, higher levels of mercury are exposed, causing damage to both the environment and to hydrocarbon processing equipment. Mercury poses several issues for refineries. In addition to the environmental and health issues, mercury is also detrimental to the refining process through amalgamation with other metals, poisoning of catalysts, and liquid metal embrittlement (cracking) with metals such as aluminum. Mercury species from crude oil may accumulate in processing equipment over time. During refinery distillation, the segment of elemental mercury vapor is predominantly distributed in liquefied petroleum gas (LPG) and light distillate streams. But due to its weight, it can also be found in the residual fraction, which also contains the majority of the insoluble and inorganic mercury salts. Of particular concern are LNG and LPG cryogenic heat exchangers made of aluminum alloy.
Mercury accumulations cause many operational concerns; elemental analysis using field-portable X-ray fluorescence can offer solutions.
- Environmental issues and potential waste issues: Handheld XRF analyzers are an industry-accepted screening tool for mercury contamination in soil samples, and in some cases for confirmatory testing. Overall, the XRF field technique provides a significant improvement over current practices to detect mercury contamination.
- Health issues, including volatile sources, surface contamination, and particulate contamination during hot work. Assets exposed to mercury must be decontaminated prior to further use. Workplace TWA exposure limits are determined as 0.025 mg/m3. Mercury is always surface contamination, which makes the coating weight analysis the best way to quantify the mercury levels. Portable XRF analyzers are available with a coatings measurement mode that provides accurate coating weight to determine the precise amount of mercury in the contaminated sample.
- Safety issues, such as corrosion by metal amalgamation or possible liquid metal embrittlement (LME). Since crude oil tanks are seldom coated, elemental mercury could form an amalgamation with the steel. Elemental analysis of piping and equipment with a portable XRF analyzer can confirm the integrity of process piping, valves, and tanks.
Read the application note, Handheld XRF Technology Determines Surface Mercury Contamination to learn more about this important emerging XRF application.