Processing of gas containing mercury invariably leads to contamination of equipment and can generate waste in the form of sludge and spent adsorbent materials. Occasional accidents can also lead to soil contamination. This paper reviews mercury contamination in the gas processing industry and discusses newly developed methods for clean-up and disposal of mercury waste.

Research and development (sponsored by the Gas Research Institute) have produced new technology for mercury removal from complex matrices. Equipment decontamination is accomplished using chemical cleaning solutions that selectively oxidize and complex elemental mercury deposits. These cleaning formulations include aqueous base solutions containing iodine as the complexing agent and organic (alcohol) base solutions using complexing agents.

Soil, sludge, and debris must be thermally processed to remove (recycle) mercury. Thermal systems use vacuum, inert gas, or air as the carrier medium. If air is used, sulfur In the matrix Is converted to SO2 and hydrocarbons are oxidized as well, depending upon design. Anaerobic thermal systems employ selective condensation and/or adsorption to separate sulfur and hydrocarbons from mercury. Spent adsorbent materials are also thermally processed using strictly anaerobic conditions to avoid exothermal reactions involving carbon.

The regulatory climate relative to mercury is changing rapidly. Regulations covering treated debris and soils may require total mercury concentrations of less than 2 mg/kg for burial. Total mercury analysis rather than leaching procedure (TCLP) is becoming the norm in regulations and specifications. Sampling and analysis procedures for contaminated surfaces are under development.

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