British Columbia Mine Reclamation Symposium

Cleaning up metal and hydrocarbon contaminated soils using the ChemTech soil treatment process Stephenson, Robert John; Yan, Vita


The ChemTech soil treatment system differs substantially from the present commercial approaches to soil remediation. Rather than the "no-tech" approach of land filling or the apparent "bio-tech" route of bioremediation, the ChemTech process configures chemical engineering and mineral processing unit operations to deliver a comprehensive, rapid, flexible and economic treatment to a range of contaminated soils. The soil treatment process is a portable treatment system which effectively removes both metals and petroleum hydrocarbons from soils or sediments. Its chemical and power cost is in the order of $20 to 25 per tonne, pricing remediation below the cost of landfilling in many jurisdictions. The treatment does not generate important quantities of solid wastes, contaminated liquid effluent, or air emissions. A mobile pilot plant is trailer mounted for on-site demonstration, requiring only a supply of fresh water, compressed air, and electrical power. The patent pending process uses the turbulent mixing of a continuously fed three phase fluidized bed with soil contaminant chemistry to separate the feed soil into coarse (clean) and fine (contaminated) fractions. Extremely high air flow velocities in the turbulent zone of the continuously fed fluidized bed provides for slurrying, wetting, and scouring of the soil particle surface to result in removal of the adhered contaminants. The continuously fed fluidized bed effectively encapsulates a number of the concepts of tar sands extraction in a single unit and does so in an physically intense but mechanically simple manner. The result is a flexible, high capacity system with attractive operating and capital costs, well suited to environmental cleanup of a range of soil and sediment types. The process has been verified at bench and pilot scales using a number of industrially contaminated soils to segregate metal and petroleum hydrocarbon contaminants from soil or sediments. The results obtained indicate that decontamination of soils can be achieved in a rapid (nominally 5 minute residence time) and effective manner with a minimum of inputs. Identifying the operating conditions would be performed at a bench scale for each soil prior to on-site demonstration and commercial scale remediation.

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