Hot Gas Decontamination - ex situ

Description

Hot gas decontamination involves raising the temperature of a contaminated material to 260 °C (500 °F) by exposing it to hot gases (e.g. propane or natural gas) for a specified period of time. The contaminant(s) are thermally decomposed or volatilized. The gas effluent from the material is extracted and treated in a system that destroys all volatilized contaminants. This technology is specifically applied to the remediation of materials contaminated with explosives such as demilitarized mines (i.e. after removal of explosives), shells, or soil from battlefields and training grounds. The hot gas decontamination treatment is also applicable to the remediation of buildings or structures associated with munitions plants, arsenals and depots involved in the manufacture, processing, loading, and storage of pyrotechnics, explosives and propellants.

A hot-gas system designed by the U.S. Army Environmental Center (USAEC) includes a hot-gas furnace, ducts and fans, a control system and a thermal oxidizer (afterburner). Treatment of contaminated gas emissions occurs in the afterburner, which has a continuous emission monitoring system to control the concentration(s) of contaminant(s) in the exhaust air before releasing it into the atmosphere. The furnace design must take into consideration possible explosions from improperly demilitarized mines or shells.

Internet links:

  • 4.21 Hot Gas Decontamination - FRTR Remediation Technologies Screening Matrix and Reference Guide, Version 4.0
  • Hot Gas Decontamination - Techtree - Center for Public Environmental Oversight (CPEO)


  • Recommended Analyses for Detailed Characterization

    Chemical Analysis

    Physical Analysis

    • Soil granulometry  
    • Contaminant physical characteristics   Footnotes2

    Recommended Trials for Detailed Characterization

    Physical Trials

    • Gas permeability trials 
    • Evaluation of the radius of influence 
    • Air flow rate  
    • Evaluation of operating pressure/vacuum 

    Applications

    • Hot gas decontamination is specifically used for treating residual explosives contamination, such as TNT, royal demolition explosive (RDX), trinitrophenyl-N-methylnitramine (Tetryl), Ammonium Picrate (Yellow D), Smokeless Powder and Mustard (H or HD);
    • Operating conditions are site-specific;
    • The contaminant(s) is completely destroyed during treatment.

    Treatment Type

    • Does not apply In situ
    • Applies Ex situ
    • Does not apply Biological
    • Does not apply Chemical
    • Does not apply Control
    • Does not apply Dissolved contamination
    • Does not apply Free Phase
    • Does not apply Physical
    • Applies Residual contamination
    • Applies Resorption
    • Applies Thermal

    State of Technology

    • AppliesTesting
    • Does not applyCommercialization

    Target Contaminants

    Does not apply Aliphatic chlorinated hydrocarbons

    Does not apply Chlorobenzenes

    Applies Explosives

    Does not apply Metals

    Does not apply Monocyclic aromatic hydrocarbons

             Does not apply Non metalic inorganic compounds

    Does not apply PCBs

    Does not apply Pesticides

    Does not apply Petroleum hydrocarbons

    Does not apply Phenolic compounds

    Does not apply Policyclic aromatic hydrocarbons

    Applies   Applies    With restrictions   With restrictions    Does not apply   Does not apply

    Treatment Time

    • Applies< 1 year
    • Does not apply1 to 3 years
    • Does not apply3 to 5 years
    • Does not apply> 5 years


    Secondary By-products and/or Metabolites

    • The largest concern is atmospheric emissions from the afterburner;
    • If chlorinated compounds are present, formation of dioxins and furans are of concern.


    Limitations of the Technology

    • The cost of this method is higher when compared to other types of explosive remediation treatments such as open pit burning;
    • The rate at which equipment or material can be decontaminated is slower when compared to other types of explosive remediation treatments such as open pit burning;
    • The hot gas furnace chamber design must take into consideration possible explosions from improperly demilitarized mines or shells.


    Complementary Technologies that Improve Treatment Effectiveness

    • Incineration of the gas emissions.


    Required Secondary Treatments

    • Collection and treatment of gas emissions;
    • Because there is a variety of materials being volatized, thorough analysis and continuous monitoring of emissions are recommended.


    Application Examples

    Application examples are available at this address:



    Performance

    This process is between the pilot scale and field demonstration stages. The United States Army Environmental Center sponsored several demonstrations showing that 99.9% decontamination of structural components is possible. Items decontaminated for 6 hours at a minimum temperature of 260 °C (500 °F) were found to be safe for public release as scrap.



    References


    Composed by:

    Josée Thibodeau, M.Sc
    National Research Council


    Latest update provided by:

    Martin Désilets, B.Sc.
    National Research Council


    Updated Date:

    3/1/2008



    Footnotes

    Return to footnote1 Contaminant concentrations: Identification and concentration of all contaminants (sorbed, dissolved, and free phase).

    Return to footnote2 Contaminant physical characteristics includes: viscosity, density, solubility, vapour pressure, etc.