Fact sheet: Hot gas decontamination—ex situ

From: Public Services and Procurement Canada

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Description

Hot gas decontamination consists of raising the temperature of a contaminated material to 260 °C (500 °F) by exposing it to hot gases, such as propane or natural gas, for a specified period of time. The contaminants present are thermally destroyed (by combustion or pyrolysis) or volatilized. The gas effluent (volatilized contaminants) from the material is extracted from the furnace and treated in an incinerator. This technology specifically applies to the remediation of materials contaminated with explosives (demilitarized mines, bomb residues or soils from training or military battlefields). The hot gas decontamination treatment is also applicable to the remediation of buildings or structures associated with munition plants, arsenals and depots involved in the manufacture, processing, loading, and storage of pyrotechnics, explosives and propellants. The method consists of sealing and isolating structures and heating them with a stream of hot gas.

Sources:

Implementation of the technology

The gas injection system is generally composed of a furnace containing the contaminated materials in which the hot gases are injected, as well as fans, a gaseous emission control system and an incinerator. Following the treatment of explosives in the furnace, gaseous emissions (volatilized contaminants) are directed to the incinerator where they are treated. The incinerator is equipped with a gas concentration meter to monitor and control the concentration of contaminants in the air. The furnace design must provide for the possibility of explosion during the hot gas injection treatment.

The incinerator including the effluent gas treatment system can be constructed temporarily on-site.

The implementation of this technology may include:

  • Site preparation for the installation of equipment.
  • Recovery of materials to be treated, such as excavation of soils, sediments, sludge or waste, in the case of solid materials.
  • The transport of materials to be treated is required if the hot gas injection system is not installed on the site.
  • Recovery and management of treated materials.
  • The dismantling of the facilities and the restoration of the site.

The installation of a temporary incinerator for the treatment of residual gases is subject to compliance with certain laws and regulations that may require obtaining permits or authorizations.

Materials and Storage

  • Infrastructure for the installation of treatment equipment.
  • The operation of an incinerator requires oxygen or sufficient air supplied, as well as fuels adapted to the type of combustion apparatus and the incinerator's capacity.

Residues and Discharges

  • Injection of hot gas generates residual material, such as ashes resulting from combustion. It also generates gaseous emissions following the volatilization of contaminants, but they are treated by the incinerator.
  • Incineration also produces combustion gases that must be treated before being released into the atmosphere.

Recommended analyses for detailed characterization

Chemical analysis

  • Contaminant concentrations in materials

Recommended trials for detailed characterization

Physical trials

  • Airflow rate
  • Evaluation of operating pressure/vacuum

Other information recommended for detailed characterization

Phase III

  • Volume of contaminated material to treat

Applications

  • Hot gas decontamination is specifically used for treating residual explosives contamination, such as trinitrotoluene, cyclotrimethylenetrinitramine (royal demolition explosive [RDX]), trinitrophenyl-N-methylnitramine, Ammonium Picrate (yellow D), Smokeless Powder and Mustard (H or HD).
  • Treatment conditions depend on the contaminants and the material being treated.
  • Contaminants are completely destroyed during treatment

Applications to sites in northern regions

Due to the types of systems to be put in place and the energy required for their operation, this technology does not seem appropriate in northern regions. Similarly, the operation of this type of technology requires rigorous monitoring by specialized personnel who may not be available in this type of environment.

Treatment type

Treatment typeApplies or Does not apply
In situ
Does not apply
Ex situ
Applies
Biological
Does not exist
Chemical
Does not exist
Control
Does not exist
Dissolved contamination
Does not exist
Free Phase
Does not exist
Physical
Does not exist
Residual contamination
Does not exist
Resorption
Applies
Thermal
Applies

State of technology

State of technologyExist or Does not exist
Testing
Exist
Commercialization
Does not exist

Target contaminants

Target contaminantsApplies, Does not apply or With restrictions
Aliphatic chlorinated hydrocarbons
Does not apply
Chlorobenzenes
Does not apply
Explosives
Applies
Metals
Does not apply
Monocyclic aromatic hydrocarbons
Does not apply
Non metalic inorganic compounds
Does not apply
Pesticides
Does not apply
Petroleum hydrocarbons
Does not apply
Phenolic compounds
Does not apply
Policyclic aromatic hydrocarbons
Does not apply
Polychlorinated biphenyls
Does not apply

Treatment time

Treatment timeApplies or Does not apply
Less than 1 year
Applies
1 to 3 years
Does not apply
3 to 5 years
Does not apply
More than 5 years
Does not apply

Long-term considerations (following remediation work)

None.

Secondary by-products and/or metabolites

  • Gaseous emissions from the volatilization of contaminants are collected and processed by the incinerator. Emissions from the incinerator must also be analyzed and processed as needed.
  • If chlorinated compounds are present, formation of dioxins and furans are of concern.

Limitations and Undesirable Effects of the Technology

The hot gas furnace chamber design must take into consideration possible explosions from improperly demilitarized mines or shells.

Complementary technologies that improve treatment effectiveness

None.

Required secondary treatments

A large number of compounds can be volatilized during hot gas injection and incineration requires monitoring of the composition of the air before it is released to the environment.

Application examples

The following site provides an application example:

Performance

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.

Measures to improve sustainability or promote ecological remediation

  • N/A (demonstration level)

Potential impacts of the application of the technology on human health

Main Exposure Mechanisms

Applies or Does Not Apply

Monitoring and Mitigation

Dust

Does not apply

N/A

Atmospheric/Steam Emissions—Point Sources or Chimneys

Applies

Emissions monitoring (choice of parameters and levels of intervention depending on source, risk and local requirements).

Atmospheric/Steam Emissions—Non-point Sources

Does not apply

N/A

Air/steam—by-products

Applies

Emissions monitoring (choice of parameters, types of samples and type of intervention [source, risk or local requirements]).

Runoff

Does not apply

N/A

Groundwater—displacement

Does not apply

N/A

Groundwater—chemical/ geochemical mobilization

Does not apply

N/A

Groundwater—by-product

Does not apply

N/A

Accident/Failure—damage to public services

Applies

Verification of files and obtaining prior permits.

Accident/Failure—fire or explosion (inflammable vapours)

Applies

Risk review, development of accident and emergency response plans, monitoring and inspection of unsafe conditions

Other—Handling contaminated soils or other Solids

Applies

Risk review, development of accident and emergency response plans, monitoring and inspection of unsafe conditions

References

Author and update

Composed by : Josée Thibodeau, M.Sc, National Research Council

Updated by : Martin Désilets, B.Sc., National Research Council

Updated Date : April 17, 2013

Latest update provided by : Nathalie Arel, P.Eng., M.Sc., Christian Gosselin, P.Eng., M.Eng. and Sylvain Hains, P.Eng., M.Sc., Golder Associés Ltée

Updated Date : March 22, 2019

Date Modified: