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Cryogenic Process Treatment Technology for Water and Soil Remediation

Cryogenic process for surface water and soil remediation is a process that remove contaminants through condensation of chemicals with the used of cryogens depending on the temperature requirements for treatment (see Figures 1 through 3). The cryogens usually have very low temperatures below -180oC with normal boiling points, are as follows: liquid nitrogen (-196oC); liquid helium (-268.93oC); liquid oxygen (-182.95oC); and neon (-240oC). Other common refrigerants (i.e., freon, R507, and hydrogen sulfide) have higher temperatures.  Liquid nitrogen is mostly used in cryogenics around the globe.  In remediation, liquid nitrogen is very effective for removal of contaminants from the soil and surface water.  People are afraid to use liquid nitrogen for the environmental remediation because of a higher risk for potential explosion when it is not carefully design. Strategic planning and techniques can achieve success in remediation using cryogenic process with liquid nitrogen. It is very cost effective and energy efficient compared to other existing technologies. When using liquid nitrogen, it is very crucial to maintain certain limits of temperatures to prevent the condensation of the oxygen in the system so that potential explosion can be mitigated (Doro-on 2011).

Content Table

Overview of Cryogenics

Cryogenic is any liquefied gases with extremely low normal boiling point (i.e., oxygen, hydrogen, helium, neon, and nitrogen).  Cryogenics usually associated with the production and utilization of materials in very low temperatures. Cryogens are normally used for freezing applications, medical treatment, large-scale chemical plants, and rocket fuels (i.e., liquid hydrogen).  The word cryogenics stems from Greek which means “ the production of freezing cold.”

Both the magnitude and toxicity of emissions of volatile organic compounds (VOCs) have led to public health concern and recent government regulations to reduce VOC emissions (Carmichael et. al., 1996). 

Cryogens Can Deplete Oxygen

The main health hazard created by cryogens is asphyxiation. For instance, liquid nitrogen (see Figure 1) depletes oxygen within an enclosed area or room without ventilation that can lead to sudden death. 

Figure 1. Liquid Nitrogen (Source: The Encyclopedia Science)

Figure1.jpg

Explosion Due to Rapid Expansion

According to Canadian Centre for Occupational Health and Safety (1997), without adequate venting or pressure-relief devices on the containers, enormous pressures can build up. The pressure can cause an explosion called a "boiling liquid expanding vapor explosion" (CCOHS, 1977). Unusual or accidental conditions such as an external fire, or a break in the vacuum which provides thermal insulation, may cause a very rapid pressure rise (CCOHS, 1977).  Meanwhile, liquid nitrogen causes immediate explosion without warning once Oxygen is condense.

Figure 2. Liquid helium and liquid nitrogen cooling (Source: NASA, 2011)

Figure2.gif

Figure 3. Machinist Mates take samples from the Liquid Oxygen Storage Tank in the Lincoln's Oxygen-Nitrogen Shop (Source: US Navy, 2002).

Figure3.jpg

Remediation for Surface Water and Soil

Cryogenic process recovers volatile organic compounds (VOCs) from the contaminated soils and can be used to extract hydrocarbons from surface water through freezing and condensation.  Moreover, this process is very effective to use particularly when the site is dominantly contaminated by total petroleum hydrocarbons and chlorinated carbons including compounds with explosive characteristics.  In soil remediation, vapors are extracted from the vadose zone then distributed into a cryogenic enclosed compartment (see Figure 5) with liquid nitrogen (or any appropriate type of cryogen) in a straightforward heat exchange process. There are technologies available for remediation using freon or R507 as cryogenic remediation but those are not capable of stripping most of the contaminants in the organic-laden vapor stream.  Liquid nitrogen is versatile, non toxic, and non corrosive coolant. In surface water remediation, hydrocarbons can be separated through cryogenic process from surface water and the vapor will be distributed into a second cryogenic freezing chamber.  Further, the condensate will be collected into a tank for reuse or disposal.  Meanwhile, the water sources and environmental contamination are presented in Figure 4. The conceptual design for water and soil remediation using cryogenic process treatment technology is presented in Figure 5. Cryogenic process technology for soil and water remediation is considered to be one of the most energy efficient and environmentally friendly technology.

Figure 4. Water Sources Contamination(Source: Safe Drinking Water Act)

(Note: This Figure can be accessed in full size by clicking the "Attachments" tab at the bottom of this page)

Figure4.jpg

Figure 5. Conceptual Design and Schematic Diagram of Cryogenic Process Treatment Technology

(Note: This Figure can be accessed in full size by clicking the "Attachments" tab at the bottom of this page)

Figure5.jpg

Further Reading

1. Combining Cryogenic Flue Gas Emission Remediation with a CO2/O2 Combustion Cycle (Meratla, 1997)

2. Cryogenic Drilling: A New Drilling Method for Environmental Remediation (Simon and Cooper, 2007)

3.  Environmental Remediation (Wikipedia)

4. Cryogenic Drilling 

5.Sustainable Remediation 

6.  Site Remediation Technologies

7. The Application of Cryogenics for Sustainable Solvent Recovery

8. Separation and Concentration of Volatile Organic Contaminants by Activated Carbon Cloth for Cryogenic Recovery

9. Dispersant 'may make Deepwater Horizon oil spill more toxic (Example of Surface Water Contamination; source of one of the images in Figure 5)

10.Soil Remediation (Source of one of the images in Figure 5)

Arsenic in Groundwater: Poisoning and Risk Assessment - M. Manzurul Hassan, Peter J. Atkins 
Publication Date: Nov 2013 - ISBN - 9781780400204

Soil and Water Contamination, 2nd Edition - Marcel van der Perk 
Publication Date: Oct 2013 - ISBN - 9781780404912

Related Article

Radioactive Clean-up

Environmental Remediation

References

Carmichael, KR, Lordgooei, M, Kelly, T.W., Rood, M.J., and S.M. Larson. 1996. Desorption of Cryogenic Recovery of Volatile Organic Compounds. http://www.anl.gov/PCS/acsfuel/preprint%20archive/Files/41_1_NEW%20ORLEANS_03-96_0374.pdf (Accessed on July 16, 2011).

Canadian Centre for Occupational Health and Safety (CCOHS). 1997.  Cryogenic Liquids and their Hazards. http://www.ccohs.ca/oshanswers/chemicals/cryogenic/cryogen1.html (Accessed on July 1, 2011).

Doro-on. 2011. Risk Assessment for Water Infrastructure Safety and Security. CRC Press and the International Water Association (IWA). http://www.iwapublishing.com/template.cfm?name=isbn9781780400211

National Aeronautics and Space Administration (NASA). 2011. Infrared Spectrometer Need Liquid Helium and Liquid Nitrogen Cooling. http://quest.arc.nasa.gov/ltc/astrobio/leonid/28.html (Accessed July 1, 2011).

The Encyclopedia of Science. 2011. Nitrogen http://www.daviddarling.info/encyclopedia/N/nitrogen.html (Accessed on July 14, 2011).

U.S. Navy. 2002.  Photo of Machinist Mates take Samples from Liquid Oxygen Storage Tank in the Lincoln's O2-N2 Shop.  http://www.navy.mil/view_single.asp?id=2909 (Accessed on July 7, 2011).

Cryogenic Condensation and Recovery of VOCs Using Liquid Nitrogen

Safe Drinking Water Act 

Groundwater and Drinking Water Protection and Treatment (U.S. Environmental Protection Agency)

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