Cryogenic Treatment Unit (TU-51) Technology for Recovery of VOCs from Highly Contaminated Environment

Content Table

• Cryogenic Treatment Unit (TU-51) Technology for Recovery of VOCs from Highly Contaminated Environment
  • Figure 1 Example of Soil Contamination Model - Plan View
  • Figure 2 Example of Soil Contamination Section View
  • Further Reading
  • Related Titles on Water Treatment from IWA Publishing

A Cryogenic Treatment Unit was developed to apply a cryogenic air treatment process to recover persistent vapor phase volatile organic compounds (VPVOCs) having extremely low boiling points. These would include explosive compounds present in the vapor stream. The portable TU-51 VPVOCs Technology (OEM) operates the following process: vapors are recovered from geologic units via soil vapor Extraction (SVE), often from a battery of extraction wells, then distributed to the cryogenic chambers. The vacuum pump and filters and sampling ports and the orifice plate installed between the extraction wells and the treatment unit are illustrated in the process flow diagram. The vapor is then distributed to the cryogenic system initially through a heat exchanger then to freezing chambers.The cryogenic separation technique for soil remediation is complicated and here it is proprietary to RAMCO Environmental Inc.(RAMCO). 

The condensate produced by this separation process contains the recovered VOCs. Condensate products are discharged to a sealed and cooled collection vessel. Condensate is periodically transferred to a DOT approved stainless steel shipping pot at the time of transfer by a licensed hauler to a material recovery refinery. Finally, the treated air shall be directed through a bed of granular activated carbon (GAC) for discharge to atmosphere under the terms of an atmospheric discharge permit from the appropriate regulatory agency.

Groundwater within the former Vinyl Chloride Plant in Santa Clarita Valley, California (hereafter called “Site”) is currently contaminated by a mix of petroleum hydrocarbons and chlorinated hydrocarbons (i.e., toluene, chloroethane, chloromethane, tetrachloroethylene (PCE), trichloroethylene (TCE), 1,2- dichloroethane (1,2 DCA), chloroform and vinyl chloride). There are traces of explosive compounds such as methyl-ethyl-ketone, acetone peroxide and a possible presence of ammonium perchlorate in the vadose zone. 

Although relatively small, the Site was compared to its contaminated neighbor Whittaker-Bermite due to similar contaminants and soil conditions, we discovered that solutions for contaminant recovery and treatment on the Site may be just as complicated. In the fall of 2010, RAMCO completed an in depth study of all appropriate prominent single or combined soil remediation technologies such as:

Also we compared the commercially available cryogenic technologies provided by Lynde Cirrus. Most of the treatment systems would require specially made components for the Site condition.  These would be very costly and energy inefficient. The systems would require enormous scrubbers made of limestone to remove the acid. A scrubber would be needed with any of the typical treatment systems, but scrubbers are costly to purchase and require a costly rebuilding between six and twelve months into SVE remediation. A GAC polishing unit fits in process behind the scrubber as ancillary treatment and polishing prior to discharge into the atmosphere. However by desorption process 1,2 DCA would consume an enormous quantity of GAC per day due to its high concentration. Of equal concern with this project is the fact that there is no historical data that GAC would successfully remove the vinyl chloride.

Figure 1 Example of Soil Contamination Model - Plan View

Figure 2 Example of Soil Contamination Section View

Upon comparative analysis of cryogenic treatments, those that are considered costly and chemical-equipment incompatible were not selected. Two of the best options were available from Lynde's Cirrus VEC System. The pitfall of using Lynde's Cirrus technology is that it targets very high flow rate and requires enormous cost for installation, rental, and mobilization. Aside, it needs a potential large amount of scrubbers prior to vapor treatment and/or utilization of GAC for final polishing. Another concern of the chemical-equipment compatibility is the presence of explosive compounds, which causing health risks and may damage the equipment. 

In summary, TU-51 Technology:

• Does not emit hazardous chemicals into the environment;
  
• Does not require specially made expensive components;
  
• Does not deplete the ozone layer;
  
• Does not need scrubbers and it requires less amount of GAC;
  
• Does have a very low downtime;
  
• Does require minimal maintenance; and
  
• Is greatly energy efficient & environmentally friendly equipment for environmental remediation.

Originally written by Alex Palmer (alexp@ramcocompanies.net) and Dr. Anna Doro-on, RAMCO Environmental Inc. California USA.

Further Reading

1. EPA finds Keysor is Superfund Site 

2. Cleaning Up Santa Clarita Valley, California

3. Former Vinyl Chloride Plant Cleanup

4. Whittaker Bermite Brownfield Hazardous Site 

5. Environmental Remediation 

6. Soil Clean up Criteria (US Environmental Protection Agency)

7.Soil Remediation Methods 

8. Soil Remediation (Texas, TCEQ)

9. Soil Vapor Extraction and Bioventing 

10. Soil Vapor Extraction Technology Resource Guide (US Environmental Protection Agency)

1. 
   
   1. Linde Cirrus VEC System 

12.Clean-up Plan for Whittaker-Bermite Project Available for Review and Public Comment (EPA 2010) 

13.Recovery of Organics Compound 

14. EPA Enforcement Reduces Threat from Polyvinyl Chloride (PVC) Manufacturing Plants 

15. Toxic Found at Plastics Site Soil, Water at Saugus Plant Could Cleanup EPA Finds Keysor is Superfund Site Acreage Needs Cleanup, Say Federal Experts

Related Titles on Water Treatment from IWA Publishing