Supercritical Water Oxidation

SCWO takes advantage of the unique properties exhibited by water when used above its critical point, 705°F and 3210 psi. The organic content of the waste feed is quickly and efficiently converted to carbon dioxide, water, and salts with negligible production of carbon monoxide, NOX, or SOX. SCWO exhibits unparalleled environmental compliance capabilities, without the need of a pollution-abatement system. The higher operating pressure, relative to alternative destruction processes such as incineration, results in a very compact unit design with high throughput capability.

For many toxic and hazardous wastes, the alternatives for safe disposal are becoming very limited. Deep well injection, open burning, and incineration are either restricted or completely unavailable in many areas and have become costly where they are still options. SCWO presents an economic alternative to these methods for many waste disposal applications.

GA is the world leader in SCWO development and operates several state-of-the-art pilot plants. GA has over 15 years of experience in the development and field demonstration of SCWO technology.

The US Air Force has been sponsoring Supercritical Water Oxidation development work at General Atomics for over 10 years. Much of the work has been performed in conjunction with the Army Defense Ammunition Center (DAC) under funding from the Joint Ordnance Commanders Group. During this time, the technology has evolved from laboratory hood experiments to full-scale units.

One of the earliest SCWO units built by General Atomics used for testing of the disposal of hydrolyzed solid rocket motor propellants

First pilot-plant-scale system for hydrolyzed propellants under the AF Large Solid Rocket Motor Disposal program.

SCWO pilot plant built by GA under DARPA funding for the destruction of chemical warfare agents. This unit was later modified and used by GA for extensive process parameterization tests under AF SCWO funding. Efforts led to a Joint Demonstration Test program conducted by GA for the AF and DARPA to produce a compact full-size SCWO unit for potential use on Navy aircraft carriers.

This program demonstrated that SCWO effectively and efficiently destroys virtually all excess hazardous materials generated on an aircraft carrier. These wastes are typical of many DOD military-industrial waste streams, thus showing the broad capability of the SCWO process. SCWO has been shown to be an environmentally friendly process capable of destroying a wide range of organic hazardous wastes streams, while meeting the most stringent US and European air, water, and solid waste discharge regulations.

SCWO system built and delivered to the DAC at McAlester Army Ammunition Plant for use in cleanup of waste streams associated with demilitarization of convention weapons. Improvements in the technology to transition from a hazardous waste disposal process to a hazardous waste conversion process are currently underway at GA.

Supercritical Water Gasification pilot plant built by GA to demonstrate conversion of organic waste streams into various forms of syngas fuel. Continued work on advances into the gasification technology is being performed under programs for the AF, DAC, and DARPA who are all anxious to extend the successes of SCWO into the resource recovery arena.

GA now offers Supercritical Water Oxidation systems for a wide range of applications. The systems can be fully automated and are modular, skid-mounted assemblies for fast and easy installation.

GA also offers technical support for permitting, operator training, and maintenance.

SCWO development presented a number of technical challenges. Two areas requiring considerable development were corrosion-resistant materials for hydrochloric, sulfuric, and other acids in the feed stream, and salts deposition, which becomes an issue if salts are in the feed or if the acids in the feed are neutralized. GA has performed comprehensive development programs in these areas and has established sound engineering approaches that resolve both of these issues. Extensive corrosion studies in the supercritical regime have led to a well-developed understanding of the behavior of materials at the temperatures and pressures encountered under SCWO operating conditions. This understanding has led to selection of advanced materials and engineering designs for key components of the system.

SCWO advantages include:

  • Very high destruction efficiencies
  • Low NOx and SOx
  • No dioxins or furans
  • Totally contained process
  • No smokestack
  • Simplified permitting
  • Relatively low temperature operation
  • Compact size
  • Competitive cost

Current SCWO Applications

A number of SCWO systems have been or are being built and delivered to customers. A system to treat pink and red water from TNT operations was provided to DAC for a facility in Korea (Korea System). A system to treat hazardous wastes and sewage sludge was provided to partner commercial companies in Japan for evaluation in the Japanese hazardous waste destruction market. (Japan System).  The Bluegrass chemical munition demilitarization plant will use SCWO systems to destroy hydrolysate from chemical agent and energetics neutralization operations (BGCAPP System).  A simplified SCWO system utilizing over 20 years of development experience is being supplied to Tooele Army Depot (TEAD System) for destruction of energetics hydrolysate from the CAD demilitarization plant. The Bluegrass Army Depot will use SCWO to destroy hydrolysate from the hydrolysis of excess explosives and propellants (BGAD System). A SCWO system is planned for waste treatment in a facility in Alaska (Alaska System).