Naval Station Norfolk (NSN), the world's largest naval installation, generates 3 million pounds of industrial waste annually. This industrial waste consists of large amounts of used paint, cleaning compounds and other chemicals, which are disposed off-site as hazardous waste. In the mid-1990s, NSN began to explore alternative methods to reduce its waste management costs and to limit future liability for the waste. In this project, a production-scale Plasma Arc Hazardous Waste Treatment System (PAHWTS) was designed and constructed for the purposes of validating the thermal plasma arc technology for hazardous waste destruction.
Plasma is a gas, to which a high amount of energy has been added, resulting in a collection of ions, electrons, charge-neutral gas molecules (or ions), free radicals and other excited gas species. Plasma can be described as either thermal or non-thermal. In a thermal plasma, the plasma constituents are in thermal equilibrium, and the high temperature may be used to melt and vitrify inorganic materials and to pyrolyze and/or combust organic materials. A plasma torch, which is essentially one or two water-cooled electrodes within a cylinder, may be used to generate thermal plasma in a controlled reactor.
The PAHWTS manufacturer, Retech, conducted a Factory Inspection Test (FIT) at its facility in Ukiah, California, prior to re-location of the plant to NSN for day-to-day operation. The operating test results from Ukiah were favorable and emissions were below regulatory limits. On the basis of reductions in the amount of hazardous waste being generated at NSN due to successful pollution prevention efforts and the poor projected payback for the PAHWTS, the Commander of Naval Region Mid-Atlantic decided to withdraw support for the project.
The best-case cost scenarios offer cumulative savings of $20-30 million over a 20-year lifetime as compared to off-site disposal of the hazardous waste. The payback period on the $9.4 million capital cost of the installed plant would be approximately 7-10 years.