Kinetic investigation of the oxidation of naval excess hazardous materials in supercritical water for the design of a transpiration-wall reactor Page: 6 of 43

                                
Introduction

Supercritical water oxidation (SCWO) technology has been demonstrated in the
laboratory to be a technically viable waste treatment method for many organic
wastes including hazardous wastes generated by routine activities on naval vessels.
In 1994, Defense Advanced Research Projects Agency (DARPA) issued BAA #94-45
to address the on-board remediation of these excess hazardous materials (EHMs). A
contract was awarded by DARPA to be administered in conjunction with the Office
of Naval Research (ONR) to Foster Wheeler Development Corporation (FWDC).
With its partners, GenCorp Aerojet and Sandia National Laboratories, FWDC is
developing a SCWO reactor and its supporting systems for this particular
application. This team elected to design, fabricate, and test a supercritical water
oxidation unit based on a novel reactor design that can effectively solve corrosion
and scaling problems that have hindered the widespread application of SCWO. The
design of the Transpiration Wall Reactor (TWR)1 is based on the principle of
containing the reacting material inside a double-walled vessel in which an outer
wall provides pressure containment and an inner wall is constructed using
transpiration platelet technology.2
Sandia's role is to provide engineering design data and laboratory scale
development and testing. This activity is divided into two phases. Phase 1 is
structured as a series of kinetic measurements on several representative EHMs and
potential auxiliary fuels to examine the relative reactivity of these materials as a
function of temperature for two purposes: 1) determining the reaction time required
to achieve a particular destruction efficiency, and 2) evaluate EHMs and other fuels
as candidates for the supplemental initiation fuel in the reactor feed injector. This
report contains the results and analysis from these tests.
The purpose of the Phase 1 testing at Sandia is not to prove that the Transpiration-
Wall reactor design strategy works. That is the purpose of the Phase 2 and final
system testing. The purpose of the Phase 1 experiments is to generate critical design
parameters for the full-size reactor with respect to temperature and reaction time
operating conditions. Because the reactor is based on transpiration wall technology,
many of the issues such as scaling and corrosion associated with an externally
heated tubular configuration or autogenic vessel design3 are not as important. On
the other hand, the key issues associated with the transpiration wall technology are
the reaction initiation rate and subsequent heat management requiring a careful
selection of operating and physical design parameters. However, an EHM       that
would be considered challenging to process in a "first generation" SCWO system
because of scaling or corrosion, may not be especially difficult in a TWR system.
Most of the experiments described here were conducted in Sandia's Supercritical
Fluids Reactor (SFR). This reactor is designed to produce a constant flow rate of
supercritical water and reactants at a fixed and constant temperature. The fuel and
oxidizer are mixed rapidly at a fixed point and samples can be withdrawn, quenched

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