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Using Supercritical Water Oxidation to Treat Hydrolysate from VX Neutralization (1998) / Chapter Skim
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4 Scale-Up, Stability, and Reliability
Pages 35-40

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From page 35...
... These include better management of salts/solids, better understanding of the phase behavior and kinetics/flow dynamics for scale-up, a better understanding of the corrosion characteristics of potential materials of construction, and the development of process monitoring and control regimes. Because a fundamental understanding of the fluid dynamics, mixing processes, and reaction kinetics occurring in a SCWO reactor does not exist, process scale-up has been based on reactor residence time, engineering judgment, and significant pilot-scale testing.
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From page 36...
... considerable shutdown and start-up time and, depending on frequency, could result in additional thermal and pressure stresses on system components. Large quantities of precipitated salts left in a reactor could significantly reduce reactor volume, with commensurate shortening of residence times, thereby leading to reduced DREs (destruction removal efficiencies)
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From page 37...
... However, this approach would require continuous feed of supple mental fuel, and a proportionate scale-up of all process components after the neutralization process step; it would also potentially increase process complexity and substantially increase capital and operating costs. Therefore, this option should be considered only if additional pilot-scale testing indicates that SCWO op eration at the currently specified hydrolysate concentra tion is not practical.
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From page 38...
... The most critical impact of changes in fluid dynamics could be on the transport of salts out of the reactor at reduced shear stresses, which may result in increased salt adhesion, reactor plugging, or lower conversion efficiencies. In the pilot-scale reactor, the solid salts were carried out by the flowing fluid intermittently with reasonable frequency (e.g., less than 30 seconds between peaks)
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From page 39...
... Additional data on materials lifetimes and failure modes under SCWO conditions representative of those with VX/NaOH hydrolysate will be necessary for making informed selections of reactor construction materials and operating parameters. Current information is insufficient for the confident selection of materials.
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From page 40...
... Given that the Army's schedule does not permit substantial fundamental work on VX hydrolysate to identify and measure fundamental data (e.g., kinetics, reaction order, fluid dynamics and mixing, corrosion, and salt nucleation and precipitation) , a substantial amount of pilot-scale work should be done to define the engineering parameters more confidently and to resolve the issues of scale-up and materials of construction discussed above.
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Key Terms

  • precipitated salts
  • fluid dynamics
  • scwo reactor
  • scwo process
  • pure oxygen

  • heat capacity
  • stoichiometric excess
  • percent excess
  • design calls
  • percent stoichiometric

  • ton container
  • supercritical water
  • excess oxygen
  • pilot testing
  • container cleanout

  • spent decontamination
  • reactor inlet
  • cold feed
  • inorganic salts
  • exit gas

  • destruction removal
  • fundamental understanding
  • reactor walls
  • cold water
  • rapid mixing

  • solid salts
  • reaction temperature
  • scwo conditions
  • residence time
  • heat balance


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