Review and Evaluation of Alternative Technologies for Demilitarization of Assembled Chemical Weapons (1999) / Chapter Skim
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3 AEA Silver II Technology Package
3 AEA Silver II Technology Package
Pages 36-57
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From page 36... ...
The output streams from the disassembly lines are either oxidized directly by SILVER II or are rendered ready for disposal. The technology provider proposes three separate SILVER II units: one for the destruction of chem~cal agent, one for the destruction of energetics, and one for the destruction and/or decontamination of dunnage (also, small metal parts, decontamination solutions, and other mixed wastes)
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From page 38... ...
Thus, the standard electrode potentials, E°, of the half-cell reactions for the desired electrolysis under standard conditions at 25°C (77°F) would be: Ag+ ~ Ag+2 + e~ E° = -1.98 V For an overall reaction: HNO3+2H++2e~ - HNO2+H2O E°= 0.94 V The overall reaction and standard potential for the electrolysis of the silver nitrate solution are therefore: 2Ag++HNO3+2H+ 2 Ag+2 + HNO2 + H2O E°= -1.04 V The electrode potentials at other concentrations are given by the Nernst equation: E = E° + RT in(Q)
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From page 39... ...
Table 3-4 shows the electrical energy requirements for the process in terms of energy per gram of material for a voltage of 2.0 V applied to the electrochemical cell. The technology provider claims that the total process will have 80 percent electrochemical efficiency (the fraction of current passing that produces useful oxidation to CO2~.
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From page 40... ...
A dilute nitric acid stream is also produced, which is recycled within the plant and used to prepare organic materials before they are fed into the SILVER II process. After leaving the NOx reformer, all off-gas passes through a caustic scrubber to remove residual NOx.
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From page 42... ...
In addition to this baseline processing, the mines are sheared into four parts to open the radial initiator charge and expose the energetic Treatment of Chemical Agent The chemical agent drained from the various components is transferred to an interim storage tank where it is mixed and continually stirred with dilute nitric acid recycled from the SILVER II process. The dilute nitric acid provides the necessary water balance for the electrochemical oxidation reactions in the agent SILVER II reaction circuit.
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From page 43... ...
ions are regenerated. Other reagents added to the anolyte vessel include calcium nitrate to precipitate CaSO4 and calcium fluoride, silver nitrate solution to maintain silver concentration (when chloride is present, silver chloride will precipitate)
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From page 44... ...
The evaporator bot toms, consisting of a silver nitrate/nitric acid solution, are returned to the anolyte circuit. The NOx reformer receives the vapor effluent from the nitric acid evapo rator and the off-gas streams from the anolyte and catholyte vessels.
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From page 45... ...
Silver chloride/filter candles Solids from anolyte solution generated during treatment of decontamination solution shipped off site for recovery of silver as silver nitrate. Caustic scrubber waste Dried salts from caustic scrubber shipped off site for disposal at a hazardous-waste landfill.
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From page 46... ...
Details/Comments Nitric acid Calcium sulfate Water Sodium nitrate Sodium nitrite Carbon dioxide Nitrogen dioxide TOTAL Solid and liquida TOTAL Off-gas Decontaminated metal parts 14.3 9.9 8.8 2.6 2.2 27.3 0.4 37.8 27.7 86 Produced as both a concentrated and dilute acid stream (mass quoted is for pure acid and does not account for any water of solution, which is detailed separately)
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From page 47... ...
and silver nitrate sludge in the spent anolyte and catholyte solutions. TABLE 3-9 Process Outputs for SILVER II per M55 Rocket The technology provider has estimated that 52,000 pounds of silver will have to be inventoried at Pueblo and 8,000 pounds of silver at Blue Grass.
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From page 48... ...
, with electrolytic regeneration of TABLE 3-11 Estimate of Spent Silver Sent for Recycling for VX-Filled M55 Rockets Source Form Mass Per Munition Silver Content Silver from spent anolyte and catholyte solutions Concentrated "sludge" following evaporation 4.2 lb of silver nitrate contained 64% by weight within the "sludge" Source: AEA, 1998b.
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From page 49... ...
These metals will all react vigorously with the nitric acid of the SILVER II reagent, causing very large quantities of metal ions to dissolve. The technology provider states that the added metal ions should not affect the reduction/oxidation reactions that destroy the agent and energetics; however, no data have been presented to show this.
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From page 50... ...
The technology provider calculated that the 14.62 kg of "as supplied VX" contained 7.21 kg of organic carbon. At the end of the run, the total organic carbon remaining in the anolyte and catholyte circuits was 0.816 kg.
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From page 51... ...
The committee identified several issues that need to be addressed during the scale-up of the process into a fully integrated system for the wide diversity of assembled chemical weapons. The key scaleup issues are discussed below.
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From page 52... ...
The committee did identify several issues (listed below) that should be addressed to ensure that the integrated technology could treat the full array of assembled chemical weapons: · behavior of the SILVER II reaction circuit with high concentrations of metals · effects of various metals on the electrochemical potential potential poisoning of electrodes by trace elements reaction times to destroy energetics and agent components completely · precipitation of silver chloride and recycling of silver from silver chloride materials Process Safety The SILVER II process requires the following unique equipment: a machine for handling sheared rocket parts SILVER II cells for the generation of Ag(II)
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From page 53... ...
Table 2~1
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From page 54... ...
54 Table 2-1 Throughput Rates Prescribed in the ACWA REP REVIEWOFALTERNATIVE TECHNOLOGIES Processing Rate Processing Rate Munition Agent (munitions/hr) (lb agent/hr)
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From page 55... ...
No data are available on the characteristics of the solid and liquid effluents of actual treatments of the components of assembled chemical weapons. Effluent Management Strategy The process effluents and treatment/disposal strategies proposed by the technology provider are listed in Table 3-5.
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From page 56... ...
Thus, the standard electrode potentials, E ° of the half-cell reactions for the desired electrolysis under standard conditions at 25°C (77°F) would be: Ag ~ Ag +e~ HNO3 + 2 H+ + 2 e~ ~ HNO2 + H2O E°= -~.98 V E° = 0.94 V The overall reaction and standard potential for the electrolysis of the silver nitrate solution are therefore: 2 Ag+ + HNO3 + 2 H+ ~ 2 Ag+2 + HNO2 + H2O E°= -~.04V The electrode potentials at other concentrations are given by the Nernst equation: E = E° + ~ 1~6Q)
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From page 57... ...
Finding AEA-6. Several issues need to be addressed during the scale-up of the process into a fully integrated system, including temperature control, reaction times, efficiency of the NOx reformer, cell flow management, efficiency of the hydrocyclone, and the tolerance of cells to particulate matter.
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