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K ADDITIONAL DATA AND MATERIAL BALANCES FOR WET AIR OXIDATION, SUPERCRITICAL WATER 287 OXIDATION, AND THE SYNTHETICA DETOXIFIER Gas products: O2: 12 percent N2: 59 percent CO2: 29 percent Volume = 2,400.5 m3 at 25°C, 1 atm. Liquid product: H2O: 81.4 percent by weight NaF: 3.8 percent by weight Na3PO4 : 14.8 percent by weight Mass = 1,106 kg The product volumes are small enough to be easily retained long enough for analysis before discharge to the atmosphere. For example, for destruction of 1,000 kg GB/day and an 8-hour retention time of products: ⢠gas volume (eight hours) at P = 250 bars, 25°C: 3.2 m3; ⢠liquid (eight hours): 368 kg (about 0.368 m3); and ⢠upset conditions would lead to off-specification liquids, as well as possibly to off-specification gases. Provision for recycling would be required. A standard gas polishing unit, e.g., catalytic oxidation or carbon adsorption, would ensure gas quality before release. SYNTHETICA DETOXIFIER Heat and Material Balances Measured or design heat and material balances have not been disclosed. Estimates have been made, based in large part on operating conditions that have been presented: ⢠Temperatures in the moving bed evaporator (MBE): 1300°F (705°c) bottom 800°F (427°c) top ⢠Detoxification unit: T = 2400°F (1316°c) ⢠Adsorption beds: T = 350°F (177°c) Agent GB has been chosen for the calculated balances.
K ADDITIONAL DATA AND MATERIAL BALANCES FOR WET AIR OXIDATION, SUPERCRITICAL WATER 288 OXIDATION, AND THE SYNTHETICA DETOXIFIER The reactions desired in the Moving Bed Evaporator (MBE) are steam reforming and acid gas neutralization. The precise alkaline agent has not been specified; NaOH is shown in the equation below for illustration only. Steam reforming: Neutralization: The overall reaction in the MBE is then the sum of these: The gas product shown is CO and H2. Excess H2O is required for the reaction, however, to reduce some stable hydrocarbons to very low concentrations, (e.g., methane, ethylene, benzoyl chloride). Additional steam will then lead to the water gas shift reaction to form CO2: Equilibrium for this reaction is favorable at the temperature of the MBE (800°F outlet). The equilibrium shifts at higher temperature, however, so that little CO2 should remain in the gas leaving the high-temperature detoxifier. Estimated heat and material balances are shown below (see Figure K-2). These values are based on estimates and assumptions that may not conform to ''Synthetica'' operating practice, but that practice has not been fully disclosed.
K ADDITIONAL DATA AND MATERIAL BALANCES FOR WET AIR OXIDATION, SUPERCRITICAL WATER 289 OXIDATION, AND THE SYNTHETICA DETOXIFIER FIGURE K-2 Heat and material balances for the Synthetica System.
K ADDITIONAL DATA AND MATERIAL BALANCES FOR WET AIR OXIDATION, SUPERCRITICAL WATER 290 OXIDATION, AND THE SYNTHETICA DETOXIFIER Basis: 1,000 kg GB destroyed. Gas composition to the MBE (assumed): CO: 16.7 percent H2: 33.3 percent H2O: 50 percent Solid balls fed to the top of the MBE: Alkali: 10 percent by weight of (assumed NaOH) Alumina: 90 percent by weight Temperature = 800°F (427°c) The unit could be operated as an enclosed system; the gas volumes to be held up would be substantial, however, because the unit operates at atmospheric pressure. ⢠The product gas going to catalytic oxidation is shown as 171.4 tool, at 177°C. Assuming an 8-hour hold-up (24-hour operation) and that the holdup gas would be cooled to 40°C, the hold-up volume requirement would be 1,600 m3. This would consist primarily of CO and H 2; most of the water would have been condensed. ⢠The solid balls from the moving bed evaporator would mount to 4,830 kg over an 8-hour period (again assuming 24-hour operation). Electric power consumption in the detoxification reactor is large-estimated at 335 kW (24-hour operation). Some of the heat supplied is recovered in a series of heat exchangers. The heat requirement of the cold stream is much less than the heat content of the hot stream, however. Less than one-half of the hot stream enthalpy change is recovered; the rest is removed by addition of 100°C steam and by external cooling. The MBE requires heat; the reaction is endothermic, and the solid balls are heated in their passage through the unit. Sixty percent of the heat goes for heating the solids; 40 percent supplies the endothermic heat of reaction. The solids removed with the circulating balls consist of 1,356 kg of sodium fluoride and sodium phosphite together with a small amount of excess caustic. The sodium phosphite will require further oxidation to the phosphate for stability. The composition of the circulating gas is the product gas (CO/H2 ratio = 1/2) with 50 percent steam. The steam supply has been selected to be in 100 percent excess over the stoichiometric requirement. The product gas to the final catalytic oxidation unit has 50 percent steam as a
K ADDITIONAL DATA AND MATERIAL BALANCES FOR WET AIR OXIDATION, SUPERCRITICAL WATER 291 OXIDATION, AND THE SYNTHETICA DETOXIFIER consequence. (If the circulating gas had been chosen to be primarily CO and H2 and steam had been limited to near stoichiometric, this product gas would have contained about 10 percent steam.) The excess steam will be useful, however, in mediating the temperature in the catalytic oxidation unit. This temperature must be kept low to avoid formation of NOx and to maintain catalytic activity. The oxidation temperature would be very high without the diluent steam. The flow rate of the circulating gas is calculated to be 50 m3/minute. A reasonable diameter for the moving bed evaporator would then be 1.9 m; the superficial gas velocity would be 0.3 m/second (i.e., 1 ft/second). The absorption beds would be expected to be about the same diameter, i.e., 1.9 m. No effort has been made to prepare a material and energy balance for propellant or explosive. It would be very different. Their decomposition would be highly exothermic, and the electric power requirement of the detoxification reactor would be greatly reduced. Little acid gas would be formed, and solid salt formation would be negligible.
