Reactor hydrogen chemistry

Sodium occurs widely as NaCl in seawater and as deposits of halite in dried-up lakes etc. (2.6% of the Earth s crust). The element is obtained commercially via the Downs process by electrolysis of NaCl melts in which the melting point is reduced by the addition of calcium chloride sodium is produced at the steel cathode. The metal is extremely reactive, vigorously so with the halogens and also with water, in the latter case to give hydrogen and sodium hydroxide. It is used as a coolant in fast-breeder nuclear reactors. The chemistry of sodium is very similar to that of the other members of group 1. 

The BWR water chemistry parameters are given in Table 4 (19). Originally, no additives were made to feedwater—condensate or the primary water. The radiolytic decomposition of the fluid produced varying concentrations of O2 in the reactor vessel, ranging from about 200 ppb O2 in the reactor recirculation water to about 20 ppm O2 in the steam. Stoichiometric amounts of hydrogen were also produced, ie, 2 mL for each mL of O2. Feedwater O2 was about 30 ppb, hence the radiolytic decomposition of the water was a primary factor in determining the behavior of materials in the primary system and feedwater systems. 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

Novel Processing Schemes Various separators have been proposed to separate the hydrogen-rich fuel in the reformate for cell use or to remove harmful species. At present, the separators are expensive, brittle, require large pressure differential, and are attacked by some hydrocarbons. There is a need to develop thinner, lower pressure drop, low cost membranes that can withstand separation from their support structure under changing thermal loads. Plasma reactors offer independence of reaction chemistry and optimum operating conditions that can be maintained over a wide range of feed rates and H2 composition. These processors have no catalyst and are compact. However, they are preliminary and have only been tested at a laboratory scale. 

Glaze, W Kang, J. Advanced oxidation processes. Test of a kinetic model for the oxidation of organic compounds with ozone and hydrogen peroxide in a semi batch reactor, Industrial and Engineering Chemistry Research, 1989 28, 1580-1587. 

The solubility of hydrogen in oil without propane can be seen at the baseline between the oil and the hydrogen in Fig. 9.3-4. The same point is illustrated by "cgi" in Fig. 9.3-2. The stoichiometric need of hydrogen depends on the reaction, but generally it is above 50 mol%. Full hydrogenation of a soybean oil requires more than 85 mol% hydrogen. To maintain the chemistry in the reaction, this ratio of oil to H2 has to be maintained also when a solvent is added ( see the dotted line in Fig. 9.3-4). For technical reasons, the stoichiometric need has to be exceeded to some extent. Thus, the composition of the feed to the reactor must be to the right of the dotted line, i.e., need in Fig. 9.3-4. 

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