I. "Yamamoto

N. Kobayashi

T. Shiozaki

T. Sugiyama

T." Uda

Y. Abe

Y. Asakura

Y. Enokida

National Institute for Fusion Science (NIFS-Repository)

§ 9. Hydrogen Isotope Separation byHydrogen-Water Chemical ExchangeReaction under Reduced PressureYamamoto, I., Enokida, Y., Kobayashi, N., Abe, Y.,Shiozaki, T. (Nagoya Univ.),Sugiyama, T., Asakura, Y., Uda, T.g/min at 12.1 kPa. Reflux liquid and hydrogen gas from theupper part of the column and effluent liquid from the lowerof the column were sampled in every 1 hour. The isotopicratio of the hydrogen in the sample was measured by massspectrometer for the stable isotopic ratio measurement.Separation factor aT was defined with isotopic ratio of HDto Hz, R HDIHZ, asaT =RHDIHZ(top of the column) / RHDIHZ(bottom of the column).Tab. 1 Comparison in different operating pressureOperating pressure [kPa] 101.3 12.1Equilibrium temperature [DC] 70 40The comparison of result at 101.3 kPa and that of at 12kPa is summarized at Table 1. The value calculated with thetheoretical plate model was also described. Clarified point issummarized in the following.(1) Process temperature could be lowered without reducingthe water vapor proportion by decompressing thecolumn, and it could obtain more large separation.(2) From the comparison with the calculated value, it wasproven that the equipment sufficiently demonstrated theperformance under reduced pressure.4.103.771 : 1.12: 2.62.563.311 : 0.27: 2.6Ratio of molar flow rateHydrogen: Vapor: LiquidaT (Estimated) [-]aT (Experimental) [-]When we carry out the LHD deuterium experiments, largeamount of tritiated drainage will be discharged by theexperiments. The tritium concentration of the drainage,however, is very low and we want reduce the volume of thedrainage by means of isotope separation (i.e., tritiumenrichment), and have adopted hydrogen-water chemicalexchange method to the system of isotope separation for theLHD deuterium experiments.The equilibrium constant of the isotopic exchangereaction, which is a measure of degree of separation,becomes larger when the temperature decreases. Then thelowering the process temperature will improve separativeperformances of the process, but, at the same time, willdeteriorate the performances because partial pressure, whichis a measure of throughput, of water decreases. As a methodfor lowering the process temperature without reducing thesteam partial pressure, we newly devised the method todecompress inside of the separation column. In this paper,the experiments with this method are reported.Cooling unitGas samplingii) Experiments under reduced pressureSeparation experiments were carried out at 70 DC underthe atmospheric pressure (101.3 kPa) and 40 DC underreduced pressure (12.1 kPa). Flow rates of hydrogen gas and 1)water are 2.0 NL/min and 4.1 g/min, respectively. Flow ratesof water vapor become 0.44 g/min at 101.3 kPa and 1.8i) Experimental apparatusSchematic drawings of the experimental apparatus newlyconstructed are shown in Figure 1. In the separation columnof 25 mm inner diameter and of 90 cm total length Kogelcatalyst (made of Showa engineering, 4.0"'-'6.7 mm particlesize, platinum-supported quantity 0.8 w-%) and DixonGauze Ring (6 mm diameter, 6 mm height) were alternatelyfilled. Heights of each layer are 5, 15 cm, respectively. Thenatural hydrogen gas which moisturized by the humidifierwas supplied from the lower of the column. The distilledwater was made to flow from the upper part of the column,and the same quantity of water was discharged from thelower of the column. Degree of vacuum in the separationcolumn was controlled in constant value using scroll typevacuum pump and vacuum control unit.416

Hydrogen Isotope Separation by Hydrogen-Water Chemical Exchange Reaction under Reduced Pressure

Hydrogen Isotope Separation by Hydrogen-Water Chemical Exchange Reaction under Reduced Pressure

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