Gas separation: processes – Selective diffusion of gases – Selective diffusion of gases through substantially solid...
Reexamination Certificate
2000-02-28
2001-12-25
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
Selective diffusion of gases
Selective diffusion of gases through substantially solid...
C095S289000, C096S004000, C096S013000, C096S221000
Reexamination Certificate
active
06332914
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method and apparatus for separating and recovering hydrogen isotopes such as deuterium (D) and tritium (T) for the production of a deuterium and tritium-enriched water or hydrogen gas. More specifically, the present invention discloses the application of a proton exchange membrane (PEM) for separating and recovering heavy and light hydrogen isotopes. This method could be used, for example, for separating heavy water (D
2
O and DHO), tritiated heavy water (DTO) and super-heavy water (T
2
O and THO) from light water.
BACKGROUND OF THE INVENTION
At the present time, a number of various processes are available for separating and recovering deuterium and tritium, wherein deuterium (D) and tritium (T) refer to elemental hydrogen isotopes having either one or two additional neutrons respectively in a hydrogen nucleus.
A temperature exchange process is one of such processes that utilize isotope exchange reactions between the hydrogen compounds. The reactions utilize such an isotope effect that, for example, when water and hydrogen sulfide gas, each at the same deuterium concentration, are mixed together the deuterium concentration in water will become higher than that of the hydrogen sulfide gas in the equilibrium state.
Also known in the prior art is the use of a dual temperature isotope exchange system that separates and enriches hydrogen isotopes with higher efficiency. This process is basically a combination of two temperature exchange reactors, one at a low temperature and the other at a high temperature. The exchange reactions to be utilized in the dual temperature process include exchange reactions between water and hydrogen sulfide gas. The exchange reaction between water and hydrogen sulfide gas has an advantage that it avoids the necessity of the use of a catalyst in the reaction, but has a disadvantage in that the separation coefficient dependent upon chemical equilibrium is small.
The use of the catalyst substantially promotes an exchange reaction rate between water and hydrogen sulfide gas. For this reason, the development of a hydrophobic, highly efficient isotope exchange reaction catalyst has progressed greatly.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for separating and recovering hydrogen isotopes that avoids the disadvantages of the prior art, is more simple, and allows for continuous hydrogen isotope separation and recovery.
The disclosed invention does not require the use of isotope exchange reaction catalysts and/or hydrogen sulfide gas. The present invention achieves the advantages of the thermal diffusion and the chemical exchange processes. The disclosed invention provides a method for separating and recovering hydrogen isotopes from a fluid containing the hydrogen isotopes by providing counter-current cold and hot streams of the fluid containing the hydrogen isotopes separated by a proton exchange membrane made of thermally insulating and chemically transparent material that allows exchange of heavy and light hydrogen isotopes therethrough. The heavier isotopes migrate to the cold stream producing a deuterium and tritium-enriched fluid, while lighter isotopes migrate to the hot stream producing a lighter isotope-enriched fluid. The heavy and light isotopes are withdrawn from the cold and hot streams respectively.
According to the present invention, the fluid is water or hydrogen gas, and the desired hydrogen isotope species are deuterium and/or tritium.
Further, according to the present invention, the streams of said high and low temperature fluids are interconnected at their respective top and bottom ends forming a continuous loop, and a feed stream is provided at an intermediate portion of either hot or cold stream to feed the process.
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Lee Myung W.
Lee Younghi Shon
Caress Virginia B.
Durkis James
Gottlieb Paul A.
Lee Younghi Shon
Spitzer Robert H.
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