[en] An overall theory of column separation is developed. A general expression for fully-developed concentration fields is found. For close-separation processes, a simple method to derive the theoretical plate height and the stage efficiency from local equations are given. Application of separation-of-variables to linearized systems is discussed and a partial range completeness of the eigenfunctions is found. (author)

[en] An overall theory of column or square cascade separation has been developed on the basis of only a few assumptions, irrespective of the particular structure of the separating element or the involved physical-chemical processes. The main advantage of the theory is that it clarifies and facilitates the derivation of the mass transfer parameters. Using examples, it is demonstrated that well-known theories, e.g. that of the thermal diffusion column, can be reproduced. The theory is also applied to spray columns whose theory has so far been only slightly developed. (author)

[en] The analysed system consists of two plane-parallel walls, a water film flows down a wall, a catalyst layer is disposed on the other, a water vapour-hydrogen mixture moves up between the walls. A mathematical treatment is presented which permits to calculate the overall transfer coefficients and other parameters of practical interest from the local differential equations. (author)

[en] Lithium isotope separation by ⁶Li/⁷Li exchange between lithium-amalgam and aqueous LiOH has been investigated by using a column consisting of a vertical Pyrex glass tube in which aqueous LiOH flows up and a fine spray of lithium-amalgam falls down. As the number of theoretical plates, a value of 48 was obtained on a single column while the amalgam stability was η = 0.74, where η is the ratio between Li concentration in amalgam at the column bottom and that at the column top. That is, a large separation may be obtained in a single column in spite of amalgam decomposition which takes place as a side reaction. (author)

No abstract available

[en] The abstract and universal theory of the separation column, developed over years by the author, is presented. By specialization to concrete processes, the universal theory offers the most simple and rigorous way to derive particular theories. This quality is illustrated by an example of practical interest: the theory of hydrogen isotope separation by thermodiffusion with inclusion of isotopic exchange reaction at the hot wall. Comparison between derived results and related literature reveals an error in the classical treatment by Furry, Johns, and Onsager and shows that the so called 'forgotten effect' is of negligible importance. (author)

[en] In Romania heavy water is produced by H₂O-H₂S chemical exchange (GS process) and by water distillation, simultaneously working two lines. The distillation plants have high separation capacity, a distillation line being able to concentrate water from two GS lines. The paper presents data regarding possibilities to use one distillation line for oxygen 18 production, as pre-concentrates or finite products. Using a simulation program it was calculated oxygen 18 concentration in heavy water produced, maximum ¹⁸O concentration of pre-concentrate obtained on distillation line and the separation cascade dimensions for obtain 95% ¹⁸O, with first and second stage having same dimensions like a distillation plant from Romanian heavy water factory. Oxygen-18 separation factor is much lower than deuterium separation factor. For this reason, oxygen-18 is a very expensive product. (author)

[en] Full text: Oxygen-18 separation is carried out by distillation and electrolysis of water, cryogenic distillation of nitric oxide, thermal diffusion, chemical exchange reactions and membrane distillation. At present in the world water distillation, cryogenic distillation of nitric oxide and thermal diffusion procedures are applied. Water distillation is used at industrial scale. There is a source of water which has the ¹⁸O concentration greater than the natural abundance and the production cost is lower. Such a source is the heavy water. Current worldwide tendency is to turn to good account all existent availabilities. In Romania, there is such an availability at the heavy water plant at Drobeta Turnu Severin and at the former heavy water pilot plant at Ramnicu Valcea. This paper presents data regarding the possibilities to use one distillation line for oxygen-18 production as pre-concentrates or finite products. Using a simulation program, the ¹⁸O concentration of produced heavy water, the maximum concentration of pre-concentrate obtained on distillation line and the separation cascade dimensions (for 95 % ¹⁸O production) were calculated. It was assumed that the first and second stage have the same dimensions like those in place at the distillation plant at the Romanian Heavy Water Plant. Single stage separation factor of ¹⁸O is much lower than in the case of deuterium separation by the same method. For this reason, ¹⁸O is an expensive product. (authors)

[en] The paper deals with the mathematical models and the computational programs utilized in the design of installations for the deuterium separation by isotopic exchange in water-hydrogen sulfide system, by water isotopic distillation and by hydrogen isotopic distillation

[en] In Romania heavy water is produced by H₂O-H₂S chemical exchange (GS process) and by water distillation, in two lines working simultaneously. The distillation plants have high separation capacity, a distillation line being able to concentrate water from two GS lines. The paper presents data regarding possibilities to use one distillation line for oxygen - 18 production, as pre-concentrates or finite products. A simulation program was used to calculate the oxygen - 18 concentration in the heavy water produced, maximum ¹⁸ O concentration of pre-concentrate obtained on distillation line and the separation cascade sizes to obtain 95% ¹⁸ O, with first and second stage having the same sizes like the distillation plant from the Romanian heavy water factory. Oxygen-18 separation factor is much lower than deuterium separation factor. For this reason, oxygen-18 is a very expensive product. (authors)