Concentric-tube Thermal Diffusion Columns Research Articles

Recovery of deuterium from H–D gas mixture by thermal diffusion in a multi-concentric-tube column device of fixed total sum of column heights with transverse sampling streams

The effect of the increment in the number of concentric-tube thermal diffusion columns on the recovery of deuterium from H 2–HD–D 2 system with fixed total sum of column heights, has been investigated. The equations for predicting the degrees of separation in single-column, double-column and triple-column devices have been derived. Considerable improvement in recovery can be achieved if a multi-column device with larger number of column is employed, instead of a single-column device with column height equal to the same total sum of column heights, especially for the case of higher flow-rate operation and larger total sum of column heights.

Improvement in deuterium recovery from water–isotopes mixture by thermal diffusion in the concentric-tube device of branch columns

The remixing effect due to the forced convection-currents in a continuous-flow concentric-tube thermal-diffusion column for enrichment of deuterium from water–isotopes mixture can be reduced by employing the device of branch columns, instead of the device of single column, with the same total column length. The improvement in deuterium recovery increases when the flow rate or the total column length increases. It is found that the improvement can reach about 50% for the numerical example given.

Theory of recovery of deuterium from water–isotopes mixture in spiral wired thermal diffusion columns of the Frazier scheme

A separation theory for the recovery of deuterium from water–isotopes mixture in the Frazier scheme of concentric-tube thermal diffusion columns with a tight fitting wire spiral, having a diameter equal to the annular spacing, wrapped on the entire inner tube, has been developed. Equations of the optimal wire angle of inclination for maximum separation, maximum production rate and minimum column height have been derived. Considerable improvement in performance is obtainable if the wire spiral is employed in the column at the optimum inclined wire-angle, instead of the absence of wire spiral, so that the convection strength can be properly reduced and controlled, resulting in suppression of the undesirable remixing effect while still preserving the desirable cascading effect.

Recovery of deuterium from the separation of H–D gas mixture in concentric-tube thermal diffusion columns with transverse sampling streams

The separation equations for predicting the recovery of deuterium from H–D gas mixture in a concentric-tube thermal diffusion column with transverse sampling streams, have been derived. The effects of column length, volume flow rate and operating pressure on the performance have been discussed. The degrees of separation, as well as separation factors, for deuterium recovery in the cryogenic-wall thermal diffusion columns were estimated, with the use of the transport coefficients correlated in the previous work from the experimental data obtained by Arita et al. The separation efficiencies obtained in feeding by transverse sampling streams are rather lower than those achieved by middle feeding.

Numerical model for separation of H–D gas mixture in batch-type concentric-tube thermal diffusion columns

The modeling simulation for the separation of H–D gas mixture in batch-type concentric-tube thermal diffusion columns have been analyzed from the transport equation coupled with the application of mass balance. The most important assumption is that the concentrations of H 2, HD and D 2 are locally equilibrium at every points in the column as H 2 + D 2 ↔ 2HD. The concentration distribution equation was derived and the concentration difference between the bottom and top ends of the column could be estimated. The degree of separation and separation factor for recovery of deuterium from H–D gas mixture in the batch-type cryogenic-wall thermal diffusion column were estimated.

Optimal rotating speed in a rotated wired thermal diffusion column with transverse sampling streams

Rotating the tubes oppositely in a transverse-flow concentric-tube thermal diffusion column inserted as a spacer in the annular region with a wire spiral, having a diameter equal to the annular spacing, was investigated. Equations of the optimal tube speed of rotation for maximum separation and maximum output have been derived. Instead of using the stationary column without wire spiral, considerable improvements in performance are obtainable if a rotated wired column is employed operating at the optimal tube speed of rotation to create the desirable cascading effect while still suitably suppressing the undesirable remixing effect.

Improvement in recovery of deuterium from water-isotope mixture in concentric-tube thermal diffusion columns

Application of thermonuclear fusion with deuterium for power generation may become a reality in the distant future. The recovery performances of deuterium from water-isotope mixture in various concentric-tube thermal diffusion columns, such as open, wired and rotated wired devices, have been compared with different flow-rate range operations. It was found that the operation in a concentric-tube column with a wire spiral inserted in the annular spacing and with tubes rotated in opposite directions, will reduce the remixing effect and enhance the cascading effect, respectively, resulting in improved performance.

THERMAL DIFFUSION IN SPIRAL WIRED COLUMNS WITH TRANSVERSE SAMPLING STREAMS

The equations that may be employed to predict the optimum wire angles of inclination for performance in a concentric-tube thermal-diffusion column with a tight-fitting wire spiral, having a diameter equal to the annular spacing, wrapped on the entire inner tube, and operating with transverse sampling streams, have been derived. Considerable improvement in performance is obtainable if the wire angle is adjusted at the optimum angle, instead of the absence of a wire spiral, so that the convection strength can be properly reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect. Accordingly, essential savings in fixed charges and operating expense can be achieved, particularly for lower production rate operations or for a smaller degree of separation.

Enrichment of heavy water in rotated wired concentric-tube thermal diffusion columns

The enrichment performances of heavy water in various concentric-tube thermal diffusion columns, such as open, wired and rotated wired devices, have been compared with different flow-rate range operations. It was found that the operation with a wire spiral inserted in the annular spacing and with tubes rotated in opposite directions will reduce the remixing effect and enhance the cascading effect, respectively, resulting in improved the separation.

Recovery of deuterium from water–isotopes mixture in concentric-tube thermal diffusion columns inserted with wire spiral for improved performance

The optimal wire angles of inclination for maximum recovery, maximum production rate and minimum column height in a continuous-type concentric-tube thermal diffusion column inserted with a wire spiral for the improvement in recovery of deuterium (D) from water–isotopes mixture (H 2O–HDO–D 2O), have been determined. Considerable improvement in performance is obtainable if the wired column is operated at the optimal wire angle of inclination, instead of operating without wire spiral, so that the convection strength can be properly reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect.

The best performance in spiral wired thermal diffusion columns

The Improvement in performance of a concentric tube thermal diffusion column by means of a wire spiral, having a diameter equal to the annular spacing and inserted as a spacer in the annular region, was investigated. Equations of the optimum wire angle of inclination from the vertical for the maximum separation, maximum output and minimum column height have been derived. Considerable improvements in performance are obtainable if the spiral wired columns are employed, instead of using the open column (without wire), so that the convection strength can be reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect.

Enrichment of Heavy Water in Spiral Wired Thermal Diffusion Columns of the Frazier Scheme

A separation theory for the enrichment of heavy water in the Frazier scheme of concentric-tube thermal diffusion columns with a tight fitting wire spiral, having a diameter equal to the annular spacing, wrapped on the entire inner tube, has been developed. Equations for the best wire angle of inclination for maximum separation, maximum production rate and minimum column height have been derived. Considerable improvement in performance is obtainable if the wire spiral is employed in the column at the optimum angle, instead of the absence of wire spiral, so that the convection strength can be properly reduced and controlled, resulting in suppression of the undesirable remixing effect while still preserving the desirable cascading effect.

A Study of the Graetz Problems in Concentric-Tube Continuous-Contact Countercurrent Separation Processes with Recycles at Both Ends

Abstract A mathematical model for the concentric-tube square-off continuous-contact countercurrent separation process with recycles at both ends is developed to predict the concentrations of product. An analytical solution is obtained by means of the orthogonal expansion method. It has been found that only the positive eigenvalues for the enriching section and the negative eigenvalues for the stripping section are required during the calculation of the concentrations of product. Numerical results are presented for the separation of a benzene-n-heptane mixture in a concentric-tube thermal diffusion column.

A Study on the Separation Efficiencies of Rotating-Tube Wired Thermal-Diffusion Columns under Higher Flow-Rate Operations

Abstract Even under higher flow-rate operations, σ > 0.42A 2, rotating the tubes oppositely in a wired concentric-tube thermal diffusion column still substantially increases the separation efficiency by improving the cascading effect. The equations for estimating the best tube speed of rotation and maximum separation, with the inclination of the wire angles as parameters, have been derived. The maximum separation increases as the inclination of the wire angle decreases; however, this also leads to increasing the best tube speed of rotation and thereby raising the operating cost.

Improvement in Separation of Concentric-Tube Thermal Diffusion Columns with Viscous Heat Generation under Consideration of the Curvature Effect

Abstract The separation efficiency of concentric-tube thermal diffusion columns with viscous heat generation has been investigated under consideration of the curvature effect. The results were obtained graphically and were compared with those obtained by Yeh and Cheng in which they neglected the curvature effect. Considerable improvement in separation was obtained by employing a rotary column instead of a stationary one.

A study of the separation efficiency of rotated concentric-tube thermal diffusion columns with helical plane inserted as a spacer in the annulus.

A study of the separation efficiency of rotated concentric-tube thermal diffusion columns with helical plane inserted as a spacer in the annulus.

A study of the separation efficiency of wired thermal diffusion columns with tubes rotating in opposite directions

Rotating the tubes oppositely in a wired concentric-tube thermal diffusion column substantially increases the separation efficiency by improving the cascading effect. Considerable improvement in separation was obtained by employing the rotating wired column, operation at the best tube-speed of rotation and the best wire-angle of inclination instead of using the stationary column without a wire spiral.

A study on the separation efficiency of rotary thermal diffusion columns

Adjustment of the velocity profile in a concentric tube thermal diffusion column substantially increases the separation efficiency by rotating outer tube. Considerable improvement in separation was obtained by employing the rotary column instead of using the stationary column.

The improvement in separation of concentric tube thermal diffusion columns

The improvement in the degree of separation of a continuous-type concentric tube thermal diffusion column by means of a wire spiral, having a diameter equal to the annular spacing and inserted as a spacer in the annular region, was investigated both theoretically and experimentally. It was shown that the undesirable remixing effect could be effectively reduced and controlled by this type of wire and a substanial improvement in separation efficiency attained. Experimental results for the benzene- n-heptane and toluene—isobutyl alcohol systems quantitatively confirm the prediction of theory.