Shifting interval

Next, we carry out a heat balance within each shifted temperature interval according to Eq. (6.1). The result is given in Fig. 6.17. Some of the shifted intervals in Fig. 6.17 are seen to have a surplus of heat... 

Next, calculate the shifted interval temperatures. Hot streams are shifted down by 2.5°C, and cold streams are shifted up by 2.5°C (Table 6.5). 

We have carried out the first measurement of the 2S /2 — 2P3/2 interval in 7V6+. Our result is in good agreement with the theory, but the precision of 0.07 cm-1, or. 17% of the Lamb Shift interval, is not sufficient to provide a useful test. However the count rates and signal-to-background ratio achieved, 100 kHz/particle-nA and 25 respectively, are consistent with obtaining a statistical precision of 0.001 cm-1. The beam current and detector solid angle can be increased in future experiments if necessary. 

Figure 5.18 illustrates the principle of SMB processes. The mobile phase passes the fixed bed columns in one direction. Counter-current flow of both phases is achieved by switching the columns periodically upstream in the opposite direction of the liquid flow. Of course, in a real plant the columns are not shifted but all ports are moved in the direction of the liquid flow by means of valves. The counter-current character of the process becomes more obvious when the relative movement of the packed beds to the inlet and outlet streams during several switching intervals is observed. After a number of switching or shifting intervals equal to the number of columns in the system, one so-called cycle is completed and the initial positions for all external streams are re-established. 

Importantly, sampling gives only a limited number of points in the axial profile. The complete curve can not be reconstructed from any temporal measurement, as the concentration fronts inside the columns change from the beginning to the end of the shifting interval. However, increasing the number of experimental samples per interval of course allows a comparison of the simulated temporal profile on a broader base without on-line measurement. 

The yield Yj of a process is the ratio between the amount of a product (component i) that can be collected in the outlet and the amount that was introduced into the system through the feed stream within a batch cycle. Due to the continuous operation mode in an SMB plant, both collected and introduced amount of component i are calculated within a shifting interval. 

In comparison with batch chromatography tt and t2 for an SMB plant are the beginning and the end, respectively, of a shifting interval. Furthermore, component i can be collected either from raffinate or extract stream. 

For an SMB plant the production rate must be determined within a shifting interval instead. 

After the process simulation applying the experimentally validated model, all axial concentration profiles are plotted in a dimensionless diagram using C /Cfeed, and L/Lc as axes. These profiles are taken at the end of a shifting interval from quasi-steady state. Figure 7.5 illustrates that all concentration profiles are completely identical. ... 

To apply the TMBR model for a SMBR process the flow rates have to be transferred. The solid flow rate can be calculated by taking into account the column length Lc and cross section Ac as well as the shifting interval, tshift ... 

The separation of an industrial feed mixture of fructose-glucose (Cfeed = 300 g 1 ) containing 6% sucrose as an impurity is displayed in Figure 6.44. Once again, good agreement between experiment and simulation is found. The individual concentration profiles of this three-component mixture cannot be determined by two-detection systems. Therefore, additional samples (two per shifting interval) were taken and analyzed by HPLC. 

D.A. Andrews and G. Newton, 1976, Radio frequency atomic beam measurement of the Lamb-shift interval in hydrogen,... 

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