Simulated dead volume

Table I indicates good agreement between the molecular weight distribution statistics obtained by coupled GPC/Viscometer method and the nominal values for t BS 706. The discrepancy between the Mark-Houwink parameters obtained here and the reported values for polystyrene standard ( ) in THF at 25°C (i.e., a = 0,706 and k = 1.60 x 10 ) may in part be due to the uncertainty involved in the determination of the dead volume between DRI and viscometer detectors. Our simulation studies over a range of dead volume values (0 to 120u)l) showed that a and k are quite sensitive to the dead volume between the detectors. Larger dead volume results in smaller o and larger k values. This is a direct result of a clockwise rotation of log [q] vs. log M(v) curve (Figure 12) which occurs when the dead volume correction is applied in quantitative analysis. The effect on the molecular weight statistics, however, appeared to...

The effect of solvent composition on the retention of a series of solutes, commonly used to measure column dead volumes, was also investigated by these authors. They employed mixtures of methanol and water as the mobile phase and measured the retention volume of the same salts together with a silica gel dispersion (containing particles 0.002 micron in diameter). They also measured the retention volume of the components of the mobile phase methanol, and water. The silica dispersion was chosen to simulate a solute of very large molecular size. The results they obtained are shown in figure (2). 

To simulate an SMB process, the model parameters of the individual columns (Section 6.5) and, if necessary, the dead volumes (Fig. 6.37) must be known. 

Simulations were performed using the extended SMB model (Fig. 6.37), which included dead volumes and synchronous as well as asynchronous port switching. The latter accounts for the dead volume in the recycle stream, which is the dominant contribution (Hotier and Nicoud, 1995 and Migliorini et al., 1999). As mentioned in the previous section, the temporal concentration profiles are shown and the partitions of the time axis mark the switching time. The additional time added after the eighth period is the asynchronous switching time. 

Hotier, G., Nicoud, R.M. Separation by simulated moving bed chromatography with dead volume correction by desynchronization of periods, Europaisches Patent, EP 688589 Al, 1995. 

Migliorini, C., Mazzotti, M., Morbidelli, M. Simulated moving-bed units with extracolumn dead volume, AIChE/., 1999, 45, 1411-1421. 

Both laboratory experiments and computer simulations have shown that the random close packing of equal-sized, spherical-shaped particles occupies a volume percentage of 64%. It follows that, if we want to eliminate porosity in such a system, then we must fill the remaining 36% of space (the dead volume ) with an inert binder. By contrast, if we want to retain some porosity, then a certain fraction of the dead volume must be kept free of binder. On the basis of a 50/50 compromise between electrode cohesion and solution access, one may therefore reasonably conjecture that the volume percentage of inert binder should be 18%, and indeed this is a good starting point in the laboratory development of inks from equalsized, spherical-shaped particles. 

What effect does the pipe segment volume have on the response Did the PFR properly simulate dead time in this situation Why or why not ... 

Capacity-dominated processes are relatively easy to control. However, the presence of dead time makes the control problem more difficult. We can demonstrate this hy adding a PFR to the system shown in Figure W4.1 in order to simulate dead time (Figure W4.2). The PFR should have a length of 2.0 m, a total volume of 0.5 m (dead... 

Build a new system consisting of two streams, two tanks, and a mixer using the Wilson thermodynamic package. Pick any two components that are liquid phase at ambient temperatures. The first stream should be pure component A at 25°C and 100 kPa. The second stream should be pure component B at the same temperature and pressure. Set the flow of the first stream to 400 kg h and the second stream to 100 kg h These flows are consistent with the desired ratio of 4 1 between components A and B. The tanks are used to simulate dead time in the system, so choose relatively small volumes for the tanks and locate them in series with the first stream. Both tanks should be on level control rather than liquid flow control. Simulate process noise with a sine-wave input to the first stream using an amplitude of 50 kg h and a period of 10 min. The system should resemble the one shown in Figure W6.4. 

Initially, a fixed-bed reactor with no separation was tested. The reactor was packed only with the catalyst and inert filler material with no adsorbent. Further, the feed gas propene (9% by volume) was mixed with helium as a carrier. No separation via PSR operation was imposed on the reactor contents. Fig. 8 shows that the steady-state conversion of propene is significantly less than 1% (about 0.03%) and the product recovery is almost negligible. The slight time lead in simulation is due to nonaccounting of the dead time in experiments. The estimated equilibrium conversion from thermodynamics is about 24 /o based on pure propene feed. Thus, the conversion in a fixed-bed reactor is far below the equilibrium conversion. 

Figure 13 In vitro assessment of aerosol output in the European Standard. A simulated breathing pattern of 500 mL tidal volume and 15 breaths per minute is generated by a breathing machine in a sinus flow pattern. A low-resistance electrostatic filter at the patient interface collects all inhaled aerosol, which can he subsequently analyzed. Dead space in the tubing and filter is required to be <10% of tidal volume (i.e., <5 mL).

Thus, a combination of reactor types might be used to simulate an actual reactor. In addition, the flow rates and/or volumes provide adjustable parameters which can be chosen to fit response data, i.e., modifications in the geometric model and phys-ical/chemical system can be made to better fit conversion data. Bypassing (the equivalent in some cases of dead space) can also be included in the analyses. 

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