Vertical processes

Vertical Pumps In the chemical industiy, the term vertical process pump (Fig. 10-40) generally applies to a pump with a vertical shaft having a length from drive end to impeller of approximately 1 m (3.1 ft) minimum to 20 m (66 ft) or more. Vertical pumps are used as either wet-pit pumps (immersed) or dry-pit pumps (externally mounted) in conjunction with stationaiy or mobile tanlcj... 

FIG. 10-40 Vertical process pump for dry-pit mounting. Coutiesif of Lawrence Pumps, Inc.)... 

Sump Pumps These are small single-stage vertical pumps used to drain shahowpits or sumps. They are of the same general construction as vertical process pumps but are not designed for severe operating conditions. 

In spectroscopy we may distinguish two types of process, adiabatic and vertical. Adiabatic excitation energies are by definition thermodynamic ones, and they are usually further defined to refer to at 0° K. In practice, at least for electronic spectroscopy, one is more likely to observe vertical processes, because of the Franck-Condon principle. The simplest principle for understandings solvation effects on vertical electronic transitions is the two-response-time model in which the solvent is assumed to have a fast response time associated with electronic polarization and a slow response time associated with translational, librational, and vibrational motions of the nuclei.92 One assumes that electronic excitation is slow compared with electronic response but fast compared with nuclear response. The latter assumption is quite reasonable, but the former is questionable since the time scale of electronic excitation is quite comparable to solvent electronic polarization (consider, e.g., the excitation of a 4.5 eV n — n carbonyl transition in a solvent whose frequency response is centered at 10 eV the corresponding time scales are 10 15 s and 2 x 10 15 s respectively). A theory that takes account of the similarity of these time scales would be very difficult, involving explicit electron correlation between the solute and the macroscopic solvent. One can, however, treat the limit where the solvent electronic response is fast compared to solute electronic transitions this is called the direct reaction field (DRF). 49,93 The accurate answer must lie somewhere between the SCRF and DRF limits 94 nevertheless one can obtain very useful results with a two-time-scale version of the more manageable SCRF limit, as illustrated by a very successful recent treatment... 

Specifically but not exclusively for the chemical industry, most pump manufacturers now build to national standards horizontal and vertical process pumps. ASME Standards B73.1—2001 and B73.2—2003 apply to the horizontal (Fig. 10-47) and vertical in-line (Fig. 10-48) pumps, respectively. 

Figure 14.2 Schematic relationship between vertical absorption and emission energies and the adiabatic energy difference between the ground and excited states. [Note that a more rigorous treatment requires inclusion of ZPVE and thermal contiibutions in the adiabatic energy difference, and consideration of Franck-Condon overlap between quantized vibrational states for the vertical processes some of these points are discussed in Section 14.5.]...

Given tlie disparate nature of the physical interactions between die different electronic states and the solvent, and the non-equilibrium nature of the solvation of at least one state in die vertical process, theoretical models require a fairly high degree of sophistication in their construction to be applicable to predicting spectroscopic properties in solution. This requirement, coupled with the rather poor utility of available experimental data (most solution spectra show very broad absorption peaks, making it difficult to assign vertical transitions accurately in the absence of a very complex dynamical analysis), has kept most theory in this area at the developers level. A full discussion is beyond the scope of an introductory text, but we will briefly touch on a few of die key issues. 

In principle, a great deal of information concerning intramolecular electron transfer is available from IT absorption band measurements. Optical electron transfer is rapid on the vibrational time-scale and, as illustrated in Figure 7, the optical transition is a vertical process in the Franck— Condon sense. 

Vertical Process.—A transition that conforms to the Franck-Condon principle. 

Unfortunately, the results are not as good as might have been expected. Whether the discrepancies originate from some inadequacy of the SCF calculation or from the invalidity of Koopman s theorem is, however, an open question. It is probably, to a first approximation only, that the removal of an electron from a molecular system can be considered as a "vertical process which leaves the distribution and energies of the... 

In this paragraph we will outline a general theory of non-radiative energy transfer with special interest to the vertical processes. First of all we define adiabatic levels for the total number of vibrational modes A. For the ground state minimum we define point A = 0 and we define the static vertical electronic basis through the relation... 

Figure 20-3. Electron binding energies for molecule M in anionic state are defined pictorially in a representation of the potential energy surfaces of the neutral molecule (M) and anion radical (M ) with the lowest vibration energy level shown for each. During a vertical process, the geometry remains unchanged but for the adiabatic process structural relaxation occurs. Thus the VDE (vertical detachment energy) and VEA (vertical electron affinity) represent the upper and lower bounds to the adiabatic electron affinity (AEA)...

Herschbach [58] noted a striking similarity between the recoil energy distribution of Cl atoms in the H + CI2 reaction and that observed in the photodissociation of CI2. This suggests that the electron attachment to the molecule is essentially a vertical process, hence he proposed the DIP extension to the model, which makes the AB repulsion after the electron jump analogous to that encountered in photodissociation experiments. This provided the necessary empirical basis for estimating the parameter of the repulsive interaction. All the mathematical expressions relevant to the model were given by Truhlar and Dixon [62]. Zare and co-workers extended the model to chemiluminescent reactions and a full account of the new model is given in Ref. [81]. It was used to predict successfully the product state distribution in the reaction Ca( So) -I- F2 —> CaF(B ) + F. 

Rectangular slabstock foams are more cost effective than conventional slabstock foams. The foams are produced by a horizontal process (36) and by a vertical process (123). 

In contrast, Ashida s patent (4) uses a vertical process, as shown in Figure 53. Vertically supplied glass mat is continuously fed int a two-sided release sheet. The mixed foam formulation is then applied onto the V-shaped release sheets. The mixture is immediately pressed by a squeezer which facilitates the impregnation of the foaming mixture into the strand mat, while at the same time, the squeezer controls the thickness of the resulting foamed composites. 

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