Pumping intermittent

Flow injection analysis (FIA) (Ruzicka and Hansen), since 1975 In continuous flow, stopped flow or with merging zones (FIA scanning or intermittent pumping) Adapted voltammetric electrodes Membranes for Partial dialysis Membrane amperometry (Clark) Differential techniques (Donnan) Computerization, including microprocessors Special measuring requirements in plant control (to avoid voltage leakage, etc., Section 5.5)... 

The expressions shown in Table 6.1 all include constants that have been found good approximate values based on experiments. These values may of course be adjusted to account for specific cases. As an example, different flow conditions in continuously and intermittently pumped mains may affect the transfer of substances and products across the biofilm-water interface, and, thereby, the production of sulfide (Melbourne and Metropolitan Board of Works, 1989). 

In lead oxide (litharge) production, molten lead is intermittently pumped into a reactor where a series of rakes, mounted on a shaft which turns at 200 rpm, violently agitate the metal. The agitation forces the molten metal to form particles and improves gas-metal reactions. The reactions are exothermic oxidation. Air pulled... 

Fig. 4.14 Flow-injection assemblies for ion-exchange preconcentration of metal traces prior to introduction into an atomic absorption spectrometer. (A) Single-line manifold (B) three-valve system for upstream elution (C) automated assembly with intermittent pumping. (Reproduced from [11] with permission of the Royal Society of Chemistry).

Figure 2.25. The principle of zone merging (a) intermittent pumping (b) and zone penetration (c) showing, from left to right, the sample (5) zone and the reagent (R) zone separately, during the initial contact, and then merged further downstream.

A and B), Because the first pump is started (and the second one stopped) only when the next sample is being injected, this approach allows an increase in sampling frequency and saves reagent solution. A review article, demonstrating applications of the intermittent pumping procedure for various practical analytical tasks, has recently been published by Krug et al. [1060]. 

Impulse response Intermittent pumping Ne ted/Sp1it-1oop injection... 

FIGURE 35.8 Response profiles for different aqueous solutions obtained by intermittent pumping of organic... 

The term gas-pressurized liquid transfer" applies to a process in which the force required to pump the liquid is obtained from a high pressure gas that acts as a piston on the free surface of an upstream liquid reservoir. Ordinarily, liquids are transferred by pumps. Gas pressurized transfer systems may, however, be preferred to pumping systems in some cases. Infrequent, intermittent pump operation may not provide economic justification for the installation of large pumps, large standby power facilities, and associated control gear, A practical example which may be cited is the transfer of liquid propellants to missiles. Here, the transfer operation is quite infrequent, and must be carried out rapidly at a time when there is a maximum drain in the base power supply and with the minimum of heat energy transfer into the fluid. 

---