Recirculation mode

The recirculating mode of SFE has also been coupled successfully to commercially HPLC-MS systems, with... 

A small residence can even act as a shield. An individual can turn off the air circulation system (or switch it to recirculation mode), and close vents, windows, and doors to create a barrier that will help prevent contaminated smoke or other airborne debris from entering the home. Because a building may not always be nearby in the event of a terrorist attack, shielding could be provided from another object such as a car (with the vents closed), a folded handkerchief over the nose and mouth, or any object that reduces the potential of exposure. The shield does not have to be sophisticated it only needs to be effective. 

Switching the heating and air conditioning system to the recirculate mode to prevent pulling outside air into the building... 

The most common method of whole broth adsorption with particulate matrices is by fluidizing the particles. Development of a stable fluidized bed with an increased interstitial volume is the key to the purification of biomass-containing feedstocks in this set-up. Two possible modes of protein adsorption can be realized The feed can be applied in a frontal mode as in packed bed chromatography or the column effluent can be recyled, leading to a situation comparable to a batch adsorption in a stirred tank. Frontal and single stage recirculating modes are illustrated in Fig. 2. 

Trtic, T.M., Vladisavljevic, G.T. and Comor, J.J. (2001) Single-stage and 2-stage solvent-extraction of Tl(III) in hollow-fiber contactors under recirculation mode of operation. Separation Science and Technology, 36, 295. 

Many commercial photochemical reactor systems make use of the batch recirculation mode for the treatment of highly contaminated wastewaters of limited volume. On the other hand, cascades of photoreactor modules (in serial or parallel mode) allow the gradual treatment of contaminated water streams with a very high photon flow Op in total. Hence, there exist powerful photochemical waste-... 

There are several modes in which trickling filters can operate—one is the recirculation mode in which trickling filter effluents are partially re-circulated through the filter media. Changes in the quality and quantity of wastewater can be handled by adjusting the recirculation rate. Recirculation does the following ... 

The first connmercially available continuous-flow synthesizers were manual instruments the PEPSYNthesiser I from Cambridge Research Biochemicals (CRB) and the Model 4175 from LKB Biochrom. In these instruments, one manual valve switches between the flow and recirculate modes and another manual valve selects the solvent, reagent or the annino acid injection port. CRB later released the semiautomatic PEPSYNthesiser II before selling the rights to the instrument to MilhGen, who ultimately released the fully automated 9050 PepSynthesizer. Pharmada-LKB Biochrom also developed an automated continuous-flow synthesizer, the Biolynx Model 4170. Several years later, the rights to this instrument were obtained by Novabiochem. Most of the automated, semiautomated, and manual continuous-flow peptide synthesizers are fisted in Table 3. 

The specifications of the membrane module, which was supplied by the Desalination Division of the BARC (Mumbai), are listed in Table 33.2. The RO setup installed at the delay tank site is shown in Figure 33.3. The delay tank water composition is given in Table 33.1. The module was operated at a pressure of 15 bar, which was adjusted by a throttle valve placed on the reject line. The experiments were performed both in once-through and recirculation modes. The alpha and beta activities, and nitrate and TDS levels were periodically monitored by sampling the feed, permeate, and reject solutions using standard analytical methods. 

Typical Analytical Results of RO Pilot Plant Studies Conducted for Delay Tank Liquid in Recirculation Mode... 

RO in recirculation mode (in the same row, value indicated in bracket shows concentrarte TDS). 

The extraction of U(VI) was performed by Roy et al. using the PEHFSD technique with TBP as an extractant [47 8]. A schematic view of the PEHFSD process for U(VI) (as a representative case 0.01 M HNO3) in recirculation mode (using a... 

Fig. 3 The media milling process is shown in a schematic representation. The milling chamber charged with polymeric media is the active component of the mill. The mill can be operated in a batch or a recirculation mode. A crude slurry consisting of drug, water, and stabilizer is fed into the milling chamber and processed into a nanocrystalline dispersion. The typical residence time required to generate a nanometersized dispersion with a mean diameter <200 nm is 30-60 min. (From Liversidge, E.M. Liversidge, G.G. Cooper, E.R. Eur. J. Pharm. Sd. 2003,18, 113-120).

Fig. 3.7. Approaches to implementing continuous ultrasound-assisted leaching. (A) With direct monitoring of the process. (B) and (C) With a derivatization step before detection. (Bl) With leaching in the recirculation mode. (Cl) With leaching in the go forward and back mode. (B2) and (C2) Derivatization-detection steps. P peristaltic pump, UP ultrasound probe, SS solid sample, DB de-bubbler, D detector, SV switching valve, LC leaching carrier, R reagent, W waste. (Reproduced with permission of Elsevier.)...

When operating percolators in recirculation mode, where the solvent is allowed to approach equilibrium concentrations, Equations 11.5 through 11.10 that were developed for dispersed solids extraction can also be used for percolator design. 

Experiments in the total recirculation mode, in which the FMC operates as a batch system in non-steady-state. The dependence of the thermometric signal on time for a chosen substrate concentration is measured ... 

For microbial challenges and juice production, the system was operated in a 50 L recirculating mode as previously described (8). 

Extractions can be performed in static, dynamic, or recirculating modes. In the static mode, the extraction cell is pressurized with supercritical fluid and allowed to equilibrate before the analyte is removed for collection. In the dynamic mode, the supercritical fluid is passed through the extraction cell and the analyte is collected continuously. In the recirculating mode, the same fluid is pumped through the sample then, after some time, it is repeatedly pumped... 

The importance of adding modifier to the supercritical fluid was discussed earlier. The modifier is added using a pump or a doped carbon dioxide cylinder. Adding the modifier to the extraction cell with the sample is an easy and effective way to introduce the modifier into the supercritical fluid. This procedure works in the static and recirculating modes, and it is not much different from adding modifier through the pump. 

Figure 2.4-3 Apparatus based upon a variable-volume view cell with a computer-controlled ISCO syringe pump. Type A recirculation mode for adding or removing solutions, emulsification through a capillary, and/or optical access. Type B reciprocating pump for turbidimetry studies of latexes or suspensions.

Diffusion contact reactors can be further subdivided according to the flow pattern of the enzyme- or substrate-containing stream. The enzyme-containing stream can be either confined or recirculated through the system, whereas the substrate-containing stream can either flow through the membrane module in a single pass or in a recirculation mode. 

The induced surface flow also gives rise to secondary bulk fluid motion, in the same way that bulk meridional vortices are generated in a fluid trapped between rotating and stationary disks in Batchelor flows [19], as depicted in Fig. 12. In this flow recirculation mode, particles dispersed in the flow are convected to the bottom by the bulk meridional recirculation. However, due to the inward radial velocity in the Ekman boundary layer (see Fig. 13), the particles begin to swirl in a helical-like manner toward the center of the base [19]. Although the flow recirculates back up a central spinal coluirm, the gravitational... 

The pH of the aqueous solution collected in the containment sump after completion of injection of containment spray and ECCS water, and all additives for reactivity control, fission product removal, or other purposes, should be maintained at a level sufficiently high to provide assurance that significant long-term iodine re-evolution does not occur. Long-term iodine retention is calculated on the basis of the expected long-term partition coefficient. Long-term iodine retention may be assumed only when the equilibrium sump solution pH, after mixing and dilution with the primary coolant and ECCS injection, is above 7 (Reference...). This pH value should be achieved by the onset of the spray recirculation mode. 

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