Phase-separation steps

Excessive mixing Limit agitator power input and provide proper of reactants or impeller design impurities which, Return process to pilot or development to rede-promotes process to eliminate or minimize this emulsification. problem Poor phase separa- tion resulting in L it shaft speed problems in subse- Monitor shaft speed quent processing, phase separation steps or in down- stream equipment. I" " de-emulsifiers CCPS G-29 Lees 1996... 

Modified spectrophotometric procedures are described for the quantitative determination of cobalt and molybdenum as the 2-nitrosonaphth-l-olate and toluene-3,4-dithiolate complexes in carbon tetrachloride. The extraction, chelation and phase separation steps permitted rapid sample handling, controlled interferences more effectively and provided accurate assays. The molar absorptivities for cobalt and molybdenum were 5.1 x 104 and 2.5 xl04mol/lcm, respectively, and the detection limits for both elements were 4 ng/g. 

Fluorous biphasic catalysis exploits not only this principle, but also the ability of certain perfluo-rocarbon/hydrocarbon biphasic mixtures to form a homogenous solution at high temperatures. An extremely fluorinated catalyst can thus be applied under homogeneous conditions and recovered from the fluorous phase subsequent to a phase separation step at lower temperatures. 

The countercurrent model as shown here is not practical for real-world separations because the material losses sustained from five phase separation steps would make the real recovery closer to 50% than the predicted 75%. To make countercurrent extractions practical, they must be implemented in a flow stream, cartridge, or other geometry, where material losses are not so devastating. One such approach is given below. 

Sampling and phase separation steps are not always uniform and are operator dependent. In the cases of rapid surface reactions sampling and phase separation are not rapid enough to follow the reaction. 

In this architecture (Fig. 8.13), the solvent is immobilised in a liquid membrane and sandwiched between two aqueous (donor and acceptor) streams [162]. Drawbacks related to a flowing organic stream are therefore circumvented and the resulting flow system is generally very simple and rugged. Only a few solvents however can be immobilised in a liquid membrane [171]. An important characteristic of this architecture is that the phase-separation step is not required. 

MPa (6500 psi) and 121 °C, the added gas comprising 67.3 volume percent of the system in each instance. Each addition was followed by a phase separation step at 27.6 MPa and 121 °C. Figures 15 and 16 depict, respectively, developmental stages of the six progressively depleted oils and their accompanying gas-condensates. 

Apart from microdiaimels, dispersed microsystems such as micromixers (see Chapter 7) are used. They provide the desired performance and allow higher throughputs by virtue of the larger pipe diameter, but the small size of the droplets and bubbles require an additional post-readion phase separation step [61]. 

A very simple method to do so is called the Successive Precipitation Fractionation (SPF). The initial solution of the polydisperse polymer 5 in a suitable solvent A forms the feed phase F. A change of temperature results in a phase separation. The polymer-rich phase II is removed and forms fraction 1. The polymer-lean phase 7 serves directly as the feed phase for step 2. A further change of temperature results in a second phase separation (step 2). Again, the polymer-rich phase II is removed forming fraction 2 whereas the polymer-lean phase / is the feed phase of the next step. This procedure is continued. The feed phase of each step equals the polymer-lean phase I of the preceding step. At the end of this process instead of the widely distributed original polymer there are several fractions (1, 2,- ) with narrow molar-mass distributions. 

Also of note in the adhesive force images, small droplets with a diameter of about 300 nm can be seen where the adhesive force appears to be different. This difference in adhesive force is due to a topography effect [20]. Heating the sample up to 97 °C, the adhesive force of the droplet structure decreases. A possible explanation for this may be that in these areas small droplets of PS are covered by PMMA. The spin-coated films are not in thermodynamical equilibrium but in a frozen state. Due to the evaporation of the solvent, it is also possible that PMMA remains at the surface because it less soluble in toluene than PS. Heating the sample close to its glass transition temperature increases the mobility of the chains and the PS droplet becomes visible by a second-phase separation step which is thermally induced. In this case the sample is in thermodynamic equlibrium. 

H2 and O2 are produced separately, so a high temperature gas phase separation step is not required. 

The volatility method can be conveniently used to process a thorium bisinuthide blanket. The process must be preceded by a phase separation step which separates the thorium bismuthide solids from the liquid carrier bismuth (Fig. 24-19). The modification of the core liquid process flowsheet is as follows (1) salt effluent from the hydrofluorination step must be stored in order to achieve Pa decay to uranium, and (2) the bismuth liquid is returned to the blanket head end process without the addition of uranium. 

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