Influence of Apparatus Design

Finally, we should draw attention to the prevalent use of air-degassed crude oil systems and foam generation by sparging at ambient temperatures and pressures. It is known that solubilities of asphaltenes, resins, PDMS, and PDMS derivatives are likely to be influenced by temperature and dissolution of natural gas. Moreover, sparging represents a poor model for foam generation in gas-oil separators, which involves depressurization and nucleation of bubbles. Use of apparatus designed to replicate the conditions in actual gas-oil separators for basic studies should therefore be encouraged. 

Back-diffusion is the transport of co-ions, and an equivalent number of counterions, under the influence of the concentration gradients developed between enriched and depleted compartments during ED. Such back-diffusion counteracts the electrical transport of ions and hence causes a decrease in process efficiency. Back-diffusion depends on the concentration difference across the membrane and the selectivity of the membrane the greater the concentration difference and the lower the selectivity, the greater the back-diffusion. Designers of ED apparatus, therefore, try to minimize concentration differences across membranes and utilize highly selective membranes. Back-diffusion between sodium chloride solutions of zero and one normal is generally [Pg.173]

The main aim of the methods described in this chapter is to obtain data for the design of chemical reactors, for the simulation of their operation behaviour, and, last but not least, to evaluate the influence of temperature and pressure on reaction rate. For this purpose, the techniques for measuring reaction rates at high pressures are presented. The details of the apparatus are mentioned in Chapter 4.3.4. 

The favorable working conditions of the thin-film evaporator enabled the equally successful application of the thin-film principle for fractionation (5), absorption, chemical reactions (6), and drying (7, 8). In these processes and applications, the thin-film apparatus is used mainly to treat heat sensitive and lower-viscosity products that flow on the influence of gravity alone. This particular type of apparatus in a special design can also be used to process highly viscous products to... 

Figure 4. Influence of different rotor designs A and B in thin-film apparatus on the mean thickness, expressed as a function of rotor speed and viscosity...

Factors Influencing Apparatus Design. Practical application of the theory presented above depends on the validity of a number of assumptions. One, which has already been mentioned, is the assumption that the flow is laminar. It has been shown by dimensional analysis that, for any given type of hydrodynamic experiment, the conditions for onset of turbulent flow depend on the magnitude of a certain combination of pertinent experimental variables that is a pure number, called the Reynolds number Re. For flow through a long, round, straight tube. 

Under the influence of ultraviolet light, or at 250-400°, chlorine or bromine converts alkanes into chloroalkanes (alkyl chlorides) or bromoalkanes (alkyl bromides) an equivalent amount of hydrogen chloride or hydrogen bromide is formed at the same time. When diluted with an inert gas, and in an apparatus designed to carry away the heat produced, fluorine has recently been found to give analogous results. As with methane, iodination does not take place at all. 

In a long and detailed paper on CO/H2 and CO2/H2 reactions on polycrystalline Rh, Sexton and Somorjai used a UHV-AES apparatus designed to allow sample scrutiny at low pressure yet to permit high-pressure (700 torr) reactions. They established good correlation of turn-over numbers between their results and results obtained on supported catalysts for the Fischer-Tropsch reaction. AES established that C was present on reactive surfaces yet this C (1 to 2 monolayers) did not influence rates of reaction or product distribution for high-pressure runs. It is however interesting to note that the most important influences on catalysis reported in this paper were found to be subsurface C and O, neither detectable by AES. The reactions studied at 250—300 °C showed that CO/H2 produced mainly Ci but also some C2, C3, and C4 hydrocarbons, whereas CO2/H2 produced CH4 exclusively. 

In this chapter, we report the influence of surface-active compounds on the stability of crude oil emulsions using the apparatus designed for bilayer lipid membrane studies. The electrical method we employed to measure the film lifetime and thickness of model oils and crude oils seems to be a convenient technique for monitoring the coalescence processes in emulsions. The results obtained show that the natural surface-active substances in crude oil, such as petroleum acids and asphaltenes, have a great effect on the film strength. The ionized acids formed by the reaction between the petroleum acids and the alkali can decrease the interfacial tension and accelerate the thinning and breakdown of the thin liquid film. The asphaltenes can adsorb on to the interface and improve the stability of the film. The order of stability of the films between different oils and alkaline solutions is as follows crude oil with asphaltenes removed < crude oil < crude oil with both asphaltenes and petroleum-acids removed (iv) < crude oil with petroleum acids removed. In addition. 

A suitable apparatus had to be constructed for experimental measurement of the influence of these variables. Prior to making a decision on the type of apparatus, three basic designs were considered spherical, cylindrical, and flat-plate P]. 

For the design of RD processes, besides information on the reaction, information on phase equUibria is of prime importance, especially on vapor-liquid equilibria and in some cases also on liquid-liquid equilibria (see above). The systematic investigation of phase equUibria for the design of RD processes will generally involve also studies of reactive systems (see examples above). Studies of phase equUibria in reactive systems generally pose no problem if the reaction is either very fast or very slow as compared with the time constant of the phase equilibrium experiment (high or low Damkohler number Da). In the first case, the solution will always be in chemical equUibrium, in the second case, no reaction will take place. The definition of the time constant of the phase equilibrium experiment win depend on the type of apparatus used. If the RD process is catalyzed and the catalyst does not substantially influence the phase equilibrium, the phase equilibrium experiments can often be performed without catalyst and again no or only little conversion will take place. 

In spite of canal geometry in tubular turbulent apparatus the way of reagents flows introduction significantly influence on quality of disperse systems. As a consequence, it is necessary to consider the influence of way of immiscible liquid flows introduction into tubular turbulent apparatus of divergent-convergent design on effectiveness of disperse systems formation process in turbulent... 

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