Liquid settling

Theoretically, electrokinetic processes should also occur in nondisperse systems, but then additional factors arise (vortex formation in the liquid, settling of the particles, etc.) which produce a strong distortion. Hence, electrokinetic processes can be regarded as one of the aspects of the electrochemistry of disperse heterogeneous systems. 

Basic design aspects of three-phase separation are identical to those discussed earlier for two-phase separation. The only additions are that more concern is placed on liquid-liquid settling rates and that some means of removing free water must be added. Liquid-liquid setding rates will be discussed later. Water removal is a function of control methods used to maintain separation and removal from the oil. Several control methods are applicable to three-phase separators and shape and diameter of the vessel will, to a degree, determine types of control used. 

Liquid drums usually are placed horizontal and gas-liquid separators vertical, although reflux drums with gas as an overhead product commonly are horizontal. The length to diameter ratio is in the range 2.5-5.0, the smaller diameters at higher pressures and for liquid-liquid settling. A rough dependence on pressure is... 

Add a few drops of chlorine water to 5 cc. of a bromide solution, for example NaBr. Then, in order to find whether bromine has been set free, add 1 cc. of carbon disulphide, shake vigorously, and let the heavier liquid settle to the bottom. The free halogen is more soluble in carbon disulphide than in water, consequently it dissolves in and imparts its characteristic color to it. Note that the globule has acquired an orange-red color. 

Unless a burette is automatic and one wishes to fill to the 0.00 mL mark, overfill the burette about 10 mm past the zero line. Let the liquid settle a minute, then release some of the liquid into a beaker or some other receptacle by slightly opening the stopcock. Let the fluid lower to the zero line. Wait another minute to allow the fluid to settle to the new level, and re-check the level of the meniscus at the zero line. Release or add more liquid as necessary. 

If immiscible liquids, which have different densities, are mixed in a container, the denser liquid settles at the bottom and the lighter one at the top. This type of mixture can be separated by using a separatory funnel as shown in Figure 7. 

Sedimentation in liquids During gravitational sedimentation particles dispersed in a liquid settle with a velocity that is a function of their size. For a single, spherical particle in an infinite body of liquid the Stokes law is valid at low settling velocity (Reynolds number <0.2) ... 

Relationship between Particle Adhesion and Conditions of Dust Deposition on Surface. Two cases may be distinguished in the deposition of dust on a surface deposition in air with subsequent transfer of the dust-covered surface to a liquid ( air-dusting ) and direct settling of the particles on the surface in a liquid ( liquid-settling ). It has been found experimentally that when an air-dusted surface was held in a liquid for not more than 2 min, all of the particles remained on the surface, even with a detaching force of 2.8 10 dyn whereas when the particles were allowed to settly in distilled water and held for the same time, 45% of the particles were removed by the same detaching force. 

In Fig. VI. 1 we show the timewise variation of adhesion number after airdusting (curve 1) and after liquid-settling (curve 2). In the case of air-dusting, the adhesion reached a maximum in 2-min exposure, dropping off when the dust-covered surface was held in liquid media for periods up to 30 min. Essentially no changes in adhesion were observed when the time was extended to 60 min or more. When the particles were settled out in a liquid (curve 2), the opposite picture was observed. As the residence time of the substrate in the liquid medium was extended, the adhesion increased the highest level of ahesion in this case was approximately the same as the lowest level of adhesion with air-dusting [164]. 

Thus we see that at the start (in our experiments, after 2 min of contact between particles and substrate in the liquid), the adhesion after air-dusting was always greater than the adhesion after liquid-settling. 

There are two capacity limits related to liquid loading, which are the downcomer baekup limit and downcomer veloeity limit. The downcomer backup limit is set at 80% of liquid settling height based on the froth level. The downcomer velocity limit is 75% of maximum velocity allowed to avoid downeomer choke. The number of tray passes is the most important parameter affeeting the downcomer loading and thus these two downcomer limits. 

Fuks [59] directed attention to the dependence of the adhesion on the period of contact between the particles and the surface on settling in the liquid. At the initial instant the adhesion of the particles is a minimum (Fig. IV.3), but with increasing contact time adhesion becomes stronger, the rise ceasing some 60-90 min after the particle first came into contact with the surface. This phenomenon has become known as aging. Fuks [59] studied the effect of contact time on adhesion specifically for the case of the liquid settling of particles. 

Figure IV.4 shows the variation in the adhesion number with time for air dusting (curves 1) and liquid settling (curves 2) [170], The adhesion reaches a maximum for a two-minute exposure in...

Fig. IV.3. Adhesion number as a function of the time of contact between the particles (detaching force 1.2 lo" dyn) and the surface for liquid settling. 1) Graphite in clean mineral oil on bronze 2) graphite in aviation oil on glass 3) graphite in Avtol 10 on glass 4). carbon scale in Av-tol 10 on glass.

Fig. IV.5. Adhesion number as a function of the time of contact between glass spheres 70 2 p in diameter in distilled water and glass (1) and perchlorvinyl enamel-painted (2) surfaces. Upper branches of the curves, air dusting lower branches, liquid settling.

Thus at the initial instant (in our own experiments after a 2-min period of contact between particles and the substrate in the liquid) the adhesion for air dusting is always greater than the adhesion for liquid settling. 

The increase in adhesion in distilled water (Fig. IV.5) for liquid settling (lower branches of curves 1 and 2) depends less on the time spent by the substrate in the liquid than in electrolyte lutions (see Fig. IV.4). The adhesion of glass particles to a glass surface in distilled water is greater (Fig. IV.5, curve 1) than to a surface painted with perchlorvinyl enamel (curve 2). 

Figure IV.20 shows the variation in the adhesion of particles 40 JJL in diameter in solutions of various SAS, particularly Sulfonol and OP-10, as a function of the time spent by the painted surface in an aqueous medium for various methods of depositing the particles on the surface, namely, air dusting followed by placing the dust-laden surface in the liquid (curves 1 and 1 ) and liquid settling (curves 2 and 2. ...

Fig. IV.20. Adhesion number of glass particles 40 2 p in diameter as a function of the time of contact with painted surfaces in SAS solutions. 1,1 ) O.l o solutions of Sulfonol and 0.25 o solution of OP-10 for air dusting 2,2 ) the same for liquid settling 3) O.S o solution of SV-102 4) O.l o solution of DB.

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