Disengagement rate

The disengagement rate was assumed to be proportional to ywhere the parameter m is related to the elasticity of the medium and depends on the polymer molecular weight distribution. An empirical equation for m is... 

The effect of the polymer diffusivity. Dp, on the dissolution time was investigated. It was shown (Fig. 7) that as Dp increases, the dissolution time decreases due to an enhanced mass transfer rate. Also, as the disengagement rate increases, the dissolution time decreases as shown in Fig. 8. 

Fauske [32] represented a nomograph for tempered reaetions as shown in Figure 12-35. This aeeounts for turbulent flashing flow and requires information about the rate of temperature rise at the relief set pressure. This approaeh also aeeounts for vapor disengagement and frietional effeets ineluding laminar and turbulent flow eonditions. For turbulent flow, the vent area is... 

The PHI-TEC or VSP bench scale apparatus can be employed to determine information about the self-heat rate and vapor disengagement when this is not readily available. Additionally, the VSP equipment can be used for flashing flow characteristics using a special bottom vented test cell. Here, the flowrate, Gq (kg/sm ), is measured... 

The heat evolution rate per unit mass, the vent capacity per unit area, physical properties (e.g.. latent heat of liquid, specific heat, and vapor/liqnid specific volumes) are constant. It allows for total vapor-liqnid disengagement of fluids that are not natural" surface active foamers. ... 

Flooded-bundle (kettle) Easy maintenance and cleaning. Convenient when heating medium is dirty. Equivalent to theoretical plate. Contains vapor disengaging space. Lower heat transfer rates. Extra piping and space required. High residence time in heated zone. Easily fouled. 

Oil is fed to meshing zones by wide jets or sprayers, and uniform distribution across the tooth faces is necessary to avoid local distortion. Clearly, the rate of flow is important the effects of too little oil are easily imagined. A sound practice is to position an extra jet on the exit or disengagement side of a meshing zone, where the teeth are at their highest temperature. If gears run in either direction, sprayers must be installed on both sides. 

In the riser, baffles are placed at intervals to break up bubbles by increasing turbulence and shear. At the top erf the riser the expanded section decreases the upward flow rate of the medium and this, together with the lack of baffles, decreases turbulence and shear, which in turn promotes coalescence of bubbles. Larger bubbles form which have increased slip velocity, so they more easily disengage from the medium. 

The case of = 1 is a reasonable approximation for a great variety of cases, while = 0 covers another common situation where the reaction rate is limited by the disengagement of molecules from the surface. SIa has its usual interpretation as moles formed per unit volume of reactor per unit time when Ai is the... 

A number of different DNA polymerase molecules engage in DNA replication. These share three important properties (1) chain elongation, (2) processivity, and (3) proofreading. Chain elongation accounts for the rate (in nucleotides per second) at which polymerization occurs. Processivity is an expression of the number of nucleotides added to the nascent chain before the polymerase disengages from the template. The proofreading function identifies copying errors and corrects them. In E coli, polymerase III (pol III) functions at the... 

Kettle reboilers have lower heat-transfer coefficients than the other types, as there is no liquid circulation. They are not suitable for fouling materials, and have a high residence time. They will generally be more expensive than an equivalent thermosyphon type as a larger shell is needed, but if the duty is such that the bundle can be installed in the column base, the cost will be competitive with the other types. They are often used as vaporisers, as a separate vapour-liquid disengagement vessel is not needed. They are suitable for vacuum operation, and for high rates of vaporisation, up to 80 per cent of the feed. 

The draft-tube airlift bioreactor was studied using water-in-kerosene microemulsions [263], The effect of draft tube area vs. the top-section area on various parameters was studied. The effect of gas flow rates on recirculation and gas carry over due to incomplete gas disengagement were studied [264], Additionally, the effect of riser to downcomer volume was also studied. The effect of W/O ratio and viscosity was tested on gas hold-up and mass transfer coefficient [265], One limitation of these studies was the use of plain water as the aqueous phase in the cold model. The absence of biocatalyst or any fermentation broth from the experiments makes these results of little value. The effect of the parameters studied will greatly depend on the change in viscosity, hold-up, phase distribution caused due to the presence of biocatalyst, such as IGTS8, due to production of biosurfactants, etc., by the biocatalyst. Thus, further work including biocatalyst is necessary to truly assess the utility of the draft-tube airlift bioreactor for biodesulfurization. 

Cyclones. According to the model presented above, Eq. (24), a minimum loss rate due to cyclone attrition requires to avoid both high inlet velocities Ue and high solids mass fluxes mc m at the cyclone inlet. The latter requirement can be fulfilled by locating the cyclone inlet above the transport disengaging height (TDH) (Kunii and Levenspiel, 1991). In addition, an enlargement of the freeboard section will reduce the amount of particles that are entrained and thus the mass flux, mc in. 

The pilot-scale SBCR unit with cross-flow filtration module is schematically represented in Figure 15.5. The SBCR has a 5.08 cm diameter and 2 m height with an effective reactor volume of 3.7 L. The synthesis gas passes continuously through the reactor and is distributed by a sparger near the bottom of the reactor vessel. The product gas and slurry exit at the top of the reactor and pass through an overhead gas/liquid separator, where the slurry is disengaged from the gas phase. Vapor products and unreacted syngas exit the gas/liquid separator and enter a warm trap (373 K) followed by a cold trap (273 K). A dry flow meter downstream of the cold trap measures the exit gas flow rate. 

The size of reactor is chosen to accommodate this holdup. The diameter is determined from the gas flow rate, q, together with, for example, an allowable superficial linear gas velocity, u (in lieu of an allowable (- AP)) D = (4qhru)m for a cylindrical vessel. The volume could be determined from an appropriate bed density, together with an overhead space for disengagement of solid and gas phases (we assume no carryover of solid in the gas exit stream). 

A fluidized-bed reactor consists of three main sections (Figure 23.1) (1) the fluidizing gas entry or distributor section at the bottom, essentially a perforated metal plate that allows entry of the gas through a number of holes (2) the fluidized-bed itself, which, unless the operation is adiabatic, includes heat transfer surface to control T (3) the freeboard section above the bed, essentially empty space to allow disengagement of entrained solid particles from the rising exit gas stream this section may be provided internally (at the top) or externally with cyclones to aid in the gas-solid separation. A reactor model, as discussed here, is concerned primarily with the bed itself, in order to determine, for example, the required holdup of solid particles for a specified rate of production. The solid may be a catalyst or a reactant, but we assume the former for the purpose of the development. 

The transfer hydrogenation methods described above are sufficient to carry out laboratory-scale studies, but it is unlikely that a direct scale-up of these processes would result in identical yields and selectivities. This is because the reaction mixtures are biphasic liquid, gas. The gas which is distilled off is acetone from the IPA system, and carbon dioxide from the TEAF system. The rate of gas disengagement is related to the superficial surface area. As the process is scaled-up, or the height of the liquid increases, the ratio of surface area to volume decreases. In order to improve de-gassing, parameters such as stirring rates, reactor design and temperature are important, and these will be discussed along with other factors found important in process scale-up. 

Figure 6.23 Prediction of stress overshoot for different tube disengagement times. The shear rate used for the calculation was 5 s l...

The size of settlers is determined by the rate of phase disengagement, which, here, is a function of the solvent concentration of LIX 64N and the aqueous phase feed rate. The capital cost of extraction equipment is a function of the number of tanks, the size of the tanks, and the solvent inventory [9] ... 

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