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Residence liquid phase

Deviations from an average K E=1 1 have been observed, because the intermediate palladium species Pd2+ or PdH+ can be reduced or oxidised respectively to one another leading to an excess of K or E chain ends, or even one type of chain end only [9], Chain termination ratios also depend on the phase in which the chain end resides, liquid phase or solid phase, as higher oligomers precipitate [34],... [Pg.250]

Increasing the pressure of irreversible vapor-phase reactions increases the rate of reaction and hence decreases reactor volume both by decreasing the residence time required for a given reactor conversion and increasing the vapor density. In general, pressure has little effect on the rate of liquid-phase reactions. [Pg.43]

As well as preventing liquid carry over in the gas phase, gas carry undef must also be prevented in the liquid phase. Gas bubbles entrained in the liquid phase must be given the opportunity (or residence time) to escape to the gas phase under buoyancy forces. [Pg.245]

The ease with which small gas bubbles can escape from the liquid phase is determined by the liquid viscosity higher viscosities imply longer residence times. Typical residence times vary from, some 3 minutes for a light crude to up to 20 minutes for very heavy crudes. [Pg.245]

More often than not the rate at which residual absorbed gas can be driven from the liqmd in a stripping tower is limited by the rate of a chemical reaction, in which case the liquid-phase residence time (and hence, the tower liquid holdup) becomes the most important design factor. Thus, many stripper-regenerators are designed on the basis of liquid holdup rather than on the basis of mass transfer rate. [Pg.1352]

Solution. For TGE in water, the Henry s law coefficient may he taken as 417 atm/mf at 20°G. In this low-concentration region, the coefficient is constant and equal to the slope of the eqnihhrinm hne m. The solnhility of TGE in water, based on H = 417, is 2390 ppm. Because of this low solnhility, the entire resistance to mass transfer resides in the liquid phase. Thus, Eq. (14-25) may he used to obtain Nql, the nnmher of overall hqnid phase transfer units. [Pg.1356]

In the liquid-hquid extraction area, in the mining industry, coming out of the leach tanks is normally a slurry, in which the desired mineral is dissolved in the liquid phase. To save the expense of separation, usually by filtration or centrifugation, attempts have been made to use a resident pump extraction system in which the organic material is contacted directly with the slurry. The main economic disadvantage to this proposed system is the fact that considerable amounts of organic liquid are entrained in the aqueous slurry system, which, after the extraction is complete, is discarded. In many systems this has caused an economic loss of solvent into this waste stream. [Pg.1640]

The reaction takes place at low temperature (40-60 °C), without any solvent, in two (or more, up to four) well-mixed reactors in series. The pressure is sufficient to maintain the reactants in the liquid phase (no gas phase). Mixing and heat removal are ensured by an external circulation loop. The two components of the catalytic system are injected separately into this reaction loop with precise flow control. The residence time could be between 5 and 10 hours. At the output of the reaction section, the effluent containing the catalyst is chemically neutralized and the catalyst residue is separated from the products by aqueous washing. The catalyst components are not recycled. Unconverted olefin and inert hydrocarbons are separated from the octenes by distillation columns. The catalytic system is sensitive to impurities that can coordinate strongly to the nickel metal center or can react with the alkylaluminium derivative (polyunsaturated hydrocarbons and polar compounds such as water). [Pg.272]

Cyclohexane is also a precursor for adipic acid. Oxidizing cyclohexane in the liquid-phase at lower temperatures and for longer residence times (than for KA oil) with a cobalt acetate catalyst produces adipic acid ... [Pg.283]

Glaser and Litt (G4) have proposed, in an extension of the above study, a model for gas-liquid flow through a b d of porous particles. The bed is assumed to consist of two basic structures which influence the fluid flow patterns (1) Void channels external to the packing, with which are associated dead-ended pockets that can hold stagnant pools of liquid and (2) pore channels and pockets, i.e., continuous and dead-ended pockets in the interior of the particles. On this basis, a theoretical model of liquid-phase dispersion in mixed-phase flow is developed. The model uses three bed parameters for the description of axial dispersion (1) Dispersion due to the mixing of streams from various channels of different residence times (2) dispersion from axial diffusion in the void channels and (3) dispersion from diffusion into the pores. The model is not applicable to turbulent flow nor to such low flow rates that molecular diffusion is comparable to Taylor diffusion. The latter region is unlikely to be of practical interest. The model predicts that the reciprocal Peclet number should be directly proportional to nominal liquid velocity, a prediction that has been confirmed by a few determinations of residence-time distribution for a wax desulfurization pilot reactor of 1-in. diameter packed with 10-14 mesh particles. [Pg.99]

Ross (R2) measured liquid-phase holdup and residence-time distribution by a tracer-pulse technique. Experiments were carried out for cocurrent flow in model columns of 2- and 4-in. diameter with air and water as fluid media, as well as in pilot-scale and industrial-scale reactors of 2-in. and 6.5-ft diameters used for the catalytic hydrogenation of petroleum fractions. The columns were packed with commercial cylindrical catalyst pellets of -in. diameter and length. The liquid holdup was from 40 to 50% of total bed volume for nominal liquid velocities from 8 to 200 ft/hr in the model reactors, from 26 to 32% of volume for nominal liquid velocities from 6 to 10.5 ft/hr in the pilot unit, and from 20 to 27 % for nominal liquid velocities from 27.9 to 68.6 ft/hr in the industrial unit. In that work, a few sets of results of residence-time distribution experiments are reported in graphical form, as tracer-response curves. [Pg.99]

Holdup and Residence-Time Distribution of Liquid Phase... [Pg.127]

From the assumption that liquid volume elements travel as bubble wakes at velocities higher than the average liquid velocity, it follows that the bubble movement must influence the residence-time distribution of the liquid phase. However, no work on this subject has come to the author s attention. [Pg.128]

The proposed technique will be used here to illustrate the case of interfacial heat and multicomponent mass transfer in a perfectly mixed gas-liquid disperser. Since in this case the holding time is also the average residence time, the gas and liquid phases spend the same time on the average. If xc = zd = f, then for small values of t, the local residence times tc and td of adjacent elements of the continuous and dispersed phases are nearly of the same order of magnitude, and hence these two elements remain in the disperser for nearly equal times. One may conclude from this that the local relative velocity between them is negligibly small, at least for small average residence times. Gal-Or and Walatka (G9) have recently shown that this is justified especially in dispersions of high <6 values and relatively small bubbles in actual practice where surfactants are present. Under this domain, Eqs. (66), (68), (69) show that as the bubble size decreases, the quantity of surfactants necessary to make a bubble behave like a solid particle becomes smaller. Under these circumstances (pd + y) - oo and Eq. (69) reduces to... [Pg.382]

Thus, we can make a reasonably accurate initial guess for Qp. This guess is used to calculate the conversion in a tubular reactor of the given dimensions. When the right guess is made, the mean residence time will be 2h and the fraction unreacted will be 20%. The following code follows the general procedure for liquid-phase PFRs. The fraction unreacted is calculated as the ratio of which is denoted as Phi/Philn in... [Pg.97]

Example 5.10 A liquid-phase, pilot-plant reactor uses a 12-ft tube with a 1.049-in i.d. The working fluid has a density of 860 kg/m, the residence time in the reactor is 10.2 s, and the Reynolds number is 8500. The pressure drop in the pilot plant has not been accurately measured, but is known to be less than 1 psi. The entering feed is preheated and premixed. The inlet temperature is 60°C and the outlet temperature is 64°C. Tempered water at 55°C is used for cooling. Management loves the product and wants you to design a plant that is a factor of 128 scaleup over the pilot plant. Propose scaleup alternatives and explore their thermal consequences. [Pg.181]

This introduces the gas-phase residence time VgjQg as a new parameter. It also introduces an ambiguity regarding the term kgAi(a — Ug). There is no resistance to mass transfer within a pure component so kgAj oo and a — Ug 0. Thus, kgAi(a — Ug) is an indeterminate form of the oo x 0 variety. Its value must continue to equal the rate at which oxygen is transferred into the liquid phase. Equation (11.5) remains true and the pair of simultaneous ODEs become... [Pg.391]

Solution Ideally, the scaleup will maintain the same inlet concentrations for the two phases, the same relative flow rates and holdups for the two phases, and the same ratio of gas transferred to liquid throughput. It is also necessary to maintain a constant residence time in the liquid phase. It is simple to set the flow rates ... [Pg.428]

The liquid mean residence time, tm, in counter-current mode was significantly lower than in co-current mode. Statistical analysis (Yates method of ANOVA) indicates that along with the liquid flowrate, the direction of liquid travel is the most significant factor in the liquid mean residence time. This variation in the liquid phase mean residence time, suggests an increase in short-circuiting or channeling in the counter-current mode as a result of the gas-liquid interactions. [Pg.671]

An investigation into the applicability of numerical residence time distribution was carried out on a pilot-scale annular bubble column reactor. Validation of the results was determined experimentally with a good degree of correlation. The liquid phase showed to be heavily dependent on the liquid flow, as expected, but also with the direction of travel. Significantly larger man residence times were observed in the cocurrent flow mode, with the counter-current mode exhibiting more chaimeling within the system, which appears to be contributed to by the gas phase. [Pg.672]

Gavrilescu, M. and R.Z. Tudose, Residence time distribution of the liquid phase in a concentric-tube airlift reactor. Chemical Engineering and Processing, 1999. 38(3) p. 225-238. [Pg.672]

Liquid- and Liquid/Liquid-phase Reactions Flow rates/residence times/voltages... [Pg.482]

Hydrogenation experiments were conducted in a flow apparatus (Figure 5.24) at 97 °C using a pressure of 2 MPa [17]. A 10% solution of p-nitrotoluene in 2-propanol was the liquid phase as gas hydrogen (5.0 purity) was applied. The nitrotoluene flows normalized per unit area were 0.013 and 0.045 g h cm . The residence times were either 85 or 280 s. The recycle ratio was 21 or 43. [Pg.625]

Chemical Kinetics, Tank and Tubular Reactor Fundamentals, Residence Time Distributions, Multiphase Reaction Systems, Basic Reactor Types, Batch Reactor Dynamics, Semi-batch Reactors, Control and Stability of Nonisotheimal Reactors. Complex Reactions with Feeding Strategies, Liquid Phase Tubular Reactors, Gas Phase Tubular Reactors, Axial Dispersion, Unsteady State Tubular Reactor Models... [Pg.722]

A fixed-bed reactor system was employed (Figure 32.2). Each of the two reactors was charged with 38 cc of Amberlyst BD20 catalyst. Sample ports located at the exit of each reactor enabled increased acquisition of residence time data. Pressure was maintained by a back pressure control valve to maintain methanol in the liquid phase. After charging, the 1st and then 2nd reactors were connected to the pumps and filled with the reaction mixture while vapor was released from each through the top vent valve. Once each reactor was filled with liquid and emptied of vapor, the pressure regulator was connected to the output and both reactors were immersed into the water bath. [Pg.282]

Large stirred tank reactors are generally not suited for use at high pressures because of mechanical strength limitations. They are used mainly for liquid phase reaction systems at low or medium pressures when appreciable residence times are required. [Pg.251]

Other advantages of the tubular reactor relative to stirred tanks include suitability for use at higher pressures and temperatures, and the fact that severe energy transfer constraints may be readily surmounted using this configuration. The tubular reactor is usually employed for liquid phase reactions when relatively short residence times are needed to effect the desired chemical transformation. It is the reactor of choice for continuous gas phase operations. [Pg.252]


See other pages where Residence liquid phase is mentioned: [Pg.113]    [Pg.699]    [Pg.1369]    [Pg.562]    [Pg.718]    [Pg.96]    [Pg.96]    [Pg.298]    [Pg.332]    [Pg.98]    [Pg.101]    [Pg.186]    [Pg.400]    [Pg.460]    [Pg.587]    [Pg.671]    [Pg.597]    [Pg.608]    [Pg.633]    [Pg.331]    [Pg.645]    [Pg.314]    [Pg.126]   
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