Mean residence time applications

Frequently, stirred tanks are used with a continuous flow of material in on one side of the tank and with a continuous outflow from the other. A particular application is the use of the tank as a continuous stirred-tank reactor (CSTR). Inevitably, there will be a vety wide range of residence times for elements of fluid in the tank. Even if the mixing is so rapid that the contents of the tank are always virtually uniform in composition, some elements of fluid will almost immediately flow to the outlet point and others will continue circulating in the tank for a very long period before leaving. The mean residence time of fluid in the tank is given by ... 

The mean residence time in the falling down region depends mainly on the structural dimensions, in addition to the properties of the particles and the gas while is little affected by operation parameters. Therefore the data shown in Fig. 3.3 are applicable for the experimental study to be discussed later in this chapter. 

The implications of being able to increase the conversion of an equilibrium reaction by using a permselective membrane are several. First, a given reaction conversion may be attained at a lower operating temperature or with a lower mean residence time in a membrane reactor. This could also prolong the service life of the reactor system materials or catalysts. Second, a thermodynamically unfavorable reaction could be driven closer to completion. Thus, the consumption of the feedstock can be reduced. A further potential advantage is that, by being able to conduct the reaction at a lower temperature due to the use of a membrane reactor system, some temperature-sensitive catalysts may find new applications [Matsuda et al., 1993]. 

Sanderman J., Amundson R., and Baldocchi D. D. (2003) Application of eddy covariance measurements to the temperature dependence of soil organic matter mean residence times. Global Biogeochem. Cycles, 17(2), 1061. 

In both models the only model parameter used is the mean residence time tpp and tpsR F gtire 6 shows the reactor dynamics of the PFR and the PSR in the normalised time and frequency domain (dimensionless time 0 = t/T, dimensionless frequency fg = l/2jt9). In the time domain the step response F(9) as well as the impulse response E(0) (which is the RTD) can be discussed. This type of data presentation is normally used in chemical engineering application. But the same data can also be presented in the frequency domain, the so called Bode plot. This type of presentation allows to identify effects which are not visible in the classical used plot in the time domain. The Bode plot consists of the magnitude Gj 030)1 and the phase arg G(jO)0). ... 

From a more preictical point of view it would be necessary to follow the reaction to higher mean residence times. Only for a higher yield of dinitrile with increa.sing residence time a practical application of this way to terephthalic acid is possible. The main advantage of the proposed route compared to the known processes would be the unification of isomer separation and reaction in one step. 

Contexts are very much like directories and you can find much written about this topic elsewhere. We will create a package called cstrresdist, which we will store in a folder called AddOns within the Applications folder. The inputs will be the forward and reverse rate constants kab and kd, the mean residence time 6m, and the variance in the residence time 66. The general form for a Package is ... 

The mean residence time, r, can be estimated if necessary from the relation for /. A value of/can be estimated from the measured atmospheric concentration of the compound and the total quantity emitted. Knowing/and r, p can be determined and r can be calculated as 1 p. For r/ 1, / r/(r + p). b. As an application of the foregoing theory, let us estimate the atmospheric residence times of the three species in Table 2.P.I, which presents atmospheric mixing ratios, together with values of / estimated from total production data (assuming that each species is of anthropogenic origin only). As noted above, the... 

The reference time, i f and concentration, Cp. f, are chosen for a specific application (e.g., in a flow reactor, the mean residence time and feed concentration, respectively). Equation 5.2.C-6 now permits a solution for the amount of poison, /Cpia, to be obtained as a function of the bulk concentration, Cp, and the physicochemical parameters. In a packed bed tubular reactor, Cp varies along the longitudinal direction, and so Eq. 5.2.C-6 would then be a partial differential equation coupled to the flowing fluid phase mass balance equation—these applications will be considered in Part Two—Chapter 11. 

MRT mean residence time the mean (average) time for a mass of intact drug molecules to transit through the body it is a composite of all disposition processes and, when applicable, drug release from the dosage form and absorption... 

Cheung BWY, Cartier LL, Russile HQ, Sawchuk RJ. The application of sample pooling methods for determining AUC, AUMC and mean residence times in pharmacokinetic studies. Fund Clin Pharmacol 2005 19(3) 347 354. 

Table 6.3 summarizes the effects of screw geometry on pumping capability, degree of fill, mean residence time, and pressure build-up capability of the screw elements. Different types of screw elements should be used to design an optimum screw configuration for an application of interest. 

Note that on scale-up situation a may change into bl We shall first consider situation a, which is usually applicable to well stirred continuous reactors with a mean residence time that is not very short. The following approximation may be used One can relate the turbulent diffusivity with the local specific energy dissipation (Tj e) and the integral length scale X (Jeurissen et al. 1994)... 

Just like a batch reactor, all the reacting species in an idealized tubular reactor have exactly the same residence time. Thus, the mechanisms and kinetics presented in Chapters 3 and 4 are also applicable to emulsion polymerization carried out in a tubular reactor. On the other hand, the feed stream introduced into a continuous stirred tank reactor at any given time becomes completely mixed with the reaction mixture already present in the reaction system. As a result, a distribution of residence times of the material within a continuous stirred tank reactor is achieved. In other words, some of the recipe ingredients entering the continuous stirred tank reactor may leave it almost immediately because material is continuously withdrawn from the reactor. In contrast, other recipe ingredients may remain in the reactor almost forever because all the material is never removed from the reactor at one time. Many of the reaction species leave the reactor after spending a period of time somewhere in the vicinity of the mean residence time. The distribution of residence... 

Catalysts and their carriers are provided in micro channels by various means and in various geometric forms. In a simple variant, the catalyst itself constitutes the micro-reactor construction material without need for any carrier [2-A], In this case, however, the catalyst surface area equals that of the reactor wall and hence is comparatively low. Accordingly, applications are typically restricted to either fast reactions or processing at low flow rates for slow reactions (to enhance the residence time). 

The main task in technical application of asymmetric catalysis is to maximize catalytic efficiency, which can be expressed as the ttn (total turnover number, moles of product produced per moles of catalyst consumed) or biocatalyst consumption (grams of product per gram biocatalyst consumed, referring either to wet cell weight (wcw) or alternatively to cell dry weight (cdw)) [2]. One method of reducing the amount of catalyst consumed is to decouple the residence times of reactants and catalysts by means of retention or recycling of the precious catalyst. This leads to an increased exploitation of the catalyst in the synthesis reaction. 

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