Model plugging

CSMPlug is capable of predicting hydrate dissociation for three scenarios two-sided depressurisation, one-sided depressurisation and electrical heating. Predictions are most sensitive to the plug porosity and in the case of the one-sided depressurisation model, plug permeability. The model should be used to perform... 

Yield-Based Reactor Fractional Conversion Reactor Combined Specification Model Well-Stirred Reactor Model Plug Flow Reactor Model Two Phase Chemical Equilibrium General Phase and Chemical Equilibrium... 

Moreover, scale up of the data obtained is virtually impossible, mainly due to different hydrodynamic conditions in the pi-lot-scale plant and the technical plant, impurities in the technical crystallizer which influence nucleation and crystal growth, and different heat transfer coefficients caused by different degrees of incrustation (or fouling) in pilot-scale and technical plants. Different models plug flow, macromixing, etc.) are discussed in [7.38] which consider deviations from ideal behavior in an MSMPR crystallizer. Results of scale up for this type of crystallizer are given in [7.48]. 

The performance of fluidized-bed reactors is not approximated by either the well-stirred or plug-flow idealized models. The solid phase tends to be well-mixed, but the bubbles lead to the gas phase having a poorer performance than well mixed. Overall, the performance of a fluidized-bed reactor often lies somewhere between the well-stirred and plug-flow models. 

To appreciate the questions raised by Knudsen s results, consider first the relation between molar flow and pressure gradient for a pure gas flowing through a porous plug, rather than a capillary. The form predicted by the dusty gas model can be obtained by setting = 1, grad = 0 in equation... 

Detailed Modeling Results. The results of a series of detailed calculations for an ideal isothermal plug-flow Langmuir system are summarized in Figure 15. The soHd lines show the form of the theoretical breakthrough curves for adsorption and desorption, calculated from the following set of model equations and expressed in terms of the dimensionless variables T, and P ... 

Consistent with this model, foams exhibit plug flow when forced through a channel or pipe. In the center of the channel the foam flows as a soHd plug, with a constant velocity. AH the shear flow occurs near the waHs, where the yield stress has been exceeded and the foam behaves like a viscous Hquid. At the waH, foams can exhibit waH sHp such that bubbles adjacent to the waH have nonzero velocity. The amount of waH sHp present has a significant influence on the overaH flow rate obtained for a given pressure gradient. 

Heat Transfer in Rotary Kilns. Heat transfer in rotary kilns occurs by conduction, convection, and radiation. In a highly simplified model, the treatment of radiation can be explained by applying a one-dimensional furnace approximation (19). The gas is assumed to be in plug flow the absorptivity, a, and emissivity, S, of the gas are assumed equal (a = e ) and the presence of water in the soHds is taken into account. Energy balances are performed on both the gas and soHd streams. Parallel or countercurrent kilns can be specified. 

The sohds are also assumed to be in plug flow. As part of the plug flow approximation, the gas and soHds are assumed isothermal in the radial direction at a given axial location. Detailed models for kiln heat transfer are available (20,21). 

Fig. 8. Combined flow reactor models (a) parallel flow reactors with longitudinal diffusion (diffusivities can differ), (b) internal recycle—cross-flow reactor (the recycle can be in either direction), comprising two countercurrent plug-flow reactors with intercormecting distributed flows, (c) plug-flow and weU-mixed reactors in series, and (d) 2ero-interniixing model, in which plug-flow reactors are parallel and a distribution of residence times dupHcates that...

The Ravenfield model BS viscometer is a wide shear rate range iastmment with several possible measurement systems cone—plate, parallel plates, concentric cylinders, and taper plug. The last gives shear rates of up to 10 , and the cone—plate of up to 8 x lO". The viscosity range is... 

Reactor types modeled A, stoichiometric conversion B, equiUbrium/free-energy minimization, continuous stirred tank, and plug flow C, reactive distillation. Some vendors have special models for special reactions also, private company simulators usually have reactors of specific interest to their company. 

Fig. 2. Schematic models of a plug flow electrochemical reactor (PFER) and a stirred tank electrochemical reactor (STER).

Example 8 Calculation of Rate-Based Distillation The separation of 655 lb mol/h of a bubble-point mixture of 16 mol % toluene, 9.5 mol % methanol, 53.3 mol % styrene, and 21.2 mol % ethylbenzene is to be earned out in a 9.84-ft diameter sieve-tray column having 40 sieve trays with 2-inch high weirs and on 24-inch tray spacing. The column is equipped with a total condenser and a partial reboiler. The feed wiU enter the column on the 21st tray from the top, where the column pressure will be 93 kPa, The bottom-tray pressure is 101 kPa and the top-tray pressure is 86 kPa. The distillate rate wiU be set at 167 lb mol/h in an attempt to obtain a sharp separation between toluene-methanol, which will tend to accumulate in the distillate, and styrene and ethylbenzene. A reflux ratio of 4.8 wiU be used. Plug flow of vapor and complete mixing of liquid wiU be assumed on each tray. K values will be computed from the UNIFAC activity-coefficient method and the Chan-Fair correlation will be used to estimate mass-transfer coefficients. Predict, with a rate-based model, the separation that will be achieved and back-calciilate from the computed tray compositions, the component vapor-phase Miirphree-tray efficiencies. 

Most plate columns operate under conditions such that gas is completely mixed as it flows between the plates, but few operate with pure plug flow of liquid. Departure from plug flow of liquid has been studied by Gautreaux and O Connell [Chem. Eng. Pi oq., 51, 232 (1955)] by assuming that hquid mixing can be represented as occurring in a series of stages of completely mixed liquid. For this model,... 

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