Slurry pressure-drop prediction

Pressure Drop Prediction for Slurries Exhibiting Power-law Rheology... 

A thick slurry with SG= 1.3 is to be pumped through a 1 in. ID pipe that is 200 ft long. You don t know the properties of the slurry, so you test it in the lab by pumping it through a 4 mm ID tube that is 1 m long. At a flow rate of 0.5 cm3/s, the pressure drop in this tube is 1 psi, and at a flow rate of 5 cm3/s it is 1.5 psi. Estimate the pressure drop that would be required to pump the slurry through the 1 in. pipe at a rate of 2 gpm and also at 30 gpm. Clearly explain the procedure you use, and state any assumptions that you make. Comment in detail about the possible accuracy of your predictions. Slurry SG= 1.3. 

Since it is not likely that the viscous slurries which exhibit Bingham plastic behavior will frequently reach Reynolds numbers appreciably greater than 200,000 it is possible to conclude that Fig. 14 may be used to predict pressure drops accurately under all conditions of interest except in the transition regions. If a problem happens to fall into what may appear to be a transition region, use of Fig. 7 is recommended instead of Fig. 4. 

It is important to be able to predict at just what level of t in the inlet cone the slurry begins to consolidate into an ice bed with brine flowing through it. If the zone at which consolidation begins is well below the level of the screens, packed ice may back up and fill the inlet pipe. The pressure drop through the ice packed in the inlet cone is important for specification of the pumping head required. 

Care is needed when modeling compressible gas flows, flows of vapor-liquid mixtures, slurry flows, and flows of non-Newtonian liquids. Some simulators use different pipe models for compressible flow. The prediction of pressure drop in multiphase flow is inexact at best and can be subject to very large errors if the extent of vaporization is unknown. In most of these cases, the simulation model should be replaced by a computational fluid dynamics (CFD) model of the important parts of the plant. 

Particle-fluid flow has been in existence in industrial processes since the nineteenth century. Applications include pneumatic conveying, which deals with pipe flow of solid material transported by a gas, slurry transport and processing of solids in a fluid. The necessity of predicting blower or pumping power for a given amount of material to be conveyed led to measurements of pressure drops and attempts in the correlation of physical parameters. That anomaly exists in the correlation in terms of simple parameter is one of the motivations for the exploration into the details of distributions in density and velocity and the present state of development of instrumentation. 

Comparison Between Different Viscometers. To validate their rheological measurements, several authors have tried to compare the results obtained using coaxial cylinder and pipe viscometers. Their findings are not necessarily in agreement. Bannister (15) was able to predict the frictional pressure drops of a cement slurry in a 1.815-in. ID pipe from pipe viscometer data corrected for wall slip. Mannheimer, who tried to reconcile coaxial cylinder and pipe viscometer data, both of them being corrected for wall slip was successful with one cement slurry formulation, but the approach failed with another one (13). Denis et al. (16) showed good agreement between coaxial cylinder and pipe viscometer data above a critical shear rate—or shear stress—that is pipe diameter dependent. 

For the same vacuum level, a crystallizing slurry will have a higher temperature than predicted for the pure solvent because the vapor pressure of the solvent is reduced by the presence of the solute (boiling point elevation). For adiabatic crystallization with the contents temperature as the input to the master control loop, the same temperature profile appropriate for crystallization by jacket cooling would apply here. However, the capability of the vacuum source and the line pressure drop should be considered in conjunction with the boiling point elevation to ensure that the desired final temperature can be met. If this is not satisfied, the desired yield may be achieved by removing some of the distillate, provided the saturation of an impurity is not reached. For most... 

There are as yet no theoretical correlations capable of predicting the viscosity, pressure drop and heat transfer coefficient in the preheater. Some empirical correlations for this purpose are available in the literature (11,13-16,38). The hydro-dynamic characteristics of three phase slurry reactors have been extensively reviewed (1,39,40,41). Suitable correlations have... 

As with slurries following a power-law flow model, it is necessary to reliably predict the pressure drop in a horizontal pipe of diameter D under laminar, fully developed flow conditions. A fundamental analysis of the Bingham plastic model yields the following expression for the mean velocity in terms of the yield stress Ty and the wall shear stress tq. 

Outline the steps in the procedure for predicting pipeline pressure drop for slurries exhibiting power-law rheology. 

Define the Hedstrom number. How is this number used in prediction of pipeline pressure drop for slurries exhibiting Bingham plastic rheology ... 

Carbonell and Guirardello (1997) performed simulations to establish the hydrodynamics (pressure drop, radial gas and slurry holdup distribution, effective eddy viscosity, and liquid-phase velocity profile). They also superimposed the thermal cracking reactions by accounting the radial variations in these transport properties so as to predict the heavy oil conversion. They found that the liquid recirculatory patterns (backmixing) strongly affect the product yields. However, the validation of the experimental was not carried out using these models. 

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