Viscosity slurry

Slurry Viscosity. Viscosities of magnesium hydroxide slurries are determined by the Brookfield Viscometer in which viscosity is measured using various combinations of spindles and spindle speeds, or other common methods of viscometry. Viscosity decreases with increasing rate of shear. Fluids, such as magnesium hydroxide slurry, that exhibit this type of rheological behavior are termed pseudoplastic. The viscosities obtained can be correlated with product or process parameters. Details of viscosity deterrnination for slurries are well covered in the Hterature (85,86). 

Deflocculation and Slurry Thinning. Sihcates are used as deflocculants, ie, agents that maintain high sohds slurry viscosities at increased sohds concentrations. Soluble sihcates suppress the formation of ordered stmctures within clay slurries that creates resistance to viscous flow within the various sytems. Laboratory trials are necessary, because the complexity of the systems precludes the use of a universal deflocculant. Sihcates are employed in thinning of limestone or clay slurries used in the wet-process manufacture of cements and bricks, clay refining, and petroleum drilling muds (see also... 

In the equation referred to above, it is assumed that there is 100 percent transmission of the shear rate in the shear stress. However, with the slurry viscosity determined essentially by the properties of the slurry, at high concentrations of slurries there is a shppage factor. Internal motion of particles in the fluids over and around each other can reduce the effective transmission of viscosity efficiencies from 100 percent to as low as 30 percent. 

Additives can alter the rate of wet ball milling by changing the slurry viscosity or by altering the location of particles with respect to the balls. These effects are discussed under Tumbhng Mills. In conclusion, there is still no theoretical way to select the most effective additive. Empirical investigation, guided by the principles discussed earlier, is the only recourse. There are a number of commercially available grinding aids that may be tried. Also, a Idt of 450 surfactants that can be used for systematic trials (Model SU-450, Chem Service... 

Figure 55 indicates that the level of percent solids is extremely important in determining the proper separation, the higher the concentration, the coarser the separation. The correction factor is a relative measure of slurry viscosity and is affected by such parameters as particle present and particle shape. A feed that contains a large amount of clay would tend to shift the curve to the left, resulting in a coarser separation. In contrast, the absence of fines would shift the curve to the right and result in a finer separation. 

Chemorheology is concerned with the chemical kinetics and the associated flow properties of a model reacting system. Energetic composite rheology is a continuously evolving process. The initial slurry viscosity is determined by the system temperature, plasticizer content... 

Dispersants are used in well cement slurries. For this application, the dispersant should be water soluble. The dispersants prevent high initial cement slurry viscosities and friction losses when the slurries are pumped. 

The flocculation responses studied are settling rate, percent solid settled, supernatant clarity, sediment volume and slurry viscosity. The polymer concentration and polymer anionicity required for maximum flocculation were seen clearly to depend on the response studied. Both the settling rate and the supernatant clarity with the nonionic polyacrylamide flocculent showed at pH 4.5 a marked increase to a maximum at about 25 mg/kg, whereas with the anionic polymer settling rate and supernatant clarity showed maxima at 10-25 mg/kg, but the system was totally... 

On the reverse, how does the presence of particles affect local and global flow features in the vessel such as the vortex structure in the vicinity of the impeller, power consumption, circulation and mixing times, and the spatial distribution of turbulence quantities more specifically colliding particles have an impact on the liquid s turbulence (Ten Cate et al., 2004) while local particle concentrations affect the effective (slurry) viscosity which may be useful in the macroflow simulations ... 

Ciystallization from solution is an important separation and purification process in a wide variety of industries. These range from basic materials such as sucrose, sodium chloride and fertilizer chemicals to pharmaceuticals, catalysts and specialty chemicals. The major purpose of crystallization processes is the production of a pure product. In practice however, a number of additional product specifications are often made. They may include such properties as the ciystd size distribution (or average size), bulk density, filterability, slurry viscosity, and dry solids flow properties. These properties depend on the crystal size distribution and crystal shape. The goal of crystallization research therefore, is to develop theories and techniques to allow control of purity, size distribution and shape of crystals. 

In various kinds of industrial production, materials need to be treated with charged colloidal particles. In such systems, the value of the zeta-potential analyses are needed to control production. For example, in paper, adhesive, and synthetic plastics, colloidal clay can be used as filler. In oil drilling, clay colloidal suspensions are used. The zeta potential is controlled so as to avoid clogging the pumping process in the oil well. It has been found that, for instance, the viscosity of a clay suspension shows a minimum when the zeta potential is changed (with the help of pH from 1 to 7) from 15 to 35 mV. Similar observations have been reported in coal slurry viscosity. The viscosity was controlled by the zeta potential. 

Runnels and Eyman [41] report a tribological analysis of CMP in which a fluid-flow-induced stress distribution across the entire wafer surface is examined. Fundamentally, the model seeks to determine if hydroplaning of the wafer occurs by consideration of the fluid film between wafer and pad, in this case on a wafer scale. The thickness of the (slurry) fluid film is a key parameter, and depends on wafer curvature, slurry viscosity, and rotation speed. The traditional Preston equation R = KPV, where R is removal rate, P is pressure, and V is relative velocity, is modified to R = k ar, where a and T are the magnitudes of normal and shear stress, respectively. Fluid mechanic calculations are undertaken to determine contributions to these stresses based on how the slurry flows macroscopically, and how pressure is distributed across the entire wafer. Navier-Stokes equations for incompressible Newtonian flow (constant viscosity) are solved on a three-dimensional mesh ... 

Although this approach does lead to stronger binding of the polymer, it will also reduce the amount of free charges on the adsorbed chains and most likely lead to a flatter conformation. As can be seen from Figure 12, as a result of these two conflicting effects there is an optimum range of initial neutralisation that leads to low slurry viscosities. 

Figure 7.33 Variation of tape thickness with carrier velocity and slurry viscosity. Adapted from J. S. Reed, Principles of Ceramics Processing, 2nd ed. Copyright 1995 by John Wiley Sons, Inc. This material is used by permission of John Wiley Sons, Inc.

Slurry Viscosities. In addition to the yield stress, the characteristic shear stress-shear rate relation of the fuel slurry should be known since the shape of the shear rate-shear stress curve (consistency curve) is an indication of the gel characteristics. Low shear rate data (102 sec."1) are useful mainly in determining batch-to-batch reproducibility, while high shear rate data (104 to 106 sec."1) are required to assess the flow characteristics in engine hardware. 

In addition to these defined functions, lignin products are also known for their ability to reduce the size of particles, reduce slurry viscosities, inhibit crystal growth, sequester and complex metals, and function as interactive carriers. 

The recovery, regeneration, and repeated reuse of the active catalyst are of prime importance in substantially reducing the overall cost of coal liquefaction. The used catalysts usually remain in the bottoms products, which consist of nondistillable asphaltenes, preasphaltenes, unreacted coal, and minerals. The asphaltenes and preasphaltenes can be recycled with the catalyst in bottoms recycle processes. However, unreacted coal and minerals, if present in the recycle, dilute the catalyst and limit the amount of allowable bottoms recycle because they unnecessarily increase the slurry viscosity and corrosion problems. Hence, these useless components should be removed or at least reduced in concentration. If the catalyst is deactivated, reactivation becomes necessary before reuse. Thus, the design of means for catalyst regeneration and recycle is necessary for an effective coal liquefaction process. Several approaches to achieving these goals are discussed below. 

The quantities pg and a are, respectively, the gas density and gas/liquid surface tension at operating pressure and temperature. The effective slurry density can be calculated by the formulae given above. K is a correlation factor, which accounts for the effect of particles on slurry viscosity ... 

Scanning electron-microscopic (SEM) studies revealed the porous surface of these wash-coats. A falling test was developed and applied to the coatings. At an impingement velocity of 3 m s-1 losses of the wash coat did not exceed 1%. The deviation of the coating mass over a set of parallel micro channels at a certain axial position was determined as less than 5%. To achieve coating profiles of equal thickness in the radial direction, optimization of the slurry viscosity was required... 

Compressibility Low swelling Low binder amounts Low slurry viscosity... 

---