Dissolving solid particles

Solving the problem on the interaction of a solid particle, drop, or bubble with the surrounding continuous phase underlies the design and analysis of many technological processes. The industrial applications of such interaction include classification of suspensions in hydrocyclones, sedimentation of colloids, pneumatic conveyers, fluidization, heterogeneous catalysis in suspension, dissolving solid particles, extraction from drops, absorption, and evaporation into bubbles [69, 107, 111, 122,137,478,505],... 

The constant K in Equation 9.29 has been shown to be equal to DIh, where D is the coefficient of the dissolving material of the drug and h is the thickness of the diffusion layer surrounding the dissolving solid particles. This diffusion layer is a thin, stationary film of a solution adjacent to the surface of a solid particle (Fig. 9.17) and is saturated with drug (4) in other words, the drug concentration in the diffusion layer is equal to Cg, the equilibrium solubility. The term (Cg - C ) in Equation 9.29... 

Protein Humidity/water content Hydrocarbons Carboxylic acids Amines Oil/fat Sucrose/glucose Additives in fuels Density Digestibility Viscosity Motor fuel octane number Reid vapor pressure of gasoline Seed germination Distillation parameters Fruit ripeness Total dissolved solids Particle size/fiber diameter Temperature Mechanical properties Thermal and mechanical pretreatment Molar masses of polymers... 

Metallic filter media may be used either for cake filtration or depth filtration, i.e., pore clogging. Regeneration of media may be achieved by dissolving solid particles inside the pores or by back thrust of filtrate. 

The most direct test of the tensile strength hypothesis would be to compare the value of Tq calculated from the closure point of the isotherm by Equation (3.61) with the tensile strength of the bulk liquid determined directly. Unfortunately, experimental measurement of the tensile strength is extremely difficult because of the part played by adventitious factors such as the presence of solid particles and dissolved gases, so that the values in the literature vary widely (between 9 and 270 bar for water at 298 K, for example). 

Erosion-corrosion can be defined as the accelerated degradation of a material resulting from the joint action of erosion and corrosion when the material is exposed to a rapidly moving fluid. Metal can be removed as solid particles of corrosion product or, in the case of severe erosion-corrosion, as dissolved ions. 

For wet ESPs, consideration must be given to handling wastewaters. For simple systems with innocuous dusts, water with particles collected by the ESP may be discharged from the ESP system to a solids-removing clarifier (either dedicated to the ESP or part of the plant wastewater treatment system) and then to final disposal. More complicated systems may require skimming and sludge removal, clarification in dedicated equipment, pH adjustment, and/or treatment to remove dissolved solids. Spray water from an ESP preconditioner may be treated separately from the water used to wash the ESP collecting pipes so that the cleaner of the two treated water streams may be returned to the ESP. Recirculation of treated water to the ESP may approach 100 percent (AWMA, 1992). 

Coliform bacteria Non-pathogenic microbes found in fecal matter that indicate the presence of water pollution are thereby a guide to the suitability for potable use. Colloids Very small, finely divided solids (particles that do not dissolve) that remain dispersed in a liquid for a long time due to their small size and electrical charge. 

Liquefaction The conversion of large solid particles of sludge into very fine particles which either dissolve or remain suspended in wastewater. 

The removal of solid particles from gas/vapor or liquid streams can be accomplished by several techniques, some handling the flow dry, others wetting the stream to settle/agglomerate the solids (or even dissolve) and remove the liquid phase from the system with the solid particles. Some techniques are more adaptable to certain industries than others. Figure 4-54 illustrates typical ranges of particle size removal of various types of common equipment or technique. All of these will not be covered in this chapter. Attention will be directed to the usual equipment associated with the chemical/petrochemical industries. 

TDS Total dissolved solids, expressed as ppm (parts per million) or as mg/1 (milligrams per liter). Evaporate the water from a sample and the residue can be weighed. TSS Total suspended solids expressed in similar terms to TDS but representing a concentration of insoluble particles. 

Many different types of external treatment processes are available to deal with typical MU water contaminants such as undesirable dissolved solids, colloidal particles, or noncondensable gases. 

The sediment surface separates a mixture of solid sediment and interstitial water from the overlying water. Growth of the sediment results from accumulation of solid particles and inclusion of water in the pore space between the particles. The rates of sediment deposition vary from a few millimeters per 1000 years in the pelagic ocean up to centimeters per year in lakes and coastal areas. The resulting flux density of solid particles to the sediment surface is normally in the range 0.006 to 6 kg/m per year (Lerman, 1979). The corresponding flux density of materials dissolved in the trapped water is 10 to 10 kg/m per year. Chemical species may also be transported across the sediment surface by other transport processes. The main processes are (Lerman, 1979) ... 

Strong acids (those that ionize completely in solution) are more likely to dissolve solids because charged particles such as hydrogen ions will interact more strongly with solids than will neutral particles. Weak acids do not readily donate hydrogen ions and consequently remain mostly in the neutral form. As a result, weak acids do not dissolve solids as readily as strong acids. 

When separating low-density solid particles or oil droplets from water, the most common method used is dissolved-air flotation. A typical arrangement is shown in Figure 8.12b. This shows some of the effluent water from the unit being recycled, and air being dissolved in the recycle under pressure. The pressure of the recycle is then reduced, releasing the air from solution as a mist of fine bubbles. This is then mixed with the incoming feed that enters the cell. Low-density material floats to the surface with the assistance of the air bubbles and is removed. 

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