Filtration problems

A further recommendation, depending on the application, is not to increase the pressure difference for the purpose of increasing the filtration rate. The cake may, for example, be highly compressible thus, increased pressure would result in significant increases in the specific cake resistance. We may generalize the selection process to the extent of applying three rules to all filtration problems ... 

Sand filters vary in sophistication. A simple filter will remove most particles down to 5 pm. Multi-media filters which use sand and anthracite, and possibly a third medium, in discrete layers, can yield very efficient filtration down to 2 pm. Granular activated carbon can be used instead of sand to add some measure of organic removal to the filtration process. The quality produced by any filter depends largely on the efficiency of the backwash. Sand filters in some form provide a satisfactory solution for the majority of water-filtration problems. 

Leaching the catalyst nnder NaOH-deficient conditions will convert the sodinm aluminate to Al(OH)3 according to eq. 4 and this can react further to form AI2O3 (see eq. 5). This series of reactions will produce a white powder that is not only hard to remove from the catalyst, but it can also cause by-products and filtration problems during the catalyst s use. Moreover, some of this Al(OH)3 and AI2O3 will adsorb onto the catalyst to block its surface and fill its pores leading to lower activity. 

Wort separation and beer filtration are two common bottlenecks in the brewing process. Poor lautering not only causes a loss in production capacity, but can also lead to losses in extract yield. Furthermore, a slow lautering negatively affects the quality of the wort, which may give beer filtration problems and problems with the flavor and stability of the beer. 

Figure 4.37 gives the combination of the simulation results obtained with the model and with an assembly of experimental data. We have to notice that the values of the factors for the relations that give the transition frequencies must respect the dimensional units from Table 4.7. These relations make it possible to formulate the optimisation of the filtration problem and then to establish the combination of factors allowing deep bed filtration at minimum financial cost. 

Several crystallization objectives have been recommended to favor downstream operations or product quality. One can maximize the number-mean or weight-mean crystal size, maximize the final size of crystals grown from seed crystals, or minimize the ratio of nucleated crystal mass to seed crystal mass.f ° Other particle size-related characteristics of product crystals that have been optimized during crystallization include the coefficient of variation and the crystal shape. Although the weight-mean crystal size is the most commonly used objective in optimal control studies, the weight-mean crystal size is too insensitive to the number of small crystals that can cause filtration problems when used as an objective to optimize the crystallization operations. 

In the production of an intermediate compound in the synthesis of a pharmaceutical product, filtration difficulty was encountered after the crystallization of that intermediate by distillation. The filtration problem was attributed to the presence of very fine needles ( 2 microns thick). 

Let us first see how this rapid filtration problem would be handled using chem lab equipment before looking at ways to improvise for the same effect. To begin with, a source of vacuum would be close at hand on the lab bench, such as an aspirator. A water bed pump would serve the same purpose just as well since a really good vacuum isn t needed. From this vacuum source, a vacuum hose similar to an automotive vacuum hose would be led to the glassware set-up shown below ... 

Hydraulic pressure. The pilot plant is able to spray at pressures up to 3000 psig. Theoretically, nozzle atomization efficiency increases with pressure. Therefore the most desirable conditions for sulfur application are the highest pressure attainable and the smallest nozzle available. However, filtration problems associated with the smallest nozzles com-... 

Phenomenological Modeling. Filtration Theory. Modeling of fines or particulate migration was first considered in deep bed filtration problems. The introduction of a more convenient time variable... 

Data on the effective metastable limit at the conditions you are interested in (composition, cooling rate, and stirring) are important because you normally wish to operate a crystallizer away from the edge of the effective metastable zone. As we will see in later chapters, formation of small crystals, which are known as fines, is a common problem. Fines cause filtration problems and... 

Where neither of these two methods may be applied, a third and technically undesirable process is sometimes used. This involves solvent extraction of the iron oxide cake, which brings with it filtration problems and costly solvent recovery. Where a cheap solvent, such as naphtha, can be used, these difficulties are somewhat mitigated. Where a water-miscible solvent can be used, it is usually added to the reduction mixture initially, as discussed above. 

In many real filtration problems, the A in Eq. 12.32 is not constant but is a function of the pressure. This occurs because many filtrates, such as the iron hydroxides and aluminum hydroxides used in water clarification, are weak-structured gels or floes. In the loose state they have a relatively low flow resistance, but under pressure they collapse and fornji denser structures which have a higher flow resistance. The common practice in describing such cakes is to write... 

Possible alternatives to cross-linked polymer supports are soluble and colloidal polymers. They would require large scale ultrafiltration for industrial use. Although ultrafiltration is not yet economical for desalination of seawater, it might be for a separation of a more expensive product. One example is the catalytic partial hydrogenation of soybean oil (361 with soluble polymer-bound transition metal complexes. Solid inorganic supports such as silica gel and alumina are usually not subject to these physical attrition and filtration problems. 

Two mock-up tests were carried at the 0-arai Engineering Center(OEC), using full-scale simulation of equipment around the leak site, to exannine the sodium leak combustion behavior and damage mechanism. The first test was terminated early due to exhaust gas filtration problems. In the second test (Sodium Leak Combustion Test II) the floor liner was perforated this had not occurred in the Monju accident. 

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