Cakes physical properties

Results from constant differential pressure filtration tests have been analyzed according to traditional filtration science techniques with some modifications to account for the cross-flow filter arrangement.11 Resistivity of the filter medium may vary over time due to the infiltration of the ultrafine catalyst particles within the media matrix. Flow resistance through the filter cake can be measured and correlated to changes in the activation procedure and to the chemical and physical properties of the catalyst particles. The clean medium permeability must be determined before the slurries are filtered. The general filtration equation or the Darcy equation for the clean medium is defined as... 

Typical values of the specific resistance r of filter cakes, taken from the work of Carman(1°), are given in Table 7.1. In the absence of details of the physical properties of the particles and of the conditions under which they had been formed, these values are approximate although they do provide an indication of the orders of magnitude. 

Whilst it may be possible to predict qualitatively the effect of the physical properties of the fluid and the solid on the filtration characteristics of a suspension, it is necessary in all cases to carry out a test on a sample before the large-scale plant can be designed. A simple vacuum filter with a filter area of 0.0065 m2 is used to obtain laboratory data, as illustrated in Figure 7.5. The information on filtration rates and specific resistance obtained in this way can be directly applied to industrial filters provided due account is taken of the compressibility of the filter cake. It cannot be stressed too... 

These parameters should not therefore be interpreted as constant, intrinsic physical properties of the soot cake, but rather as dynamic properties that depend on the deposit growth mechanism and its history. 

At first consideration, there may appear to be little, if any, relationship between the physical and chemical behavior of coal, but in fact the converse is very true. For example, the pore size of coal (which is truly a physical property) is a major factor in determining the chemical reactivity of coal (Walker, 1981). And chemical effects that result in the swelling and caking of coal(s) have a substantial effect on the means by which coal should be handled either prior to or during conversion operations. This is the reason for the study and measurement of these very important properties of coal. 

Failure to meet specifications for appearance and physical properties (e.g., color, phase separation, resuspendablity, delivery per actuation, caking, hardness, and as appropriate to the product type)... 

Equilibrium saturation of the cake, = w /w,, will initially depend on the physical properties of the filter cake. They are characterized by a, e, and K. represents the contact angle (degree of wettability) and K any other grain parameters such as roughness and so on. Furthermore, the physical properties of the wash liquid (density, p, and surface tension, o) and, finally, centrifugal acceleration, b, as process parameter will be of importance ... 

In dead-end filtration, a cake forms on the surface of the pad as the filtration proceeds. The cake permeability is the most important physical property of a porous medium and the hydraulic properties of the flow and the specific cake resistance are described by Darcy s Law ... 

SODIUM HYDROXIDE (CAUSTIC SODA) Physical Properties Sodium hydroxide, NaOH, mol wt 39.998, is a brittle, white, translucent crystalline solid. Because of its corrosive action on all human body tissue, it is also known as caustic soda. Physical properties of the pure material are noted in Table 20. Sodium hydroxide is produced and shipped in the anhydrous state in the form of solid cakes, flakes, or beads, but is used in solution (4). Properties of aqueous sodium hydroxide solutions relevant to industrial operations are available from manufacturers and in handbooks (79). Table 21 lists the significant uses. Table 20. Physical Constants of Pure Sodium Hydroxide ... 

Pastry, Cake, and Biscuit Products. In general, fats play several essential nutritional, technological, functional, and organoleptic roles in most all-bakery applications. As a result of its physical properties, fat plays a major part in the production of the majority of items in the pastry, cake, biscuit, and chocolate confectionery sector for example, in the preparation of pastry cream and in the desired appearance and texture of the end product. These physical properties include, above all, the rheological properties (consistency, plasticity, texture, etc.), and the properties of fusion and crystallization depend on the type of fat, the temperature, and the working conditions of the product. 

K, is mainly determined by the filter cake structure thus closely related to the physical properties of the dust itself. 

Sorbitol occurs as an odorless, white or almost colorless, crystalline, hygroscopic powder. Eour crystalline polymorphs and one amorphous form of sorbitol have been identified that have slightly different physical properties, e.g., melting point. Sorbitol is available in a wide range of grades and polymorphic forms such as granules, flakes, or peUets that tend to cake less than the powdered form and have more desirable compression characteristics. Sorbitol has a pleasant, coohng, sweet taste and has approximately 50-60% of the sweetness of sucrose. 

Example 1—Dry 100 lbs. ofwetcake with an/ /fto/ volatiles content ofl5%(wetbasis) dovmXodiflnalvolatilescontent of less than 1 %. This will be achieved in a batch operation for lot identification, GMP and high quality standards. The loose bulk density of the wet cake is 45 lbs../ft. and the loose bulk density of the diy powder is 12 Ibs./ft. The temperature limit of the product is 145°F and the feed material is wet with ethanol. The product is a pharmaceutical which will be a finished product. The solvent is to be recovered for reuse, and its physical properties can be found in a handbook of hydrocarbons. The product is freeflowing in the dry state, but very tacky and pasty in the wet state. 

Fertilizers are packaged in a variety of different forms including solids, liquids (solutions and suspensions), and gas (anhydrous ammonia). The important physical properties of solid fertilizers are particle size, particle strength, caking tendency, chemical stability, and hygroscopicity. 

From Eq. (30.15), a is the resistance of a cake that gives a unit pressure drop when p, u, and mjA all equal 1.0. Equation (30.166) shows that a is influenced solely by the physical properties of the cake, especially the particle size Dp and the porosity s. 

Suspension flow in porous media is governed by many factors. Depending on the physical properties of the solid particles, the porous media, and operating conditions, solids form external cake, internal filter cake, or just flow through the media without causing any damage. 

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