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Attrition factor

Table 5.20 shows the relationship between hardness, time and bake temperature. A lower attrition factor indicates a harder powder. [Pg.60]

Table 5.20. Relationship Between Particle Hardness (Attrition Factor), Time, and Bake Temperature ... Table 5.20. Relationship Between Particle Hardness (Attrition Factor), Time, and Bake Temperature ...
Pressure Drop. The prediction of pressure drop in fixed beds of adsorbent particles is important. When the pressure loss is too high, cosdy compression may be increased, adsorbent may be fluidized and subject to attrition, or the excessive force may cmsh the particles. As discussed previously, RPSA rehes on pressure drop for separation. Because of the cychc nature of adsorption processes, pressure drop must be calculated for each of the steps of the cycle. The most commonly used pressure drop equations for fixed beds of adsorbent are those of Ergun (143), Leva (144), and Brownell and co-workers (145). Each of these correlations uses a particle Reynolds number (Re = G///) and friction factor (f) to calculate the pressure drop (AP) per... [Pg.287]

Much effort has been made by catalyst manufacturers to improve catalyst atttition resistance and thus reduce the formation of fines (see Catalysts, supported). In the 10-year petiod from 1980 to 1990, most catalyst manufacturers improved the atttition resistance of their catalyst by a factor of at least 3—4. This improvement was achieved even though the catalyst zeoHte content duting this petiod was continually increasing, a factor that makes achieving catalyst hardness more difficult. As an example of the type of atttition improvement that has been achieved, the catalyst atttition index, which is directiy related to catalyst loss rate in a laboratory attrition test, decreased from 1.0 to 0.35 for one constant catalyst grade during 1989—1990 (37). [Pg.214]

Figure 5.17 Effect of scale-up factor ( Figure 5.17 Effect of scale-up factor (<i/4ab) ow overall attrition rate for constant (Synowiec etai, 1993)...
Interesting features of this process include the potential for one-stage methanation to completion without the need for gas recycle. This feature was cited by Chem Systems, but, according to Rheinpruessen-Koppers work on the Fischer-Tropsch (52, 53), gas recycle was necessary with high H2 CO ratios. Drawbacks include such factors as catalyst attrition (48, 50), and low volume productivities of the methanator (less than one-tenth that reported for fixed bed adiabatic reactors) (48, 50, 52, 53, 61). [Pg.37]

Most types of ion-exchange resin suffer some breakdown and volume loss over time because of attrition, excessive heat, or other factors. Water softeners should be inspected annually, and a double backwash procedure should be provided. This generally lifts the broken resin ( fines ) to the top of the bed, where it can be removed and replaced to restore capacity. Allow for 5 to 10% resin operating capacity loss per year because of physical breakdown. At many sites the resin is unfortunately not inspected regularly but merely replaced when a serious decline in operating capacity is noticed. Here a resin life expectancy of, say, 6 to 8 years probably is the norm. [Pg.197]

In practice, it is prudent to increase Lmin by a factor of 50 to 100%. A shroud length less than Lmin causes significantly more erosion and attrition than no shroud at all. Significant attrition can also occur if the shroud is not centered over the smaller hole. [Pg.219]

If properly sized and installed, particle attrition is reduced by a factor (Karri, 1990) calculated from ... [Pg.220]

If excessive particle attrition is expected, it is a common practice to place a shroud/nozzle around a grid hole as discussed in Sec. 3.5. For properly sized nozzles, one can derive from Eq. (17), particle attrition is reduced by a factor ... [Pg.222]

Particle attrition rate will be reduced by a factor calculated from Eq. (16)... [Pg.230]

Both, the mechanism and the extent of particle degradation depend not only on the process type but also on properties of the solid material, and to a large extent on the process conditions. Clift (1996) has stated that attrition is a triple-level problem, i.e., one is dealing with phenomena on three different length and time scales the processing equipment, the individual particles, and the sub-particle phenomenon such as fracture which leads to the formation of fines. The appearance of attrition can, therefore, differ very much between the various applications. For that reason, the following section deals with the various modes of attrition and the factors affecting them. [Pg.436]

The large amount of variables affecting attrition can be classified into two major groups, i.e., the various factors related to material properties and factors related to process conditions. [Pg.438]

Particle Size Distribution. The particle size distribution is a significant factor with respect to attrition. Coarser particles tend more to fragmentation while smaller particles have a stronger inclination to abrasion because of their large specific surface. Since the particle degradation is composed of fragmentation as well as abrasion, both the amount and the... [Pg.439]

The cyclone inlet velocity is thus shown to be the most significant factor influencing the solids loss due to attrition in the cyclone. [Pg.473]

Physicochemical profiling at the early discovery stage is important in the pharmaceutical industry because poor bioavailability is a leading factor in compound attrition. The ability to rapidly measure absorption properties such as solubility, log P, and log D allows promising compounds to quickly pass into exploratory development. [Pg.237]

Clinical success rates and attrition rates by phase of clinical trial for new drugs are important indicators of how effectively companies are utilising drug development resources. The proficiency with which this is done reflects a complex set of regulatory, economic and company-specific factors. Success rates differ by therapeutic class, and t)q)ically vary from about 28% success rate for an anti-infective compound to 12% for respiratory drugs. Table 9.3 shows the details. [Pg.316]


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