Fine powder ratio

From equation (8.39), one can obtain the relationship between the stack fine powder ratio (the relative amount of broken) and the external load, jdelding a simplified overall model for the stack crush strength of the catalyst. ... 

Equation (8.42) shows that the relation between the fine powder ratio and external force P can be expressed by the Weibull equation. The broken curve (the relationship curve between the fine powder ratio and external force) is a Weibull curve. This is closely related to the agreement between SPCS and the Weibull distribution. Experimental results in the literature show that the parameter M of the WSCS has a value very close to the Weibull modulus in the SPCS data. Both relationships are reflections of the distribution of defects in the material. In the measurement of WSCS, the disabled probability of [E(P)] is the fine powder ratio (dm/m). 

If the fine powder ratio obtained after particles are subjected to an external force is regarded as an index of strength disabled, the WSCS model may also be extended to describing the disabled behavior of non-spherical particles in a catalyst bed. Taking the logarithm of equation (8.42) twice, we have ... 

The SPCS cannot be used to measure the abrasion of irregular-shaped fused iron catalysts. The abrasion of these catalysts should be characterized by the WSCS method. Figure 8.40 shows the relationship between the external load and the fine powder ratio for irregular-shaped Fei xO based fused iron catalyst measured by WSCS. The figure shows the results fitted according to equation (8.43) and the data of Fig. 8.40. The fitting parameters are shown in Table 8.34. In the experiments, there are two different particle sizes of fine powder (<0.42mm and <0.85 mm) used for the calculation of the fine powder ratio (dm/m). 

Fig. 8.40 Relation between fine powder ratio and loadings of irregular-shaped fused iron catalyst measured by WSCS...

However, the WSCS model can only be used for a certain range of fine powder ratio. When the external load exceeds a certain limit, the measured fine powder ratio will depart from the model. The main reason for this is that when the pressure is high enough, a large number of fine powders appear and fill the interstices between the particles in the stack bed. The contact force between the particles is reduced, increasing the coordination number between particles, thus the actual probability of particles crushing in the bed is reduced. In addition, the diameter of the sample particles should be much smaller than the internal diameter of the container, in order to reduce the effect of the container wall on the spatial distribution of the particles. As a result, the WSCS model is applicable only when the external load meets a threshold value in equation (8.42). Different catalysts will have different threshold values of external load. 

Amount of material required. It is convenient to employ an arbitrary ratio of 0 10 g. of solid or 0 20 ml. of liquid for 3 0 ml. of solvent. Weigh out 0 10 g. of the finely-powdered solid to the nearest 0 01 g. after some experience, subsequent tests with the same compound may be estimated by eye. Measure out 0-20 ml. of the liquid either with a calibrated dropper (Fig. 11,27, 1) or a small graduated pipette. Use either a calibrated dropper or a graduated pipette to deliver 3 0 ml. of solvent. Rinse the delivery pipette with alcohol, followed by ether each time that it is used. 

Different resins have been developed for use in different reduction—ratio appHcation ranges (111,112). The powders suitable for high reduction—ratio appHcations, such as wire coatings, are not necessarily suitable for the medium reduction—ratio appHcations, such as tubings, or the low reduction—ratio appHcations, such as thread-sealant tapes or pipe liners. AppHcations and processing techniques are being used, which utilize the unique combination of properties offered by PTFE in fine powder form (113—115). 

Limestone is pulverized to 80 to 90 percent through 200 mesh. Shiny concentrations of 5 to 40% have been checked in pilot plants. Liquid to gas ratios are 0.2 to 0.3 gaLMSCF. Flue gas enters at 149°C (300°F) at a velocity of 2.44 m/s (8 ft/s). Utilization of 80 percent of the solid reagent may be approached. Flow is in parallel downward. Residence times are 10 to 12 s. At the outlet the particles are made just diy enough to keep from sticking to the wall, and the gas is within 11 to 28°C (20 to 50°F) of saturation. The fine powder is recovered with fabric filters. 

Critical Binder Liquid/Powder Ratio. When a liquid is mixed into a bulk powder made of fine particles, the liquid distributes itself first into small spaces between particles forming liquid bridges as can be seen in Fig. 12a. For very small amounts of liquid, these bridges are randomly spaced and do not influence the bulk properties of the powder. Upon introduction of larger... 

In some cases, especially for very fine powders, researchers have looked at other properties to explain or classify product behavior. For example, Gel dart et al. (1984) have found that the ratio of tapped to aerated bulk density provides a good indication of the likely fluidization characteristics of fine and cohesive powders. 

Solvents can increase reaction rates by dispersing reactant molecules and increasing the collision frequency (Figure 1.7a). In solution, all of the solutes are potential reactants. Reactions between solids, however, tend to be much slower than reactions in liquids as there is only a small amount of contact between the solid reactants. Even fine powders will have a relatively small surface area-to-mass ratio, so the bulk majority of the reactant is not in the right place to react (Figure 1.7b). 

A novel method of generating finely divided zinc metal is by the use of pulsed sonoelectrochemistry using an ultrasonic horn as the cathode [85], Normal electrolysis of ZnCl2 in aqueous NH4CI affords a zinc deposit on the cathode. When the electrolysis is pulsed at 300 ms on/off and the cathode is pulsed ultrasonically at a 100 ms 200 ms on off ratio the zinc is produced as a fine powder. This powder is considerably more active than commercial zinc powder e. g. in the addition of allyl bromide to benzaldehyde (Eq. 3.9). 

A 500-mL Schlenk tube equipped with a magnetic stirring bar and rubber septum is charged with finely powdered cis/tra .s-[PtCl2(SMe2)2] (3.90 g, 11.0 mmol) suspended in dry diethyl ether (160 mL). The ratio of the cis/trans isomers is not important. Indeed either pure cis- or trans-[PtCl2(SMe2)2]... 

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