Median particle diameter

The median particle diameter is the diameter which divides half of the measured quantity (mass, surface area, number), or divides the area under a frequency curve ia half The median for any distribution takes a different value depending on the measured quantity. The median, a useful measure of central tendency, can be easily estimated, especially when the data are presented ia cumulative form. In this case the median is the diameter corresponding to the fiftieth percentile of the distribution. 

When a distribufion of particle sizes which must be collected is present, the aclual size distribution must be converted to a mass distribution by aerodynamic size. Frequently the distribution can be represented or approximated by a log-normal distribution (a straight line on a log-log plot of cumulative mass percent of particles versus diameter) wmich can be characterized by the mass median particle diameter dp5o and the standard statistical deviation of particles from the median [Pg.1428]

Jackson and Calvert [Am. Inst. Chem. Eng. J., 12, 1075 (1966)] studied the collection of fine fuel-oil-mist particles in beds of V2-iu glass spheres, Raschig rings, and Berl and Intalox saddles. The mist had a mass median particle diameter of 6 Im and a standard deviation of 2.0. The collection efficiency as a function of particle size and gas... 

Mineral Median Particle Diameter (microns) Surfac Area (meter /gram)... 

The median particle diameter, dm, seems to provide a better indication of fluidization performance, as described by Geldart... 

For a given bulk solid, determine particle size distribution, median particle diameter dv50 (e.g., using a Coulter Counter or a Malvern Laser Diffraction Analyser) and ps. 

Median particle diameter, 18 136 Media recovery wet magnetic drums, 15 443... 

For the reconstruction of the size distribution, the theoretical signal course of a particle collective is calculated directly by a weighted summation of LII signals from monodisperse size classes, which are computed from the numerical solution of the power balance. The count median particle diameter dp,med, the distribution width a and the ambient temperature T0 are input parameter for this calculation. Fitting of this theoretical signal of a size-distributed particle ensemble in two different time intervals after the laser pulse ((Af)j, (Af)2) provides two characteristic signal decay times (tj = r((Af)j), r2 = t((Af)2)). 

TABLE 3.4 Maximum Volume Median Particle Diameter Predicted to Pass USP Stage I Content Uniformity Criteria with 99% Confidence for the Doses Listed and a Geometric Standard Deviation of 2 Taken from Figure 3.3 of Rohrs et al.4 Also Shown are the Minimum and Maximum Particle Diameters Calculated for the Listed Maximum Median Diameters Using Eqs. (3.1) and (3.2)... 

TABLE 3.5 Predicted Potency Distributions Using the Ideal Mixing Model and the Maximum Volume Median Particle Diameters and Particle Distribution Minimum and Maximum Diameters from Table 3.4 and a Geometric Standard Deviation of 2... 

Emphasis has also been placed on the particle size distribution and the uniform size distribution of the API rather than on the mean particle size alone by other authors.1416 Rohrs et al.16 give a nomograph for identifying the maximum median particle diameter to pass USP 28 stage I content uniformity criteria with 99% confidence as a function of dose as well as width of particle size distribution (geometrical standard deviation). 

The median particle diameter can be determined by listing all diameters in order from the smallest to the largest and then finding the particle diameter that splits the list into two equal halves. 

If a straight line can be fitted to the plot, then the median particle diameter can be determined as being the 50 percent value on the plot (remember that when you are plotting number distribution, geometric mean and median for the number distribution are the same if there is a lognormal distribution). The geometric standard deviation is determined by the ratio... 

The trend to improved attrition resistance as the CP particle size decreases is illustrated in Figure 6. The bar graph plots the AI against median particle diameter of the aluminas. We suspect that CP-2 offers the most binding sites per unit volume of particles. Also, there are more nuclei of CP-2 than CP-25 in equivalent slurry volumes. Consequently, more surface functionality is available for condensation of the polysilicic acid moieties and the CP-2 material is the least attritable. 

Median Particle Diameter (microns) % less than 10 microns 15-20 Bulk Density - loose (gm/cm3) 0.9 Bulk Density - packed (gm/cm3) 1.2 Specific Gravity (gm/cm3) 2.42 Surface Area (m2/gm) 2-3... 

Measurements on dust accumulation in a laboratory PPR module, carried out by Calis [6] with a silica powder and a fly ash (median particle diameter between 20 and 30 xm) at a solids concentration between 5 and 10 g/m in air at ambient conditions and a gas velocity of about 1 m/sec showed that about 10% of the dust introduced is trapped, the major part of 90% being entrained by the exit gas. 

The MIP method seems to be the most relevant since, as seen from the results, it provides additional information as for the median particles diameter and Specific Surface Area. 

Bulk density of bed Bulk density of fines Product-to-fines ratio Mass median particle diameter Attrition resistance index Structure (x-ray diffraction)... 

The anode active material of the alkaline Zn/Mn02 cell is zinc powder with median particle diameters of... 

Properties BET specific surface area 56 mVg [127], 62 mVg [1767], specific surface area 149m7g [186,1766], median particle diameter 15.6 pm, detailed chemical analysis available [186],... 

Properties Specific surface area, median particle diameter (see Table 3.773). Detailed chemical analysis, particle size distribution, and pore volumes and diameters available [186]. 

Figure 12.5 Sizes of A1 and Cu particles produced in an evaporation-condensation generator. Median particle diameter increased with increasing inert gas pressure and atomic weight. (After Granqvist and Buhrman, 1976.)...

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