Mode diameter

Mixtures of the Iron-Group Metals. It was first reported by Seraphin et al. (50) that a binary mixture of Fi and Ni yielded more abundant SWNTs than Fe or Ni alone catalyst. Saito et al. (51) showed that a mixture of Fe and Ni with the ratio of 1 1 (by weight) gave the highest yield of SWNTs, and deviation from the 1 to 1 composition reduced the yield. Approximately 10% of all the carbon in the raw soot (both the chamber and cathode soot) was incorporated into SWNTs at the highest yield. Diameters of SWNTs produced from Fe/Ni range from 0.9 to 1.4 nm, and the mode diameter is located in 1.1-1.2 nm. 

With this brief consideration of variations in catalyst pore structure, let us examine the pore structure of two catalysts used in this refractoriness study. One observes in Table V only slight differences between the two cobalt moly catalysts, T and R. They are typified by high surface area, small micropore mode diameters and low macropore volumes. 

PORE VOLUME, ml/g MICROPORE VOLUME, ml/g MODE DIAMETER, A... 

Figure 5 Is a histogram showing the distribution of pore volume vs. pore diameter for alumina carrier, fresh cobalt molybdenum catalyst and used cobalt molybdenum catalyst. There was a slight change In mode diameter when the carrier was loaded with about 20% active metal oxides. The pore volume was reduced from 0,60 to 0.53 ml/g. However, accumulation of about 17% coke during the processing of West Coast resld greatly shifted the mode downward and reduced the total pore volume from 0.53 to 0.30 ml/g. (All of these pore volumes have been normalized to 1.0 gram of alumina).

SAMPLE DESCRIPTION AND DESIGNATION PORE MACRO VOLUME, MICRO ml/g TOTAL MODE DIAMETER A SURFACE AREA 2, Itl /g... 

The characteristic data of particles are given by the mode diameter (MD) as the most frequent size of a particle population, the geometric mean diameter (OMD) of the particles and the total number concentration (TNC) as the total amount of particles over the whole measured range. The TNC is based on the flue gas volume at a standard oxygen content of 13%. 

The particle size distribution of the 70 kW boiler is shown in Fig. 2. All size distribution data were averaged over a time period of 45 minutes at a feed rate of 20 kg/h. The mode diameters of the particles vary from 62.6 nm at oxygen concentration of [Oi] 11.6 % in the flue gas up to 87 nm at [Oj]=2.7 %, depending on excess air supply. 

The combustion chamber of the moving grate boiler system was run over a wide range ofbum rates, starting from 150 kW up to 600 kW. The analysis of particle emissions such as particle diameter or total number concentrations (TNC) showed only little variations with the process parameters (Fig. 3). Similar to the 70 kW burner system, all test runs resulted in mode diameters most frequent size diameter) of 100 nm. The geometric mean diameter (GMD) has been analysed in the range of 90.45 nm up to 95.0 nm. The total number concentration (TNC) was between 2.8IE-i-7 and 5.12E-I-7, depending on excess air supply. 

For measurement of particles and gaseous emissions the same equipment and methods were applied for the PDU as for the previously tested commercial wood chip boilers. The patterns of particle size distribution of emissions from the PDU showed similar characteristics as those from commercial boilers. The mode diameters (MD) are at sizes between 80 and 100 nm Figure 8). 

Figure 19. RH values observed for the efflorescence of ammonium sulfate (120 sec residence time) by heterogeneous nucleation as a function of mode diameter of the inclusions for corundum ( ) and hematite ( ). The hnes show F = 0.50 of the optimized fit to the active site model (Eqn. 24). Right axes show saturation ratios, S, of the aqueous phase with respect to crystalline ammonium sulfate and salt mole fractions, x, of the aqueous phase, as calculated from the model of Clegg et al. (1998) when assuming equihbrium between RH and water activity and omitting Kelvin effects. Adapted from Martin et al. (2001). Used by permission of the American Geophysical Unioa...

Silica Support Apparent Density (g/cm3) Porosity Pore Volume (mL/g) Mode Diameter (iMl) Diameter Range0 (fim)... 

Mode diameter, Dmode Local maximum of the number distribution... 

FIGURE 7.24 Frequency of observed occurrence of sulfate modes of various sizes as a function of mode diameter for Los Angeles during the summer of 1987 (John et al., 1990). 

Silica Apparent density Pore volume Mode diameter Diameter range"... 

Figure 8-2. Mode diameter of ferrite particles formed from solutions containing Se(IV) or Se(VI).

Statistically, the particle size distribution can be characterized by three properties mode, median, and mean. The mode is the value that occurs most frequently. It is a value seldom used for describing particle size distribution. The average or arithmetic mean diameter, d, is affected by all values actually observed and thus is influenced greatly by extreme values. The median particle size, is the size that divides the frequency distribution into two equal areas. In practical application, the size distribution of a typical dust is typically skewed to the right, i.e., skewed to the larger particle size. The central tendency of a skewed frequency distribution is more adequately represented by the median rather than by the mean (see Fig. 9). Mathematically, the relationships among the mean, median, and mode diameter can be expressed as... 

---