Sieving, data presentation

Fig. 11 Sieving data presented as a cumulative percentage undersize plot. The data were used to determine the geometric mean diameter of ethylcellulose microcapsules. (Adapted from Ref. 19.)...

It was concluded that approximately three minutes sieving time was adequate with the air-jet sieve even with waxlike materials such as cadmium stearate whereas, 20 minutes or longer was required for vibrating or shaking screens. The data presented (Refs 19 35) for AP by the Alpine, Tyler Ro-Tap, and Micromerograph agree remarkably well... 

Special attention must be paid to the interpretation of particle size data presented in terms of either weight or number of particles. Particle weight data may be more useful in sedimentation studies, whereas number data are of particular value in surface-related phenomena such as dissolution. Values on the basis of number can be collected by a counting technique such as microscopy, while values based on weight are usually obtained by sedimentation or sieving methods. Conversion of the estimates from a number distribution to a weight distribution, or vice versa, is also possible using adequate mathematical approaches, e.g., the Hatch-Choate equations. 

HT and large scale experiments were performed as described in [7], In HT runs, 116 2-ml GC vials (thin film, no stirring) were heated at 100° C for 3 h under 1500 psi of 02/C0 (10% 02 in CO) The presented results are the average of at least two runs (three of four when RSD data presented). Large-scale (60 g) experiments were carried out in 450 mL Hastelloy C Parr reactor under the same conditions in the presence of 3 A molecular sieves (35 g) s a desiccant. 

Existing literature and data will be used to avoid personal or institutional bias. One system involves relatively inert (nitrogen) physisorption on chars of interest as sorbents, catalysts, molecular sieves, separation substrates, storage media, etc. All of the sorption data presented here exist in tabular form, such that verification of this work and development of alternate theories, verification, and methodology is facilitated. 

Many industries have large data banks on product size distributions by sieve analysis and want to continue using this form of presentation. In order to accommodate this need Cho et. al. [48] converted Sedigraph data to sieve data using wet screened powder in the 38 to 53 pm size range and fitted the data to a logarithmic distribution to give the slope and median size. This procedure must be use with caution since the conversion factors are shape dependent and a new calibration is required for each product. 

Mechanical pulverizing and sieving procedures reduced the particle size to 100 x 200 and 200 x 325 mesh, although the data presented here are largely for the former size range. The mineral and elemental composition as a function of shale richness were determined from X-ray diffraction measurements (Phillips APD-3500) and energy dispersive X-ray fluorescence data (Kevex Model 0700). Low-temperature ash samples were prepared using a 13.56 MHz radio frequency asher (LFE Corp., Model LTA 504). 

Next, enter the data presented above into the Mathcad sieve-tray design computer program of Appendix E. Since the dimensions of the tray are known, the fractional approach to flooding is adjusted until the tray design coincides with the tray dimensions determined in part (a) of this example. Convergence is achieved at a value of/= 0.431. This means that at the bottom of the distillation column the gas velocity is only 43.1% of the flooding velocity. Other important results obtained from the program are as follows ... 

This program calculates the diameter of a sieve-trey tower to satisfy an approach to flooding criterium, and estimates the trey efficiency. The data presented are from Example 4.10... 

The data presented in the Table I showed that surface area of ruthenium molecular sieves prepared at constant pH have higher values than in the cases in which no HCI was added. In... 

To interpret sieve data, graphical and statistical methods of data presentation are used. The distribution curve that is widely used in industrial practice was developed by Rosin, Rammler, Sperling, and Bennett in the 1930s (Rosin, Rammler, Sperling, 1997 Rosin and Rammler, 1933 Bennett, 1936). They found out that the size distribution of coal dust and of other crushed and milled materials like cement follows a probability curve with a similar pattern as well-known physical functions such as the Maxwdl-BoUzmann distribution (Section 3.1.4) of the speed of gas molecules (Schubert and Waechtler, 1969). The so-called Rosin-Rammler-Sperling-Bennett (RRSB) function is given by ... 

For sieve or valve plates, h = h , outlet weir height. For bubble-cap plates, h = height of static seal. Tbe original references present vaH-dations against laboratoiy and small-commercial-column data. Modifications of tbe efficiency equation for absorption-stripping are also included. 

W1 is Bond work index based on 100 percent passing a 200-mesh sieve, is the sohds feed rate in kg/min, and S is weight percent solids in the feed. This represents experimental data for limestone, feldspar, sulfide ore, and quartz. The influence of Wl is believed to be due to its effect on amount of fines present in the mill. Parameters that did not affect are specific gravity of feed material, and feed size over the narrow range studied. 

Use of arithmetie graph paper tends to buneh at the lower end (due to the expansion of the sieve size seale). This ean be overeome by use of semi-log or log-log graph paper. Also note that eumulative graphs have the effeet of smoothing out the data. This ean be a useful effeet in the presentation of data Care should be exereised, however, to prevent important features of the distribution being obseured in analytieal work. 

Perforated plates without downcomers have only recently been included in commercial equipment. The data for rating the performance is not adequately covered in the literature, since the present developments in industrial equipment have not been released. The information included here is based only on available data and experience, yet it may serve as a basis for rating, because the basic nature of the contact is quite analogous to the sieve tray. The limits of performance are not well defined therefore the methods oudined cannot be considered firm. However, they are adequate for many applications and as the basis for further study. 

Conclusive evidence has been presented that surface-catalyzed coupling of alcohols to ethers proceeds predominantly the S 2 pathway, in which product composition, oxygen retention, and chiral inversion is controlled 1 "competitive double parkir of reactant alcohols or by transition state shape selectivity. These two features afforded by the use of solid add catalysts result in selectivities that are superior to solution reactions. High resolution XPS data demonstrate that Brpnsted add centers activate the alcohols for ether synthesis over sulfonic add resins, and the reaction conditions in zeolites indicate that Brpnsted adds are active centers therein, too. Two different shape-selectivity effects on the alcohol coupling pathway were observed herein transition-state constraint in HZSM-5 and reactant approach constraint in H-mordenite. None of these effects is a molecular sieving of the reactant molecules in the main zeolite channels, as both methanol and isobutanol have dimensions smaller than the main channel diameters in ZSM-S and mordenite. 

Particles come in all shapes and sizes and in large numbers. Data are presented graphically using histograms, fractional plots, or cumulative plots. These graphs are primarily useful as pictures of the size distribution of the mixture. Table 15.4 gives a typical screen analysis for a 900-g sample. The measured experimental data are the mesh sizes, and the masses of the particles on each of the sieves are the masses of the residuals or fines. The other quantities are calculated. 

Tn presenting the adsorptive properties of molecular sieve zeolites, most authors (1, 2) report isosteric heats. These are obtained from the application of the thermodynamically derived Clausius-Clapeyron type equation to experimentally measured equilibrium data. At a constant... 

In the performance data of various polyamide and related membranes published to date there should be valuable information for molecular design of more excellent barrier materials. But at present a means for their evaluation and optimization is still not clear. One of the reasons may at least come from the competitive flood of proposals for the detailed mechanisms of reverse osmosis, e.g. the solution-diffusion model, the sieve model, the preferential sorption model and so on. 109)... 

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