Sieve system

Coffee and tea extracts are therefore foamed by N2 or C02 during cooling and partially freezing (e. g. to -5 °C) in a type of ice-cream machine. This foam must have a desired Density, with the inclusion of certain amount of small ice crystals. The foam is cooled on a conveyor belt not to -18 °C, but to -40 °C or colder, as this product must pass a grinding and sieving system to achieve a desired grain size and density. 

A typical grinding and sieving system (Fig. 2.5) produces dust which has to be collected. If in addition a CIP (cleaning in place) installation is installed, the total preparation equipment becomes a major part of the whole freezing and freeze drying installation. Figure 2.6 shows only the collecting container for the dust, which is sorted by size while below the container is the vibration transport system. 

The 4 A Molecular Sieves System. The initial procedure for the Sharpless reaction required a stoichiometric amount of the tartrate Ti complex promoter. In the presence of 4 A molecular sieves, the asymmetric reaction can be achieved with a catalytic amount of titanium tetraisopropoxide and DET (Table 4-2).15 This can be explained by the fact that the molecular sieves may remove the co-existing water in the reaction system and thus avoid catalyst deactivation. Similar results may be observed in kinetic resolution (Table 4-3).15... 

The heat of adsorption data of the C02-5A sieve system exhibit homogeneous surface properties as shown by the relatively invariant heat of adsorption. The agreement between the calorimetric heats and those predicted by Equation 1 are reasonably good, and the application of Equation 4 provides little improvement. On the other hand, the C02-NaX sieve system and the C02-H-mordenite system show significant heterogeneous character. In these cases the model described by Equations 3 and 4 is necessary to obtain acceptable predictions. 

Carbon molecular sieves are produced by controlled pyrolysis and subsequent oxidation of coal, anthracite, or organic polymer materials. They differ from zeolites in that the micropores are not determined by the crystal structure and there is therefore always some distribution of micropore size. However, by careful control of the manufacturing process the micropore size distribution can be kept surprisingly narrow, so that efficient size-selective adsorption separations are possible with such adsorbents. Carbon molecular sieves also have a well-defined bi-modal (macropore-micropore) size distribution, so there are many similarities between the adsorption kinetic behavior of zeolitic and carbon molecular sieve systems. 

However, a price is paid in return for these advantages nongel sieving systems usually have a lower resolving power compared to gel-filled capillaries. The resolving power, however, depends on the nature of the nongel sieving medium, and a recently introduced polymeric hydroxyethylcellulose shows a separation power close to that of gel-filled capillaries (Nathakarnkitkool et al., 1992). 

One of the major advantages of a molecular sieve system is the almost complete removal of heavy and unsaturated hydrocarbons, notably acetylene. Acetylene if precipitated out of LOX will detonate. It is, therefore, very important to monitor and keep acetylene levels signi cantly belo w the solubility limits, 8 ppm in LOX at 20 psia (138 kPa). In a reversing ASU it is necessary to add cryogenic silica gel adsorbers to scavenge any acetylene entering the column system. 

In all sections macro-, meso-, and microporous (molecular sieving) systems will be treated separately. The focus will be on the most promising systems to obtain high selectivity (separation factors) in combination with reasonable permeation values. 

J. C. Vartuli, C. T. Kresge, W. J. Roth, S. B. McCullen, J. S. Beck, K. D. Schmitt, M. E. Leonowicz, J. D. Lutner, E. W. Sheppard, Designed synthesis of mesoporous molecular sieve systems using surfactant directing agents, in W. R. Moser(Ed.), Advanced Catalysts and Nanostructured Materials Modern Synthetic Methods, Academic Press, San Diego, 1996, pp. 1-19. 

The authors recognize that some of the results presented in this paper parallel published findings based on other types of infrared spectroscopic techniques, but feel that their presentation in the context of this paper serves to establish the credibility of the DRIFT/GC/MS procedure in advance of the publication of similar studies currently under way on other molecular sieve systems that have not been investigated in detail by such methods. 

A definite amount of leady oxide is separated by a series of sieves of different mesh size placed above each other into fractions with different particle size distribution. The leady oxide is usually fed in the form of suspension. After a certain period of vibration of the sieve system, the weights of the different powder fractions are measured. A particle size distribution curve is plotted. 

In gel-ffee sieving systems, the medium consists of an electrolyte solution containing linear hydrophilic polymers (e.g., polyethylene glycols). Separation according to size is obtained because of the resistance provided by entangled polymers. Compared to gel CE, gel-ffee sieving is easy to perform, the capillary system has a long... 

The grain size distribution of aggregate should be carefully designed and checked if concrete of good quality is to be prepared. The grading is established after sieve analysis using sieves in accordance with local standards usually separate sieve systems are used for coarse and fine aggregates. 

Nielsen and Bucklin compared the cost of a methanol injection plant for 600 psig natural gas to costs of solid-bed dehydration. They concluded that the methanol injection plant would have lower capital and operating costs than an activated alumina system for low water content gas (4 Ib/MMscO and a lower capital cost, but about the same operating cost as a molecular sieve system for high water content feed gas (23 Ib/MMscO. 

The quantities of heat energy required for a molecular sieve system are... 

Sieving techniques are required for separation of species which have no differences in mass-to-charge ratio such as nucleic acids and sodium dodecylsulfate (SDS)-protein complexes. Sieving systems include cross-linked or linear polymeric gels cast in the capillary or replaceable polymer solutions. 

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