Pelletizer, disk

Fig. 1. (a) Industrial disk pelletizer (diameter 8 ft) (courtesy of Ferro-Tech, Inc.), (b) Schematic front view of a disk,... 

Polycrystalline or powdered samples can be prepared as a suspension in mineral oil (Nujol mull), as a potassium bromide disk (pellet), or as thin films deposited on infrared-transparent substrates. The potassium bromide pellet is the most common way of preparing powder samples in this method a small amount, usually 1 mg, of finely-ground solid sample is mixed with powdered potassium bromide, usually 300 mg. and then pressed in an evacuated die under high pressure. The resulting disks are transparent and yield excellent spectra. The only infrared absorption in the potassium bromide matrix is due to small amounts of adsorbed water, which can. however, be confused with OH-containing impurities in the sam-... 

The different samples are mostly inorganic solids. The preparation method consists of pressing the powder sample ( 25 mg) in order to form a self-supporting disk (pellet). Experiments should be performed under conditions where the surface is completely contaminant firee [2-4]. 

The conductivity measurements were performed using a standard four-point probe method at a constant current of 0.5 mA and ambient temperature. About 0.05 g of dried PANI salt (and nanocomposites) powders was compressed into a disk pellet of 13 nun in diameter with a hydraulic pressure at, 3000 psi to measure the conductivity. Each measurement was repeated three times and the average values reported as the result. 

Two types of continuous flow solid oxide cell reactors are typically used in electrochemical promotion experiments. The single chamber reactor depicted in Fig. B.l is made of a quartz tube closed at one end. The open end of the tube is mounted on a stainless steel cap, which has provisions for the introduction of reactants and removal of products as well as for the insertion of a thermocouple and connecting wires to the electrodes of the cell. A solid electrolyte disk, with three porous electrodes deposited on it, is appropriately clamped inside the reactor. Au wires are normally used to connect the catalyst-working electrode as well as the two Au auxiliary electrodes with the external circuit. These wires are mechanically pressed onto the corresponding electrodes, using an appropriate ceramic holder. A thermocouple, inserted in a closed-end quartz tube is used to measure the temperature of the solid electrolyte pellet. 

Plant material should be added to a disk mill (grain or seed matrices) or a vertical batch processor (all other matrices). Add an equal portion of pelletized dry-ice to the sample (vertical processor only). Macerate the plant sample (or sample -I- dry-ice) until a homogeneous mixture is obtained. Soil samples should be well mixed or... 

Rotating drums, disks, and to a lesser extent, cones are used in continuous large-scale balling of iron ores (E3). A pelletizing disk of industrial type is shown in Fig. 1. Fertilizers are granulated in twin-shaft pug mills, drums,... 

The performance of the pelletizing disk depends on its size, speed, angle to the horizontal, collar height, positions of the feed chutes, water sprays and scrapers, and the feed throughput. The critical speed at which the balls no longer roll down but stick to the collar wall under centrifugal force is given by (P3)... 

Fig. 2. Disk operating in the snowballing mode of pellet growth.

Since densification of the granules in the drums and disks is brought on by gravitational force, there is a definite upper limit on both the rate and the extent of compaction that is attainable. This is specially true in the case of fine solids. In general, compaction of the granules occurs concurrently with their growth, and it is seldom possible to exercise independent control over these two actions of the pelletizer. 

The experimental results of Capes and Danckwerts (C6) and Kanetkar (K1), using a balling drum and a disk granulator, respectively, have shown that the thickness of the snowballed layer is approximately independent of the initial size of the seed pellet. It then follows that the rate of pick up of the loose particulate material is proportional to the surface area of the granule hence,... 

Fig. 22. Mean diameter of iron ore pellets as a function of the number of disk revolutions. [From Kanetkar (K1).]... 

Kanetkar (Kl) pelletized iron ore in a small-batch disk and found that the distributions are self-preserving in the reduced size D/D and that the mean pellet diameter increases in the following manner (Fig. 22) ... 

Fig. 23. (I) Effect of water content on the growth rate of agglomerates sand granules grown by crushing and layering mechanism [from Capes and Danckwerts (C5)]. (II) Limestone nuclei by random coalescence [from Kapur (K2)]. (Ill) Limestone balls by nonrandom coale-scene [from Kapur (K4)]. (IV) Iron ore pelletized in a disk.[From Kanetkar (K1)].

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