Distribution of feed

The uniform distribution of feed liquor is achieved by the use of a specially engineered distribution pipeline running internally along the base of each compartment and containing a number of carefully designed apertures along its length. 

Figure 15.17. Two designs of fixed bed gas adsorbers, (a) Vertical bed with balls on top for hold-down and distribution of feed (Johnson, Chem. Eng. 79, 87 (27 Nov. 1972)]. (b) Horizontal fixed bed for low pressure drop operation [Treybat, Mass Transfer Operations, McGraw-Hill, New York, 1980 Logan, U.S. Pat. 2,180,712 (1939)].

Increase pore size to increase rate of fluid penetration. Decrease pore size to increase extent of fluid penetration. Modify particle size distribution of feed ingredients. Alter milling, classification or formation conditions of feed if appropriate to modify particle size distribution. 

In principle, the safest way to represent an industrial reactor on a laboratory scale is to reduce the diameter while keeping the bed length the same. In a well-designed industrial fixed-bed reactor where proper care is taken to ensure uniform distribution of feed over the cross section of the bed, there are theoretically no cross sectional differences. Hence, a more slender but equally tall test reactor would be a good representation of the commercial reactor, provided that the diameter of the test reactor is not so small that wall effects become appreciable (to be discussed later). 

The product from industrial grinding circuits oscillates due to variation in hardness and particle size distribution of feed. Heiskanen and Niemelia [47] demonstrated that, using automatic sampling, on-line analysis and autocorrelation procedures, they could map out a frequency of oscillation. 

Fig. 1. The size distribution of feed and product vanadium for Hondo asphakenes is compared with model calculations without thermal effects.

However, as shown in Table VI multiple stage combustion is preferable in order to decrease NOx formation without fail. The factors which influence the behaviour of N0X are temperature of the chamber, numbers of stage, feeding position of air, overall air ratio and distribution of feed air in multiple stage combustion method. It was found possible to minimize the formation of N0X by multi-stage combustion under the condition of total air ratio of about 1.1 and temperature at the outlet of the chamber of below 950°C. 

Design of the roller surfaces In designing a roller press surface, some fundamental considerations do influence the possible shape, size, and distribution of the cups or indentations.Limitations include the relationships of circumferential pocket dimension/roller circumference and pocket depth/roller diameter as well as the pocket shape. Associated with these are problems of release, clam-shelling (splitting), extrusion, removal of air from the compaction zone, and uneven distribution of feed as well as compaction pressure. In spite of those limitations, a large variety of shapes can be produced. 

The most important factors that determine the selection of the size-reduction equipment are the mechanical characteristics (shear strength, ductility, etc.) of the feed material, as well as the size distribution of feed and comminuted product. From the aforementioned analysis, it is clear that the mechanical characteristics determine the acting force for size reduction and, consequently, the selection of the proper equipment. The size distribution of the feed stream and product determines the type of the corresponding equipment as well as the dimensions of feed and discharge openings. 

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