Granulation balling

Capes, C. E., A Note on Size Distributions in Granulation, Balling and Wet... 

C.E. Capes, A note on size distribution in granulation, balling and wet pelletization, Chem. Eng. (London), 45 (207) (1967) CE78-CE80. 

Typically, dry potassium nitrate is pulverized in a ball mill. Sulfur is milled into cellular charcoal to form a uniform mix in a separate ball mill. The nitrate and the sulfur—charcoal mix are screened and then loosely mixed by hand or in a tumbling machine. Magnetic separators may be used to ensure the absence of ferrous metals. The preliminary mix is transferred to an edge-mimer wheel mill with large, heavy cast iron wheels. A clearance between the pan and the wheels is required for safety purposes. The size of this gap also contributes to the density of the black powder granules obtained. Water is added to minimize dusting and improve incorporation of the nitrate into the charcoal. The milling operation requires ca 3 to 6 h. 

Various methods are used for evaluatiag the quaflty, ie, physical strength and ensyme dust formation, of the granulate. In the elutriation process, a sample of product is fluidised ia a glass tube with a perforated bottom plate for 40 miautes. Dust from the sample is collected oa a filter and the ensyme activity measured. An acceptable dust level is when less than 5—10 ppm of the activity of the sample has been collected. In the so-called Heubach method, 20 g of granulate is elutriated. During the elutriation, four steel balls are rotated ia the bed ia order to evaluate the impact of attritioa oa the dust release of the ensyme. The dust is collected oa a filter and measured. The acceptable dust level is very low. 

G, E. O Connor and T. W. E Russell, Heat Transfer in Tubular Fluid-Fluid Systems P. C. Kapur, Balling and Granulation... 

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,... 

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