Particle size granulation

Solids handling frequently has the potential for dusting, which can lead to potential health and explosion hazards. Handling solids in the form of larger particle size granules or pellets rather than a fine powder reduces the potential for worker exposure. Worker exposure hazards are reduced by formulating dyes as liquids or wet pastes rather than dry solids or powders (Burch, 1986). 

A granular formulation is basically the same as a dust formulation. It contains toxicant (1%—10%) and an inert diluent. The major difference is in the particle size, granules ranging from 20 to 100 mesh, whereas dusts pass through 300 mesh screens. 

The feed frame height should be maintained between 0.05 and 0.10 mm (0.003-0.004 in.). For very fine particle size granulation, the clearance should be reduced to 0.025-0.05mm (0.001-0.002 in.). 

Gramilaflon/Ground Plastic The size reduction of plastic containers to approximate 3/8" or less particle sizes. Granulators have rotating and stationary knives that cut the material. The most efficient nxxleis have a tangential feed with blades positioned to produce a scissor-like cut. Capacities range from a few hundred pounds to 5,000 pounds per hour. 

Various grades with different particle sizes (granules to fine powders). It was formerly official in N.F. and is currently official in F.C.C. 

Essentially all the ammonium sulfate fertilizer used in the United States is by-product material. By-product from the acid scmbbing of coke oven gas is one source. A larger source is as by-product ammonium sulfate solution from the production of caprolactam (qv) and acrylonitrile, (qv) which are synthetic fiber intermediates. A third but lesser source is from the ammoniation of spent sulfuric acid from other processes. In the recovery of by-product crystals from each of these sources, the crystallization usually is carried out in steam-heated sa turator—crystallizers. Characteristically, crystallizer product is of a particle size about 90% finer than 16 mesh (ca 1 mm dia), which is too small for satisfactory dry blending with granular fertilizer materials. Crystals of this size are suitable, however, as a feed material to mixed fertilizer granulation plants, and this is the main fertilizer outlet for by-product ammonium sulfate. 

Fumaric acid is sold as resia-grade and food-grade. The general sales specification under which resia-grade fumaric acid is sold ia the United States specifies white, crystalline granules with a minimum assay of 99.6% and maximum ash content of 0.05%. The moisture specification is 0.3% maximum with < 10 ppm heavy metals. The color of a 5% solution ia methanol is to be less than 10 APHA. Food-grade fumaric acid calls for somewhat lower impurity levels. Particle size and particle size distribution are important ia many appHcations. 

During the preformulation stage, the chemical and physical properties of the dmg moiety are studied exhaustively to ensure stabdity, safety, bioavadabdity, and therapeutic efficacy. Tablets are produced directly by compression of powder blends or granulations, which include a small percentage of fine, particle-sized powders. 

Direct Compression. This process is relatively simple and time saving. AH the ingredients are blended and then compressed into the final tablet. This is an excellent method, but encumbered by a number of problems. Not all substances can be compressed directly, necessitating a granulation step. Likewise, the flow properties of many blends of fine, particle-sized powders are not such as to ensure even filling of the die cavities of tablet presses. In addition, air entrapment can occur. 

Many friction material formulations contain 5—15 wt % of friction particles, the granulated cross-linked products of the reaction of CNSL, a phenol substituted at the meta position with a unsaturated side chain, and formaldehyde. Friction particles range in size from 50 to 500 p.m. They reduce frictional wear and increase pedal softness (86). 

Sedimentation (qv) techniques, whether based on gravitational forces or centrifugation, derive the particle size from the measured travel rates of particles in a Hquid. Before the particle analysis is carried out, the sample is usually dispersed in a medium to break down granules, agglomerates, and aggregates. The dispersion process might involve a simple stirring of the powder into a Hquid, but the use of an ultrasonic dispersion is preferred. 

Product particle sizes vary from standard size of 6/14 mesh—U.S. Std. Sieves to mini-size granules of 10/16 mesh—U.S. Std. Sieves for small particle blends, to micro-size granules of 14/35-U.S. Std. Sieves for use on golf course tees and greens. Approximate mm corresponding to mesh sizes are 6 mesh/3.36 mm 10 mesh /2 mm 35 mesh/0.5 mm. 

The Immobili dEn me System. The glucose isomerases used are immobilized and granulated to a particle size between 0.3 and 1.0 mm. The enzyme granulates must be rigid enough to withstand compaction when they are packed iato the column. Ca " acts as an inhibitor in the system, and therefore calcium salts need to be removed from the feed symp. Conversely, Mg " acts as an activator, and magnesium salts are added to the feed symp. 

FIG. 20-81 Atypical disc granulator Capes, Particle Size Enlargement, Elsevier, 1980). 

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