Solids Crushing and Grinding

Chemical treatment via acids, bases, solvents or detergents. 

Mechanical homogenizer cell disintegration while in suspension in a liquid. Wet milling. 

Homogenizer first order process In (Rmax/( f max - R) oc p where = maximum amount of released protein/unit mass R = amount of protein released/ unit mass at time t p = pressure. 

Homogenizer Temperature control is difficult. Usually operated at constant throughput. 

Capacities are expressed for open-circuit operation. For closed circuit with the same size reduction ratio, power, reduce the capacity by a factor of 2. Rod mill product is usually larger diameter than from a ball mill. Selection depends on the size of feed, the reduction ratio, the target diameter, the capacity, and the hardness, toughness, fibrous, and sticky nature and whether wet grinding is OK. Ball and rod mills can be used for most hardnesses including fibrous, friability and stickiness. Use jaw crushers for hard materials but shift to cone crushers when hardness Mohs 8 but not for sticky materials. 

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Carstensen J. Advanced Pharmaceutical Solids. New York Marcel Dekker, 2000. Austin LG. Size reduction of solids crushing and grinding equipment. In Fayed ME, Otten L, eds. Handbook of Powder Science and Technology. New York Van Nostrand Reinhold, 1984 562-606. 

Dusts are solid particles generated by such processes as handling, crushing, and grinding. 

Salts pH of hydrolysed solutions of, 431 Samples crushing and grinding of, 155 dissolution of, 110, 801 weighing of, 76, 110 see also Analysed samples Sampling 150 errors in, 153 hazards of, 155 of gases, 153 of liquids, 153 of solids, 153... 

Alternative terms for size reduction to describe the operations that subdivide solids mechanically are crushing and grinding. An ideal crusher or grinder should (i) have a large capacity (ii) require a small power input per unit of the product and (iii) yield a product of the size and/or the size distribution desired. 

Solid (particulate) emissions are produced from incomplete combustion of fuels, solids, drying operations, crushing and grinding operations, solids handling operations, and so on. The largest volume of emissions is from products of combustion (C02, CO, NOv, SO.v and particulates). Acid... 

Solids can be separated on the basis of their particle size. When crushing and grinding equipment is used, a determination of the distribution of the various particle sizes is important in evaluating the performance of the equipment. The size of particles in soil gives an indication of the porosity and the ability for the soil to hold moisture and nutrients. It affects manufacturing processes and the formulation of products. The size of particles in dry feed for farm animals, such as swine, is related to its nutritional value. Many times the size of particles in a process may be specified in a standard method, such as the USP or FDA. 

Materials mined from the Earth s crust are usually highly heterogeneous mixtures of amorphous and crystalline solid phases. Crushing and grinding operations are employed to liberate individual pure grains in the 10-50 pm size range. One of the most widely used (10 tons per... 

Dry Powder A tenn applied to the extinguishing agent suitable for use on combustible metals. Dusts Solid particles generated by mechanical processes such as crushing and grinding, without any chemical change from the paren material. Their size range is typically between 0.1 and 100 microns. 

The particle-size and size-distribution of solid materials produced in industrial processes are not usually those desired for subsequent use of these materials and, as a result comminution and recrystallization operations are carried out. Well known processes for particle size redistribution are crushing and grinding (which for some compounds are carried out at cryogenic temperatures), air micronization, sublimation, and recrystallization from solution. There are several practical problems associated with the above-mentioned processes. Some substances are unstable under conventional milling conditions, and in recrystallization processes the product is contaminated with solvent, and waste solvent streams are produced. Applying supercritical fluids may overcome the drawbacks of conventional processes. 

J.Gross, "Crushing and Grinding , US BurMines Bull 402 (1938), 148pp 4)E.R.Riegel, "Chemical Machinery , Reinhold, NY (1944), 8-40 (Devices for reducing the size of solid particles) 5)C-E-Berry, IEC 38, 672-78 (1946)... 

Cutting. In addn to Crushing and Grinding (qv), there are other methods of size reduction techniques of a specialized nature which take advantage of unique props of solid materials. 

Materials mined from a mineral deposit usually consist of a heterogeneous mixture of solid phases that are generally crystalline and contain various minerals. Crushing and grinding operations are used to liberate the mineral species from one another and to reduce the size of the solids to a range suitable for subsequent processing. Of the various separation techniques, those of froth flotation and agglomeration exploit the chemical and physical properties of the surfaces of minerals, which can be controlled by various chemical interactions with species in an aqueous phase. 

A certain amount of crushing and grinding is usually required to decrease the particle size of solid samples. Because these operations tend to alter the composition of the sample, the particle size should be reduced no more than is required for homogeneity (see Section 8B-4) and ready attack by reagents. 

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