Size reduction equipment operation

A wide variety of size-reduction equipment is available. The chief reasons for lack of standardization are the variety of products to be ground and product quahties demanded, the limited amount of useful grinding theory, and the requirements by different industries in the economic balance between investment cost and operating cost. Some differences exist for the sake of difference sometimes similarities are advertised as differences [Rumpf, Chem. Jng. Tech., 37(3), 187-202 (1965)]. 

Control of Crushers Lower-grade raw materials, higher energy costs, larger-scale operations, and more complex, capital-intensive plants make automatic control of size-reduction equipment more important (Suominen, 21st International Symposium—Applications of Computers and Operations Research in the Mineral Industry, 1011-1018). Benefits are increased productivity, process stability and safety, improved recoveiy of mineral values, and reduced costs [Horst and Enochs, Engineering Mining J., 181(6), 69-171 (1980)]. 

Characteristics of the main common types of size reduction equipment are listed in Table 12.3, including size of feed, size of product, capacity, power consumption, and average reduction ratio. Coarse comminuters perform with reduction ratios less than 10, fine ones with ratios of 100 or more. From very large to very fine may require several operations in series, as in the flowsketch of Figure 12.4(b), where three stages of crushing and two of classification are shown. 

TABLE 12.3. Operating Ranges for Commonly Used Size Reduction Equipment... 

A key consideration in the selection of size reduction equipment is the trade-off between the capital cost of the equipment and the operating expenses. This equipment is large, hence a high capital investment, and large quantities of utihties are required, resulting in high operating expenses. 

Forces commonly used in food processes for particle size reduction are compressive, impact, attrition (or shear), and cutting forces. More than one force usually participates in the comminution operation in industrial size-reduction equipment. In particular, crushing rolls use mainly compressive forces, hammer mills are based on impact, disc mills cause particle attrition through shear force application, and rotary knife cutters use cutting forces. 

Principles of Comminution Computer Simulation of Milling Operations Size-Reduction Equipment Crushers Grinders... 

Breaking is the term applied to size operations on large material (say +75 mm) and crushing to particle size reduction below 75 mm the term grinding covers the size reduction of material to below about 6 mm. However, these terms are loosely employed. A general term for all equipment is size reduction equipment, and because the term comminution means size reduction, another general term for the equipment is comminution equipment. 

The previous section discussed the mechanical hazards associated with operation of size-reduction equipment. There will also be hazards related to the feed material or product. These hazards can be associated with the solid product itself or with impurities, residual solvent, or the like. Several problems are covered below in separate sections ... 

In order to make a multipurpose plant even more versatile than module IV, equipment for unit operations such as soHd materials handling, high temperature/high pressure reaction, fractional distillation (qv), Hquid—Hquid extraction (see Extraction, liquid-liquid), soHd—Hquid separation, thin-film evaporation (qv), dryiag (qv), size reduction (qv) of soHds, and adsorption (qv) and absorption (qv), maybe iastalled. 

Size reduction (qv) or comminution is the first and very important step in the processing of most minerals (2,6,10,20—24). It also involves large expenditures for heavy equipment, energy, operation, and maintenance. Size reduction is necessary because the value minerals are intimately associated with gangue and need to be Hberated, and/or because most minerals processing/separation methods require the ore mass to be of certain size and/or shape. Size reduction is also required in the case of quarry products to produce material of controlled particle size (see Size measurement of particles). In some instances, hberation of valuables or impurities from the ore matrix is achieved without any apparent size reduction. Scmbbers and attritors used in the industrial minerals plants, eg, phosphate, mtile, glass sands, or clay, ate examples. 

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