Equipment size reduction

Equipment Feed size (mm) Product Size (mm) Size Reduction Ratio Capacity [ton/hr (1 ton = 2,000 lb)] Power (Hp) 

Solid-Liquid Separation Equipment (Thickeners, Clarifiers, FUters, Centrifuges, and Expression) 

Continuous wet classifiers, of the rake and spiral type, and hydroclones (hydrocyclones) can also produce concentrated slurries, but the overflow liquid is not clear, containing the smaller particles. A separation of particles by size and density occurs. Hydroclones are inexpensive, typically 6 in. in diameter or less, and a single unit can handle only low flow rates. For high flow rates, parallel units are employed in a multiclone. Table 16.32 contains f.o.b. purchase costs for wet classifiers and hydroclones. The size factor is the solids flow rate for classifiers and the liquid flow rate for hydroclones. 

Wet cakes can be produced by sending concentrated slurries to filters operating under pressure or vacuum. Liquid passes through a porous barrier (filter media), which retains most of the solid particles to form a wet cake. Filters are designed to operate either continuously (e.g., the continuous rotary-drum vacuum filter or the rotary pan filter) or batchwise (e.g., the plate-and-frame filter or the pressure leaf filter). Table 16.32 contains f.o.b. purchase costs for most of the widely used filters. All costs are based on filtering area, which must be determined by laboratory experiments with a handheld vacuum or pressure leaf filter. For preliminary cost estimates, in the absence of such tests, select a continuous rotary-drum vacuum filter operat- 

Some wet sohds consist of fibrous pulps or othm compressible materials, fiem which liquid cannot be removed by settling, filtmng, or centrifuging. Instead erqtression is used with screw presses or roll presses. Table 16.32 contains f.o.b. purchase costs for these two presses in stainless steel. 

The list shown in Table 4.2 is not exhaustive, since there is a diversity of size reduction equipment and machinery used in a wide range of processing 

Size Reduction Machines Used in Food Process Engineering 

Range of Reduction Generic Name of Equipment Type of Equipment 

The range of applications of size reduction is very wide. It includes the preliminary breakup of large masses into pieces that can be handled in a process and the grinding of smaller particles into fine powders. The size and design of equipment reflect this situation. Broadly, size reduction apparatus can be divided into those types which depend on mechanical crushing and those which use impact to fracture the solids. Table 3-13 shows some of the common types of equipment with their principal characteristics. Major hazards are those associated with the machinery and with the material being processed. 

Size reduction usually requires a great deal of energy. Mechanical apparatus can seriously harm persormel in a very short time. Vendors should provide information on specific machinery, and interlocks can prevent operation when equipment is open or safety guards removed. Drivers and transmission systems will be robust, and it is important to observe the precautions described in Section 3.8. 

The typical mill or grinder will be in a nearly closed system with obvious dangers. Few employees will think of approaching too closely or reaching inside the apparatus. The feed system often lacks secure cover and is not so imposing a hazard. The hazardous section should be clearly identified and posted with warning signs. Other useful precautions include  

Hammer Mills Hinged hammers attached to horizontal shafts. High productivity coarse product. 

Vibrating Mills Vibration of confined grinding medium inside cylinder or torus. Uniform fine grinding. Low capacity feed size must be quite small. 

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Hardness. There are several hardness (qv) scales. In selecting size reduction equipment generally hardness is expressed according to the Mohs s scale, where a body in one range scratches a body in the immediately previous range ... 

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)]. 

Bond terms Ei the work index, and expresses it as the amount of energy required to reduce unit mass of material from an infinite particle size to a size L2 of 100. im, that is q = 00. The size of material is taken as the size of the square hole through which 80 per cent of the material will pass. Expressions for the work index are given in the original papers 8,9) for various types of materials and various forms of size reduction equipment. 

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. 

Some of the many available kinds of size reduction equipment can be described here. Manufacturers catalogs have the most complete descriptions of the equipment and almost always provide typical or expected performance data. Useful compilations of such information are by Taggart (1945) and the Chemical Engineers Handbook (1984, Section 8, as well as older editions). 

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

TABLE 12.4. Size Reduction Equipment Commonly Used in the Chemical Process Industries... 

Thank you for your interest in Williams size reduction equipment and /or systems. 

The process by which a solid is reduced to particle sizes of less than about 100 pm by using any type of particle-size reduction equipment. Examples micronized talc, micronized pigment. 

FIGURE 4.3 Average energy required for size-reduction equipment, O is typical product size, is typical feed size. 

Thank you for your interest in Williams size reduction equipment and/or systems. As a first step toward giving you a highly personalized answer to your need, we would appreciate your supplying the following information. 

Some of the many kinds of size reduction equipment are described in this section. The best source for complete equipment descriptions is manufacturers catalogs. They often provide technical or expected performance data. Compilations of typical performance information may also be found in the Chemical Engineers Handbook, especially the earlier editions. Chemical Engineers Buyers Guide 2004 (2003) is a source of the companies that manufacture 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. 

TABLE 12.6. Size Reduction Equipment Commoniy Used in the Chemicai Process industries... 

If the particle size of the biomass fuel or feedstock is not predetermined by its history, as is the case for sawdusts, nutshells, and a few other waste biomass materials, size reduction is usually carried out with one or more units that make up the front end of the total processing system. Many different kinds of machines are employed. Generally, the size of the feed is reduced by grinding, cutting, or impact mechanisms. Not all of the designs are suitable for biomass energy applications because the equipment is customized for certain uses or the cost of size reduction is excessive. Agricultural crops and woody biomass are also usually processed by different types of machines. A brief review of the basic types of machines that are or have been used for biomass follows to illustrate the variety of size-reduction equipment and their biomass applications. 

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