Equipment, selection size-reduction

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 ... 

Selection of Size-reduction Equipment. The following factors are determinants in the selection of equipment for size reduction of materials ... 

Figure 14.14. Factors to consider in selecting size reduction equipment for a plastics recycling plant. Adapted from reference 10.

Preliminary Guide for Selecting Size Reduction Equipment... 

Toxicity. Toxicity has no influence on the actual size reduction, but equipment is often selected for ease of product containment or safe cleaning. 

The selection guides given by Lowrison (1974) and Marshall (1974), which are reproduced in Tables 10.12 (see p. 465) and 10.13, can be used to make a preliminary selection based on particle size and material hardness. Descriptions of most of the equipment listed in these tables are given in Volume 2, Chapter 2 or can be found in the literature Perry et al. (1997), Hioms (1970), Lowrison (1974). The most commonly used equipment for coarse size reduction are jaw crushers and rotary crushers and for grinding, ball mills or their variants pebble, roll and tube mills. 

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. 

API processing has specific concerns that are shared by some, but not all industries, and these are important to consider in selecting a milling process or milling equipment. For example, ability to easily clean all equipment surfaces and material of construction concerns are critical for API, where typically no further chemical purification occurs after the final size reduction step. The risks of metal shedding, lubricants, or seal fluid entering the process stream, and cross-contamination... 

The particle size reduction tests for various selected biomass types have been executed in the pilot installation of CIEMAT. A flow diagram of the installation is shown in Figure 1. Basically, the equipment consists of two hammer mills connected in series, the first one has a nominal power of 11 kW and is used for pre-grinding (emshing). The second hammer mill has a nominal power of 15 kW and is used for refining the pre-ground biomass. 

Factors Affecting the Selection of Size-reduction Equipment... 

The most important factors that determine the selection of the size-reduction equipment are the mechanical characteristics (shear strength, ductility, etc.) of the feed material, as well as the size distribution of feed and comminuted product. From the aforementioned analysis, it is clear that the mechanical characteristics determine the acting force for size reduction and, consequently, the selection of the proper equipment. The size distribution of the feed stream and product determines the type of the corresponding equipment as well as the dimensions of feed and discharge openings. 

Also, there are some other factors that influence the selection of the size reduction equipment. These factors are related to process economics (energy... 

Size-reduction equipment used to prepare solids for leaching is usnaily selected so as to provide the desired mean particle size without excessive generation of fines or oversize panicles. Therefore, in many instances grinders or cutters employing sharp uniformly spaced kaives are used, in certain cases these carters also provids corrugated particle surfaces that manimize surfnce exposure to the extract. 

For the proper selection and economical operation of size-reduction machinery, attention must be given to many details of procedure and of auxiliary equipment. A crusher, grinder, or cutter cannot be expected to perform satisfactorily unless (1) the feed is of suitable size and enters at a uniform rate (2) the product is removed as soon as possible after the particles are of the desired size (3) unbreakable material is kept out of the machine and (4) in the reduction of low-melting or heat-sensitive products, the heat generated in the mill is removed. Heaters and coolers, metal separators, pumps and blowers, and constant-rate feeders are therefore important adjuncts to the size-reduction unit. Factors to consider in specifying a size-reduction system, including energy efficiency and environmental issues, are discussed by Kukla and Hixon, ... 

As previously discussed, one of the determinant factors for the right selection of size reduction equipment is consideration of the hardness of the material to be processed. The second factor of great relevance is the required capacity, either fixed or subjected to variations by process requirements. Taking these two main considerations along with a thorough analysis of as many other factors as necessary, flowcharts can be devised to select and locate the most suitable comminution units for a size reduction plant. The combination of different criteria may be summarized in charts, like the one given in Table 4.3, which includes some typical applications of the principal size reduction equipment. 

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