Milling and Classification

It is apparent from the data that particles of a few nanometers in size can only be made on industrial scale by synthetic methods. On the other hand, these particles are either intentionally or unintentionally aggregated and agglomerated in their powder forms. Thus, for the dispersion of fillers, agglomerate and aggregate size is usually as relevant as the primaiy particle size. Fillers, which are obtained by various milling and classification processes, can also be obtained in the form of small particles, but usually not below 100 nm. 

Other processes exist where the top of the battery is removed by saw and the battery plates extracted via a trommel. The plates and separators are then dried and are charged directly to the furnace. The case, top-lead and other residual lead are recovered via hammer mill and classification. This process, referred to as plate extraction, is mainly used for rotary furnaces utilizing the soda-iron system (see Section 15.3). 

A product sample is shown in the inset (courtesy Turbo Kogyo, Kanagawa, Japan) Fig. 6.3-11 Flow diagram of a compaction/ granulation system with multiple crushing/ milling and classification steps and fines recirculation for the reduction of undersized material in the product [6.3.2.1]... 

Ball mills or tube mills can be operated in closed circuit with external air classifiers with or without air sweeping being employed. If air sweeping is employed, a cyclone separator may Be placed between mill and classifier. (The principles of size reduction combined with size classification are discussea under Characteristics of Size Classifiers. ) Likewise other types of grinding mill can be operated in closed circmt with external size classifiers (Fig. 20-12), as will be described at appropriate places on succeeding pages. However, many types of grinders are air-swept and are so closely coupled with their classifiers mat the latter are termed internal classifiers. 

Starch content of field peas (Pisum sativum L., cv. Trapper) ranges from 43.7 to 48% and, after being subjected to pin milling and air classification, produces a flour containing 78% starch (9,12,13). 

The composition of protein and starch fractions produced from pin milling and air classification are related to a number of variables variability in composition of field pea cultivars, number of passes through pin mill and air classifier, vane settings and protein content of peas, and seed moisture (5,9,23,31). 

Figure 1. Flow diagram for pin milling and air classification of field pea and fababean into protein and starch fractions.

Dry bean flour fractions produced by dry roasting, milling and air classification resulted in versatile food ingredients. Fractions possessed good functional and nutritional properties which were found to be acceptable in a variety of food systems. These processes and products appear to have potential for improving nutritive status through improved dry bean utilization. 

Vasanthan and Bhatty (1995) reported the use of pin milling and air classification as a technique for preconcentrating starch prior to wet isolation (Fig. E2.1.1, route D). Air classi-... 

Vasanthan, T. and Bhatty. R.S. 1995. Starch purification after pin milling and air classification of waxy, normal, and high amylose barleys. Cereal Chem. 72 379-384. 

Let /Ji(yj,Xi,tn) denote the total amount of particles in the (/,/)th cell at time tn. Then, the governing equations of the system [6,7] because of the boundary conditions at the inlet and outlet of the mill depending on the feed and classification conditions can be divided into three groups. Namely,... 

The quantity of barley starch produced around the world is very little when compared to starch production from corn, wheat, rice, potato or tapioca. There are only a few processing plants around the world that produce starch concentrate or purified starch from barley. Barley starch concentrates containing up to —78% (dry basis) starch are now produced in North America by milling and air-classification of barley grains. Milling disintegrates the grain into fine particles and air-classification separates them on the basis of differences in density, mass and projected area in the direction of air... 

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