Screening sieving

The methods used for laboratory particle size analysis are discussed in detail in Volume 2, Chapter 1. 

Numbers refer to the sections in this chapter. Processes in brackets are used for separating dissolved components (solutions). The terms major and minor component only apply where different phases are to be separated i.e. not 

Screen sizes are defined in two ways by a mesh size number for small sizes and by the actual size of opening in the screen for the larger sizes. There are several different standards in use for mesh size, and it is important to quote the particular standard used when specifying particle size ranges by mesh size. In the UK the appropriate British Standards should be used BS 410 and BS 1796. A comparison of the various international standard sieve mesh sizes is given in Volume 2, Chapter 1. 

The simplest industrial screening equipment are stationary screens, over which the material to be screened flows. Typical of this type are Grizzly screens, which consist of rows of equally spaced parallel bars, and which are used to scalp off over-sized rocks in the feed to crushers. 

Dynamic screening equipment can be categorised according to the type of motion used to shake-up and transport the material on the screen. The principal types used in the chemical process industries are described briefly below. 

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The wastes were milled and screen-sieved. Wastes composition was determined in terms of the major constituent biopolymers, holocellulose (cellulose + hemicellulose) and lignin, and extractive components that are soluble in ethanol-benzene. Lignin and extractives were isolated according to TAPPI standard methods. Holocellulose was obtained following the procedure described elsewhere (9). 

Compact a homogeneous mixture of the three components and break up by forcing through a screen. Sieve off the coarse fraction. 

Fixed, inclined wedge wire screen (sieve bends, DSM) removal of particles >0.15 cm. Variable inclination from 65 to 45° to the horizontal feed concentration 200 mg/L. For dewatering minerals, dewatering particles of diameter >40 pm. Vibrating screens typical exit liquid concentration for <8-mm particle size, 20 to 45 vol% liquid for >40-mm particle size, 2 to 10% v/v liquid. Belt, gravity see Section 16.11.5.13. 

The reservoir solids are most conveniently classified according to their size. Because the particles are of irregular shape, classification is on the basis of sieve opening of sieve screens. Sieve opening is the width of the minimum square aperture through which the particle can... 

Special care should be taken to protect against contamination of the product by fragments of metal, glass or wood. Glass equipment is to be avoided, and screens, sieves,punches and dies should be examined for wear or breakage before and after each use. 

Fixed inclined wedge wire screen (sieve bends, DSM) removal of particles... 

Fixed inclined wedge wire screen, sieve bend fluid loading 6.7 to 20 L/s nf or 10 to 40 L/s m of width solids loading 1.4 to 4.2 g/s m exit solids concentration 12 to 15% w/w soUds. For dewatering minerals, fluid capacity of 0.0015 to... 

One can use the information produced by a screen size analysis to calculate a weight average particle diameter, by knowing the wire spacing and the weight amount on each screen (sieve). 

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