Feeds fibre

World production of I2 in 1992 approached 15 000 tonnes, the dominant producers being Japan 41%, Chile 40%, USA 10% and the former Soviet Union 9%. Crude iodine is packed in double polythene-lined fibre drums of 10-50-kg capacity. Resublimed iodine is transported in lined fibre drums (11.3 kg) or in bottles containing 0.11, 0.45 or 2.26 kg. The price of I2 has traditionally fluctuated wildly. Thus, because of acute over-supply in 1990 the price for I2 peaked at 22/kg in 1988, falling to 12/kg in 1990 and 9.50/kg in 1992. Unlike CI2 and Br2, iodine has no predominant commercial outlet. About 50% is incorporated into a wide variety of organic compounds and about 15% each is accounted for as resublimed iodine, KI, and other inorganics. The end uses include catalysts for synthetic rubber manufacture, animal- and fowl-feed supplements. 

Gas separation Hollow-fibre for high-volume applications with low-flux, low-selectivity membranes in which concentration polarisation is easily controlled (nitrogen from air) Spiral-wound when fluxes are higher, feed gases more contaminated, and concentration polarisation a problem (natural gas separations, vapour permeation). 

Two other major factors determining module selection are concentration polarisation control and resistance to fouling. Concentration polarisation control is a particularly important issue in liquid separations such as reverse osmosis and ultrafiltration. Hollow-fine-fibre modules are notoriously prone to fouling and concentration polarisation and can be used in reverse osmosis applications only when extensive, costly feed solution pretreatment removes all particulates. These fibres cannot be used in ultrafiltration applications at all. 

Another factor is the ease with which various membrane materials can be fabricated into a particular module design.1618 Almost all membranes can be formed into plate-and-frame, spiral-wound and tubular modules, but many membrane materials cannot be fabricated into hollow fine fibres or capillary fibres. Finally, the suitability of the module design for high-pressure operation and the relative magnitude of pressure drops on the feed and permeate sides of the membrane can be important factors.4-11 The types of module generally used in some of the major membrane processes are listed in Table 16.2. 

Kreuzer M, Machmuller A, Hanneken H, Gerdemann M and Wittmann M (1999), BFS-Fermentable fibre in feeds for growing fattening pigs , Zuchtungskunde, 71, 306-322. 

B Foods low in tannins selected, but fibre is major negative feeding cue. 

Calculation. Subtract the weight of the crucible plus fibre after oxidation from the weight of the crucible plus ADF, divide by the initial sample weight and multiply by 100 to obtain the % lignin in the sample DM (air-dry matter for animal feeds). 

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