Subject milling

Soft-wheat flours are sold for general family use, as biscuit or cake flours, and for the commercial production of crackers, pretzels, cakes, cookies, and pastry. The protein in soft wheat flour mns from 7 to 10%. There are differences in appearance, texture, and absorption capacity between hard- and soft-wheat flour subjected to the same milling procedures. Hard-wheat flour falls into separate particles if shaken in the hand whereas, soft-wheat flour tends to clump and hold its shape if pressed together. Hard-wheat flour feels slightly coarse and granular when mbbed between the fingers soft-wheat flour feels soft and smooth. Hard-wheat flour absorbs more Hquid than does soft-wheat flour. Consequently, many recipes recommend a variable measure of either flour or Hquid to achieve a desired consistency. 

In pyrolysis employing molten tin, a flow of the urea on the surface is eventually converted to a sheet of cmde CA 15—20 mm thick. After reaching the edge of the tin bath, the moving sheet falls into a mill. The resultant powdered cmde CA (contaminated with tin metal) is subjected to acid hydrolysis to convert aminotriazines (30—40%) to CA. Tin losses can amount to 15 kg/1 product. 

Calcined diatomite is produced from natural diatomite, which is then subjected to high temperature calcination in a rotary kiln at about 980°C. The calcined material is then again milled and classified to remove coarse agglomerates as well as extreme fines. 

Figure 7.20 Close-up of general wastage on a carbon steel bracket subjected to low-pH (<2) mill coolant.

Below we give a brief idea of the mechanical system of such a mill and its various controls, as a passing reference. For more details on the subject, see the Further reading at the end of the chapter. 

Normally such mills are installed in groups known as wind farms to provide a sizeable power source, except in remote areas, where power demand may be restricted to a very limited area and small mills may suffice. When mills are installed in groups, precautions are necessary to ensure that there is enough distance between any two mills so that there is no hindrance to routine maintenance, on the one hand, and obstruction of wind to other mills, on the other. For more details, refer to the literature available on the subject in the Further reading at the end of the chapter. 

To produce a moulding composition, aniline is first treated with hydrochloric acid to produce water-soluble aniline hydrochloride. The aniline hydrochloride solution is then run into a large wooden vat and formaldehyde solution is run in at a slow but uniform rate, the whole mix being subject to continuous agitation. Reaction occurs immediately to give a deep orange-red product. The resin is still a water-soluble material and so it is fed into a 10% caustic soda solution to react with the hydrochloride, thus releasing the resin as a creamy yellow slurry. The slurry is washed with a counter-current of fresh water, dried and ball-milled. 

In a comparison of shock-modified powder to powder subjected to other intense deformation, data on shock-modified TiC was compared to a well annealed TiC powder wet milled for many hours to similar values of residual strain. As depicted in Fig. 7.4 the anisotropies observed in residual strain and crystallite size in the two cases are quite different. The shock-modified powders show less anisotropy in strain and more anisotropy in crystallite size... 

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