Traditional milling

FIGURE 7.1 Schema of antique stone mill moved by domestie animals or men. 

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PLA is commercially produced utilizing com as the feedstock according to the process diagramed in Fig. 1. Com first undergoes the traditional milling... 

Foxtail millet is possibly one of the oldest grain crops. Its name is due to the characteristic panicle that resembles the tail of a fox. It is especially important in China, Japan, and India. Its cultivation in China dates to 3000 BC. On the other hand, Proso or common millet (P. miliaceum) appears to be even older. It originated in Manchuria, and first appeared as a crop in Transcaucasia and China around 5000 BC. It has been reportedly found in Neolithic sites in Georgia and East China. It is extensively cultivated in India, China, Russia, Ukraine, Middle East, Turkey, and Rumania. Proso is considered one of the most drought-resistant millets. It is documented that Proso continued to be used as bread grain in Europe until medieval times. The kernels are small (2-3 mm) and can be cream, yellow, orange-red, or brown in color. Kernels are usually traditionally milled into flours for preparation of a wide array of traditional foods. Today, Proso millet is also of economic importance in developed countries becanse of its use for birdseed (National Research Council 1996). 

Traditional dry-milling processes are still widely practiced around the world. Investigate and describe at least three different traditional milling systems applied to different cereal grains. 

Cost bilizers. In most cases the alkyl tin stabilizets ate particularly efficient heat stabilizers for PVC without the addition of costabilizers. Many of the traditional coadditives, such as antioxidants, epoxy compounds, and phosphites, used with the mixed metal stabilizer systems, afford only minimal benefits when used with the alkyl tin mercaptides. Mercaptans are quite effective costabilizets for some of the alkyl tin mercaptides, particularly those based on mercaptoethyl ester technology (23). Combinations of mercaptan and alkyl tin mercaptide ate currendy the most efficient stabilizers for PVC extmsion processes. The level of tin metal in the stabilizer composition can be reduced by up to 50% while maintaining equivalent performance. Figure 2 shows the two-roU mill performance of some methyl tin stabilizers in a PVC pipe formulation as a function of the tin content and the mercaptide groups at 200°C. 

Urethanes are processed as mbber-like elastomers, cast systems, or thermoplastic elastomers. The elastomer form is mixed and processed on conventional mbber mills and internal mixers, and can be compression, transfer, or injection molded. The Hquid prepolymers are cast using automatic metered casting machines, and the thermoplastic peUets are processed like aU thermoplastic materials on traditional plastic equipment. The unique property of the urethanes is ultrahigh abrasion resistance in moderately high Shore A (75—95) durometers. In addition, tear, tensUe, and resistance to many oUs is very high. The main deficiencies of the urethanes are their resistance to heat over 100°C and that shear and sliding abrasion tend to make the polymers soft and gummy. 

In recent years high compression roll mills have become commercially important. In contrast to traditional roU mills, these machines apply stress to a bed of material rather than to single particles (Fig. 7). By applying extremely high pressures to the roUs, ranging from 50 to 500 MPa (7,250—72,500 psi), fine particles can be produced. The end fineness depends on the cmshing pressure, and the output is determined by the roU speed. 

In the alcohol industry, grain or potato raw materials are milled and water added to form a slurry or mash which is heated either batchwise or continuously. Traditionally, the mash is heated to 150°C by the injection of Uve steam. To reduce viscosity, a-amylases are added both during beating to 150°C and during cooling. Thermostable a-amylases from Bacillus licheniformis are the most commonly used enzymes for these processes (68). 

Triglycerides are important constituents of resin. In softwood, the triglycerides account for 20—40% of total resin content, and in hardwood, 40—50%. The paper industry uses the term pitch for resins that create problems in paper machines. Traditionally, pitch is controlled or reduced by aging the wood, by use of chemicals to avoid deposits on the roUs, or by intensive washing of the pulp. AH these methods add to the cost of paper production. An alternative is to add a Upase to the pulp in a reaction lasting about one hour with the help of agitation. Results from Japanese paper mills show substantial... 

Flour and Feed Meal The roller mill is the traditional machine for grinding wheat and lye into high-grade flour. A typical mill used for this purpose is fitted with two pairs of rolls, capable of making two separate reductions. After each reduction the product is taken to a bolting machine or classifier to separate the fine flour, the coarse produc t being returned for further reduction. Feed is supphed at the top, where a vibratoiy shaker spreads it out in a thin stream across the full width of the rolls. 

A maintenance shop should have the traditional horizontal and vertical lathes, mills, drill presses, slotters, bores, grinders, and a good balancing machine. A balancing machine can pay for itself in a very short time in... 

Impeller construction for the cover-disk style impeller historically has been by built-up construction and welding. The traditional method uses die formed blades (see Figure 5-34). More recently, with the increased use of 5-axis milling, blades have been milled integrally with the hub disk. This alternate construction method is somewhat more costly because of the machining but produces a more accurate and repeatable gas path, which offsets the added expense (see Figure 5-35). Cover disks arc w ddcd to the blades to complete the milled impeller. Physical prop-... 

Fig. 3. Two routes to rubber/resin tapes 1, Traditional calender-mill and 2, solution polymer method for high performance tape.

Most electricity from biofuels is generated by direct combustion. Wood fuels are burned in stoker boilers, and mill waste lignin is combusted in special burners. Plants are generally small, being less than 50 MW in capacity. There is considerable interest in combustion of biomass in a process called cofiring, when biomass is added to traditional fuels for electricity production. Cofiring is usually done by adding biomass to coal, but biomass also can be cofired with... 

FIGURE 6.12 Traditional application of the Mills-Nixon effect theory to a-tocopherol-type henzopyranols and benzofuranols, having an anullation angle sum of (a + (3). 

In October 1974, the Watermill, Little Salkeld (in the Eden Valley), together with its traditional machinery, was taken over by Ana and Nick Jones. They had always been interested in the preservation of old crafts and skills and were determined that the mill would be kept, made to work and not be converted into stables, a marina or a craft shop. Since neither had previous experience of flour milling, Nick Jones embarked on a ten day training stint in Wales, and a millwright from Staffordshire was called in to get grinding underway. 

Traditionally, Irganox B blends (Irganox 1010/1076 and Irgafos 168) are analysed by HPLC methods, which require a long sequence of preliminary actions milling,... 

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