Sieving and grinding

After drying, suspension PVC is usually sieved to remove coarse particles which could cause problems during transformation. Emulsion PVC is classified and ground if required for the end application. Polymers for paste applications are normally ground those for general emulsion applications are not. The fracturing of the secondary particles formed in the dryer enables them to break down more easily in the plastisol and return to their original latex particle size distribution. 

The grinding/powder mills may be of a hammer type, or consist of a classifier and rotating rotor fitted with pins or bars. The classifier may be separate or an integral part of the mill itself. 

The end-product from suspension or emulsion PVC is bagged or transferred to storage silos for packaging or bulk transportation. 

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Easy to prepare. Dry it in the sun. Sieve and grind NH4N04 very well. The speed of explosion is 3400 M/sec. 

The general pieces of equipment used in grinding flake mica or mica concentrate into saleable mica products are hammer mills of various types, fluid energy mills, Chaser or Muller mills for wet grinding, and Raymond or WiUiams high side roUer mills. Another method is being developed, called a Duncan mill (f. M. Huber, Inc.), that is similar in many respects to an attrition mill. AH of these mills are used in conjunction with sieves, and all but some types of hammer mills incorporate air classifiers as a part of the circuit. 

Coke The grinding characteristics of coke vary widely. Byproduct coke is hard and abrasive, while certain foundry and retort coke is extremely hard to grind. For certain purposes it may be necessary to produce a uniform granule with minimum fines. This is best accomplished in rod or bah mihs in closed circuit with screens. Hourly capacity of a 1.2- by 3-m (4- by 10-ft) rod mill with screens, operating on by-product-coke breeze, was 8.1 Mg (9 tons), 100 percent through No. 10 sieve, and 73 percent on No. 200 sieve power requirement, 30kW(40 hp). 

Collect 1 kg of rice grains and grind with a mill. Collect about 1 kg of rice straw and grind with a grinder. Soil, collected from the top 10-cm surface layer, is homogenized and passed through a 5-mm sieve. 

Some more recent safety AN blasting expls have been described by Taylor Reid (Ref 86), Davis et al (Ref 84), Rinkenbach Carroll (Ref 89), Scalera Bender (Ref 90) and Taylor (Ref 91). Taylor Reid described an expl prepd by grinding together AN 53.1 TNT 11,9 parts so that all the mixt passed through a 150 mesh Brit Std Sieve. To this was added 35 parts of AN, all of which passed a No 60 sieve and only 50% of which passed a No 120 sieve. The resulting expl compn had a vel of deton of 2400 m/sec and was sensitive to a No 3 commercial fulminate detonator (Ref 86). Davis et al (Ref 84) described a NG-free blasting compn contg AN/NaNO, mixt 60, DNT/TNT mixt 10—30 and finely divided metallic fuel 0,5—10%. The nitrate mixt contained 30—80% AN which passed a 100 mesh sieve. 

Table 28-3 illustrates another problem with heterogeneous materials. Nickel ore was crushed into small particles that were sieved and analyzed. Parts of the ore that are deficient in nickel are relatively resistant to fracture, so the larger particles do not have the same chemical composition as the smaller particles. It is necessary to grind the entire ore to a fine power to have any hope of obtaining a representative sample. 

A powdered sample for analysis may be prepared safely by grinding granulated black powder, in small portions at a time, in a porcelain mortar. The powder may be passed through a 60-mesh sieve and transferred quickly to a weighing bottle without taking up an appreciable amount of moisture. 

Microcline, albite and labradorite were obtained from Ward s Canada Limited. Cleaved crystal fragments and 60 mesh-sized samples were ultrasonically cleaned prior to use. Powdered samples (particle size < 25 ym) were prepared by grinding in a tungsten carbide ball mill, wet-sieving and washing in water. 

The maj ority of these new plants are corn dry-grind ethanol plants. Approximately 2.5-2.7 gal of ethanol, 17.5 lb of dried distiller s grain (DDG), and 17 lb of carbon dioxide are produced from each bushel of corn processed through a corn dry mill (2). Since 1980, process improvements in enzymes, thermal-tolerant yeasts, molecular sieves, and cogeneration have achieved a 50% reduction in the energy required to produce ethanol from corn (2). Further improvements in efficiencies and reductions in production costs can be expected in the future. 

Samples and Reagents. The bamboo samples used were three-year old Muli (Melocanna baccifera), obtained from the Taiwan Forest Research Institute. The samples were prepared by stripping off the outermost waxy surface and then grinding them into powder. The bamboo powder was then screened through a 60 mesh sieve and dried in an oven at 110°C to constant weight. 

Dried vegetables. Grind the sample to pass a ca. 0.5 mm mesh sieve and store in an air-tight container. 

Grind spices to pass through a 1mm mesh sieve and mix. Immediately prior to analysis, thoroughly mix the material and remove a portion of not less than 2 g for analysis to insure uniformity. For prepared mustard, transfer the entire contents of the container to a vessel, stir well, store in an airtight container and stir before removing a portion for analysis. Vinegars need only to be mixed and filtered. 

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