Coarse materials

A novel approach for suppression of grain noise in ultrasonic signals, based on noncoherent detector statistics and signal entropy, is presented. The performance of the technique is demonstrated using ultrasonic B-scans from samples with coarse material structure. 

Experimental results on real ultrasonic B-scan data, acquired from samples with coarse material structure, are presented to demonstrate the power of the novel approach. 

The 45° transducer was used to inspect side drilled holes, with their centres located 40 mm below the surface. Due to the coarse material structure the echoes from the holes were totally masked by clutter. An example of an ultrasonic response signal, emanating from a hole with a diameter of 8 mm, is shown in the left part of Figure 3. Scanning the surface above the 8 mm and 10 mm holes resulted in the B-scan image shown in the upper part of Figure 4. 

Extra coarse 170-220 Filtration of very coarse materials. Gas dispersion, gas washing, and extractor beds. Support of other filter materials. 

After cleaning to remove coarse material, ie, cobs, and fines (broken com, dust, etc), the com is steeped in a sulfurous acid solution to soften the com and render the starch granules separable from the protein matrix that envelopes them. About 7% of the kernel s dry substance is leached out during this step, forming protein-rich steep-water, a valuable feed ingredient and fermentation adjunct. 

In the case of thickeners, the process of compaction of the flocculated material is important. The floes settle to the bottom and gradually coalesce under the weight of the material on top of them. As the bed of flocculated material compacts, water is released. Usually the bed is slowly stirred with a rotating rake to release trapped water. The concentrated slurry, called the underflow, is pumped out the bottom. Compaction can often be promoted by mixing coarse material with the substrate because it creates channels for the upward flow of water as it falls through the bed of flocculated material. The amount of compaction is critical in terms of calculating the size of the thickener needed for a particular operation. The process of compaction has been extensively reviewed in the Hterature (41,42). 

Much effort is made to obtain a representative sample from bulk dry soHds. This can be a difficult task for very coarse material and from large... 

The following variables can affect wall friction values of a bulk soHd. (/) Pressure as the pressure acting normal to the wall increases, the coefficient of sliding friction often decreases. (2) Moisture content as moisture increases, many bulk soHds become more frictional. (3) Particle size and shape typically, fine materials are somewhat more frictional than coarse materials. Angular particles tend to dig into a wall surface, thereby creating more friction. (4) Temperature for many materials, higher temperatures cause particles to become more frictional. (5) Time of storage at rest if allowed to remain in contact with a wall surface, many soHds experience an increase in friction between the particles and the wall surface. (6) Wall surface smoother wall surfaces are typically less frictional. Corrosion of the surface obviously can affect the abiUty of the material to sHde on it. 

Trickling Filters. The so-called trickling filter is not a filter but a bed of stones or other coarse material (packing) over which the sewage flows. In terms of the total number of installations, it is the most widely used biological treatment process. However, the greatest total volume of waste is treated by the activity-sludge process (12). 

The calcium carbonate industry is one of the most competitive of the industrial minerals industry. The market for fine products (97% <45 fim) is estimated to be between 5—9 million tons annually in the United States. The pricing is dependent on the grade which is determined by fineness, purity, and brightness it ranges from 30/kg for coarse materials to over 440/kg for some ultrafine coated or food grades (4). 

When the ore contains a large amount of clay minerals, these form difficult to separate slimes, which hinder the recovery of the minerals (see Clays). The tailing from the scavenger cells can be cycloned to remove the slimes before the coarse material is floated in a tailings retreatment plant. The flotation product from the rougher cells of this plant can be reground and cleaned. This additional treatment of the tailings from the main copper flotation plant may improve the recovery of metal values by 1—3%. 

Alternating-polarity drum separator. This device is used for the treatment of coarse material (minus 40 mm, plus 0.15 mm) containing strongly magnetic particles when a high-grade concentrate is required. The capacity of this device varies with feed-particle size, up to 100 t/(h m). 

The kinetic equation can vary with a number of factors. For the reaction between tricalcium phosphate and urea, relatively coarse material (-180-1-200 mesh) obeyed the law x = kt with E = 18 kcaP g mol (32,400 Btu/lb mol) and finer material (—300f320 mesh) obeyed a first-order equation with E = 28 kcaPg mol. 

Bulk surface discharge In rapid heaping of highly insulated bulk material, particularly when coarse material (diameter > 1 mm) is present MIE<1I (silo diameter 3 m)... 

Note that this relationship indicates that it is more difficult to break down fine than coarse material. 

Kutty and Murthy [1159] have made a kinetic study of the solid—solid reaction between tricalcium phosphate and urea nitrate, a process of possible technological importance. A reduction in particle size, notably of Ca3(P04)2, increased the rate of reaction in powder mixtures and also changed the kinetic characteristics (318—338 K). Reaction in relatively coarse material (between —180 and +200 mesh) obeyed the parabolic... 

Duckworth, R. A., Pullum, L., Addie, G. R. and Lockyear, C. F. Hydrotransporl 10 (BHRA Fluid Engineering, Innsbruck, Austria) (October 1986). Paper C2. The pipeline transport of coarse materials in a non-Newtonian carrier fluid. 

The fineness of the material being processed governs the selection of machines. Both the feed and the product sizes are involved in the selection process. Some machines, by their very design, can treat only coarse material, while some others can treat only fine material. Some machines produce a very uniform product, whereas some others, by virtue of their construction, produce a product with considerable variations in size. 

Revolving screens inclined, cylindrical screens, rotated at low speeds (10-20 rpm). Used for the wet screening of relatively coarse material, but have now been largely replaced by vibrating screens. 

ChemFix Technologies, Inc., has used silicates and silicate setting agents to stable polyvalent metal ions. Usually, there is a need to separate coarse and fine pollutants so as to crush coarse materials and reduce the material size required for the stabilization technology. 

Improvement of the form grinding and homogenizing of solid and coarse materials... 

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