Wet-milling

It is effective for dry (deagglomeration elumping) and wet milling of soft to medium hard materials. 

The comminution chamber consists of an impeller rotating at variable speed, imparting a compression or shear force inside a conical screen. 

The impeller imparts a vortex flow pattern to the feed material, and the centrifugal acceleration forces the particles to the screen surface and up the cone (360°) in a spiraling path (13) (Figs. 3A and B). 

The size and shape of the screen holes, screen thickness, impeller configuration, and mill speed are important variables. 

It is used for difficult-to-mill, heat-sensitive material and hard granules. Low heat and lower amounts of lines are produced compared with the hammer mill hence, it produces a narrower particle size distribution. 

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Corn syrups [8029-43-4] Corn wet-milling Corn whiskey Coronadite [12414-82-3] Corona resistance Coronary bypass Coronary heart disease Coronates Coronavims Coronene [191-07-1] Coromte... 

The United States wet millers buy ca 15% of the com used in the U.S. (worldwide, wet millers consume about 10% of the com used). There are two dozen com wet mills in the United States ranging in capacity from 600—10,000 metric tons/day. SheHed com is shipped to wet millers by tmck, rail, or barge. 

A higher density sol—gel abrasive, produced by the introduction of seed crystaUites formed by wet-milling with high alumina media or by introduction of submicrometer a-alumina particles, was patented (28) and designated Norton SG. The microstmcture of this abrasive consists of submicrometer a-alumina crystals (Fig. 1) and its bulk density approaches that of fused alumina. Norton SG has proven to be an exceptional performer in coated and bonded abrasive products it was awarded the 1989 ASM Engineering Materials Achievement Award (29). 

Some of the information available on designs of com wet-milling plants in which com oil and other products are produced indicate that integration with an alcohol plant may be more efficient than a conventional com alcohol plant. 

Gasohol in the United States. Over 90% of the fuel ethanol in the United States is produced from com. Typically, 0.035 m (1 bushel) of com yields 9.5 L (2.5 gal) of ethanol. Ethanol is produced by either dry or wet milling (87). Selection of the process depends on market demand for the by-products of the two processes. More than two-thirds of the ethanol in the United States is produced by wet milling. Depending on the process used, the full cost of ethanol after by-product credits has been estimated to be between 0.25—0.53/L ( 1—2/gal) for new plants (88). Eeedstock costs are a significant factor in the production of fuel ethanol. A change in com price of 0.29/m ( 1.00/bushel) affects the costs of ethanol by 0.08/L ( 0.30/gal). 

Pigments Aftertreatments. The surfaces of pigment particles can have different properties and composition than the particle centers. This disparity can be caused by the absorption of ions during wet milling, eg, the —OH groups, on the surface. In some cases, surfaces are modified intentionaHy to improve the pigments appHcation properties, interaction with the organic matrix, and weather resistance. 

Hot Hthopone leaving the calciner has to be cooled quickly to prevent the oxidation of ZnS to ZnO. Rapid cooling is accompHshed by its suspension in water that might contain a small amount of sulfuric acid to remove any traces of undesirable 2inc oxide. The suspension is then wet milled, filtered off, and dried to the commercial product. 

In the calciaation process, a mixture of corresponding oxides and an optional modifier, eg, molybdic acid, are milled together to achieve a homogenous mixture. The mixture is calciaed at 750—950°C and milled to a desired particle size. Wet milling ia an alkaline medium is recommended to remove any unreacted vanadium salts that ate beheved to degrade the pigmentary properties of bismuth vanadate (39). 

Hydroxylall l Starch Ethers. Starch hydroxyethyl ethers with a degree of substitution (DS) of 0.05—0.10 ate produced in various ways, but usually their preparation begins at the end of the wet-milling process, utilizing a high soHds-starch suspension. The ether modification of ungelatinized starch is filterable and can be produced economically in a pure form. 

During com wet-milling, a 40—50% soHds-starch suspension is treated with a metal hydroxide and ethylene oxide at approximately 50°C to produce DS of 0.1 and the product is purified by filtration and washing. 

CO, and fermentation of glucose from wet milling of com (165). None of these methods has found commercial application. 

In recent years, several wet milling operations have been initiated with obvious advantages in dust control and potential advantages in the separation of mineral contaminants from the fiber product. On the other hand, large-scale industrial wet classification methods are not in use at present. 

Extraction of Bertrandite. Bertrandite-containing tuff from the Spor Mountain deposits is wet milled to provide a thixotropic, pumpable slurry of below 840 p.m (—20 mesh) particles. This slurry is leached with sulfuric acid at temperatures near the boiling point. The resulting beryUium sulfate [13510-49-1] solution is separated from unreacted soflds by countercurrent decantation thickener operations. The solution contains 0.4—0.7 g/L Be, 4.7 g/L Al, 3—5 g/L Mg, and 1.5 g/L Fe, plus minor impurities including uranium [7440-61-1/, rare earths, zirconium [7440-67-7] titanium [7440-32-6] and zinc [7440-66-6]. Water conservation practices are essential in semiarid Utah, so the wash water introduced in the countercurrent decantation separation of beryUium solutions from soflds is utilized in the wet milling operation. 

To measure a residence-time distribution, a pulse of tagged feed is inserted into a continuous mill and the effluent is sampled on a schedule. If it is a dry miU, a soluble tracer such as salt or dye may be used and the samples analyzed conductimetricaUy or colorimetricaUy. If it is a wet mill, the tracer must be a solid of similar density to the ore. Materials hke copper concentrate, chrome brick, or barites have been used as tracers and analyzed by X-ray fluorescence. To plot results in log-normal coordinates, the concentration data must first be normalized from the form of Fig. 20-15 to the form of cumulative percent discharged, as in Fig. 20-16. For this, one must either know the total amount of pulse fed or determine it by a simple numerical integration... 

The vibratoiy-tube mill is also suited to wet milhng. In fine wet milling this narrow residence time distribution lends itself to a simple open circuit with a small throughput. But for tasks of grinding to colloid-size range, the stirred media mill has the advantage. 

Combined gas-dispersion, blending, and material drawdown (corn wet milling)... 

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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