Coarse fraction

Cla.ssifica.tion. Slurry leaving precipitation is classified into a coarse and one or more fine fractions, usually by elutriation in hydroclassifiers. Cyclones and combinations of hydroclassifiers and cyclones are gaining popularity. In smelting grade alurnina plants, the coarse fraction, called primary product, is sent to calcination the fine fractions, called secondary and tertiary seed, are recycled to be grown to product size. 

AU processed material is screened to return the coarse fraction for a second pass through the system. Process feed rates are matched to operating variables such as rpm speed and internal clearances, thus minimizing the level of excess fines (—200 mesh (<0.075 mm mm)). At one installation (3) the foUowing product size gradation of total smaller than mesh size (cumulative minus) was obtained ... 

The finer soil fraction contains adsorbed organics, small metallic particles, and bound ionic metals. This fraction may be treated further to remove the contaminants, or it may be incinerated or landfilled. The "clean" coarse fraction may contain some residual metallic fragments. With metal contamination, both the fine and coarse soil fractions may be leached with an acid solution to remove the metals. 

FIG. 12-95ii Strong-Scott flash dryer with integral coarse-fraction classifier to separate undried particles for recycle. (Bepex Cotp.)... 

Q Capacity of roll crusher cmVmin ftVmin of coarse fractions ... 

Other studies have been performed to investigate the effect of surface area and tablet lubricant efficacy. In a comparison study between sodium stearyl fumarate and magnesium stearate, it was found that sodium stearyl fumarate was effective as a lubricant to about the same degree as magnesium stearate [15]. It was also reported that the lubricating properties correlated better to the surface area of the lubricant than to the amount of lubricant used. A micronized lubricant was more efficient than a coarse fraction, and it was suggested that the surface area be standardized to obtain reproducible effects. 

Note that the chemical dimensions do not yield such robust "markers", or tracers, as the isotopic dimensions. For a given combustion source, for example, one is apt to find chemical--but not isotopic—fractionation varying significantly with time, particle size, particle history (differential volatilization or reaction), etc. The ratio K/Fe, for example, was quite different in the fine and coarse fractions from a slash burn (1.5 vs. 0.3) [33] and Pb/Br, which has been popular as an automobile exhaust tracer, varies with the "age" of urban particles [22]. 

Particulate matter (PM) is associated with adverse human respiratory health effects. Although much research has focused on the fine particle component (PM2.5), recent results from the USC Children s Health Study suggest that the coarse fraction may also affect respiratory health in children. Specific components of the coarse fraction responsible for these effects have not been identified, but ambient endotoxin is a strong candidate, based on toxicologic and epidemiologic studies. This study is collecting... 

Previously, it was noted that organic matter associated with the coarse fraction of a sorbent was a substantially weaker sorbent than the organic matter associated with smaller materials (15). 

The suspended solid particle size and the volume of effluent also must be considered in examining deposition in the subsurface. For example, under leaching of a waste disposal site or following irrigation with sewage effluent, the coarse fraction of suspended solids is retained in the upper layer, while the finer colloidal fraction is more mobile, and its transport is controlled by the porosity of the subsurface solid phase. 

This study has shown that there are important differences in the alteration effects observed in the fine and coarse fractions of the host turbidite units. It is critical to examine and analyse these end members separately as many of the key lithogeochemical features of the alteration would be obscured in bulk samples. 

Conventional regional soil geochemical surveys based on coarse fractions of soils (>20 mesh) to avoid windblown sand dilution for elemental contents failed to delineate uranium geochemical anomalies for blind sandstone-type uranium deposits in desert basin terrains in China. 

The experimental results reported in this paper demonstrate the ability of a flat-bottom hydrocyclone to separate the coarse fraction of ammonium sulfate crystals from a slurry which contains crystals of a wide size range. It appears that the grade efficiency curve, which predicts the probability of a particle reporting to the underflow of the cyclone as a function of size, can be adjusted by a change in the underflow diameter of the hydrocyclone. These two observations lead to the suggestion to use hydrocyclone separation to reduce the crystal size distribution which is produced in crystallisers, whilst using a variable underflow diameter as an additional input for process control. 

A typical grade efficiency curve for the product classification step is given in Figure 4. A value of nearly 100 percent is attained at large sizes, whereas normally a value equal to or larger than the so-called dead flux is attained at small sizes. This is caused by the diluted discharge of the coarse fraction. It represents the minimum amount of residual fines in the product after one separation stage. 

The sample collected from the crystaUizer was diluted with filtered electrolyte (2.0 wt% aqueous NaCl) and decanted to separate the fines from the coarse crystals. The dilution and decantation were repeated 5-7 times till 200 ml of the decanted sample was obtained. Preliminary tests by hoh (8) have shown tiiat these repeated decantantions were sufficient to recover at least 95% of the fines present in the original sample. Both the fine and coarse fractions were then analysed with the Coulter Counter using a 50 p.m orifice tube for the former and a 280 im orifice tube for the latter. By adjusting the Coulter Counter s settings, a set of particle number counts at different sizes (successive sizes differing by a factor of 21/3) was made for each of the 2 orifice tubes used. 

The aqueous soil washing system is used to classify the particles into a coarse and fine fraction. The coarse fraction is cleaned by the use of heat, chemicals, and mechanical energy. This material can be returned to the site as clean backfill. The fine fraction is thickened and sent to the solvent extraction unit. 

For the coarse fraction, the first factor contains the majority of the variance and represents soil. There are high loadings for Al, Si,... 

The tests to determine the number of factors to retain are given in table for both the fine and coarse fractions. For the fine fraction there appear to be three strong sources and two weaker ones. The coarse fraction results do not give a clear indication of the number of factors and parallel analyses with and 5 retained factors were performed until it was found that sources gave the best results. 

The refined source profiles that best reproduced the coarse fraction are listed in table 7. The calculated profiles of the two crustal components follow those of Mason ( ), though the calcium concentration of 20 in the limestone factor is less than the reported value. The paint pigment profile strongly resembles that calculated for the fine-fraction data. The only major difference is that unlike the fine fraction, the coarse-fraction profile does not associate barium with the paint-pigment factor. The calculated sulfur concentration in the coarse-fraction sulfate factor is much less than that in the fine-fraction and there are sizable concentrations of elements such as aluminum, iron, and lead not found in the fine-fraction profile. The origin of this factor is not clear although as described earlier a possible explanation is that a small part of the sulfate particles in the fine fraction ended up in the coarse samples. 

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