Sand fraction

FIGURE 6.9 Flexicoking is a commercial process for refining petroleum that has been applied to heavy oil and tar sand fractions. The process employs circulating fluidized beds and operates at moderate temperatures and pressures. The reactor produces liquid fuels and excess coke. The latter is allowed to react with a gas-air mixture in the gasifier fluidized bed to provide a low-value heating gas that can be desulfurized and used as a plant fuel. Courtesy, Exxon Research and Engineering Company. 

Wind transport. Wind-blown components are carried away over a more or less important distance as a function of wind velocity and particle size of the material. Wind speeds up till 6.5 m/sec transport dust and fine sand with a diameter of less than 0.25 mm sand grains up to 1 mm diameter are uplifted at wind speeds of 10 m/sec. At 20 m/sec also particles of 4-5 mm may be removed. Based on these physical laws, the transportation of coarse fragments, in casu the sand fraction, occurs over-relatively short distances from the deflation zones. These sand grains settle then in more or less continuous layers and either become progressively mixed with the underlying soil layers, or concentrate in dune formations. 

The flowsheet used to treat dolomitic oxide copper ores is somewhat different from that used in the beneficiation of siliceous oxide copper ores. This is due to the fact that dolomitic ore usually contains elevated amounts of slimes, in which case a split circuit flowsheet has been adopted in a number of operations. The typical flowsheet used for treatment of dolomitic ores is shown in Figure 19.8. Usually, the scavenger tailings are deslimed and the sand fraction is retreated in a scalp copper flotation stage. When the ore is deslimed before flotation, a large amount of fine copper is lost in the slime fraction. 

Figure 3. Aqueous-surfactant tar sand extraction with NPE surfactants (0.02% (M) Bitumen concentration in residual tar sand (B/RTS) percent of total bitumen in sand fraction (/ ) bitumen concentration in sand fraction (B/S) (O) percent of total bitumen in surface fraction (0) composite index of extraction efficiency.

The Snrbec-ART Environmental, L.L.C. (Snrbec), soil washing technology is a process based on mining and mineral processing principles that incorporates physical and chemical separation techniqnes (D12463A, p. 3). The technology separates and treats oversized fractions and sand fractions so that they can be placed back on the site as clean backfill. Contaminants are concentrated in the fines, and this fraction can be managed separately for further treatment or disposal. 

Purification and Preparation of Clay Samples. The sand fraction of the clay samples was separated by slow-speed centrifugation of a suspension of the clay before the purification steps. 

Following pipeline transport and deposition into a tailings pond, the coarse sand fraction will begin to settle out and can be dredged and used to form beaches and dykes around the tailings ponds, for containment [606], This is not as straightforward as it may seem and the material properties of these barriers must be carefully controlled since poor construction, or subsequent events like erosion or liquefaction of the solids can cause severe failures, with catastrophic results [606],... 

Liquid hydrocarbon. This can include, for example, liquid petroleum (crude oil), synthetic hydrocarbon liquid, bitumen from oil (tar) sands, fractions obtained from crude oil, and liquid fats (e.g., triglycerides). 

In Table 3, susceptibility to weathering increases down the list as fewer silicon-oxygen bonds need to be broken to release silicate. Consequently, quartz and feldspars especially, but also mica in temperate soils, are common inherited minerals in the coarse particle size fractions of soil (the silt and sand fractions, 0.002-2 mm). The amphiboles, pyroxenes, and olivine are much more easily weathered. Thus, soils derived from parent material with rock containing a predominance of framework silicates e.g. granite, sandstone) tend to be more sandy, while those derived from rocks containing the more easily weathered minerals tend to be more clayey. 

In a number of cases, geochemically similar elements are well correlated to each other in the sand fractions from each unit (e.g., Sm and Eu in Figure 7). This correlation is not surprising if the trace elements are associated with the heavy minerals. Small variations in the amount of a particular heavy mineral will cause large differences in the trace element content measured, if the sand fraction is mostly quartz and feldspar, which contain so few trace impurities. Figure 7 shows the relationship between Sm and Eu. There is a correlation between these elements in the samples from each of the two levels. Figure 7 suggests that there is a different Sm/Eu ratio for the sands from these two Nile sediment deposits. 

A mass balance using data from the density fractions and the entire sand fraction suggests that heavy minerals containing Cr, Th, and Hf represent about 1-2% of the sand-sized material from Unit B and 4-5% from Unit N. 

However, the nature of the adsorbent affects the adsorption-pH profiles (9,10,11,12). Although the difference in the Fe content of the sand fractions used in this study is small, the large change in the mobility of both As (III) and As(V) between the fine and medium fractions may be due to the difference in the nature of the sand i.e. due to a higher amount of discrete iron oxides in the coarse fraction (13). 

Adsorption experiments were carried out using only the silt fraction because this fraction lends itself to batch experiments and is similar in composition to the sand fraction, consisting primarily of quartz and feldspar. Furthermore, it was felt that the application of double-layer theories of adsorption would be less appropriate on the clay fraction, where the effects of valence deficiencies resulting from isomorphic substitution in actual clays are probably more important. 

The X-ray diffraction patterns for the sand and silt fractions had a nearly identical predominance of quartz and feldspar peaks. The "clay" fraction, however, showed X-ray peaks from quartz and feldspars as well as for chlorite/montmorillonite. Our use of the silt fraction in the following adsorption experiments is supported by the similarity in composition (i.e., mostly quartz and feldspars and no clays) between the silt and sand fractions. The silt fraction, more easily suspended than sand, was an indicator of the adsorption characteristics that might logically be expected of the sand fraction as well. 

Table V shows metal distributions in two other domestic tar sand fractions. In the Battle Creek bitumen from Wyoming, bitumen metals and porphyrins are concentrated in the asphaltenes, as expected. Fractions obtained from the Edna, California outcrop have vanadium-to-...

Figure 5. Effect of acid leaching on >250jum sand fraction DST-MTR...

Figure 6. Effect of magnetic separation on >250jam sand fraction DST-MTR. The trio of bars shown are for mass (g), concentration (Bq/g) and inventory (Bq)...

Figure 28 shows measurements for the same sand fraction at dimensionless radial positions (R = 2r/D) of 0.0, 0.7, and 0.8, where r is the radial position measured from the pipe center. The effect of position on [e(C,R) -e(0,R)]/e(0,R) is significant. Results obtained at the other positions show the same deviation from Maxwell s relation at higher concentrations. 

In sediments of this type, the harder heavy minerals are usually found in the coarser (sand) fraction (along with the quartz). The differences in the amount of sand in a particular sample may therefore result in differences in the concentrations of those elements associated with the heavy minerals. In addition, the mineralogical composition of this heavy mineral fraction varies and is dependent upon the source of the... 

Fig. 1 shows a cross section of a filter element and the principle for the construction of the filter is illustrated. The figure shows that the outer surface of the filter element consists of louvers. There are two layers of sand along each outer surface. A layer of fine sand on the outside and a layer of coarse sand on the inside facing the clean gas duct in the center. The sand fractions are physically separated. 

The reactor is constructed of Inconel 600 alloy and has an international diameter of 15 cm at the bottom and 30 cm in the free-board area. Fluidizing gas (air and steam mixture) is introduced through a specially designed Inconel distributor plate. The reactor is insulated with Kaowool ceramic fibre. The bed materials consist of a graded sand fraction of 60—80 mesh. 

Methods for correcting for grain-size effects in studies on heavy metal concentrations in estuarine and coastal sediments have been discussed by Ackermann (1980). There is, unfortunately, no one standard method for particle-size normalisation and a wide range of techniques are in use (Table 2.3). The method which often involves the least effort is the correction which uses comparison with rubidium (Rb) as a conservative element (Ackermann, 1980). This technique relies on the fact that Rb has a similar ionic radius to potassium (K) and so substitution of Rb for K will take place in clay minerals. Furthermore, Rb is present in the sand fraction in very much smaller concentrations than in the clay or silt fraction and concentrations of the element in sediments are rarely influenced by anthropogenic activity. Another advantage of the use of Rb is that it is often routinely analysed by X-ray fluorescence along with a suite of pollutant trace metals. 

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