Sink-and-float separators

Magnetic fluids can be used as a high-density solution for the sink-and-float separation of solids in suspension. This separation technique for non-ferrous metals is based on the anomalous viscosity increase of a magnetic suspension as a function of applied field. The magnetic fluid consists typically of magnetite particles with an average diameter of 100 A in water, with 15-25 wt% of ferrite. To prevent particle aggregation, a surfactant such as kerosene and oleic acid, or a polymer is usually... 

Suspension systems of sticky slurry and paste-like liquid explosives with solid particles, based on the dispersion of suspended solid particles, should belong to suspension or coarse multiphase systems in colloid chemistry. In these suspension systems, the main issue is its dynamic instability, because the density of the dispersed particles and the density of the dispersion medium are different (generally, the density particle is greater than that of the medium), settlement or floating can occur with the role of gravitational field to separate the system, resulting in unevenness in composition and density of liquid explosive. Stability is the ability to overcome the so-called sink-and-float separation of two-phase components, therefore, within a certain period of use, the composition and density of explosive and other physical parameters remained unchanged and its properties are stable and reliable. 

Schimpf describes a process for separating polyolefins from household and industrial plastic waste which relies on a two step process comprising firstly a sink-and-float separator and then a hydrocyclone. The hydrocyclone separation allows separation of polyst5rrene and PVC. ... 

In heavy media separation, the use of hydrocyclones is for solid-solid separation by solid density as required in mining and mineral processing. The density of the suspending medium is chosen to be between the densities of the two minerals to be separated and the cyclone is then used as a sink-and-float separator. 

Sorting of particles, particularly of bidisperse mineral mixtures, is more cleanly effected by sink-and-float separation. This is most simply done by using a liquid nonsolvent intermediate in density between that of the two particle species. With overflow and underflow discharge streams, and a continuous feed suspension introduced at an intermediate position, the sharpness of separation decreases as the feed rate, the feed solids concentration, and the under-flow/overflow ratio are increased (Nasr-El-Din et al., 1988, 1990). In the absence of an acceptable liquid, a homogeneous suspension, viz., a water-fluidized bed of narrowly cut fine sand (e.g., —325 - - 400 mesh), could... 

Dense-medium separators (sink and float processes)... 

Feed Solids Content. A good HMS plant operation keeps the medium as free of fines as possible by effective screening of the heavy-media separation vessel feed. Reduced fines reduce viscosity problems in the medium and result in sharper separation of sink and float products. It also improves magnetic recovery on the magnetic drum separators and gives a cleaner magnetic concentrate. The use of cyclones in the HMS circuit, either as the heavy-media separation vessel or as a densifier for rinse or wash water, increases the solids content and must be evaluated in selecting the media recovery wet dmm separators for plants in which cyclones are used. 

The procedure we have developed to determine the VMI of a particular FCC unit involves obtaining approximately 100 grams of an FCC Beat. This Beat is first calcined in a muffle furnace at 593°C for 2 hours to remove any residual carbon. After cooling, the Beat is separated into eight fractions by a sink/fioat density separation. The density separation is performed by mixing the catalyst sample with tetrabromoethane (TBB) which has a density of 2.96 g/cc. This material is heavier than most FCC catalyst (excluding additive materials) so the catalyst sample will float in the TBB. Tetrochloroethane (TCB), which has a density of 1.58, is then added to the mixture to lower the density of the liquid and cause some of the denser catalyst particles to sink. The amount of added TCB is controlled to obtain the desired amount of sink and float fractions. 

SORTING CLASSIFIERS. Devices that separate particles of differing densities are known as sorting classifiers. They use one or the other of two principal separation methods—sink-and-float and differential settling. 

Sink-and-float methods. A sink-and-float method uses a liquid sorting medium, the density of which is intermediate between that of the light material and that of the heavy. Then the heavy particles settle through the medium, and the lighter ones float, and a separation is thus obtained. This method has the advantage that, in principle, the separation depends only on the difference in the densities of the two substances and is independent of the particle size. This method is also called heavy-fluid separation. 

This process takes place in two phases. In the first, the batteries are shredded, the active matter is separated and dried, and the acid is neutralised. In the second, lead is separated from ebonite (or polypropylene) with the so-called sink and float process. 

Sink-and-float methods. Devices for the separation of solid particles into several fractions based upon their rates of flow or settling through fluids are known as classifiers. 

There are several separation methods to accomplish this by sink-and-float and differential settling. In the sink-and-float method, a liquid is used whose density is intermediate between that of the heavy or high-density material and the light-density material. In this method the heavy particles will not float but settle from the medium, and the light particles float. 

Separation by Sink-and-Float Method. Quartz having a specific gravity of 2.65... 

After this purification, the material is submitted to another separation by density (sink and float). 

The more dense, more mature peas sink and are drawn off near the bottom of the separator, while the less dense, less mature peas float and are carried off at the top. During the process the peas absorb salt, and unless it is removed by thorough washing enough may be retained to make the product objectionable to the taste. In a packing specification it is necessary to state the amount of salt that will be tolerated. Available methods for the determination of salt are not applicable to production-line control. One which is sufficiently simple and rapid for this purpose is definitely needed. 

Two bituminous coals of moderate ash content were chosen for this paper to illustrate this method of determining coal-mineral association. The first sample was an Upper Freeport coal with 1.3% moisture, 9.88% ash, and 1.56% total sulfur. The second sample was an Indiana No. 3 coal having 10.5% moisture, 7.35% ash, and 4.26% total sulfur. Both coals had been precleaned at a coarse particle size, ground to minus 325 mesh (44 ym), and then separate samples were cleaned by float-sink and by froth flotation techniques, as described elsewhere [5]. Analyses of the feed coals are included in Table I. 

Preparative II DGC in Figure 1 is a scaled-up version of Preparative I which uses a combination of the sink-float separations followed by non-linear density gradient separation. With this technique 20-25 g of a maceral concentrate can be separated. In effect, for a three-fold increase in time for separation, isolation, and characterization, we obtain at least a ten-fold increase in the yield of maceral materials. 

The chemistry of macerals separated by DGC, float-sink and hand picking has been investigated recently by several techniques including solid I3C nmr (3,4), oxidation (5,6), and... 

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