Overflow particle size

When used to separate solid-solid mixtures, the material is ground to a particle size small enough to liberate particles of the chemical species to be recovered. The mixture of solid particles is then dispersed in the flotation medium, which is usually water. Gas bubbles become attached to the solid particles, thereby allowing them to float to the surface of the liquid. The solid partices are collected from the surface by an overflow weir or mechanical scraper. The separation of the solid particles depends on the different species having different surface properties such that one species is preferentially attached to the bubbles. A number of chemicals are added to the flotation medium to meet the various requirements of the flotation process ... 

The products are an oversize (underflow, heavies, sands) and an undersize (overflow, lights, slimes). An intermediate size can also be produced by varying the effective separating force. Separation size maybe defined either as a specific size in the overflow screen analysis, eg, 5% retained on 65 mesh screen or 45% passing 200 mesh screen, or as a d Q, defined as a cut-off or separation size at which 50% of the particles report to the oversize or undersize. The efficiency of a classifier is represented by a performance or partition curve (2,6), similar to that used for screens, which relates the particle size to the percentage of each size in the feed that reports to the underflow. 

By convention, classification has been defined as the particle size of which 1 % to 3 % reports to the cyclone overflow with coarser particles reporting to the cyclone underflow. Recent investigations reported by Arterbum (1999) have defined classification as the particle size of which 50% reports to the overflow and 50% to... 

Consider a thin layer solid bowl centrifuge as shown in Figure 4.20. In this device, particles are flung to the wall of the vessel by centrifugal force while liquor either remains stationary in batch operation or overflows a weir in continuous operation. Separation of solid from liquid will be a function of several quantities including particle and fluid densities, particle size, flowrate of slurry, and machine size and design (speed, diameter, separation distance, etc.). A relationship between them can be derived using the transport equations that were derived in Chapter 3, as follows. 

A settling tank contains solid particles that have a wide range of sizes. Water is pumped into the tank from the bottom and overflows the top, at a rate of 10,000 gph. If the tank diameter is 3 ft, what separation of particle size is achieved (That is, what size particles are carried out the top of the tank, assuming that the particles are spherical ) Solids density = 150 lbm/ft3. 

The feed enters near the center of the tank, and the liquid flows upward and overflows the top of the tank. The solids loading of the feed is 0.5 lbm of solids per gallon of slurry, and the feed rate is 50,000 gpm. What is the total solids concentration and the particle size distribution in the overflow Density of solids is 100 lbm/ft3. Assume that (1) the particles are spherical (2) the particles in the tank are unhindered and (3) the feed and overflow have the same properties as water. 

A sludge is to be clarified in a thickener that is 50 ft in diameter. The sludge contains 35% solids by volume (SG = 1.8) in water, with an average particle size of 25 pm. The sludge is pumped into the center of the tank, where the solids are allowed to settle and the clarified liquid overflows the top. Estimate the maximum flow rate of the sludge (in gpm) that this thickener can handle. Assume that the solids are uniformly distributed across the tank and that all particle motion is vertical. 

In a batch thickener, an aqueous sludge containing 35% by volume of solids (SG = 1.6), with an average particle size of 50 pm, is allowed to settle. The sludge is fed to the settler at a rate of 1000 gpm, and the clear liquid overflows the top. Estimate the minimum tank diameter required for this separation. 

A scoop that is positioned in the hydrocyclone vortex to obtain the desired particle size distribution in the overflow stream. 

Most studies of hydrocyclone performance for particle classification have been carried out at particle concentrations of about 1 per cent by volume. The simplest theory for the classification of particles is based on the concept that particles will tend to orbit at the radius at which the centrifugal force is exactly balanced by the fluid friction force on the particles. Thus, the orbits will be of increasing radius as the particle size increases. Unfortunately, there is scant information on how the radial velocity component varies with location. In general, a particle will be conveyed in the secondary vortex to the overflow, if its orbital radius is less than the radius of that vortex. Alternatively, if the orbital radius would have been greater than the diameter of the shell at a particular height, the particle will be deposited on the walls and will be drawn downwards to the bottom outlet. 

Mesh of separation—Particle size that equals 1-3% plus Dy weight of overflow soflds. 

The goal of sideline extraction is to regain the starch (fine granules) that has been lost in the overflow of the classification. Figure 11.19 indicates that the particle sizes of starch and fiber are sufficiently different to enable separation by sieving. This is done by the same conical rotating sieves that were used in the fiber extraction, but with a... 

It (1 ) deals with the derivation of relations giving the particle size distribution in the bed, overflow, and carryover streams and their respective weights. This theory will be extended to include the effects of particle growth or shrinkage (Z>1 or Z<1). For typical combustion of char containing sulfur followed by sulfur dioxide absorption by limestone, relations will be derived to determine the extent of sulfur retention. The reaction, carryover, and overflow rates will be evaluated with particular attention to their dependence on Z. 

P3(Cs) Is the size distribution of the particles in the bed and overflow stream for a feed of fixed particle size The... 

Preparation, particle size, and moisture will influece how fast liquid flows through the bed. Preparation should be controlled so that the flow is not too fast. Worse than that, however, is too slow a flow. The cell will then flood, and the liquid will overflow into the next cell. This could stop extraction in the flooded cell. 

Figure 21. Overflow rate in sedimentation tank effects on particle size distribution function...

The operation of the fines-destruction process is similar to that of clear-liquor advance as shown in Figure 64.4, the difference is that when the clear liquor is used, the small particles return back to the product flow, thus increasing the proportion of small crystals. For the fines-destruction operation, very small fines can be withdrawn, and the suspension density of the overflow is very small. The number of crystals in the crystallizer decreases as a result of eliminating the small-sized particles. This operation is very useful in increasing the size of crystals in a system that has a high rate of nucleation. This method does, however, lead to a wide particle size distribution. 

Increased moistening of the feed mixture was found to increase the particle size of the overflow calcine as long as the moisture content of the feed was lower than 11 % H2O. The larger partieles drop to the bed and the oxidation reactions increase both the bed temperature and furnace heat production. Simultaneously, the furnace control system decreases the feed rate in order to keep the bed temperature constant. Figure 15. The feed rate may be increased with more effective cooling of the furnace if the sulfide level is not too high. The process gas temperature in the top of the furnace deereases because fewer fine particles bum above the bed, while simultaneously dust carry-over decreases, Figures 16. 

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