In general, the energy dissipation per unit volume around the propeller is about 100 times greater than in the rest of the tank. The fluid flow is mainly circular or helical (see Figure 18-7) in the direction of rotation of the armature.
MIXING OF VISCOUS FLUIDS, PASTES, AND DOUGHS
The material passing between the rollers can be turned into feed by the rotation of the rollers. The pressure drop through a stationary mixer is usually expressed as an open pipe loss multiplier or as a valve CV coefficient. The value of the multiplier depends strongly on the geometry of the mixer details, but is usually available through information from the supplier.
CRYSTALLIZATION FROM SOLUTION
The polygons shown in the figure represent different stages in the growth of the crystal. The product discharged from the crystallizer is characterized by the integral of the distribution from size Lfto infinity:. 18-74, so that the heat of vaporization of the coolant cools the slurry by direct contact.
Proposed productivities for concentration driving forces depend on crystal settling rates. What is the tendency of the material to grow on the walls of the crystallizer.
LEACHING
Rapid cooling of the autoclave product is usually accomplished in one or more pressure-reducing vessels with abrasion-resistant nozzles and targets. Each plate has a radial opening offset 180° from the openings of the plates immediately above and below it, and each plate is wiped by a rotating radial blade. In the De Danske Sukkerfabriker, the axis of the extractor hood is tilted approximately 10° from the horizontal, eliminating the need for two screws with different angles of inclination.
The solvent is pushed by the baffle to the bottom of the tank at the lower end before it overflows. Rapid cooling of the product from the autoclave is usually done in one or more pressure reducing vessels with wear-resistant nozzles and targets.
Algebraic calculation This method begins with the calculation of the quantities and compositions of all the terminal streams, using a convenient quantity of one of the streams as the basis of calculation. Calculations are repeated for each successive ideal stage from one end of the system to the other until an ideal stage corresponding to the desired conditions is obtained. Graphical Method This method of calculation is simply a diagrammatic representation of all the possible compositions in a leaching system, including equilibrium values, at which material balances over ideal (or, in some cases, non-ideal) stages can be evaluated in the graphical equivalent of the stage-by-stage algebraic calculation.
It is normally simpler than the manual calculation of the algebraic solution, and it is considered useful by many because it allows visualization of the process variables and their effect on the operation. Any of the four types of composition diagrams described above can be used, but modified Ponchon-Savarit or right-angled triangular plots (Fig. 18-92) are most useful for leaching calculations.
GRAVITY SEDIMENTATION OPERATIONS
The concentration of suspended particles can be plotted on log-log paper as a function of the sampling time (detention time). High turbidity caused by short-circuiting the supply to the overflow can be reduced by increasing the depth of the supply well. There are three basic underflow arrangements: (1) the underflow pump adjacent to the side wall of the thickener with underground piping from the discharge cone, (2) the underflow pump under the thickener or adjacent to the side wall with the piping from the discharge cone in a tunnel, and (3 ) the underflow pump located in the center of the thickener on the bridge, or using pipes through the center column.
It is also important to consider the sludge bed level in the thickener. The weight of the ball can be adjusted to float on top of the bed of solids.
FILTRATION
Equation (18-49) applies to a system in which the circuit receives dry solids with which the second stage thickener overflow is mixed to extract the soluble component. In this case, O' refers to the overflow volume from the thickeners after the first step.
DESIGN SIZING CRITERIA
Excessively dirty filtrates should be avoided as the solids can be abrasive and damaging to the internals of the filter or possibly cut the fabric thread. Here the purpose of the filter medium is to act as a support for the sacrificial bed of substrate material. The end of the operation can be determined by a noticeable increase in the temperature of the gas coming out of the sheet.
One side of the leaf is grooved to provide large filtrate drainage passages and a support for the filter medium. A threaded drain connection is provided in the center of the other side of the blade.
At the start of the leaf test run, the hose between the test leaf and
Immerse the test sheet face down to about half the depth of the slurry. At the end of the cake-forming period, remove the leaf from the liquid and record the time. This test sheet is designed so that the cake and liner are axially extruded from the open end of the sheet.
It is obviously preferable to use one that provides a single curve for all data. The shape of this curve will be a function of the permeability of the deposited cake.
Objective: Determine the filter size and vacuum capacity required to dewater
Tests should be performed at several pressures to determine the compressibility of the cake solids. The performance of the filter cloth depends on the weave and type of thread. The application of body feed is the continuous addition of filter aid to the filter feed to increase the porosity of the cake.
The remainder of the wash flow will flow through cracks or channels in the cake. In some units, wet cake can be discharged by mechanical vibration of the leaves while the filter is filled with liquid.
Continuous Cake Filters Continuous cake filters are applicable
The entire interior of the drum is subjected to vacuum, with its surface perforated to pass the filter. The correct liquid level is maintained by overflow and immersion varies from 5 to 70 percent of the drum circumference. The filtrate is removed from the bottom of the drum by means of a tube passing through the logs.
Several manufacturers offer horizontal belt filters, the main differences between which lie in the construction of the drain belt, the method of retaining the sludge/cake on the belt, and the method of maintaining the stretch of the filter medium. The indexing of horizontal belt filters is done away with the elastomer drain belt of the original design in favor of large drain pans directly under the filter media.
The method of feeding, washing, dewatering and discharging is
Fiber type micronic elements cannot be cleaned and are priced so that they can be discarded or the filter media replaced economically. However, there are some published general suggestions to guide the thinking of the engineer faced with the selection of filtration equipment. As indicated, one of the factors influencing the choice of a filter is the total cost of carrying out the separation with the selected machine.
An important component of this cost item is the installed cost of the filter, which starts with the purchase price. The factory delivery cost can be approximated as 3 percent of the FOB price [Pikulik and Diaz, Chem.
CENTRIFUGES
INTRODUCTION
The Coriolis acceleration distorts the trajectory of the body as it moves rectilinearly in the rotating frame. In a sedimenting centrifuge, the separation may be in the form of clarification, in which solids are separated from the liquid phase in which the clarity of the liquid phase is of the greatest importance. Performance criteria Separation of a given solid-liquid suspension is usually measured by the purity of the separated liquid phase in the concentrate (or liquid effluent) in sedimenting mode or filtrate in filtering mode, and the separated solids in the cake.
Dewatering the cake by compression and rearrangement of the solids in the cake matrix reduces ε, but the cake is still saturated with S = 1. Total solids recovery For clarification, effluent clarity is measured indirectly by of the total solids recovered in the cake.
The clarity of the supernatant and the solids concentration in the sediment can also be evaluated. The feed slurry is introduced into the lower part of the bowl through a small opening. The fluid collects at the top of the disk stack and is drained through overflow ports.
The cake is submerged in the pool when it is in the cylinder and at the beginning of the beach. The denser solids settle against the vessel wall, and the effluent escapes through openings at the large end of the machine.
The feed slurry is fed to the basket through one or more feed pipes or by other means such as a rotating feed cone to help distribute the solids to the basket wall. Solids build up on the basket wall during the feed step until the desired load is achieved. Pneumatic heel removal can be done from the inside of the basket (often fitted with a knife) or from the outside of the basket.
Early machines supported the basket from both sides, but virtually all modern machines are cantilever supported for purposes of accessibility to the basket and internal components. This unit has an extremely robust construction compared to vertical baskets, which is necessary due to the full speed feed and discharge capability of the skimmer centrifuge.
To re-establish the siphon for the next cycle, feeding is preceded by an initial step in which the siphon skimmer is rotated inwards near the edge of the siphon chamber and liquid is introduced into the siphon chamber, flowing back up through the heel cake and displacing gas from the chamber. After a time delay, the siphon turns downwards to the working position (δhof+20 to 30 mm), where it remains for the rest of the cycle. In practice, this has not been used to date due to the complexity of the installation.
The filter cloth is attached to the axially fixed bowl at one end and to the axially movable bowl insert at the other end. In the filter position, the bowl insert sits in the bowl, with the filter cloth covering the perforations.
With incompressible cake, the pressure distribution and velocity depend on the resistance of the filter medium and the permeability of the cake. Both the filtration speed and the pressure distribution depend on the medium resistance and that of the cake. At the end of pumping, the filter chamber opens and the belt moves the cake out of the filter chamber for discharge.
At the end of the filtration step, the membrane is inflated to press the cake around the filter lumen. Most of the challenges in operating a belt press are slurry conditioning and optimizing flocculant dosing.
SELECTION OF A SOLIDS-LIQUID SEPARATOR
SELECTION OF SOLIDS FROM LIQUIDS SEPARATOR 18-151 in the slurry sample and vacuum is used to draw the filtrate into the collecting flask. The time required to form each of several 3 to 25 mm (1⁄8 to 1 in) thick cakes under a given vacuum is recorded, as is the volume of filtrate collected. The filtrate is recycled into the basket at such a rate that a thin layer of liquid is barely visible on the surface of the cake.
The test is repeated with cakes of other thicknesses to determine the productive capacity of the centrifugal filter. Changes in process stream temperature, solute content, or chemical nature of the suspended liquid also affect the rate of solids settling.
