Pumping Slurries Liquid-Solid Systems

Solid concentration 25-65 % w/w solid particle size 20-300 [tm. For finer particle size, watch for non-Newtonian behavior. For higher concentration, consider short pumping runs only for small concentrations, beware of settling out. For larger particles, watch for settling out. 

Include high pressure water purge for both forward and reverse flow at velocity 1 m/s. Avoid dead ends and pockets. Arrange for flushing of the line with water place nozzles on the top of the primary loop. Avoid flow restrictions, including orifices. 

Choice depends on particle characteristics (size, flowability, corrosiveness, abrasiveness, handling characteristics and safety-hazard (static electrification, fumes, flammability and vertical vs. horizontal distance). Related topic Section 2.5, mixing Section 7.4 and bins for storage, Section 10.3. 

Johanson s definitions of terms used to characterize solid particles are given in Section 1.6.4. The important terms are AI, RI, HI, FRI, FDI, BDI, Cl, RAS and SBI. 

Belt conveyors 10° incline 10 to 100 m horizontal distance capacity 3-270 kg/s. OK for most diameters of particles but not for particles that cake or are light and fluffy. 

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A direct liquefaction technique, the SRC process involves mixing dried and finely pulverized coal with a hydrogen donor solvent, such as tetralin, to form a coal-solvent slurry. The slurry is pumped together with hydrogen into a pressurized, vertical flow reactor. The reactor temperature is about 825°F (440°C) and pressures range from 1,450 to 2,000 psi. A residence time in the reactor of about 30 minutes is required for the carbonaceous material to dissolve into solution. From the reactor, the product passes through a vapor/liquid separation system. The slurry solids remaining in the reactor are then removed and filtered. Various filtration techniques have been developed to remove solids from recoverable oil. 

Most PTC reactions are carried out on an industrial scale in the batch mode in mixer-settler arrangements. In view of the reactor design in the liquid-solid-liquid PT-catalyzed reaction, Ragaini and coworkers [147-149] reported the use of fixed-bed reactors with a recycling pump or with a recycling pump and an ultrasonic mixer, and emphasized the importance of effluent recycle concept. Schlunt and Chau [150] reported the use of a cyclic slurry reactor, which allowed the immiscible reactants to contact the catalyst sites in controlled sequential steps. However, for triphase reactions in liquid-liquid systems where... 

Expression is the separation of a liquid from a two-phase solid-liquid system by compression, due to movanent of the retaining wall rather than the pumping of the solid-liquid system into a fixed chamber as in filtration. In filtration, the original mixture is sufficiently fluid to be pumpable in expression, the material may appear either entirely sani-solid or slurry. Based on an expression theory [6,7], the time for expression is also proportional to the square of cake thickness. 

Systems for pumping slurries around a process plant are similar to systems for pumping liquids, in regard to the calculation of performance on a basis of head. The slurry can be regarded as a fluid having a density computed from the ratio of solids to liquid (usually water) and the respective densities of the two phases. If the slurry composition is stated on a mass basis, the slurry density is calculated by calculating the volumes of each component of mass, and dividing the sum of the masses by the sum of the volumes. 

No major changes have been made to the SCWO system, but there are some differences between the SCWO unit previously tested and the SCWO units proposed for EDS and for full-scale operation. Changes have also been made to equipment downstream of the SCWO reactor to facilitate processing of the suspended solids in the reactor effluent, especially for aluminum-rich feeds. The effluent flows from the pressure letdown valves to a knockout drum that contains a venturi scrubber, which separates liquid and suspended solids from the uncondensed vapor. The slurry is pumped to an evaporator/crystallizer system that replaces the flash separator in the original design. 

Not all filtration applications require body feed. If there is little to be gained from its use, it becomes counterproductive as it once again reduces the holding capacity of the filter for the precipitated solids. In some applications, body feed is added directly to the liquid to be filtered, removing the need for a tank and slurry delivery system. This approach has problems of its own, including extra wear on the main pump and sometimes inadequate dispersion. It is not common in the chlor-alkali industry. 

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