Suspensions slurries

Foam-mat drying is a process in which a suspension, slurry, or solution is transformed into a stable foam by inert gas injection. The foam stmcture provides porosity and the mat is dried in trays or on a belt in a tunnel compartment, either under vacuum or with ckculating gas. A free-flowing powder capable of rapid rehydration results. Emit juices (qv) are dried successfully in this manner. 

The flow of compressible and non-compressible liquids, gases, vapors, suspensions, slurries and many other fluid systems has received sufficient study to allow definite evaluation of conditions for a variety of process situations for Newtonian fluids. For the non-Newtonian fluids, considerable data is available. However, its correlation is not as broad in application, due to the significant influence of physical and rheological properties. This presentation is limited to Newtonian systems, except where noted. 

Many polymers can be produced via interfacial polymerization. These multiphase reactions occur in emulsions, suspensions, slurries, or at the interface between a gas and a solid. 

A slurry is a liquid containing solid particles in suspension. Slurries can be divided into two classes settling and non-settling. 

Herri and coworkers (Fidel-Dufour et al., 2005) have developed a flow loop reactor (in Saint Etienne, France) operating at pressures of 1-10 MPa at 0-10°C. The flow section is 36.1 m long, 1.0 cm internal diameter, and has a constant slope of 4°. The unique feature of this flow loop is that the exit of the flow section is connected to a gas lift riser (10.6 m long and 1.7 cm internal diameter) in which gas coming from a separator located at the top of the column is re-injected. The gas lift is thereby able to move an emulsion or suspension slurry without any pump or mechanical system. 

The carbamazepine-nicotinamide cocrystal system has been used to illustrate a mechanism for the formation of cocrystals, for which nucle-ation and growth of solid products are determined by the combination of the reactant components to reduce the solubility of the intermolecular complex that eventually becomes crystallized [42], The principles were studied through the use of in situ monitoring of the cocrystallization process in solutions, suspensions, slurries, and wet solid phases of the... 

The heat of polymerization of ethylene is high (93.6 kJ/mol). Heat removal is thus a key issue in commercial polymerization processes. Polyolefins are produced primarily by suspension (slurry), gas-phase, or solution processes (20). Solution processes have been developed by various companies using hydrocarbons, such as heptane or cyclohexane, or hydrocarbon mixtures as solvents. The reaction temperature is in the range of 200-300°C. An advantage of these processes is that they readily accommodate a wide range of comonomer types and product densities. Like the high-pressure process, which is also a solution process, they are unable to accommodate highly viscous products. 

HDPE is produced mainly by a suspension (slurry) process in various types of reactors and with various polymerization procedures. In these processes, a supported Ziegler-Natta catalyst system or a Phillips catalyst in a solvent is used. Because the temperature (80-100°C) is lower than the melting point of the polyethylene (140°C), the polymer produced is separated as a solid. This process is highly versatile and can be used to produce many kinds of polyethylenes. 

Crystallizers should operate with a minimum of 10% by weight crystals in suspension (slurry density). 

The most widely applied type of spray dryers by one supplier is provided with a rotary atomizer (Fig. 7.55 and 7.56). The system disperses fluids by centrifugal force. It has a high degree of flexibility, with capacities from small (a few kg/h) to very large (over 200 t/h). Various wheel designs (Fig. 7.55) have been developed for the handling of different types of liquid feed such as solutions, emulsions, suspensions, slurries, pastes, and melts. Fig. 7.56 is the photograph of a rotary atomizer in operation. 

Many fluids including colloidal suspensions, slurries, and paints exhibit this type of behavior. 

Several configurations have been proposed for artificially illuminated photocatalytic reactors. These can be grouped into two main categories, as described in Table 2.2, with respect to the state of the Ti02 catalyst as either immobilized or in suspension (slurry). 

Dual-shaft mixers are available from this company to process pastes, gels, suspensions, slurries and other viscous formulations. Composed... 

The process may lead to a liquid (emulsion, suspension, slurry) or a solid (paste, powder) or a gas where the aroma will be protected until release in the wanted conditions. Solid forms represent 95% of the delivery systems, of which 78% are obtained by spray-drying (Bouquerand et al., 2012). 

Solid Liquid Sol or colloidal sol Suspension, slurry, jelly... 

In spray dryers, the feed material, in the form of a solution, suspension, slurry, or paste, is sprayed in a high-tanperature gas zone by centrifugal disks or pressure nozzles. Such dryers are used in polymer industries in which the polymers cannot be separated mechanically from the carrier liquid, e.g., emulsion-polymerized PVC. 

Uses Thickener for coatings, adhesives, sizes, disps. used in upholstery, drapery, carpet, paper, paints, wallpaper, printing, textiles thickener for suspensions, slurries, disps. of inorg. pigments, min. fillers, clays thickener for liq. prods, applied by spraying (incl. defoamers, cleaners) Regulatory FDA 21CFR 175.105,176.170,176.180 Properties 14.75% act. 

CAS 2634-33-5 EINECS/ELINCS 220-120-9 Uses Preseivative, bactericide, fungicide, yeast inhibitor for aq. coatings, polymer disps., filler suspensions, slurries, sol ns. and disps. of adhesives and thickeners, concrete additives, other aq. formulations Features Broad spectrum Preventol Cl 8-100 [Bayer AG Sea-Land]... 

Ultrasonic cavitation in liquid-solid systems produces interesting effects. Physical effects include (a) improvement of mass transfer in turbulent mixing and acoustic flow, (b) generation of surface damage at the liquid-solid interfaces due to shock waves, (c) generation of high-velocity interparticle collisions in the suspension (slurry), and (d) fragmentation of solids to increase their surface area. 

A flow diagram of the traditional polypropylene suspension ( slurry ) process is shown in Figure 3.13. Propylene, diluent (Cg to saturated hydrocarbons), hydrogen, a catalyst and a cocatalyst are continuously fed to the polymerisation section, which normally consists of one or more stirred tank reactors in series. Polymerisation is carried out at 60 - 80 °C and at pressures below 2 MPa. The polymerised polypropylene forms small powder particles suspended in the diluent. A small amount of atactic polypropylene is formed as a by-product in the polymerisation step and is partly dissolved in the diluent. The slurry is continuously withdrawn from the last reactor after which unreacted propylene is removed from the slurry and recycled to the reactor. 

Figure 3.13 Generic flow diagram showing the traditional suspension ( slurry ) process...

Feed Liquid/suspension/slurry Inert particle bed No Inert particle bed Inert particle bed... 

Powdered Ti02 is widely used in suspension (slurry) with excellent performance, but it requires filtration. Immobilisation of Ti02 on solid supports such as glass, polymers and ceramics removes the need for filtration to separate the catalyst from treated water, making the process less expensive. 

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