Slurry uniformity

Agitation levels 3 and 5 characterize most chemical process industries solids-suspension applications and are typically used for dissolving solids. Agitators capable of scale levels of 3 will Suspend all the solids of design settling velocity completely off the vessel bottom Provide slurry uniformity to at least 1 /3 of fluid-batch height Be suitable for slurry draw-off at low exit-nozzle elevations. 

Agitation levels 9 and 10 characterize applications where the solid-suspension uniformity is the maximum practical. Agitators capable of scale levels of 9 and 10 will a. Provide slurry uniformity of solids to 98% of the fluid-batch height b. Be suitable for slurry drawoff by means of overflow... 

In the plant, the type of pump and piping system used to feed the filter are often of great importance, as time spent on crystallization and improving crystal size and particle size distributions can be quickly undone through particle damage. Recirculation loops and pumps for slurry uniformity may not always be necessary. 

Deposition Sequence. The diaphragms are formed by applying vacuum to the cathode to draw the slurry uniformly from the bath, and this is done in three stages. 

Provide slurry uniformity to at least one-third of the fluid batch height... 

The two procedures primarily used for continuous nitration are the semicontinuous method developed by Bofors-Nobel Chematur of Sweden and the continuous method of Hercules Powder Co. in the United States. The latter process, which uses a multiple cascade system for nitration and a continuous wringing operation, increases safety, reduces the personnel involved, provides a substantial reduction in pollutants, and increases the uniformity of the product. The cellulose is automatically and continuously fed into the first of a series of pots at a controlled rate. It falls into the slurry of acid and nitrocellulose and is submerged immediately by a turbine-type agitator. The acid is deflvered to the pots from tanks at a rate controlled by appropriate instmmentation based on the desired acid to cellulose ratio. The slurry flows successively by gravity from the first to the last of the nitration vessels through under- and overflow weirs to ensure adequate retention time during nitration. The overflow from the last pot is fully nitrated cellulose. 

The incorporation of aluminum increases the blast effect of explosives but decreases the rates of detonation, fragmentation effectiveness, and shaped charge performance. Mixes with aluminum are made by first screening finely divided aluminum, adding it to a melted RDX—TNT slurry, and stirring until the mix is uniform. A desensitizer and calcium chloride may be incorporated, and the mixture cooled to ca 85°C then poured. Typical TNT-based aluminized explosives are the tritonals (TNT + Al), ammonals (TNT, AN, Al), minols (TNT, AN, Al) torpexes and HBXs (TNT, RDX, Al) (Table 14) (223-226). 

Subsequent to stock preparation and proper dilution, the paper furnish usually is fed to the paper machine through one or more screens or other devices to remove dirt and fiber bundles. It then enters a flow spreader which provides a uniform flowing stream and which is the width of the paper machine. The flow spreader, or manifold, discharges the slurry into a headbox, where fiber flocculation is minimised by microturbulence and where the proper pressure head is provided to cause the slurry to flow at the proper velocity through the slice and onto the moving Fourdrinier wire. 

In papemiaking, chemicals can be added either to the pulp slurry prior to sheet formation, ie, internal or wet-end addition, or to the resulting sheet after complete or partial drying, ie, surface or dry-end addition. The method chosen depends on retention and the desired effect. For example, strength additives usually are added internally if uniform strength throughout the sheet is wanted, but they are applied to the surface if the need is for increased surface strength. If an additive caimot be retained efftciendy from a dilute pulp slurry, then it is better to apply it to the surface of the sheet. 

Rosin sizing usually involves the addition of dilute aqueous solutions or dispersions of rosin soap size and alum to a pulp slurry (44—46). Although beater addition of either coreactant is permissable, addition of both before final pulp refining is unwise because subsequently exposed ceUulose surfaces may not be properly sized. The size and alum should be added sufficiendy eady to provide uniform distribution in the slurry, and adequate time for the formation and retention of aluminum resinates, commonly referred to as size precipitate. Free rosin emulsion sizes, however, do not react to a significant degree with alum in the pulp slurry, and addition of a cationic starch or resin is recommended to maximize retention of size to fiber. Subsequent reaction with aluminum occurs principally in the machine drier sections (47). 

To add surface area, the supports are uniformly coated with a slurry of gamma-alumina and recalcined under moderate conditions. The wash coat acts to accept the active metals, typically low levels of platinum and palladium, in a conventional impregnation process. In the United States in passenger car apphcations the spherical catalyst is used almost exclusively, and methods have been developed to replace the catalyst without removing the converter shell when vehicle inspection reveals that emission standards are not met. 

A successful variation of oil agglomeration was used for removal and dewatering of soot from a 1—3% soflds suspension consisting of <5 — fim particles in refinery process waters (Fig. 8). Heavy oil was added to the dilute slurry and intensely agitated in a multistage mixer. The soot agglomerated with the oil to form 3—5 mm pellets that were easily screened from the water (95). The pellets contained only 5—10% water. The process was modified to recover very fine clean coal, and it produced highly uniform, hard, spherical pellets 1—2 mm in diameter. 

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