Ribbon blender

Fig. 37. Various mixer types for dry soflds (a) the V-mixer, (b) ribbon blender, (c) vertical screw mixer, and (d) Nautamix.

Bulk Blenders Vlanv of the mixers used for solids blending (Sec, 19) are also suitable for some liquid-solids blending. Ribbon blenders can be used for such tasks as wetting out or coating a powder, When the final paste product is not too fluid, other solids-handling equipment finds frequent use. 

Ribbon blenders are essentially self-contained mixers. They are employed in a variety of solid-liquid, solid-solid, and liquid-liquid blending applications in the chemical process industries. Examples include plastics, pigments, pharmaceuticals, specialty chemicals, confectionary. 

Figure 4. Ribbon blender agitator configurations (A) continuous ribbon, arranged for center discharge (B) continuous ribbon arranged for end discharge (C) interrupted ribbon (D) paddle-type ribbon.

The ingredients of each blend were thoroughly mixed in a large ribbon blender. The entire food preparation and packaging operation was carried out in a sanitary manner. A quantity of each blend was appropriately subpackaged for the various physical, chemical and microbiological tests. 

Powder and flakes Dry blending V-shaped mixer, ribbon blender... 

Use continuous V-shaped mixer only for handling powder of diameter >0.01mm. For smaller powders, use ribbon blender. 

Ribbon blender Powders filled to >70 % of vessel volume [331... 

Dry products can include dusts, powders, and granules. Dusts and powders are manufactured by mixing technical grade material with the appropriate inert carrier and grinding the mixture to obtain the correct particle size. Several rotary or ribbon blender-type mixers mix the product. Figure 6 shows a typical dry formulation unit for pesticides [8]. 

Carefully identify at least 10 sampling locations in the blender to represent potential areas of poor blending. For example, in tumbling blenders (such as V-blenders, double cones, or drum mixers), samples should be selected from at least two depths along the axis of the blender. For convective blenders (such as a ribbon blender), a special effort should be made to implement uniform volumetric sampling to include the corners and discharge area (at least 20 locations are recommended to adequately validate convective blenders). 

Assay one sample per location (number of samples n = 10, or n = 20 for ribbon blender). 

Convection mixers use a different principle for blending. These mixers have an impeller. This class includes ribbon blenders, orbiting screw blenders, vertical and horizontal high-intensity mixers, as well as diffusion blenders with an intensifier bar. Scale-up considerations are similar to those for the tumble blenders. 

Convection Mixers Ribbon Blenders Aaron Paul O. Abbe Automatic Industry Machines Azo-Ruberg Custom Metal Craft Jaygo Kemutec Lowe Pneuvac Ross Vrieco-Nauta (Hosokawa)... 

Figure 10.15. Some mixers and blenders for powders and pastes, (a) Ribbon blender for powders, (b) Flow pattern in a double cone blender rotating on a horizontal axis, (c) Twin shell (Vee-type) agglomerate breaking and liquid injection are shown on the broken line, (d) Twin rotor available with jacket and hollow screws for heat transfer, (e) Batch muller. (f) Twin mullers operated continuously, (g) Double-arm mixer and kneader (Baker-Perkins Inc.), (h) Some types of blades for the double-arm kneader (Baker—Perkins Irtc.).

Solid—solid blending can be accomplished by a number of techniques. Some of the most common include mechanical agitation which includes devices such as ribbon blenders, impellers, paddle mixers, orbiting screws, etc a rotary fixed container which includes twin-shell (Vee) and double-cone blenders and fluidization, in which air is used to blend some fine powders. 

Production must be carried out in an area of controlled (low) humidity. To prevent separation after blending all components should be as similar as possible in particle size and bulk density. The ingredients must be sieved before addition and it is often preferable to prepare a pre-blend of some ingredients to facilitate the addition of small mass items and mixing in. Mixing is earned out in ribbon blenders and can be on either a batch or a continuous basis. Packaging is in sachets or jars. 

Ribbon blenders consist of some moving elements, such as a spiral element, that induce convective motion. They are good for cohesive particulate mixtures, but they require more power than tumbling blenders and are more difficult to clean. In ribbon-type blenders, as well as some other types, PVC dry blend can be prepared by slowly spraying small amounts of liquid additives into the mixture. Such additives may sometimes generate the formation of small, soft balls, which should be avoided if a free-flowing dry blend is desired. Ribbon blenders generate considerable static electricity. 

Typical pilot plant operation began by preparing an intimate mixture of ground coke and KOH in a ribbon blender in a range of KOH/coke weight ratios of 2 to 4. The blend was stored in N2" blanketed and sealed drums. 

Ribbon blenders. Price includes standard floor-mounted support, baffled shell cover, antifriction pillow blocks mounted on outboard bearing shelves, stuffing box, flanged inlet opening, and lever-operated discharge gate. 

A vertical helical ribbon blender can be combined with an axial screw of smaller diameter (Fig. 18-25). Such mixers are used in polymerization reactions in which uniform blending is required but in which high-shear dispersion is not a factor. Addition of the inner flight contributes little more turnover in mixing newtonian fluids but significantly shortens the mixing time in nonnewtonian systems and adds negligibly to the impeller power [Coyle etal.. Am. Inst Chem. Eng.J., 15, 903 (1970)]. 

PVC bulk polymerizations are two-slage processes in which a very porous PVC seed particle is produced in a vessel provided with very high speed agitation. The wet polymer powder from this stage is fed to horizontal autoclaves in which the polymerization is finished. Reaction heal is removed by cooling the helical ribbon blender-type agitators as well as the vessel jacket. 

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