Paste blenders

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. 

To study reaction kinetics, cement batches of total mass 300 g were prepared using ingredients measured to the nearest 0-1 g. Mixing was carried out for 10 minutes using a kitchen blender, after which specimens were cast in slabs 10 x 10 x 1-2-1-5 cm in polyethylene moulds. When the setting reaction had proceeded to a sufficient extent and viscosity had risen to give a reasonably stiff paste, a small portion was removed, placed on a glass microscope slide and immediately examined by X-ray diffraction. The remainder of the sample was allowed to set. 

The polysiloxane from experiment b) is soluble in toluene. It can be converted by hot vulcanization into an insoluble silicone rubber. Using a small blender, 10 g of the polymer are kneaded with 10 g of quartz powder or 7.5 g of ground kieselguhr,and 0.6 g of dibenzoyl peroxide paste (50% in silicone oil).To work the additives into the silicone rubber without a mechanical blender is very tedious and difficult to achieve completely. 

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.).

The stomacher is used to evenly blend the water into the paste without incorporating air into the sample. Other blenders of this type could also be used. 

While the squash is cooking, combine in a blender the remaining V2 cup coconut, the garlic, and the cumin seeds with V2 cup water, or enough to make a pestolike paste. 

Some solids processing applications involve the addition of hquids, and the same blenders may transition from dry powders to cohesive pastes. 

Ribbon blenders typically have multiple helical ribbons with opposing pitches operating in a horizontal trough with a half-cylinder bottom. These mixers can be used for wetting or coating a powder. The final product may have a paste consistency but must remain at least partially flowable for removal from the blender. 

The major situations are gas-solid, gas-liquid, liquid, and solids. Solids blending can include dry solids blenders extruders for foodstuffs and polymers and pug mills for clays, thick pastes, and fertilizers. 

MIXING INDEX IN BLENDING GRANULAR SOLIDS. The effectiveness of a solids blender is measured by a statistical procedure much like that used with pastes. Spot samples are taken at random from the mix and analyzed. The standard deviation of the analyses s about their average value x is estimated, as with pastes, from Eq. (28.18). 

In the past, chromium analysis of foods has not been routine, at least partially because of methodological problems such as the need to avoid stainless steel blenders and knives in sample preparation. Therefore, little is known about regional variations in chromium concentrations in foods. In one study, the mean chromium daily intake for males was 33 3 pg (range 22-48 pg), and intake for females was 25 1 pg (range 13-36 pg) (Anderson and Kozlovsky 1985). Chromium concentration of 22 well-balanced diets ranged from 8.4 to 23.7 pg per 1000 kcal, with a mean of 13.4 ... 

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