1. Read the text, prepare an abstract with the key words.

Hydromechanic processes and apparatus. Mixing Equipment

Mixtures of solids and liquids are blended in a variety of equipment types, depending on the physical characteristics of the mixture. Relatively thin, pumpable suspensions are usually handled in tanks agitated with an impeller or fluid jet; non-flowing pastes are handled in slow-speed non-circulating mixers.

For many medium-duty mixing applications, requiring up to 3 hp., the fixed-mounted propeller mixer shown in Fig. 29 is used. Such mixers are also mounted, as a rule, angularly off center to give top-to-bottom flow. They have the same speed ranges as portable mixers. They may be equipped with stuffing boxes or mechanical seals if the tank must be closed. Since propellers turn at relatively high speeds, the drive required for a given power transmission is not expensive. Top-entering propeller mixers, however, cannot deliver more than about 3 hp., and the shaft length is limited to a maximum of about 6 ft.

Fig. 29. Typical fixed-mounted propeller mixer.

Side-entering propeller mixers (Fig. 29) are used most commonly on applications where abrasive slurries are not present. Seals and stuffing boxes are best avoided if possible.

Anchor and gate impellers either sweep the tank bottom or, more commonly, sweep the entire peripheral area of the tank in contact with the fluid. They are normally used where it is desired to have a close clearance between the impeller and the tank wall.

Most large-scale mixing of solid-liquid suspensions is done with top-entering turbine or paddle agitators.

Solid-Solid Mixing Equipment. There are several basic mechanisms by which solid particles are mixed. These include small-scale random motion (diffusion), large-scale random motion (convection), and shear. There are several types of solids-mixing machines. In some ma­chines the container moves. In others a device rotates within a stationary container. In some cases, a combi­nation of rotating container and rotating internal device is used. Sometimes baffles or blades are present in the mixer.

Tumbler is suitable for gentle blending; capable of handling large volumes; easily cleaned; suitable for dense powders and abrasive materials. Not for breaking up agglomerates.

Vocabulary

sоlid твердий

blend суміш

pumpable накачувана

tank цистерна

agitate розмішувати

fluid jet струмінь рідини

propeller гвинт

stuff box набивна камера, сальник

abrasive slurry абразивна грязь

vehicle розчинник

2. Complete the sentences.

1. Mixtures of solids and liquids are blended ____. 2. Relatively thin, pumpable suspensions are usually handled ____. 3. For many medium-duty mixing applications____. 4. Such mixers are also mounted____. 5. Side -entering propeller mixers are used ____. 6. Anchor and gate impellers

either sweep ____. 7. They are normally used ____8. . Most large-scale mixing

of solid-liquid suspensions is done with ____. 9. Solid-Solid Mixing Equipment include ____.10. In some ma­chines ____.11. In some others ____.

12. Tumbler is suitable for ____.