yashchuk_tsepkalo (1)

5.Change the following sentences according to the model:

Model A: If this mixture is placed in a test tube, it will glow dull red.

B: If this mixture were placed in a test tube in two hours, it would glow dull red.

C: If this mixture had been placed in a test tube two hours ago, it would have glowed dull red.

1.If metals are heated, oxides will be formed.

2.If any liquid is in a vessel, it will take the shape of the vessel containing it.

3.If some air is allowed to mix with hydrogen, the reaction will take place with a characteristic sound.

6.Translate into Ukrainian paying attention to the word “since”:

1.Since diamond is the hardest substance known, it must be polished with diamond dust.

2.Many years have passed since Mendeleyev made his great discovery.

3.This method of mixing has been used since the days of World War II.

4.This process was developed twenty years ago, since then it has been used in many countries.

5.Carbon is one of the most important and interesting elements, since its compounds are widely distributed in nature and play such an important part in daily life.

7. Say if the following statements are true or false. If the statement is false

and explain why:

1)A motor puts an object in rotation around a fixed axis, applying force perpendicular to the axis.

2)Centripetal acceleration is used to separate substances of greater and lesser density.

3)The ultracentrifuge, devised in the 1883 by the Swedish chemist Theodor Svedberg, found wide application in scientific research.

30

4)A mechanical method of separating immiscible liquids or solids from liquids by the application of gravity force.

5)Tensile stress in the cylinder wall limits the centrifugal force which can be generated in a unit of a given size and material of construction.

6)There are two major types of centrifuges: sedimenters and filters.

7)A filtering centrifuge contains a solid-wall cylinder or cone rotating about a horizontal or vertical axis.

8)In filtering centrifuge the filtration rate increases with the centrifugal force and with the permeability of the solid cake.

9)If the material to be processed has low residual impurities and a high washing requirement, the greater flexibility of the batch process allows the necessary adjustments.

10)Centrifugal processing provides a number of unique advantages.

8.Choose the correct continuation to complete the following statements:

1)Centrifugal force is generated inside

a)a cylindrical-conical chamber

b)stationary equipment

2)Very high forces can be developed only in

a)very small centrifuges.

b)mechanically driven bowls

3)A sedimenting centrifuge contains

a)a solid-wall cylinder

b)filters

4)A filtering centrifuge operates on the same principle as

a)the spinner

b)a household washing machine.

31

LESSON 6

1.Read and memorize the following words:

2.Read and memorize the following word combinations

33

3.Read and translate the text into Ukrainian.

Mixing and blending

Mixing is the process of thoroughly combining different materials to produce a homogenous product. The mixture is generally a combination of dissimilar materials, e.g. coal ash and cement are blended in a specified ratio to produce Pozzocrete cement. In other cases, a chemically homogenous material may be mixed to produce a uniform lot of a desired weight/volume with consistent particle size distribution, color, texture, and other required attributes, e.g. metal powders produced in 1 ton batch size are blended to a homogenous lot size of 4 tons (or pre-specified quantity).

The terms "mixing" and "blending" are often used interchangeably, but technically they are slightly different. Blending is a process of combining materials, but blending is a relatively gentle process compared to mixing. In terms of the phase of material, blending is the process of solid-solid mixing or mixing of bulk solids with small quantity of liquid. The terminology mixing is more closely associated with liquid-liquid, gas-liquid, and viscous materials.

Mixing and blending are the most demanding unit operations in the chemical process industries (mixing and blending of specialty chemicals, explosives, fertilizers, dry powdered detergents, glass or ceramics, and rubber compounds). Pharmaceutical and food industries also rely heavily on mixing and blending technology (blending of active ingredients of a drug with excipients like starch, cellulose, or lactose; preparation of cake mix, spices, and flavours)

The wide variety and ever increasing complexity of mixing processes encountered in industrial applications requires careful selection, design, and

34

scale up to ensure effective and efficient mixing. Improved mixing efficiency leads to shorter batch cycle times and operational costs. Today's competitive production lines necessitate robust equipment that are capable of fast blend times, lower power consumption, equipment flexibility, ease of cleaning, and a gamut of customized features. In addition to blending components, many modern mixers are designed to combine different process steps in a single equipment, e.g. coating, granulation, heat transfer, drying, etc.

At the numerous enterprises of chemical, food, pharmaceutical and other industries, the equipment with machine mixing devices is practised on a large scale in processes requiring dissolution, leaching, emulsification, formation of suspension as well as homogeneous and heterogeneous systems mixing. Industrial mixers are machines that blend, homogenize, emulsify or otherwise mix components into a homogenous substance.

Industrial mixers are used to thoroughly combine any type of liquid or solid during the manufacturing process. They are usually large tanks or vats with motorized blades or paddles that rotate on a stationary shaft or remain stationary themselves. Depending on the application, some models may have sharp blades while other may have large flat paddles. The attachments or heads are generally removable to maximize the mixer's effectiveness with different materials. Stainless steel is most commonly used, especially within the food and beverage industry because of the metal's sanitary and hygienic properties.

Other possible materials include aluminum, steel or cast iron. Industrial mixers are widely used across many industries including the cosmetic, pharmaceutical, chemical, agricultural, pulp and paper, automotive, water treatment, adhesive and sealant industries. These mixers are equipped to handle glue, petroleum products, cement, biodiesel, dry and wet chemicals, medicines, toothpaste, food colouring, syrups, medical ointment, lotions, creams, vitamins, shampoos, detergents, hair dye, petroleum products, silicone, adhesives, polyurethane and many other products or ingredients.

35

Within the single category of industrial mixers, there are many kinds and varieties of these machines that have been specialized. Blenders are very similar if not identical to mixers; some prefer to differentiate between the two because blenders sometimes have sharper blades that move at faster speeds. In terms of processing speed and style, there are two modes. Batch mixers are the more common of the two kinds. Mixing begins after a substance is poured into the industrial mixer. Once mixing is complete, the substance is poured out of the mixer for further processing and the mixer is then cleaned before being refilled. Continuous-feed mixers can handle a steady flow of material. Static mixers are inline and continuous feed mixers because they do not move. The materials are mixed as they flow around the strategically-placed blades and paddles.

Another kind of industrial mixer is a drum mixer which consists of a rotating drum on the frame. There are multiple mixers used to accomplish a solution or substance that is the same throughout. High shear mixers offer shorter mixing times than standard mixers. The speed of the product at the tip of the rotor is higher than the speed at the centre which emulsifies immiscible materials. Similarly, homogenizers and emulsifiers achieve the same results by forcing substances to pass through a screen. Also known as mixers, agitators are the only machines that can blend chemicals, foods and other low-viscosity materials with ease. Because they have relatively small blades, they're also best used for slow, low-shear mixing processes where it's more important to keep the mixture moving than it is to actually blend its ingredients.

4.Answer the questions to the text:

1.What is mixing?

2.What is blending?

3.What is the difference between the terms “mixing” and “blending”?

4.What different process steps in a single equipment can many modern mixers combine?

36

5.What are industrial mixers?

6.What materials are most commonly used in the design of industrial mixers?

7.How do batch mixers work?

8.What are agitators used for?

5. Fill in the gaps with the words from the text and translate these word

combinations into Ukrainian:

Ukrainian translation

1.to produce a homogenous __________

2.consistent __________ size distribution

3.dry __________ detergents

4.effective and efficient __________

5.metal's sanitary and hygienic

__________

6.handle a steady __________of material

7.to consist of a rotating __________ on the frame

8.to emulsify __________ materials

6.Choose the correct grammar form for each sentence:

1.Blending_____ a relatively gentle process compared to mixing. a) has

b) is

c) can be

2.Many modern mixers _______to combine different process steps in a single equipment.

a) designed

b) are designed

37

c) design

3.Mixing ______after a substance is poured into the industrial mixer. a) is beginning

b) begins

c) has begun

4.Industrial mixers are widely used across many industries _______chemical, agricultural and water treatment industries.

a) having included b) included

c) including

5.Air conditioning and refrigeration systems are some other important fields where heat exchangers_______.

a) are applied b) apply

c) are applying

6.Pharmaceutical and food industries also _____heavily on mixing and blending technology.

a) relies b) rely

c) will rely

7.To prevent any blockage due to impurities______ in a heat exchanger, a regular and timely examination of heat exchangers is essential.

a) collected

b) having collected

38

c) being collected

6. Say if the following statements are true or false. If the statement is false explain why:

1)Mixing is the process of thoroughly combining different materials to produce dissimilar materials.

2)Blending is the process of solid-solid mixing or mixing of bulk solids with small quantity of liquid.

3)Pharmaceutical and chemical process industries deal with mixing and blending of specialty chemicals, explosives, fertilizers, dry powdered detergents, glass or ceramics, and rubber compounds.

4)Many modern mixers are designed to combine different process steps in a single equipment.

5)Industrial mixers are usually large tanks or vats with stationary blades or paddles that rotate on a motorized shaft.

6)Blenders are not identical to mixers.

7)Continuous-feed mixers can handle a steady flow of material.

8)Agitators are the machines that can blend chemicals, foods and other low-viscosity materials.

7. Imagine you have gained over 5 years of experience in a scientific and industrial firm which is one of the world leading manufacturers for mixing equipment specializing in development of units with mechanical mixing devices. You belong to a team of experienced specialists who design, develop and supply equipment, system and modules for mixing. Every year the company's staff publishes articles in leading technical journals, takes part in international conferences and congresses. You’ve been given a task to make up a brief presentation on theoretical and practical issues of mixing to

39