7. Crushing

1. When (heating, having heated) this substance» one

should

be very careful. 3. (Investigated, having investigated,

Investigating) all the

properties of new water, they could understand the mistery

of silvery clouds.

3. The (dissolving, dissolved, having dissolved) materials may be soluble solids, liquids or gases.

4. later (using, used, having used) in steam boilers, should be free from substances that cause corrosion. ^

5. (Purified, having purified, purifying) the water from the. substance that cause corrosion, we can use it in steam boilers

III. Ask questions on all the parts of the following sentences:

1. Last year a great number of young specialists graduated from our Institute.

2. The new laboratory will be built next year.

IV. Translate the following text using a dictionary. Retell the text:

Comminution by crushing and grinding involves the production of new surface and requires the effective utilization of energy consumed is considerably increased on account of losses due to the elasticity and plasticity of the material and also of course due to friction and the abrasion of the wearing surfaces.

The particle size reduction that one machine can achl-^e is limited. Therefore, the machine required to mak# the final product is often unable to accept the initial.feed so that reduction in stages is necessary. The terra grinding is applied to powder production, and the term crushing to the reduction of coarser materials. There is no hard and fast definition of the limiting particle size for distinguishing between these terms.

Particle-size analysis and the particle shape of a crushed or ground product can be considerably influenced by the choice of machine and by operating conditions. These factors aire of prime importance because they affect the physical properties of the finished product, surface area, chemical reactivity, flow

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of a fluid through the mass, particle strength, and packing density.In fine-particle sizes, such factors influence th dispersibility and the settling rate ^ in a fluid medium. The yield of useful materials is of vital importance because it directly affects the cost of production..

In the first stages pf reduction by crushing, there is a choice between those machines that reduce by compression between two faces and those that reduce by impact. In each case, there is also some reduction by attrition, but the particle-size distribution produced by impact and by attrition shows rather similar characteristics.

For the primary reduction of a mined material, the jaw crusher is well^ established, Aut the gyratory, cru-isher is preferred where the^higher capacity is ^^iffifified. Both are compression crushers that reduce the material to a piece size related to the crusher settling. Both types of crusher are suitable for intermediate stages of reduction.

Jaw and roll crushers are suitable for fine-crushing modest quantities but the gyratory crusher can reduce larger tonnages.

4.

5.

6.

7.

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9.

10,

11,

12,

13.

14,

15.

16.

17,

18,

19 20

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grinding -дробление, размалывание, растирание

utilization - использование

to consume -потреблять

friction -трение

abrasion -истирание, абразивный износ

to reduce -уменьшать reduction -уменьшение

feed - подача (материала, сырья)

density - плотность

settling rate - скорость оседания

fluid medi;m:i - жидкая среда

yield - выход (продукции)

face - поверхность syn:surface

impact - толчок, удар, столкновение

attrition - трение

jaw crusher - щековая дробилка

gyratory crusher - конусная дробилка

roll crusher - валковая дробилка

related to - связанный с

settling - настройка, установка; регулировка

tonnage - тоннаж

Commentary ,,

1. ... on account of losses due to the elasticity and plasticity of the materiai - ... за счет потерь, обусловленных упругостью и пластичностью материала

2. due to - обусловленный, вследствие

Answer the following questions

Words and word combinations:

1. comminution -измельчение

2. crushing - дробление, раздавливание

3. crusher - дробилка, дробильная установка, мялка

1. What does comminution by crushing and grinding involve?

2. What does this process require?

3. Why is the total energy consumed considerably increased?

4. Why is the reduction in stages necessary?

5. What is the term grinding applied to?

6. What is the term crushing applied to?

7. What factors effect the physical properties of the finished product? What else do they effect?

8. Why is the yield of useful material of vital importance?

9. What two types of machines for crushing do you know?

10. What types of crushers do you know? What are they suitable for?

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Exercises I. Translate the following sentences into Russian, mind the Participle:

1. The products produced were of high quality.

2. The method involved depended on a number of factors described earlier.

3. The experiments carried out in our laboratory resulted in many new investigations in the field of ceramics.

4. Hydrogen burns readily in air and the product formed la water.

5. There are only few elements not attacked by oxygen.

6. Radioactivity is the property uninfluenced by any known catalyst.

7. The problem discussed is of great importance for the development of chemical engineering.

II. Translate the following sentences paying attention to passive constructions:

1. This law is generally spoken of as the Second Law of Ther-aodyaamlcs.

2. This problem will be dealt with in a number of articles. 3. The rate of a reaction is influenced by many factors. 4. Sold is not effected by air.

5. Particle - size analysis of a crushed product can be considerably influenced by the choice of machine.

6. This scientist's report is being waited for with great interest.

7. Unlike iron, cobalt is not attacked by air and water.

8. The state of water but not its composition can be affected by the process of heating or cooling.

9. Shall we be informed about the conference in time?

10. When the students arrived at the plant, they were shown modern chemical apparatus.