Cracking

The pyrogenic decomposition of petroleum with the consequent breaking up of the molecules and the production of both lighter and heavier hydrocarbons is termed “cracking”. In the terminology of the industry “cracking processes” are those designed to utilize the above decomposition for the conversion of heavier oils into the more valuable gasolines and naphthas.

All petroleum hydrocarbons have a characteristic temperature above which the cracking reaction takes place. This temperature varies for the different cuts from a given crude oil and for similar cuts from different crude oils.

Historically, cracking dates back to the early years of the nineteenth century when the formation of volatile compounds by cracking animal oils was discovered. These early discoveries were regarded merely as scientific phenomena of no commercial value. In the early days of the petroleum industry attention was paid to increasing the yields of illuminating oils, then the most valuable constituent of the crude. Since these early days the demand for gasoline has resulted in many different processes.

The systems in commercial use may be broadly classified as cracking in the vapour phase and cracking in the liquid phase. Cracking in the vapour phase consists in vapouring the oil and then producing the reaction by the addition of heat, or of heat and pressure together. High gas loss and difficulty with apparatus tended to retard the development of this type of process. Consequently, the liquid phase processes received a tremendous impetus, and the great majority of commercial installations are of this type.

Lesson Four natural gas

I. Words and expressions to be remembered:

1. stream - поток

2. volume - объем

3. quantity - количество

4. inversely proportional - обратно пропорциональный

5. to exert upon - оказывать (давление)

6. constant - постоянный

7. inflammable - горючий

8. to define – определять

9. to occupy – занимать

10. directly proportional – прямо пропорциональный

11. to exist – существовать

12. to occur - встречаться

13. marsh – болото

14. amount - количество

15. vapour - пар

16. methane – метан

17. ethane - этан

18. propane - пропан

19. butane - бутан

20. water vapour - водяной пар

21. сarbon dioxide - двуокись углерода

22. hydrogen sulphide - сероводород

23. helium - гелий

24. carbon disulphide - сероуглерод

II. Read and translate the following word combinations:

natural gas, inflammable gas, solid gas, atmospheric conditions, weather conditions, hard conditions, pressure, absolute pressure, atmospheric pressure.

III. Translate the words of the same root:

nature – natural, industry - industrial, gas - gaseous, differ – different - difference, exist - existence, define - definition.

IV. Translate into Russian paying attention to the Complex Subject with the Infinitive construction:

1. This element is said to occur in the earth’s crust.

2. Natural gas is considered to be inflammable.

3. The volume is assumed to be inversely proportional to its absolute pressure.

4. Natural gas is considered to be a valuable raw material.

5. It is likely to contain one or more of the following components.

V. Read and translate the text: