II. Answer the following questions.

1. What does crude oil often contain?

2. What is the purpose of crude-oil desalting?

3. What are the main methods of crude-oil desalting?

4. How is crude oil separated into various fractions?

5. How can the main fractions be classified?

6. Where can smaller distillation towers be found?

III. Translate the following words and word combinations.

inorganic salts, suspended solids, water-soluble trace metals, plugging, fouling, crude-oil desalting, surfactant, impurities, settle out, suspended water globules, settling tank, diatomaceous earth, straight-run cuts, boiling-point ranges, decreasing volatility, distillation towers

IV. Translate the following sentences into English.

1. Эти примеси должны быть удалены в процессе обессоливания (обезвоживания).

2. Поверхностно-активные вещества добавляются лишь тогда, когда нефть содержит значительное количество взвешенных твёрдых частиц.

3. Третий, менее распространённый метод подразумевает фильтрацию подогретой нефти с использованием инфузорной земли.

4. У всех ректификационных колонн аналогичный принцип работы.

Figure 2. Atmospheric Distillation

Figure 3. Vacuum Distillation

Text 5

I. Read the text and fill in the gaps with the sentences (a-j).

Treatment Processes: Solvent Extraction and Dewaxing, Sweetening, Catalytic Hydrotreating

(1) ……………..These include organic compounds containing sulfur, nitrogen, and oxygen; inorganic salts and dissolved metals; and soluble salts that were present in the crude feedstock. (2) ………….Solvent refining processes including solvent extraction and solvent dewaxing usually remove these undesirables.

Petroleum refiners have a choice of several different treating processes, but the primary purpose of the majority of them is the elimination of unwanted sulfur compounds. (3) ……….. . Sweetening, a major refinery treatment of gasoline, treats sulfur compounds (hydrogen sulfide, thiophene and mercaptan) to improve color, odor, and oxidation stability. Sweetening also reduces concentrations of carbon dioxide.

Catalytic hydrotreating is a hydrogenation process used to remove about 90% of contaminants such as nitrogen, sulfur, oxygen, and metals from liquid petroleum fractions. (4) ……….. . Typically, hydrotreating is done prior to processes such as catalytic reforming so that the catalyst is not contaminated by untreated feedstock. Hydrotreating is also used prior to catalytic cracking to reduce sulfur and improve product yields, and to upgrade middle-distillate petroleum fractions into finished kerosene, diesel fuel, and heating fuel oils. (5) ……….

Treating can be accomplished at an intermediate stage in the refining process, or just before sending the finished product to storage.

A. In addition, kerosene and distillates may have trace amounts of aromatics and naphthenes, and lubricating oil base-stocks may contain wax.

B. A variety of intermediate and finished products, including middle distillates, gasoline, kerosene, jet fuel, and sour gases are dried and sweetened.

C. Since distillation (fractionation) separates petroleum products into groups only by their boiling-point ranges, impurities may remain.

D. These contaminants, if not removed from the petroleum fractions as they travel through the refinery processing units, can have detrimental effects on the equipment, the catalysts, and the quality of the finished product.

E. In addition, hydrotreating converts olefins and aromatics to saturated compounds.