Look through the text and say what is the difference between this text and the previous one.

Read the first two paragraphs and say a few words about the burner.

Read the following two paragraphs and say what goes on in the flame room.

5. What is meant by residence time?

6. Read the rest of the text and answer the questions.

1) What is a spray used for?

2) Where is a series of sprays located?

3) What goes on in a spray chamber?

4) What composition do gases have after a spray chamber?

5) What is the capacity of burner trains?

6) What is done with residual soot?

7) How are polyformers removed?

8) What is a flashing and stripping operation used for?

9) How is acetylene stripped from the solvent?

10) What is removed by stripping under reduced pressure.

11) What purity has the product acetylene?

12) What are the main impurities?

13) How can acetylene be further purified?

Fig. 4. Acetylene (II) production scheme

TEXT 7. BUTYLENE AND ETHYLENE (TRIOLEFIN PROCESS)

 

Application. A process for converting propylene to ethylene and butylene.

Description. The Triolefin Process utilizes a disproportionation reaction whereby relatively low cost propylene can be upgraded to more valuable ethylene and butenes. For every two moles of propylene converted, approximately one mole of ethylene and one mole of butene are produced. The reactor operation is cyclic and carbon is burned off periodically with air mixed with an inert diluent.

Propylene conversion per pass is approximately 40 percent. Unconverted propylene is recycled back to the reactors. Propane and other alkanes can be used as a diluent. Any ratio of propane-propylene is permissible in the unit feed although the internal recycle stream becomes larger as the propane content is increased.

A small percent of the propylene that is converted forms pentenes and heavier material. No more than trace quantities of methane, ethane, isobutene, and butanes are produced in the disproportionation reactors.

Ethylene suitable for polyethylene production can be fractionated easily from the C₃ and heavier product from the reactor provided that the feed to the Triolefin Process unit has previously been deethanized. If a high-purity butene product is desired, the reactor feed can be debutanized, leaving nearly pure C₃’s, and an additional purification column can be added to the Triolefin Process unit to remove C₅’s and heavier. High-purity products can be produced in this way by relatively inexpensive fractionation rather than by difficult ethylene-ethane and butane-butene-2 separations.

Usually more than 90 percent of the butenes from the reactors is butene-2, an excellent feed stock for alkylation to produce high octane motor fuel. Since only trace quantities of C₄’s other than normal butenes are present, Triolefin Process butenes are a highly desirable feed stock for dehydrogenation to butadiene.

Reactor onstream cycle times can be extended by reduction of the acetylene and diolefin content of the feed. This can be done easily by selective hydrogenation over a catalyst containing palladium. Catalysts for this purpose are available from well known catalyst suppliers. It is also necessary for the feed to be dry and free of sulfur for satisfactory operation.

Operating Condition. The reactors can be operated at from 0 to 500 psig without affecting the reaction a great deal. The WHSV is practical in the range of 10 to well over 100.

Yields. The conversion of propylene to ethylene and butene is normally over 95 percent.

 

Tasks on the text

1. Memorize the following terms.

1. triolefin(e)[,traI`qVlIfJn] – углеводород с тремя двойными связями; триолефин 2. disproportionation 1) диспропорционирование (перераспределение атомов или групп между двумя одинаковыми или разными соединениями); 2) самоокисление-самовосстановление 3. disproportionation reaction – реакция перераспределения; реакция превращения одной молекулы в две другие, отличные друг от друга (окисление-восстановление) 4. butene [`bjHtJn] – бутен 5. to upgrade – облагораживать, повышать качество 6. reactor operation – работа реактора 7. diluent [`dIljVqnt] – разжижитель; разбавитель 8. per pass – за один проход, за цикл 9. feed, feed stock – исходное сырье

10. pentene [`pentJn] – пентен 11. to fractionate [`frxkS(q)neIt] – фракционировать, ректифицировать 12. trace quantities [`kwPntqtIz] – очень малые (едва уловимые) количества 13. to deethanize – деэтанизировать, отгонять этан 14. dehydrogenation [,dJhaI`drPGqneIS(q)n] – дегидрирование, дегидрогенизация 15. butadiene [,bjHtq`daIJn] – бутадиен 16. onstream time – период непрерывной работы 17. pounds per square inch gage, psig – избыточное давление, равное 6894,757 Па 18. WHSV, weight hour space velocity – объёмная скорость (количество нефтепродукта на единицу веса катализатора в час)

 

2. Read the text. Complete the following sentences, using information from it.

1) The Triolefin Process converts propylene to…

2) In this process a … reaction is carried out.

3) Propylene is converted approximately by 40 % …

4) It is possible to use … of propane-propylene in the unit feed.

5) Methane, ethane, isobutene and butanes are produced in … quantities.

6) If it is necessary to get a high-purity butane product, it is possible to …the reactor feed.

7) Butene-2 is … for alkylation to produce high octane motor fuel.

8) By reducing acetylene and diolefin content of the feed it is possible to extend …

9) This can be achieved easily by selective …

10) A catalyst containing … can be used for this purpose.

3. Find the English equivalents.

Относительно дешевый, более дорогой, на каждые две моли, циклическая операция, допустимый, рециркулирующий поток, содержание пропана, более тяжелое вещество, подходящий для, предварительно, почти чистый, очистная колонна, дополнительный, относительно недорогой, превосходное сырье для алкилирования, моторное топливо с высоким октановым числом, поставщик, свободный от серы (обессеренный), удовлетворительное ведение процесса.

4. Describe the Triolefin Process.

5. Say a few words about reactor onstream cycle time extension.