Model Answers of Fractionation

7/27/2019 Model Answers of Fractionation

1/16

Distillation & Fractionation Model Answers

________________________________________________________________________

Question No.1: MULTIPLE CHOICES: Place the letter of thestatement that best completes the sentence in spaceprovided.

1. Hydrocarbon molecules are made up of: ----------

A. hydrogen and oxygen atomsB. carbon and nitrogen atomsC. hydrogen and carbon atomsD. none of the above

2. Most products produced in a refinery or petrochemical plantpass through: ----------

A. several different distillation columnsB. only one distillation columnC. sieve-deck trays

3. A product formed in the distillation process will containhydrocarbons with: ----------

A. very different boiling points or boiling point rangesB. similar boiling points or boiling point ranges

4. The purpose of the distillation process is to: ----------A. removes water and sediment from hydrocarbonsB. chemically crack or reform hydrocarbon moleculesC. separates a mixture of hydrocarbons into relatively pure tractions

5. When a mixture of hydrocarbons is heated, which fractionsare the last to vaporize? ----------

A. Heavy componentsB. Light components

C. Medium-sized componentsD. Depends on the particular mixture

6. One way to separate a mixture of hydrocarbons is to: ----------A. partially vaporizes them and then condenses the vapors back to

liquidB. completely vaporizes them and then condenses the vapors back to

liquid.C. places the mixture under a complete vacuum

D. keeps the vapor pressure of the hydrocarbons below 14.7 psi

______________________________________________________________________________________

(REV.0) Oct. 2006 Page 1 of 16


2/16


________________________________________________________________________

7. What kind of heat is removed when a vapor is condensed toliquid? ---------

A. Sensible heat

B. Thermal heatC. Latent heatD. Atomic heat

8. When the vapor pressure of a liquid equals the pressureagainst that liquid, it: ----------A. condenses.B. boils.C. does not change its state.

9. Heavy hydrocarbons have: -----------A. low vapor pressures and low boiling pointsB. high vapor pressures and high boiling pointsC. high vapor pressures and low boiling pointsD. low vapor pressures and high boiling points

10. Which hydrocarbon mixture is more difficult to separate?-----------

A. A mixture with very narrow boiling point differencesB. A mixture with wide boiling point differences

11. When the pressure against a liquid is increased, the liquidboils at: -----------A. a lower temperatureB. the same temperatureC. a higher temperature

D. None of the above. It depends on the composition of the liquid.

12. Why is steam sometimes added to a distillation column?-----------

A. Steam strips out light components by reducing the hydrocarbonpartial pressure

B. Steam strips out heavy components by increasing the hydrocarbonpartial pressure

______________________________________________________________________________________



3/16


________________________________________________________________________

13. Reflux is the: -----------

A. liquid that enters a distillation column as feedB. vapor that boils light components out of the downward flowing liquid

in a distillation columnC. cool liquid that flows down a column and removes heat from hot,

rising vapors

14. What happens when the reflux rate is increased? ----------A. More heat is removed from the towerB. Less heat is removed from the towerC. More heat is added to the towerD. Less heat is added to the tower

15. Hot vapors bubble through the liquid: ----------A. on each tray in a distillation columnB. in the downcomersC. only in the bottom of a columnD. only in the top of a column

16. A heavier fraction will develop on a tray when: ----------A. the tray temperature is decreasedB. the feed rate is increasedC. the tray temperature is increasedD. a bubble cap is removed from the tray

17. The liquid on the bottom trays of a distillation column is:----------

A. lighter than the liquid on the top traysB. heavier than the liquid on the top traysC. the same composition as the liquid on the top trays

18. Material balance means that: ----------A. whatever material enters the tower as feed must leave the tower as

products.B. half of the feed leaves from the top of the tower while the other half

leaves from the bottom.C. light and heavy fractions will always balance each other out

______________________________________________________________________________________



4/16


________________________________________________________________________

19. A vacuum distillation column operates at a very lowpressure in order to: ----------A. decrease the amount of heat that is needed to distill hydrocarbons

B. minimize the amount of vapors that are formedC. reduce stress damage

20. For good fractionation to occur there must be: ----------

A. good vapor-liquid contact on each trayB. a temperature difference (or gradient) between trays in the towerC a two-way flow of fluids inside the columnD. All of the above

21. Which of the following is a heat exchanger? ----------

A. Kettle-type reboilerB. Thermosyphon-type reboilerC. CondenserD. All of the above

22. A product with an initial boiling point (IBP) specification of100-105F tests at 95F. This product: -----------

A. contains material that is too light

B. does not contain enough light materialC. contains material that is too heavy

23. A product with an end boiling point (EP) specification of150-155? tests at 158F. This product: -----------A. contains material that is too lightB. contains material that is too heavyC. does not contain enough heavy material

24. A product with a flash point specification of 100-105Ptests at 95F. Thisproduct: -----------

A. contains material that is too heavyB. contains material that is too lightC. is too dense

______________________________________________________________________________________



5/16


________________________________________________________________________

25. A product with a low API gravity is relatively: ----------A. lightB. heavyC. pureD. Depends on the product being tested

26. When the heat balance in a distillation column is adjusted:-----------

A. product composition changesB. more of one product and less of another will be producedC. both A and B

27. Cut point changes can be made in a distillation column by:

-----------A. changing the reboiler temperatureB. changing the reflux rateC. changing the furnace temperatureD. changing any of the above variables

28. If the reflux rate in distillation column is increased andother tower operating conditions are kept constant, whichof the following occurs? ------------

A. Heavier overhead, bottom, and side draw products are producedB. Lighter overhead, bottom, and side draw products are producedC. The amount of top product produced increasesD. None of the above

29. If we increase the reboiler temperature for a depropanizerand keep other tower operating conditions constant, whichof the following occurs? ------------A. Heavier overhead and bottom products are produced.

B. Lighter overhead and bottom products are produced.C. The amount of bottom product produced increases.D. None of the above

30. Opening a stripper draw makes this product and theproducts below this tray: -----------A. heavierB. lighterC. vaporize

D. condense

______________________________________________________________________________________



6/16


________________________________________________________________________

31. How can you change the composition of one side drawproduct without affecting the composition of productsbelow this tray? ------------

A. Close a stripper draw

B. Open a stripper drawC. Close one stripper draw and open another

32. The four main process variables are: ------------

A. pressure, temperature, liquid level, and flowB. viscosity, density, temperature, and pressureC. liquid level, temperature, viscosity, and pressure

33. A control loop is: ------------A. a combination of instruments that works together to keep a process

variable at a desired valueB. a series of controllers that keeps a distillation column producing

products that are on-specificationC. a group of valves that keeps process variables at setpointD. a device that records and indicates the condition of a process

variable

34. What does this symbol stand for? PRC

---------------- --------------- ------------

35. Can instruments automatically correct all process upsets?------------

A. YesB. No

36. Light hydrocarbons have: -------------

A. low vapor pressures and low boiling pointsB. low vapor pressures and high boiling pointsC. high vapor pressures and high boiling pointsD. high vapor pressures and low boiling points

37. A liquid will not boil until its: ------------A. vapor pressure is double the pressure against the liquidB. vapor pressure equals the pressure against the liquidC. molecules move faster than the gas molecules above it

D. latent heat is converted to sensible heat

______________________________________________________________________________________



7/16


________________________________________________________________________

38. A distillation column that operates at or slightly above 14.7psi is called: -----------A. a vacuum tower

B. a pressure towerC. a stripping columnD. an atmospheric tower

39. In order to make useful products, hydrocarbons must beseparated into: ------------A. Completely pure fractionsB. relatively pure fractionsC. a mixture of fractions

D. Doesn't really matter

40. When the reflux rate is decreased: ------------A. more heat is removed from the tower.B. less heat is removed from the tower.C. more heat is added to the tower.D. less heat is added to the tower.

41. What happens on each tray in a distillation column? ----------

A. Cool vapors bubble through a warmer liquid on the trayB. Hot vapors bubble through a cooler liquid on the trayC. The liquid does not come in contact with vapors on the tray

42. A lighter fraction will develop on a tray when: ------------A. the tray temperature is increasedB. the feed rate is increasedC. the tray temperature is decreasedD. a bubble cap is removed from a tray

43. The liquid on the top trays of a distillation column is: --------A. lighter than the liquid on the bottom traysB. heavier than the liquid on the bottom traysC. the same composition as the liquid on the bottom trays

______________________________________________________________________________________



8/16


________________________________________________________________________

44. When heat is added to a mixture of hydrocarbons, whichfractions are the first to vaporize? ----------

A. Heavy componentsB. Light componentsC. Medium-sized componentsD. Depends on the particular mixture

45. What kind of heat is added to vaporize a substance alreadyat boiling temperature? -----------

A. Sensible heat

B. Latent heatC. Thermal heatD. Atomic heat

46. Which hydrocarbon mixture is easier to separate? ----------

A. A mixture with very narrow boiling point differencesB. A mixture with wide boiling point differences

47. When the heat balance in a distillation column is adjusted:-----------

A. product composition changesB. more of one product and less of another will be produced.C. Both A and B

48. If the reflux rate in crude distillation column is decreasedand other tower operating conditions are held constant,which of the following occurs? -----------

A. Heavier overhead, bottom, and side draw products are producedB. Lighter overhead, bottom, and side draw products are producedC. The amount of top product produced decreasesD. None of the above

______________________________________________________________________________________



9/16


________________________________________________________________________

49. If the reboiler temperature for a depropanizer is decreasedand other tower operating conditions are kept constant,which of the following occurs? ------------

A. Heavier overhead and bottom products are producedB. Lighter overhead and bottom products are producedC. The amount of bottom product produced decreasesD. None of the above

50. Closing a stripper draw makes this product and theproducts below this tray: ------------A. vaporize

B. condenseC. heavierD. lighter

52. A product with an initial boiling point (IBP) specification of100-105F tests at 110F. This product: ------------

A. contains material that is too lightB. does not contain enough heavy materialC. does not contain enough light material

53. A product with an end boiling point (EP) specification of150-155? tests at 140F. This product: ------------A. contains material that is too heavy.B. does not contain enough heavy material.C. does not contain enough light material.

54. A product with a flash point specification of 110-115F testsat 125F. This product: ------------

A. contains material that is too lightB. does not contain enough light materialC. does not contain enough heavy material

55. Which of the following process upsets can instrumentscorrect automatically? ------------

A. Pump failureB. Stuck valveC. Feed composition change

D. Leak in condenser

______________________________________________________________________________________



10/16


________________________________________________________________________

56. A product with a high API gravity is relatively: ------------

A. lightB. heavyC- pureD. Depends on the product being tested

57. The four main process variables are pressure, temperature:------------

A. liquid level, and viscosityB. density, and viscosityC. liquid level, and flowD. flow, and density

58. What does this symbol stand for? FRC

--------------- ---------------- ----------------

59. The molecules that form crude oil are called: ------------

A. hydrocarbonsB. carbonatesC. petroleum

D. water, salt, and sediment

60. What atoms make up hydrocarbons? (Pick two)

--------- & --------

A. WaterB.CarbonC. thaneD. Hydrogen

61. When we heat a mixture of hydrocarbons, the firstmolecules to boil andvaporize are: ------------

A. the heavy, or large, hydrocarbonsB. the light, or small, hydrocarbonsC. the medium-sized hydrocarbonsD. none of the above. They all start boiling at the same temperature

______________________________________________________________________________________

(REV.0) Oct. 2006 Page 10 of 16


11/16


________________________________________________________________________

62. What happens when a mixture of hydrocarbons is distilled?-----------

A. The hydrocarbons are physically separatedB. They are chemically changed

63. Most of the products produced in a refinery orpetrochemical plant pass through: -----------

A. several distillation processesB. atom splittersC. vacuum towersD. all of the above

64. Why can we separate hydrocarbon mixtures by heatingthem and then condensing the vapors? -----------

A. Different hydrocarbons have different boiling pointsB. Different hydrocarbons have the same boiling pointC. Heat causes hydrocarbon molecules to break in halfD. Latent heat equalizes the vapor pressure of hydrocarbons

65. During the distillation process, heat put into the tower: ------

A. is consumed by the hydrocarbonsB. is always less than heat taken outC. is taken out as latent heat of condensation and as sensible heat in

the products themselves

66. Choose two characteristics of light hydrocarbonmolecules: ------- & -------A. High boiling temperaturesB. Low boiling temperatures

C. High vapor pressuresD. Low vapor pressures

67. Distillation of hydrocarbons is easiest when thecomponents have boilingpoints that are: -----------

A. dose togetherB. far apartC. neither of these. Boiling points do not affect distillation

______________________________________________________________________________________

(REV.0) Oct. 2006 Page 11 of 16


12/16


________________________________________________________________________

68. What happens to the boiling point of a liquid whenpressure against that liquid is increased? -----------

A. The boiling point temperature is increased

B. The boiling point temperature is decreasedC. The boiling point does not change unless the vapor pressure of thatliquid changes

D. It depends whether the liquid is water or a mixture of hydrocarbons

69. The temperature on each tray in the tower is controlled by:------------

A. the downward flow of reflux and upward flow of vaporsB. the downward flow of vapors and upward flow of reflux

C. the composition of the feedD. none of the above

70. Inside the distillation column: ------------A. vapors by-pass the liquid through downcomersB. vapors bubble through the liquid on the trayC. vapor-liquid contact occurs in the chamber space between the traysD. liquid flows down the tower through bubble caps

71. What happens on each tray as a result of vapor-liquidcontact? -----------A. Light materials in the liquid tend to condense, and heavy materials in

the vapor tend to vaporizeB. Light materials in the liquid tend to vaporize, and heavy materials in

the vapor tend to condense

72. The vaporization-condensation cycle eventually produces:------------

A. a different fraction on each trayB. the same fraction on each trayC. a heavy product at the top of the column and a light product at the

bottom

73. As vapors rise up the column, they become progressively:------------

A. heavierB. lighter

______________________________________________________________________________________

(REV.0) Oct. 2006 Page 12 of 16


13/16


________________________________________________________________________

74. Liquid moving down the column becomes: ------------

A. heavierB. lighter

75. In a crude distillation column, products drawn from theside of the tower pass through a: ------------

A. condenserB. reboilerC. stripping column

76. The temperature in a distillation column decreases from:

------------A. bottom to topB. top to bottom

77. The heaviest fraction will be formed on the tray with the:------------

A. lowest temperatureB. highest temperature

78. An atmospheric tower is a distillation column thatoperates: ------------

A. at or slightly above 14.7 psiB. below 14.7 psi

79. In order to maintain a vacuum in a distillation column: -------A. steam must be injected into the towerB. all noncondensibles vapors must be continually removed from the

tower

C. only the heavy hydrocarbon molecules must be removedD. none of the above functions must be performed

80. Which type of tower is generally used to distill reducedcrude? -----------A. Atmospheric towerB. Vacuum tower

______________________________________________________________________________________

(REV.0) Oct. 2006 Page 13 of 16


14/16


________________________________________________________________________

81. Good fractionation requires: ------------

A. a tower with a large number of traysB. a multiple feed-port towerC. multi-pass downcomersD. good vapor-liquid contact on each tray

82. "Entrainment" occurs when: ------------A. vapor rates are too lowB. not enough heat is put into the towerC. small drops of liquid suspended in vapor are carried up from one

tray to the next

83. Which of the following can generate the most heat tovaporize feed? ------------

A. CondenserB. Heat exchangerC. Furnace

84. A heat exchanger is a device in which: ------------A. heat is transferred from one fluid to another

B. burners heat feed using radiant and convection heatC. vapors bubble through liquid to increase surface areaD. products drawn from the side of a tower are further distilled

85. A product with an IBP specification of between 115-120 Ftests at 110 F. This product contains too much: ------------

A. light materialB. heavy materialC. medium weight material

D. None of the above

86. A product with a flash point specification of between 95-100 F tests at 105 F. This product does not containenough: ------------

A. light materialB. heavy materialC. medium weight materialD. None of the above

______________________________________________________________________________________

(REV.0) Oct. 2006 Page 14 of 16


15/16


16/16


________________________________________________________________________

92. Opening a stripper draw makes this product and productsbelow this tray: -----------A. heavier

B. lighterC. Does not affect the stripper draw product

93. The products made in a distillation column: ------------A. should just meet product specificationsB. should exceed product specificationsC. do not always have to meet product specifications

______________________________________________________________________________________

(REV.0) Oct. 2006 Page 16 of 16

Model Answers of Fractionation

Documents

Transcript of Model Answers of Fractionation