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The University of Western Ontario Faculty of Engineering DEPARTMENT OF CHEMICAL AND BIOCHEMICAL ENGINEERING CBE 4432/9132 –Oil Refining and Processing

Quiz # 1 - Allowable Time: 40 minutes CLOSED BOOK Answer All Questions (February 10, 2015) XXX Student No: XXXX

Student Name: Question 1.

What is the significance of Watson characterization factor in petroleum refining? Discuss with its equation (8) This factor is expressed by the following correlation:

KW 

(1.8Tbm )1 / 3 S

where Tbm S KW

= is mean or average normal boiling point (oK) = is specific gravity at 15oC = Watson characterization factor

The average boiling temperature for crude oil and its fractions can be estimated from distillation data obtained from ASTM distillation tests. Values of KW for hydrocarbons of different chemical families are as below. paraffins: naphthenes: aromatics:

KW KW KW

13 12 10

The characterization factor is close to 13 when paraffins are dominant hydrocarbon types in the crude oil or its fraction. When aromatics dominate, the value is close to 10.

Question 2. a) What are the main impurities found in crude oil? (4) Sulfur Nitrogen Salts and Sand Metals

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b) What are their effects on crude oil processing? Discuss briefly. (6) Sulfur Crudes with high sulfur content (> 0.5 wt %) generally require more expensive processing than those with lower sulfur content. Sulfur compounds in present in petroleum lead to acid gas (SOx) formation during combustion. Sulfur is also poisonous to number of catalytic processes used in downstream processing of crude oil. Nitrogen

Organic nitrogen compounds present in crude oils cause severe poisoning of catalyst used in processing and are the main cause of NOx formation during combustion. Crude containing nitrogen in excess of 0.25% by weight require special processing to remove nitrogen. Metals

The metal content of crude can vary from a few parts per million to more than 1,000 ppm. Minute quantities of some of these metals (nickel, vanadium and copper) can severely affect the activities of catalysts and result in a lower-value product distribution. Salts and Sand

These impurities can cause plugging and corrosion problems in the refinery. Question 3. a) 1. 2. 3.

Which of the followings are specifications for gasoline product stream? (2) Reid vapor pressure (RVP) Octane number Cetane number

b) What are their significances? Discuss briefly (8) Reid vapor pressure (RVP) RVP is the vapor pressure of the gasoline at 100oF. High RVP improves engine starting but also increases losses low RVP prevents vapor lock. It changes with season of the year: RVP is high in winter compared to summer so that more vapors are available for quick engine startup.

Octane numbers It is an indicator of fuel quality for the induced ignition gasoline engine. Improper quality gasoline fuel can cause knocking, an undesirable phenomenon due to a sudden and massive auto-ignition of a part of the fuel not yet burnt. There are two standard procedures to determine the octane number: Research octane number (RON) and Motor octane number (MON). The posted octane number on the service station is the arithmetic average of the research and motor octane numbers.

Question 4. List the following products from an atmospheric distillation column in their right order from top to bottom. (5) 1. Naphtha 2. Liquefied petroleum gas 2

3. Straight run gasoline 4. Atmospheric residue 5. Middle distillates Correct order from top to bottom 1. 2. 3. 4. 5.

Liquefied petroleum gas Straight run gasoline Naphtha Middle distillates Atmospheric residue

Question 5. What are the four main types of reaction taking place in catalytic reforming reactor? Discuss briefly – you can use chemical name instead of formula (12)

1. Dehydrogenation of cyclohexanes to aromatics. CH3

CH3

⇆

+ 3H2

Methylcyclohexane

Toluene

This is highly endothermic reaction leading to temperature drop across reactor. The reaction is fast and controlled by chemical equilibrium.

2. Dehydrocyclization of paraffins to aromatics. CH3

⇆

n-C7H16 n-heptane

+ 4H2 Toluene

dehydrocyclization is slower reaction than dehydrogenation due to cyclization step.

2. Isomerization Reactions CH3 CH3(CH2)5 CH3 n-heptane

⇆

CH3-CH (CH2)3 CH3 isohepane

Isoparaffins have higher octane number than normal paraffins, therefore boost octane number of the product.

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3. Hydrocracking Reactions The hydrocracking reactions are exothermic and result in the production of lighter liquid and gas products. The major hydrocracking reactions involve the cracking and saturation of paraffins. C10H22 +

H2

i- C6H12

n-decane

iso-heptane

+ C4H10 butane

Question 6. Add the two missing equipment label and three missing stream labels in the process flow diagram below. (5)

Light straight run naphtha

Gases

Isomerization

Fractionator iC5 –C6

Combined Naphtha Feed Cat-reforming Hydrotreater

Heavy straight run naphtha

4

C5+ reformate...