**Answers to Lesson 3 Exercise 2**

#### Question 1

A refinery has access to two different crude oil stocks A and B with the following compositions:

Naphthenes % | Aromatics % | |
---|---|---|

Crude A | 10 | 60 |

Crude B | 60 | 10 |

- What type of crude oils are A and B according to the ternary classification based on composition?
- What type of crude would be obtained if A and B are blended in a proportion of A/B =2/3?

#### Answer:

- What type of crude oils are A and B according to the ternary classification based on composition?

$\begin{array}{l}\text{A}=\text{Aromatic:}60\%\text{,Naphthenes:}10\%\end{array}$

Aromatic-Intermediate crude (Aromatics > 50% , Paraffins > 10 % )

$\begin{array}{l}B=\text{Aromatic:1}0\%\text{,Naphthenes:6}0\%\end{array}$

Naphthenic crude ( P + N > 50 % , N > P , N > 40 % ) - What type of crude would be obtained if A and B are blended in a proportion of A/B =2/3?

In the blend with A/B = 2/3: A: 40%, B=60%

Binary Blend C: Naphthenes = (0.4)(10) + (0.6)(60) = 40%

Aromatics = (0.4)(60) + (0.6)(10) = 30%, P=30%

Binary Blend C: Border-line between Paraffinic-Naphthenic (A<50%, P<40, N<40%) and Naphthenic ((P+N>50%, N>P, N>40%) crude oils.

You may solve the problem graphically using a ternary diagram, as described below.

#### Video: FSC 432 Blend Triangle (4:43)

#### Question 2

The compositions of three crude oils available to a refinery are as follows:

Crude A: 60%wt paraffins, 20%wt naphthenes

Crude B: 50%wt aromatics, 30%wt paraffins

Crude C: 10%wt paraffins, 20%wt naphthenes

The refiners would like to maintain a weight ratio of 1/1, Crude B/Crude C in a ternary blend of the oils A, B, and C. What would be the minimum concentration of Crude A (% wt) in a ternary blend that could be classified as paraffinic oil?

#### Answer:

aromatics | naphthenes | paraffins | |
---|---|---|---|

Crude A | 20%wt | 20%wt | 60%wt |

Crude B | 50%wt | 20%wt | 30%wt |

Crude C | 70%wt | 20%wt | 10%wt |

Set A+B+C = 100g and B=C

Paraffin balance:

0.60A + 0.3(100-A)/2 + 0.1(100-A)/2 > 40

1.2A + 30 - 0 .3A + 10 - 0.1A >80

.8A > 40

A>50, Therefore, A must be greater than 50% to maintain a paraffinic crude blend.