23-Chem-B6 Petroleum Refining and Petrochemicals · December 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exam 04-Chem-B6, Petroleum Refining and Petrochemicals — December 2016. 3 hours, OPEN BOOK (any non-communicating calculator permitted). Per the exam notes, FIVE questions constitute a complete paper — Question 1 is multiple-choice and Questions II–V require essay-format answers of equal value (10 marks each); clarity and organisation are explicitly marked. This paper contains exactly five questions, so all five are answered here in full. The exam is almost entirely qualitative; the only computed quantities are the two standard crude-characterisation relations used to justify the multiple-choice answers.
Reference texts: Gary, Handwerk & Kaiser, Petroleum Refining: Technology and Economics, 5th ed.; Fahim, Al-Sahhaf & Elkilani, Fundamentals of Petroleum Refining; J. G. Speight, The Chemistry and Technology of Petroleum, 5th ed.; Perry's Chemical Engineers' Handbook, 9th ed. (generic distillation / equipment methods).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
The true-boiling-point (TBP) curve plots cut temperature against volume-percent distilled; a refinery "cuts" the crude into successive boiling-range fractions (pseudo-components) by drawing vertical divisions on this curve. The annotated curve below answers all three parts.
[Figure not reproduced: True-boiling-point (TBP) curve of the crude, redrawn from the exam schematic. Cuts A–E map to increasing boiling range; IBP and EP mark the 0% and 100% points; the blue verticals at 60% and 80% are the lower/upper cut points of product D (T₁, T₂). See the official exam paper.]
(a) Pseudo-components (increasing boiling range). Reading the five bands left-to-right:
| Cut | Distilled range | Pseudo-component |
|---|---|---|
| A | 0–20% | Light ends + light straight-run naphtha (fuel gas / LPG and light gasoline) |
| B | 20–40% | Heavy naphtha (gasoline range) |
| C | 40–60% | Kerosene / jet (light distillate) |
| D | 60–80% | Diesel / light gas oil (atmospheric gas oil) |
| E | 80–100% | Heavy gas oil + atmospheric residue (bottoms) |
(b) IBP and EP. The initial boiling point (IBP) is the temperature at 0% distilled — the lower-left start of the curve; the end point (EP, or FBP) is the temperature at 100% distilled — the upper-right end of the curve. Both are marked in red on the figure.
(c) Cut points of product D. A "cut point" is the TBP temperature at a chosen % distilled that separates one fraction from the next. Product D (60–80% distilled) is bounded by two cut points: its lower cut point $T_1$ at 60% distilled (shared with cut C) and its upper cut point $T_2$ at 80% distilled (shared with cut E). These are the blue verticals on the figure, with dashed lines projecting $T_1$ and $T_2$ onto the temperature axis.
