Despite elevated pressure having a suppressing effect on cracking reactions, commercial units maintain a positive pressure of 10-15 kgf/cm2 primarily to__________________?
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Answer: B. Suppress coke formation
Explanation
Maintaining a moderate positive pressure in thermal cracking units helps suppress rapid coke formation. Elevated pressure alters reaction equilibria and keeps reactive fragments dissolved in the liquid phase. Controlling coking reactions prevents premature fouling and plugging of high-temperature furnace tubes. Thermal cracking breaks heavy hydrocarbon molecules into lighter gasoline and distillate fractions. Commercial thermal cracking units typically operate at moderate positive pressures of ten to fifteen kgf/cm2. Excessive coking reduces heat transfer efficiency and forces costly unscheduled shutdown maintenance.
Refinery thermal cracking units require careful pressure management to balance conversion and run length. Operators monitor reactor skin temperatures and pressure drops to detect early signs of coke buildup. Minimizing coke deposition extends the continuous operating cycle of visbreakers and coker furnaces. Option A relates primarily to catalytic cracking and severity control rather than pressure suppression of coke. Option C refers to catalytic reforming where pressure is managed to optimize aromatic dehydrogenation. Option D describes gum reduction which is achieved through hydrotreating and chemical sweetening steps.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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