Refining conversion technologies: Among the classic and modern cracking routes, which process is the most widely used in oil refineries for converting heavy gas oils to gasoline and lighter products?
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ADubbs thermal cracking process
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BT.C.C. moving-bed catalytic cracking
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CFluidised-bed catalytic cracking (FCC)
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DHoudry’s fixed-bed catalytic cracking
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EVisbreaking only
Answer
Correct Answer: Fluidised-bed catalytic cracking (FCC)
Explanation
Introduction:Crude fractions above the naphtha range must be converted to yield gasoline, LPG, and light olefins. Several historical and modern cracking technologies exist; identifying the dominant contemporary workhorse is essential for refinery literacy.
Given Data / Assumptions:
- Feed: vacuum gas oil and heavy gas oils.
- Objective: high gasoline yield and propylene/butylene by-products.
- Comparison across thermal and catalytic methods.
Concept / Approach:Fluidised catalytic cracking (FCC) uses a circulating, powdered zeolite catalyst in a riser reactor, enabling continuous operation and regeneration. It largely displaced early fixed-bed (Houdry) and moving-bed (T.C.C.) systems and supplanted purely thermal approaches (Dubbs) due to higher selectivity and flexibility.
Step-by-Step Solution:
Recognise FCC as the industry standard for gas oil conversion.Note that older processes are historically significant but not dominant today.Select FCC.Verification / Alternative check:Refinery capacity summaries worldwide show FCC as one of the largest conversion unit capacities after crude distillation and hydrotreating.
Why Other Options Are Wrong:
- Dubbs: Thermal, largely obsolete for gasoline manufacture.
- T.C.C. / Houdry: Early catalytic systems, replaced by FCC.
- Visbreaking: Mild thermal cracking to reduce resid viscosity, not the main gasoline maker.
Common Pitfalls:Assuming “older named” processes are still the mainstay; technology migrated to FCC.
Final Answer:Fluidised-bed catalytic cracking (FCC)