Crude distillation hardware\nThe most widely used type of trays in atmospheric crude topping columns is the ______ column.

Introduction / Context:
Atmospheric crude distillation is the first major separation step in refineries. Hardware choices for contacting vapor and liquid include various tray types and packings. Many classical references cite the dominant tray styles historically employed in crude towers.

Given Data / Assumptions:

• Conventional large-diameter atmospheric towers.
• Historical and widely adopted industrial practice.

Concept / Approach:
Bubble-cap trays were historically prevalent in crude towers due to their wide operating range, good liquid/vapor handling, and tolerance to fouling. Although modern designs frequently adopt sieve (perforated) or valve trays for lower cost and pressure drop, the traditional “most widely used” designation in many exam contexts remains bubble-cap trays for crude topping service.

Step-by-Step Solution:

Verification / Alternative check:
Older refinery texts and question banks emphasize bubble-cap usage in crude distillation; modern plants may also favor sieve/valve trays, but the canonical answer remains bubble-cap.

Why Other Options Are Wrong:

• Packed beds are less common in fouling-prone crude service.
• Fluidised beds are not used for fractionation trays.
• Perforated (sieve) and dual-flow trays are used but traditionally not cited as “most widely used” in such questions.

Common Pitfalls:
Assuming current procurement trends override the conventional answer required by standardized tests.

Final Answer:
Bubble-cap