Basket-type natural-circulation evaporator: Pick the WRONG statement about configuration and typical service.

Introduction:
Basket-type evaporators are a form of natural-circulation vertical evaporator in which the tube bundle is hung from the top like a “basket.” Correctly recalling their flow path and suitable service is important for preliminary selection and troubleshooting.

Given Data / Assumptions:

• Natural circulation, not forced circulation.
• Vertical cylindrical shell with an internal tube bundle.
• Circulation produced by density difference between two-phase mixture and liquid in the downcomer.

Concept / Approach:
In a basket-type design, liquid-vapor mixture rises inside the tubes, and the downflow occurs in the annulus between the tube bundle and the shell. There is no separate central downtake. Because circulation is natural and relatively weak, basket designs are not the first choice for very viscous or heavily scaling liquors; forced-circulation or falling-film units are preferred for such duties to control fouling and maintain high shear at surfaces.

Step-by-Step Solution:
Check (b): Tube bundle suspended from top → characteristic of basket type → true.Check (c): “No central downtake” → correct for basket type (downcomer is annular).Check (d): Downtake is the annular space between bundle and shell → true.Check (a): Claims suitability for high viscosity and heavy scaling → this is generally false for natural-circulation units; better handled by forced-circulation or scraped-surface designs → wrong statement.

Verification / Alternative check:
Design texts note basket-type units for moderate viscosities and relatively clean services; viscous/scaling liquids push designers to forced-circulation or special surfaces.

Why Other Options Are Wrong:

• (b), (c), (d) accurately describe the basket configuration.
• (e) restates the operating principle and is correct.

Common Pitfalls:
Assuming all vertical natural-circulation evaporators are interchangeable with forced-circulation units for fouling services.

Final Answer:
It is used for high-viscosity liquor with a large tendency to scale.