Best conveyor for gummy and sticky materials (e.g., molasses, sugar pastes):\nWhich conveyor is generally preferred for transporting sticky, pasty materials?

Introduction / Context:
Material handling selection depends strongly on rheology. Sticky and pasty materials such as molasses-bearing mixes or moist sugar pastes can pack, smear, or bridge in open conveyors. Enclosed positive-displacement devices that force material along a trough with a rotating helix are widely used to overcome these issues.

Given Data / Assumptions:

• Material exhibits stickiness and some plasticity.
• Short-to-moderate conveying distances.
• Desire for containment and simple cleanup.

Concept / Approach:
Screw conveyors provide continuous, forced conveying in an enclosed trough, tolerating sticky or pasty consistencies better than drag or slat systems which can experience carryback and chain fouling. Ribbon screws (a variant) improve mixing and reduce buildup for especially gummy products. Drag and slat conveyors are excellent for granular/packaged materials but struggle with smear-prone pastes. Vibratory troughs work with free-flowing powders/granules; pasty materials may rat-hole or adhere excessively.

Step-by-Step Solution:

Verification / Alternative check:
Food and chemical plants routinely specify screw/ribbon screws for molasses, wet sugar mixes, and similar pastes.

Why Other Options Are Wrong:

• Drag/slat: chains and flights foul with sticky materials.
• Ribbon conveyor (as a type of belt): belts slip and cake; “ribbon screw” is different.
• Vibratory: best for free-flowing solids.

Common Pitfalls:
Confusing “ribbon conveyor” (a belt variant) with “ribbon screw” (a screw type). The latter indeed helps with pastes, but it is still a screw conveyor.

Final Answer:
Screw conveyor