ANS:B - sticky (e.g. clay paste)

Bucket elevators are not suitable for the vertical lifting of sticky (e.g., clay paste) materials. Here's why:

1. Fine materials (e.g., -200 mesh size coal):
   • Bucket elevators can handle fine materials, provided they are free-flowing and not prone to dusting excessively.
2. Sticky materials (e.g., clay paste):
   • Sticky materials can cause significant issues in bucket elevators as they tend to adhere to the buckets and the casing, leading to clogging and maintenance problems.
3. Small lumpy materials (e.g., grains and sand):
   • Bucket elevators are well-suited for handling small lumpy materials like grains and sand, as they can be easily scooped up and transported without sticking.
4. Free-flowing materials:
   • Bucket elevators are ideal for free-flowing materials, as they can be efficiently lifted vertically without any issues.