ANS:B - 50

The speed of a rotary drum vacuum filter typically ranges around 1 to 2 revolutions per minute (rpm). Here's why:

1. Rotary Drum Vacuum Filter:
   • These filters operate slowly because they rely on the rotation of a drum to achieve filtration and cake formation.
   • The slow rotation allows for effective cake formation and dewatering without disturbing the filter cake.
2. Typical Speed:
   • Speeds for rotary drum vacuum filters are usually in the range of 0.5 to 2 rpm, depending on the size of the filter and the characteristics of the material being filtered.
   • Very high speeds are not necessary and can lead to inefficiencies or disruption of the filtration process.

• 1 rpm is the most appropriate speed for a rotary drum vacuum filter, ensuring efficient filtration and cake formation while maintaining operational stability.