Mechanical Operations problems
- 1. A tube mill as compared to a ball mill
Options- A. employs smaller balls.
- B. gives finer size reduction but consumes more power.
- C. has larger length/diameter ratio (>2 as compared to 1 for ball mill).
- D. all (a), (b) and (c). Discuss
Correct Answer: all (a), (b) and (c).
- 2. Bucket elevators are not suitable for the vertical lifting of __________ materials.
Options- A. fine (e.g. - 200 mesh size coal)
- B. sticky (e.g. clay paste)
- C. small lumpy (e.g. grains and sand)
- D. free flowing Discuss
Correct Answer: sticky (e.g. clay paste)
- 3. Traces of solids are removed from, liquid in a
Options- A. classifier
- B. clarifier
- C. sparkler filter
- D. rotary vacuum filter Discuss
Correct Answer: clarifier
- 4. Driving force in case of filtration by a centrifuge is the
Options- A. speed of the centrifuge.
- B. centrifugal pressure exerted by the liquid.
- C. narrow diameter of the vessel.
- D. formation of highly porous cake. Discuss
Correct Answer: centrifugal pressure exerted by the liquid.
- 5. Addition of filter aid to the slurry before filtration is done to ...... of the cake.
Options- A. increase the porosity
- B. increase the compressibility co-efficient
- C. decrease the porosity
- D. decrease the compressibility co-efficient Discuss
Correct Answer: increase the porosity
- 6. A. __________ mill is a revolving mill divided into two or more sections by perforated partitions in which preliminary grinding takes place at one end and the finishing grinding at the discharge end.
Options- A. compartment
- B. tube
- C. rod
- D. pebble. Discuss
Correct Answer: compartment
- 7. The study on washability of coal is done by using the __________ technique.
Options- A. tabling
- B. elutriation
- C. heavy media separation
- D. none of these Discuss
Correct Answer: heavy media separation
- 8. Kick's law assumes that the energy required for size reduction is proportional to the logarithm of the ratio between the initial and the final diameters. The unit of Kick's constant is
Options- A. kW. sec/kg
- B. kWh/kg
- C. kWh/sec. kg
- D. kg/sec. Discuss
Correct Answer: kW. sec/kg
- 9. For separation of sugar solution from settled out mud, we use a __________ filter.
Options- A. sparkler
- B. plate and frame
- C. centrifugal
- D. rotary drum vaccum Discuss
Correct Answer: centrifugal
- 10. Specific surface area is the surface area of a unit __________ of materials.
Options- A. weight
- B. volume
- C. either (a) or (b)
- D. neither (a) nor (b) Discuss
Correct Answer: either (a) or (b)
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