As the product becomes finer, the energy required for grinding___________________?

Related Mcqs:

1. The energy required per unit mass to grind limestone particles of very large size to 100 μm is 12.7 kWh/ton. An estimate (using Bond’s law) of the energy to grind the particles from a very large size to 50 μm is________________?

   A. 6.35 kWh/ton
   B. 9.0 kWh/ton
   C. 18 kWh/ton
   D. 25.4 kWh/ton

2. At low Reynold’s number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied: Po = ρ/ρN3 D5: Power number Re = ρ N D2/μ: Reynold’s number N is the impeller rotational speed, and D is the impeller diameter ?

   A. Po ∝ Re-1.0
   B. Po ∝ Re0.0
   C. Po ∝ Re0.5
   D. Po ∝ Re1.0

3. In coal washeries, three products namely the valuable product (i.e. clean/washed coal), discarded product (i.e. mineral matter) and an additional concentrated product called _____________ is produced?

   A. Concentrate
   B. Tailing
   C. Middling
   D. None of these

4. Which of the following gives the crushing energy required to create new surface ?

   A. Taggarts rule
   B. Fick’s law
   C. Rittinger’s Law
   D. None of these

5. 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_________________?

   A. kW. sec/kg
   B. kWh/kg
   C. kWh/sec. kg
   D. kg/sec

6. Which of the following equations is Rittinger’s crushing law? (Where P = power required by the machine, m = feed rate, k = a constant, D̅ sa & D̅ sb = volume surface mean diameter of feed & product respectively) ?

   A. P/m = K/ √Dp
   B. P/m = K . ln D̅ sa/D̅ sb
   C. P/m = K . (1/ D̅ sb – 1/D̅ sa)
   D. None of these

7. According to Bond crushing law, the work required to form particle of size ‘D’ from very large feed is (where (S/V)p and (S/V)f are surface to volume ratio of the product and feed respectively) ?

   A. (S/V)p
   B. √(S/V)p
   C. (S/V)2p
   D. (S/V)f

8. Work index is the gross energy (kWh/tonne of feed) necessary to reduce a very large feed to such a size that 80% of product particles will pass through a 0.1 mm screen. The value of work index determined for wet grinding should be multiplied with ______________ to get the same for dry grinding?

   A. 1.0
   B. 0.5
   C. 1.34
   D. 4.34

9. The power number for a stirred tank becomes constant at high Reynolds number. In this limit, the variation of power input with impeller rotational speed (N) is proportional to___________________?

   A. N°
   B. N1
   C. N2
   D. N3

10. Horsepower required for a roll crusher is directly proportional to its__________________?

    A. Reduction ratio
    B. Capacity
    C. Both A. & B.
    D. Neither A. nor B.