Food Processing Unit Operations Multiple Choice Questions on “Crystallization Equipment”.
1. What are the advantages of vacuum crystallizers?
a) Low yield of crystals
b) Small crystals
c) Increase in color formation
d) Reduced color formation
Answer: d
Clarification: Advantages of vacuum crystallizers are controlled crystallization and bigger and more uniform crystals. Reduced color formation and high yield of crystals.
2. What is the principle behind forced-circulation crystallizers?
a) Evaporative crystallization
b) Cooling crystallization
c) Perceptive cooling crystallization
d) Freezing crystallization
Answer: a
Clarification: Forced circulation crystallizers are evaporative crystallizers. They create a super saturated solution by evaporating solvent of the saturated solution. The solute of this supersaturated solution cools down, thus forming the crystals.
3. Are these statements about the Forced circulation crystallizers true?
Statement 1: Difficult to control crystal size.
Statement 2: Least expensive type of crystallizer.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Advantages of membrane separation process are least expensive type of crystallizer and high rate of circulation reduces particle deposits on vessel walls and limitation is that difficult to control crystal size.
4. What is the name of the unwanted crystals in draft tube baffle crystallizers?
a) Fines
b) Powder
c) Soap
d) Low quality crystals
Answer: a
Clarification: The draft Tube Baffle crystallizers are used where excessive nucleation occurs. Small, and unwanted crystals called as fines are removed from larger particles using gravitational settling method.
5. What is residence time for draft tube baffle crystallizers?
a) 1 to 3 hours
b) 4 to 6 hours
c) 7 to 9 hours
d) 10 to 11 hours
Answer: b
Clarification: The draft tube baffle crystallizers usually have circulation rates of 1 to 4 times/min and a total residence time of 4 to 6 hours.
6. Are these statements about the draft tube baffle crystallizers true?
Statement 1: Frequent flushing required minimizing deposits on the crystallizer wall.
Statement 2: Cannot effectively handle a high density slurry
a) True, False
b) True, True
c) False, True
d) False, False
Answer: b
Clarification: Disadvantages of draft tube baffle crystallizers frequent flushing required minimizing deposits on the crystallizer wall and cannot effectively handle a high density slurry whereas the merits are easy control of crystal size and more energy efficient.
7. What is surface-cooled crystallizer?
a) Combination of draft tube baffle crystallizer body with a heat exchanger
b) Combination of forced circulation crystallizer body with a heat exchanger
c) Combination of vacuum body with a heat exchanger
d) Combination of crystallizer body with a heat exchanger
Answer: a
Clarification: The surface cooled crystallizer is the combination of a draft tube baffle crystallizer body with a heat exchanger. The slurry is strained from the crystallizer body and then cooled before being pumped back into crystallizer.
8. What is not true about scraped surface crystallizers?
a) Low energy
b) Low cost
c) Ideal for small scale operation
d) Less consumption of time
Answer: d
Clarification: The advantages of scraped surface crystallizers are that it has low energy, low cost, ideal for small scale operations. These are used mainly for the crystallization of melts.
9. Is organic substance produce by cooling crystallizers?
a) True
b) False