This set of Food Processing Unit Operations Multiple Choice Questions & Answers (MCQs) focuses on “Crystallizers”.
1. What is the main feature of circulating liquid crystallizer?
a) Efficiency is high
b) Supersaturation is created in a separate region
c) Low capital cost
d) Easy maintenance
View Answer
Explanation: The specialty of circulating liquor crystallizer is that supersaturation is produced in a separate region before the liquor flows into crystal suspension vessel.
2. What is evaporative crystallization?
a) Evaporation of the solvent
b) Separate components at higher temperature
c) Separate components at lower temperature
d) Mix components at higher temperature
View Answer
Explanation: Crystallization is due to evaporation of the solvent. It creates a vapor and a suspension of crystals in the mother liquor. The evaporation heat is added in the vapor stream.
3. Which of the manufacturing unit use melt crystallizers?
a) Ice creams
b) Automobiles
c) Salt preparation
d) Semiconductor
View Answer
Explanation: Crystals form in these crystallizers is from the high-quality melts which has large yields, pure and defect free crystals. These are typically used for semiconductor manufacture.
4. How are crystals in precipitation vessels?
a) Small size
b) Large size
c) Medium size
d) Very large size
View Answer
Explanation: In precipitation vessels, the feed streams entering the vessel produce high supersaturation levels by chemical reaction and therefore produces very rapidly a large numbers of small crystals.
5. Which of the following statements about crystallizers design are correct?
Statement 1:Selection of supersaturation generation method is not necessary.
Statement 2:Choice of batch or continuous operation is important.
a) True, False
b) True, True
c) False, True
d) False, False
View Answer
Explanation: A crystallizer’s design sequence involves the basic data collection following selection of the supersaturation generation method and choosing the batch/continuous operation.
6. What is salting out process?
a) Addition of salt to precipitate the product from solvent
b) Addition of salt to precipitate the product from solution
c) Removal of salt to in the product
d) Removal of salt to precipitate the product from solution
View Answer
Explanation: Salting out is the process where salt with common ion is added to precipitate product from solution. This is similar to the characteristics of reaction crystallization.
7. How is product purity increased?
a) Boiling
b) Sweating
c) Freezing
d) Adding solute
View Answer
Explanation: The purity of is increased by sweating process. In this process, the impurities are removed out of the solidified crystals before recovery process. The period of released pressure from the substance is used as sweating time
8. What are the key parameters of rate of generation of supersaturation?
a) Cooling and addition rate
b) Evaporation and addition rate
c) Cooling and evaporation
d) Cooling, evaporation or addition rate
View Answer
Explanation: This is a low temperature distillation method which allows for separation of nonvolatile, water immiscible substances at temperatures below boiling point of individual constituents. This preserves components that will be disrupted at high temperatures.
9. Which of the following statements about continuous crystallizers are correct?
Statement 1:These produce a consistent product.
Statement 2: More energy efficient.
a) True, False
b) True, True
c) False, True
d) False, False
View Answer
Explanation: Continuous crystallizers produce a consistent product and more energy efficient than batch process. Therefore the continuous crystallizers are used in high-production rate systems. More process knowledge is required.
10. Is feed rate the only adjustable parameter in continuous crystallizers?
a) True
b) False
View Answer
Explanation: The only adjustable parameters in the continuous crystallizers are usually the feed rate, residence time and supersaturation generation rate.
Sanfoundry Global Education & Learning Series – Food Processing Unit Operations.
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