This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Pulp Washing”.
1. Pulp washers are also known as ‘Black stock washers’.
a) True
b) False
View Answer
Explanation: Pulp washers are called so because of the color of the raw material which is utilized to feed the tank. The crude material is of dirty black color which is then washed.
2. Pulp washers use counter-current flow between stages such that the pulp moves opposite in direction to the flow of wash water.
a) True
b) False
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Explanation: This design allows for the most removal of pulping material and the lignin with the least amount of water.
3. Following the reason behind the removal of lignin in Pulp washers:-
a) To reduce bleaching chemical demand
b) To increase bleaching chemical demand
c) To maintain constant bleaching chemical demand
d) To freeze bleaching chemical demand
View Answer
Explanation: To reduce bleaching chemical demand. This is done to improve paper making with brown papers.
4. The dilution factor is a measure amount of ___________ used in washing.
a) Acid
b) Base
c) Water
d) Salt
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Explanation: The dilution factor is a measure of the amount of water used for washing. It’s compared to the amount theoretically required to displace the liquor from the thickened pulp.
5. Following is the way to calculate dilution factor:-
a) Mass of water per unit mass of dry pulp
b) Mass of acid per unit mass of dry pulp
c) Mass of buffer solution per unit mass of dry pulp
d) Mass of base per unit mass of dry pulp
View Answer
Explanation: The dilution factor is a measure of the amount of water used in washing. It is compared to the amount theoretically required to displace the liquor from the thickened pulp.
6. Low dilution factor ___________ the energy requirements of the multiple effects evaporators.
a) Increases
b) Decreases
c) Freezes
d) Skips
View Answer
Explanation: Low dilution factor decrement the energy requirements of the multiple effects evaporators. Using more washers increment removal of pulping chemicals with less water dilution but increment capital and operating costs.
7. The soda loss in pulp is traditionally measured as ___________ pulp on a Na2SO4 basis.
a) Kg/lb
b) Lb/kg
c) Lb/ton
d) Ton/lb
View Answer
Explanation: The soda loss in pulp is traditionally measured as lb/ton pulp on a Na2SO4 basis.
8. A ___________ is used to siphon the water from the washer so that a vacuum pump is not usually required.
a) Drop hand
b) Drop leg
c) Drop finger
d) Drop thumb
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Explanation: A drop leg is used to siphon the water from the washer so that a vacuum pump is not usually required. The bottom leg goes to a filtrate storage tank that is designed to prevent air from entering.
9. The vacuum supplied by drop leg for the first stage is of range ___________
a) 12kPa
b) 15kPa
c) 20kPa
d) 24kPa
View Answer
Explanation: A drop leg is used to siphon the water from the washer so that a vacuum pump is not usually required. The bottom leg goes to a filtrate storage tank that is designed to prevent air from entering.
10. Drop leg is ideally a vertical drop. It’s horizontal section is a needed, and it should be exactly horizontally placed at least __________m below the washer.
a) 1
b) 5
c) 55
d) 7
View Answer
Explanation: Drop leg is ideally a vertical drop. It’s horizontal section is needed which should be horizontally placed at least 7 m below the washer. Drop legs that are not entirely horizontal or vertical allow air to separate from the stock and rush upward, thereby accumulating and decreasing the vacuum.
Sanfoundry Global Education & Learning Series – Pulp and Paper.
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