1. Which pulping process is suitable for manufacturing of the middle layer of multi-ply boards?
a) Mechanical pupling
b) Kraft pulping
c) Thermomechanical pulping
d) Chemithermomechanical pulping
Discussion
Explanation: Chemithermomechanical pulping – CTMP is suitable for the middle layer of multi-ply boards. It is because CTMP pulps have a greater long fiber fraction and lower fines fraction than comparable thermomechanical pulping -TMP pulps.
2. What is used for pretreatment in Chemithermomechanical pulping?
a) Calcium propionate
b) Calcium carbonate
c) Sodium nitrate
d) Sodium sulfite
Discussion
Explanation: Chemithermomechanical pulping (CTMP) pulps are obtained by a comparatively mild chemical treatment followed by pressurized refining. Sodium sulfite is used for the mild chemical pretreatment. It increases the strength properties of TMP pulps even further.
3. . Thermal treatment increases flexibility of mechanical pulps.
a) True
b) False
Discussion
Explanation: The given statement is true. Thermomechanical pulping (TMP) presteams chips between 110°C and 150°C so that they become malleable and do not fracture readily under the impact of the refiner bars. This material is highly flexible and gives good bonding and surface smoothing to the paper.
4. Chemical pulping mostly uses which of the following chemical?
a) Sodium Nitrate
b) Potassium Hydroxide
c) Calcium Carbonate
d) Sodium Hydroxide
Discussion
Explanation: All chemical pulping methods are based, either directly or indirectly, on the use of sodium hydroxide. The chemical is selectively chosen, because, the nature of the pulping chemicals influences the properties of the residual lignin and the residual carbohydrates.
5. The primary goal of chemical pulping is to selectively remove as much lignin as possible.
a) True
b) False
Discussion
Explanation: The given statement is true. The primary goal of chemical pulping is to selectively remove as much lignin as possible, especially from the middle lamella, without degrading the carbohydrate components and negatively effecting pulp properties.
6. The kappa number of bleachable softwood pulps is _______
a) 10-20
b) 20-30
c) 30-40
d) 40-50
Discussion
Explanation: The kappa number of bleachable softwood pulps is 30–40. The pulp and paper industry uses the “kappa number” to express the lignin content of a pulp, a high kappa number indicating high lignin content.
7. The kappa number of bleachable hardwood pulps is ________
a) 20–30
b) 30–40
c) 10–20
d) 18–20
Discussion
Explanation: The kappa number of bleachable hardwood pulps is 18–20. This indicates that hardwood pulp has lower lignin content than softwood pulp. Lignin does not have fiber forming properties, hence, hardwood pulp does not make as strong paper as softwood pulp.
8. Chemical pulping method uses acid for the process.
a) True
b) False
Discussion
Explanation: The given statement is false. Chemical pulping method uses alkali for the process. It includes- soda process, kraft process and sulfite process, all of which used sodium hydroxide (alkali) either directly or indirectly.
9. Kraft process is also known as ______
a) Soda process
b) Sulphate process
c) Sulphite process
d) Semichemical process
Discussion
Explanation: Kraft process is also known as sulphate process. It is commonly called kraft, because it is the German and Swedish word for strength. The new sulfate process produced a much stronger pulp than that from the soda process.
10. Which of the following is also known as the white liquor?
a) Sodium hydroxide and Sodium hydride
b) Sodium sulphite and Sodium sulphate
c) Sodium sulphate and Sodium hydroxide
d) Sodium hydride only
Discussion
Explanation: A solution of sodium hydroxide and sodium hydride is also known as the white liquor. It is widely used in the chemical pulping industry for cooking the wood chips, hence, also called cooking liquor.