This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Kraft Pulping”.
1. Kraft pulping is a full chemical pulping method using sodium hydroxide and sodium sulfide at pH above 12.
a) True
b) False
View Answer
Explanation: Kraft pulping is a full chemical pulping method using sodium hydroxide and sodium sulfide at pH above 12. At 160 – 180 degree celcius, corresponding to about 800kPa steam pressure, for 0.5 – 3 hours to dissolve much of the lignin of wood fibers.
2. Wood species is an important variable during Kraft cooking process.
a) True
b) False
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Explanation: Wood species (though all species can be pulped) and chip geometry.
3. The degree of Kraft cook for bleachable grades of pulp, have a lignin content of 3 – 5.2% for softwood and 1.8 – 2.4% for hardwood.
a) Soft
b) Medium
c) Hard
d) Ultra
View Answer
Explanation: In softwood degree of Kraft cook for bleachable grades of pulp, have a lignin content of 3 – 5.2% for softwood and 1.8 – 2.4% for hardwood.
4. What is the correct definition of H – factor?
a) It is a pulping variable that combines ignition temperature and time into a single variable
b) It is a pulping variable that combines cooking temperature and time into a single variable
c) It is a pulping variable that combines sublimation temperature and time into a single variable
d) It is a pulping variable that combines vaporization temperature and time into a single variable
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Explanation: It is a pulping variable that combines cooking temperature and time into single variable that indicates the extent of the reaction.
5. __________ is a fresh pulping liquor for the Kraft process, consisting of the active pulping species NaOH and Na2S, small amounts of Na2CO3.
a) Black liquor
b) White liquor
c) Red liquor
d) Green liquor
View Answer
Explanation:White liquor is a fresh pulping liquor for the Kraft process, it consist of the active pulping species NaOH and Na2S, small amounts of Na2CO3.
6. __________ is the waste liquor from the Kraft pulping process after pulping is completed.
a) Black liquor
b) White liquor
c) Red liquor
d) Green liquor
View Answer
Explanation: Black liquor is the waste liquor from the Kraft pulping process after pulping is completed.
7. __________ is the partially recovered form of Kraft liquor. It is obtained after burning of the black liquor in the recovery boiler.
a) Black liquor
b) White liquor
c) Red liquor
d) Green liquor
View Answer
Explanation: Green liquor is produced by dissolving the smelt from the recovery boiler in the water.
8. Fill in the blank.
__________ =(Na2S)/(NaOH + Na2S)X 100%
a) Sulfifdity
b) Causticity
c) Effective alkali
d) Active alkali
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Explanation: Sulfidity of white liquor is the ration of Na2S to the active alkali, expressed as percent. A mill runs in the vicinity of 24-28% sulfidity, depending largely on the wood species pulped.
9. Fill in the blank.
__________ =(NaOH)/(NaOH + Na2S)X 100%
a) Sulfifdity
b) Causticity
c) Effective alkali
d) Active alkali
View Answer
Explanation: Causticity is the ratio of NaOH to active alkali (as always both chemicals are on a Na2O basis), expressed as a percentage.
10. Fill in the blank.
__________ =(Na2S)/(Na2SO4 + Na2S)X 100%
a) Reduction efficiency
b) Causticity
c) Effective alkali
d) Active alkali
View Answer
Explanation: The ratio of Na2S to Na2S and Na2SO4 in green liquor is called reduction efficiency. This is a measure of reduction efficiency of sulfur in the recovery boiler.
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