This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Recovery Boiler”.
1. The purpose of the recovery boiler is to recover the inorganic chemicals as smelt, burn the organic chemicals so they are not discharge from the mill as pollutants, and recover the heat of combustion in the form of heat.
Explanation: The purpose of the recovery boiler is to recover the inorganic chemicals as smelt, burn the organic chemicals so they are not discharge from the mill as pollutants, and recover the heat of combustion in the form of heat. Smelt is sodium carbonate and sodium sulfide.
2. There are three zones in recovery boilers; which are as follows in top to bottom order?
a) Oxidation, drying and reducing zone
b) Reducing, drying and oxidation zone
c) Drying, oxidation and reducing zone
d) Drying, reducing and oxidation zone
Explanation: The upper section is the oxidizing zone, the middle section is the drying zone, and the bottom section is the reducing zone where, in a bottom bed of char, the sulphur compounds are converted to Na2S.
3. What is the full form of ESP in Recovery boiler?
a) Emergency shutdown point
b) Emergency shutdown procedure
c) Emergency start procedure
d) Emergency shared procedure
Explanation: Due to the possible adverse reaction of molten smelt with water, all recovery boilers have an ESP in the event of trouble.
4. The newest recovery boilers may support 2500-3000 tons of pulp production per day.
Explanation: The recovery boiler is the largest and the most expensive equipment in the Kraft mill costing over 100 million dollars.
5. Which of the following is the chemical react. in the recovery boiler in addition to combustion?
a) 2NaOH + CO2U → Na2CO2+H2O and Na2SO2 +4C ↔ 6Na2S + 4CO
b) 2NaOH + CO2 → Na2CO2 and Na2SO2+4C ↔ 4CO
c) 2NaOH + CO2 → Na2CO2+H2O2 and Na2SO2+4C ↔ Na2S +4CO2
d) 2NaOH + CO2 → Na2CO2+H2O and Na2SO2+4C ↔ Na2S +4CO
Explanation: The lower zone is deficient in oxygen, so reduction reaction occurs. This allows the sulfur (S) in the smelt to occur as Na2S2O2 or Na2SO2, which could be unsuitable for fresh liquor.
6. Which of the following is the reaction which takes place in the Oxidation zone in the Recovery Boiler?
a) CO+1/2O2 → CO2
b) Organics →C+CO+H2
c) C+H2O → CO+ H2
d) 2C+ O2→2CO
Explanation: Oxygen is made to react with the species. Simple oxidation reaction.
7. Which of the following is the reaction which takes place in the Drying zone in the Recovery Boiler?
a) Organics→C+CO+ H2
b) CO+1/2 O2→ CO2
c) C+ H2O→CO+ H2
d) 2C+ O2→2CO
Explanation: This is the part where black liquor is injected to the system.
8. Which of the following is the reaction which takes place in the Reduction zone in the Recovery Boiler?
a) Na2SO2+4C→Na2S+4 CO
b) 2C+ O2→2CO
c) CO+1/2 O2→CO2
d) H2S+1/2 O2→SO2+ H2O
Explanation: This is the part where sulfur compounds are converted to Na2S.
9. Fill in the blank.
thermal efficiency =(__________)/total heat input
a) steam to heat
b) heat to steam
c) heat recovery
Explanation: Many of the heat loss has occurred as steam in flue gases from water in black liquor.
10. What is cogeneration?
a) Producing electricity from steam
b) Producing steam from electricity
c) Producing light from steam
d) Producing power from steam
Explanation: Cogeneration is the process of producing electricity from steam and utilizing the waste heat as steam in chemical processes.
Sanfoundry Global Education & Learning Series – Pulp and Paper.
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