This set of Power Plant Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Deaerator – 2”.
1. Which of the following type heater is known as deaerator?
a) Contact-type open heater
b) Contact-type closed heater
c) Closed heater
d) None of the mentioned
View Answer
Explanation: A deaerator is a closed-type open feedwater heater while all the other heaters are closed heaters.
2. What is the solubility of dissolved gases at boiling or saturation temperature?
a) Positive
b) Negative
c) Zero
d) None of the mentioned
View Answer
Explanation: The solubility of dissolved gases in water decreases with an increase in pressure and becomes zero at boiling or saturation temperature.
3. In the deaerator, the feedwater is heated to the saturation temperature by the steam extracted from?
a) compressor
b) turbine
c) pump
d) none of the mentioned
View Answer
Explanation: The steam extracted from the turbine is used to heat the feedwater to the saturation temperature.
4. The heat exchanger after passing through which, the feedwater is sprayed from the top is called?
a) Vent condenser
b) Vent evaporator
c) Vent economiser
d) Vent heater
View Answer
Explanation: Feedwater after passing through a heat exchanger, is sprayed from the top & bled steam from the turbine is fed from the bottom.
5. What kind of steam comes through the other side of the feedwater spray?
a) pure steam
b) bled steam
c) saturated steam
d) superheated steam
View Answer
Explanation: Feedwater after passing through a heat exchanger, is sprayed from the top & bled steam from the turbine is fed from the bottom.
6. The chemical injected into the feedwater at the suction of the boiler feed pump is?
a) Sodium Sulphide
b) Sodium Sulphate
c) Sodium Sulphite
d) Sodium Hydride
View Answer
Explanation: To minimise the effect of the residual dissolved oxygen & carbon dioxide gases in water, Sodium Sulphite & Hydrazine are injected in suitable calculated doses into the feedwater at the suction of the boiler feed pump.
7. Why is Sodium Sulphite added into the feedwater at the suction of the boiler feed pump?
a) to maximise the effect of dissolved gases
b) to minimise the effect of dissolved gases
c) to increase feedwater concentration
d) none of the mentioned
View Answer
Explanation: To minimise the effect of the residual dissolved oxygen & carbon dioxide gases in water, Sodium Sulphite & Hydrazine are injected in suitable calculated doses into the feedwater at the suction of the boiler feed pump.
8. Name another chemical apart from Sodium Sulphite which is into the feedwater at the suction of the boiler feed pump?
a) Calcium peroxide
b) Hydroxide
c) Hydrazine
d) Oxymes
View Answer
Explanation: To minimise the effect of the residual dissolved oxygen & carbon dioxide gases in water, Sodium Sulphite & Hydrazine are injected in suitable calculated doses into the feedwater at the suction of the boiler feed pump.
9. Where is the deaerator placed in the feedwater system?
a) in the beginning
b) in the middle
c) at the end
d) there is no deaerator in the feedwater system
View Answer
Explanation: The deaerator is usually placed in the middle of the feedwater system so that the total pressure difference between the condenser & the boiler is shared equally between condensate pump & boiler feed pump.
10. Why is the deaerator placement in the feedwater system so important?
a) to maximise pressure difference between the condenser & the boiler
b) to minimise pressure difference between the condenser & the boiler
c) to make the pressure difference between the condenser & the boiler Zero
d) none of the mentioned
View Answer
Explanation: The deaerator is usually placed in the middle of the feedwater system so that the total pressure difference between the condenser & the boiler is shared equally between condensate pump & boiler feed pump.
11. Which gases are vented out of the deaerator?
a) Oxygen only
b) Carbon dioxide only
c) Oxygen & Carbon dioxide
d) None of the mentioned
View Answer
Explanation: The exhaust of the feedwater deaerator contains Oxygen & Carbon dioxide both.
12. Net positive suction head(NPSH) is provided because?
a) to prevent vapour lock
b) to prevent cavitation
c) to prevent friction
d) none of the mentioned
View Answer
Explanation: In order to prevent the cavitation arising, a net positive suction head is provided for the pump. The deaerator is placed at a sufficient height from the basement.
13. The output of the boiler heat pump is to?
a) the high pressure heater
b) the low pressure heater
c) simultaneously to the low & high pressure heaters
d) none of the mentioned
View Answer
Explanation: The Boiler feed pump give an output which goes to the high pressure heater.
14. Why is the deaerator not employed in water cooled & moderated nuclear power plant?
a) due to radioactivity release in degeneration
b) due to emissivity of degeneration
c) due to reheating
d) due to regeneration
View Answer
Explanation: The deaerator is not employed in water cooled & moderated nuclear power plant because of the radioactivity released in degeneration.
15. Which among the following goes to the Vent Condenser along with Oxygen & Carbon dioxide?
a) Sodium sulphite
b) Carbon monoxide
c) Water vapour
d) None of the mentioned
View Answer
Explanation: The gases Oxygen, Carbon dioxide & Water vapour are subjected to the vent condenser wherein the moisture gets absorbed & so the exhaust gases vented out are Oxygen & Carbon dioxide.
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