This set of Power Systems Multiple Choice Questions & Answers (MCQs) focuses on “Feed Water”.
1. Which of the following is not a reason of heating feed water?
a) It improves overall efficiency
b) It removes dissolved impurities
c) It prevents from thermal stress which may cause due to enter of cold water into boiler
d) It produces steam from feed water
Explanation: Steam production is work of boiler. Feed water is heated only for four reasons : to improve overall efficiency, to remove dissolved impurities, to avoid thermal stress going to entering of cold water to the boiler and to precipitate impurities carried by steam and condensate outside the boiler.
2. Feed water for boiler of thermal power plant is obtained from:
a) Natural sources like river and lake
b) Partly from condensed steam and natural sources
c) Condensed steam and small percentage from natural resources
d) Natural sources and small percentage from condensed steam
Explanation: The steam coming out of turbines is condensed and the condenset is fed back to the boiler. Some of water losses due to the blow-down, leakage etc.. and to make up these losses additional water called “makeup water” is taken from natural sources after treatment. This makeup water is obtained from natural sources like river and lake and about 1 – 4% of total feed water.
3. Mechanical method of water treatment is done to _____________
a) Heat the feed water
b) To remove solid matter and impurities
c) To add some solid materials
d) To remove dissolved gases
Explanation: Mechanical method of water treatment involvs sedimentation and filtration. During sedimentation water kept at standstill or flow with a very low velocity which causes the solid matter to settle down and finally removed. During filtration the dirty water is allowed to flow downword through the beds of filtering materials to remove suspended matters.
4. Which method is used in large modern thermal power plants to heat feed water?
a) Open type heatre is used
b) Close type heater is used
c) Steam is directly taken from main turbine and used to heat it feed water
d) Surface type heater is used
Explanation: Open and contact type haters are in small power plants. Such heaters recives steam from back pressure turbine. In large modern power plants heaters bleed steam from the main turbine and use it for heating of feed water.
5. Thermal treatment methods used to remove impurities like:
a) Dissolved carbon dioxide and other gases
b) Solid materials
d) Bacterial impurities
Explanation: Thermal treatment method involves distillation and derative heating of feed water. During distillation water is evaporated then condensed and collected. During derating heating water is broken up into fine droplets and heated to produced vapour within the deaerator. During these process carbon dioxide and other days of devices separated from feet water.
6. Heat treatment arrangement used to separate or remove deserved gases and impurities from feed water is called the year later.
Explanation: A deaerator is a device that is widely used for the removal of oxygen and other dissolved gases from the feedwater to steam-generating boilers. These gases make house corrosion scale formation.
7. Chemical method of treatment is used for treatment of:
a) Diissolve gases
b) Carbonate and carbon dioxide
c) Bacterial impurities
d) Send and suspended materials
Explanation: Chemical treatment involvs line treatment, soda treatment, lime and soda treatment. Zeolite treatment and demineralisation. Iime treatment is done for treatment of carbonate hardness, carbon dioxide in water. soda treatment is done for treatment of water containing non carbonate hardness and line soda treatment is used when both carbonate and none carbonate hardness for feed water.
8. Scall formation in boiler tube causes ____________
a) reduction of heat transfer and overheating of boiler tube
b) corrosion of boiler surface
c) feeling up of steam passage
d) cracks in the ages rivites
Explanation: Dissolved gases include oxygen and carbon dioxide which may lead to scale formation corrosion, carry over and imbrittlement in boiler and other apprature. Scale formation reduces the heat transmission through the heating surface.
Sanfoundry Global Education & Learning Series – Power Systems.
To practice all areas of Power Systems, here is complete set of 1000+ Multiple Choice Questions and Answers.