1. Which do you mean by pulverization?
a) Burning of crushed coal
b) Burning of uncrushed coal
c) Crushing of coal into small partials
d) Breaking coal into small particsl
Explanation: Pulverization is crushing of coal into fine particles. This exposes large surface area to the action of oxygen and consequently helps the combustion. Solids fuels can be used in a powderd and burn like oil and gas.
2. What is the amount of air required to burn the pulverised coal?
a) Less than air required to burn lumped coal
b) More than air required to burn lumped coal
c) No air required to burn the lapped coal
d) None of the Above
Explanation: The surface area of pulverised coal is increased in almost the ratio of 400:1, therefore high rates of combustion are possible. Moreover a smaller quantity of air is required than when the fuel is burnt in lumped form
3. Capital cost of pulverised fuel firing is less than hand firing.
a) True
b) False
Explanation: Hand firing does not require any capital investment. For pulverised fuel firing separate coal preparation plant is required which makes the installation expensive.
4. What is the main requirement of good coal burner?
a) Minimum operating and maintenance cost
b) Production of uniform flame with complete combustion
c) The burner should be easy to handle and control
d) Attainment of proper designed
Explanation: Main requirement of good coal burner is complete combustion with production of uniform flame. Minimum operating and maintenance cost, simplicity in operation, attainment of proper design all are requirements of complete combustion.
5. Coal burners are employed to fire the pulverised coal along with primary air in the furnace.
a) True
b) False
Explanation: Coal burner’s fire pulverised coal with stream of primary air into the furnace. Secondary air is then admitted separately below the burner, around the burner or elsewhere.
6. Spread stockers can be employed for boiler capacitors of _________
a) 1000 kg/hr – 14000 kg/hr
b) 586 kg/hr – 1086 kg/hr
c) 1500 kg/hr – 40000 kg/hr
d) 70,000 kg/hr – 140,000kg/hr
Explanation: In spreader stoker coal is fed from the coal hopper into the path of the rotor by means of a conveyor and rotor throws the coal into the furnace. Grate collects the ash and moves it out of the furnace.
7. 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
8. 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.
9. 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.
10. 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.