This set of Power Systems Multiple Choice Questions & Answers (MCQs) focuses on “Fuel Combustion and Combustion Equipments”.
1. Which of the following is not an advantage of stoker firing?
a) Zero capital investment
b) Greater combustion capacity
c) Uniform feeding of coal into furnance
d) Saving in labour cost
Explanation: Stokers are the mechanical arrangement which is used to feed coals into the furnace. Due to the mechanical equipment combustion capacity increases with uniform feeding of coal of into furnace, also labour cost is reduced. Stoker firing requires installation of mechanical stoker hence, capital investment requires.
2. In case of underfeed stokers fuel is supplied in the furnace _________
a) below the point of air admission
b) above the point of air admission
c) beside the point of air admission
d) by shovels
Explanation: Mechanical stokers are of two types namely underfeed stokers and overfeed stokers. The two differ in manner of feeding of coal below or above the level at which primary air is admitted in the furnace. In case of underfeed stokers fuel is supplied into the furnace below the point of air admission.
3. Which of the following is most advantageous and most widely method of solid fuel firing?
a) Stoker firing
b) Underfeed firing
c) Spreader stoker firing
d) Pulverised fuel firing
Explanation: The advantages of using pulverised fuel outweigh the disadvantages and all the modern power plants uses pulverised fuel firing method. In pulverised fuel firing better combustion is achieved. Pulverization is a means of exposing a large surface area to the action of oxygen and consequently helping the combustion.
4. What is the main disadvantage of spreader stoker?
a) Poor control
b) Difficult operation
c) More unwanted fly ash
d) Dangerous operation
Explanation: In spreader stoker the coal is not fed into the furnace by means of grate. Coal is fed by means of hopper, and function of grade is only to collect and remove the ash out of furnace. Spreader stokers can burn any type of coal from lignite to samianthracite, whether they are free burning or cocking. Their disadvantage is that fly ash is more.
5. 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.
6. 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) More than air required to burn lumped coal
d) No air required to burn the lapped coal
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.
7. Capital cost of pulverised fuel firing is less than hand firing.
Explanation: Hand firing does not require any capital investment. For pulverised fuel firing separate coal preparation plant is required which makes the installation expensive.
8. 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.
9. Coal burners are employed to fire the pulverised coal along with primary air in the furnace.
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.
10. 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.
Sanfoundry Global Education & Learning Series – Power Systems.
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