This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Type of Stokers – 1”.
1. In what aspect does chain gate travelling stoker and bar grate travelling stoker differ?
a) Differ in supply of reactants
b) Differ in process of operation
c) Differ in construction
d) Differ in terms of feeding mechanism
Explanation: The travelling grate stoker may be of chain grate type or bar grate type. These two, differ only in the construction of grate. The chain stoker employs an endless chain which is constructed to form a support for the fuel bed. The traveling grate stoker consists of grate bars carried by steel chains.
2. How does the chain run in travelling grate stoker?
Explanation: The chain travels over two sprockets. In both chain type and in bar type stokes. One sprocket is placed at the front end and other sprocket is placed at the rear end of the furnace. The front sprocket is connected to a variable speed driving mechanism.
3. In what way is the supply coal/fuel is done in travelling grate stoker?
a) Screw conveyor
c) Reciprocating mechanism
d) Gravity hopper
Explanation: The coal is fed by gravity from a hopper located in front of the stoker. The depth of fuel on the grate is regulated by hand adjusted gate. The speed of the grate varies at the rate at which the coal is fed to the furnace.
4. Automatic combustion control in travelling stoker regulates speed of grate to maintain ____________
a) Steam generation
b) Air flow
c) Fuel supply
d) Conveyor speed
Explanation: The combustion control automatically regulates the speed of the grate to maintain the required steam generation rate. The ash containing a small amount of combustible material is carried over the rear end of the stoker and deposited in the ash pit.
5. Depending on what factor are the air ducts opened and closed in travelling grate stoker?
a) On the type of grate used
b) On the speed that is attained
c) On the type of coal used
d) Depending on intensity of boiler
Explanation: Depending on type of coal burned, the grate has air openings in the range of 20-40 percent of the total area. The air supply to different parts of the stoker is regulated to meet the changing demand through these sections.
6. What does both primary and secondary air ports combined provide in travelling grate stoker?
b) Evaluating temperature
d) Heat intensity
Explanation: The air required for the combustion is supplied through the air inlets situated the below the grate. The secondary air is supplied through the openings provided in the furnace will be above the grate. The combination of primary air and over fire supplied provide turbulence required for rapid combustion.
7. Why is it necessary to control burning in different areas of travelling grate stoker?
a) Minimize the coke carried into ash pit
b) To avoid the smoke
c) To form a maintain temperature throughout the stoker
d) To get the proper efficiency
Explanation: The operator controls rate of burning in different zones to minimize the coke carried over to ash pit. The coal supplied to the grate is regulated either by varying depth of coal on the grate with the help of grate valve and by varying the rate of grate travel.
8. Which type of coal fuel is avoided in travelling grate stoker?
a) Anthracite coal
c) Pulverized coal
d) Caking bituminous
Explanation: Any type of fuel except caking bituminous coal can be used with travelling grate stoker because of the formation of large percentage of fines resulting in increased carbon loss. The rate of burning of fuel in this stoker is 200 to 300kg/m2 per hour when forced draught is used.
9. What type of stoker is spreader/sprinkler stoker?
a) Over feed
b) Single retort
c) Multi retort
d) Under feed
Explanation: Spreader stoker is an over feed type of stoker. The coal burned on this stoker remains partly in suspension and partly on the grate. The spreader stoker consists of variable feeding device, a mechanism for throwing the coal uniformly on the grate and suitable openings for admitting the air.
10. Where is the coal feeding mechanism located in spreader type stoker?
a) Above the grate
b) Right side of the grate
c) Left side of the grate
d) Below the grate
Explanation: The coal feeding and distribution mechanism is located in the front above the grate of a spreader stoker. A portion of coal is supplied containing fine particles fine particles of coal burns in suspension and remaining falls to the grate.
Sanfoundry Global Education & Learning Series – Energy Engineering.
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