Power Plant Engineering Objective Questions
76. The maximum length of a screw conveyer is about
(a) 30 metres
(b) 40 metres
(c) 60 metres
(d) 100 metres
Ans: a
77. The efficiency of a modern boiler using coal and heat recovery equipment is about
(a) 25 to 30%
(b) 40 to 50%
(c) 65 to 70%
(d) 85 to 90%
Ans: d
78. The average ash content in Indian co als is about
(a) 5%
(b) 10%
(c) 15%
(d) 20%
Ans: d
79. Load centre in a power station is
(a) centre of coal fields
(b) centre of maximum load of equip-ments
(c) centre of gravity of electrical system
Ans: c
80. Steam pressure in a steam power station, which is usually kept now-a-days is of the order of
(a) 20 kgf/cm2
(b) 50 kgf/cm2
(c) 100 kgf/cm2
(d) 150 kgf/cm2
Ans: d
81. Economisers improve boiler efficiency by
(a) 1 to 5%
(b) 4 to 10%
(c) 10 to 12%
Ans: b
82. The capacity of large turbo-generators varies from
(a) 20 to 100 MW
(b) 50 to 300 MW
(c) 70 to 400 MW
(d) 100 to 650 MW
Ans: b
83. Caking coals are those which
(a) burn completely
(b) burn freely
(c) do not form ash
(d) form lumps or masses of coke
Ans: d
84. Primary air is that air which is used to
(a) reduce the flame length
(b) increase the flame length
(c) transport and dry the coal
(d) provide air around burners for getting optimum combustion
Ans: c
85. Secondary air is the air used to
(a) reduce the flame length
(b) increase the flame length
(c) transport and dry the coal
(d) provide air round the burners for getting optimum combustion
Ans: d
86. In coal preparation plant, magnetic separators are used to remove
(a) dust
(b) clinkers
(c) iron particles
(d) sand
Ans: c
87. Load carrying capacity of belt conveyor is about
(a) 20 to 40 tonnes/hr
(b) 50 to 100 tonnes/hr
(c) 100 to 150 tonnes/hr
(d) 150 to 200 tonnes/hr
Ans: b
88. Method which is commonly applied for unloading the coal for small power plant is
(a) lift trucks
(b) coal accelerators
(c) tower cranes
(d) belt conveyor
Ans: b
89. Bucket elevators are used for
(a) carrying coal in horizontal direction
(b) carrying coal in vertical direction
(c) carrying coal in any direction
Ans: b
90. The amount of air which is supplied for complete combustion is called
(a) primary air
(b) secondary air
(c) tertiary air
Ans: b
91. In ______ system fuel from a central pulverizing unit is delivered to a bunker and then to the various burners
(a) unit
(b) central
(c) none of the above
Ans: b
92. Under-feed stokers work best for _______ coals high in volatile matter and with caking tendency
(a) anthracite
(b) lignite
(c) semibituminous and bituminous
Ans: c
93. Example of overfeed type stoker is
(a) chain grate
(b) spreader
(c) travelling grate
(d) all of the above
Ans: d
94. Where unpulverised coal has to be used and boiler capacity is large, the stoker which is used is
(a) underfeed stoker
(b) overfeed stoker
(c) any
Ans: b
95. TravelUng grate stoker can burn coals at the rates of
(a) 50—75 kg/m per hour
(b) 75—100 kg/m per hour
(c) 100—150 kg/m per hour
(d) 150—200 kg/m2 per hour
Ans: d
96. Blowing down of boiler water is the process
(a) to reduce the boiler pressure
(b) to increase the steam temperature
(c) to control the solid concentration in the boiler water by removing some of the concentrated saline water
(d) none of the above
Ans: c
97. Deaerative heating is done to
(a) heat the water
(b) heat the air in the water
(c) remove dissolved gases in the water
Ans: c
98. Reheat factor is the ratio of
(a) isentropic heat drop to useful heat drop
(b) adiabatic heat drop to isentropic heat drop
(c) cumulative actual enthalpy drop for the stages to total is isentropic enthalpy heat drop
Ans: c
99. The value of the reheat factor is of the order of
(a) 0.8 to 1.0
(b) 1.0 to 1.05
(c) 1.1 to 1.5
(d) above 1.5
Ans: c
100. Compounding of steam turbine is done for
(a) reducing the work done
(b) increasing the rotor speed
(c) reducing the rotor speed
(d) balancing the turbine
Ans: c