This set of Energy Engineering Questions and Answers for Freshers focuses on “Feed Water and Steam Generation System, Working of Thermal Power Plant”.
1. What is the storage used to hold the condensed water?
c) Hot well
Explanation: Hot well is used for storage of the condensed water in a power plant. A tank or reservoir in which hot water is collected before being recirculated, especially condensed steam about to be returned to a boiler is called Hot well.
2. Feed water from the hot well is supplied to steam generator by using the _________
c) Water trough
d) Feed pump
Explanation: Feed pump is used to pump/supply feed water from hot wall to steam generator. The water may be freshly supplied or returned condensate produced by the boiler. These pumps are positive displacement generator and are of very high capacity.
3. Super heater tubes are made up of what type of material?
a) Copper alloy
b) Carbon steel
c) Titanium alloy
Explanation: The steam generated in the boiler is superheated in super heater tubes made of carbon steel for operating at a steam temperature of up to 950°F and carbon molybdenum steel for operating at steam temperature of 1050°F and stainless steel for operating temperature of 1200°F. The tubes of super heater have an outside diameter which ranges from 25mm to 64mm.
4. By what means the power in the steam power plant is developed?
b) Electric power system
c) Prime mover
Explanation: The prime move s used to develop power in the steam power plant. The water is heated, turns into steam and is made to enter into steam turbine. The steam spins and it drives electric generator connected to it, which generates electricity.
5. Chemicals are added in the feed water.
Explanation: Chemicals are put into feed water through the chemical feed tank to keep water within chemical range. These chemicals are mostly oxygen scavengers and phosphates. The boiler water also has frequent blow downs in order to keep the chloride content down.
6. What is the main objective beyond treating feed water?
a) To remove solid particle
b) To prevent damage by scaling
c) To speed up the steaming process
d) To control conductivity
Explanation: The main objective to treat feed water is to prevent damage by scaling and exchange heat without scaling to produce high quality steam. Since a high amount of water is converted into steam back and forth, there is pretty good chance of scale formation in the tubes if the water is not treated.
7. What is the pH value at which the boiler is alkalized?
Explanation: The boiler is alkalized to pH value of 9.0 to reduce oxidization and to support the formation of a stable layer of magnetite on water side surface of the boiler protecting from oxidation. And also oxygen scavengers are used to remove residues of oxides, especially O2 & CO2 [oxygen and carbon dioxide] must be removed. Sodium hydroxide or ammonia is used for alkalization of the feed water.
8. What does steam power plant mainly use to generate steam?
a) Boiled water
b) Fresh steam
c) Flue gas
d) Condensed water
Explanation: Steam power mainly uses hot products of combustion known as flue gas to generate steam in a boiler. Heat is generated by burning coal, oil or gas. For this purpose boiler furnace is designed for firing coal, air or gas. The flue gas is exhausted via chimney after making maximum utilization of it.
9. What type of steam is produced in the steam boiler?
a) Low pressure steam
b) High pressure steam
c) Saturated steam
d) Unsaturated steam
Explanation: The boiler is an integral component of steam engine. A boiler incorporates a firebox or furnace in order to burn the fuel and generate heat. The generated heat is transferred to water to make steam. This produced saturated steam at a rate which can vary according to pressure. The saturated steam thus can produced can either be used immediately to produce power via turbine.
10. What is the main purpose of using an economizer in a boiler?
a) To control the process of steam conversion
b) To reduce energy consumption
c) To increase the temperature of boiler
d) To maintain a constant temperature inside a boiler
Explanation: Economizer in boilers is used to heat fluids, upto a certain degree not beyond the boiling point of that fluid. Economizers are named so because they can make use of enthalpy in fluid stream that are hot, thereby making more useful enthalpy and improving the boiler’s efficiency.
11. In what form is the coal used in boiler?
a) Big chunks.
b) Medium size crushed
c) Powder form
d) Mixed with fluid
Explanation: The coal used for boiler is in powder form, in order to increase thermal efficiency. The different types of coal used in boiler are generally bituminous coal, brown coal and peat. Commonly bituminous coal is most preferred boiler fuel since it has volatile matter from 8 to 33% and ash content of 5 to 16 %.
12. Why is air pre-heater used in the boiler?
a) To draw in the atmospheric air
b) To increase thermal efficiency
c) To heat the air to superheated level
d) To heat the air in advance
Explanation: the purpose of the air preheater is to recover the heat from the boiler flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost in the flue gas. As a consequence the flue gases are also conveyed to the flue gas struck at a lower temperature, allowing simplified design of conveyance system and flue gas stack.
13. What is the advantage of condensing the steam?
a) To cool down the steam
b) To discharge the same amount of feed water taken
c) Reduces the amount of pollution
d) Reduces the amount of fresh feed water
Explanation: The principle advantage of condensing operation is to reduce the amount of fresh feed water. A condenser is usually installed after the turbine to convert the exhaust steam from the turbine. They convert gaseous steam into liquid state, at a pressure below atmospheric temperature. Condensing of steam turbine below the atmospheric temperature, the steam pressure drops between the inlet and exhaust of turbine is increased, which increases amount of heat available.
14. How is water dispensed over to the turbine blades?
Explanation: Nozzle is used to dispense the water over to the turbine blades of steam turbine. A nozzle is a duct that increases the velocity of the flowing fluid at the expense of pressure drop. It’s a duct which decreases the velocity of fluid and increases pressure difference.
15. In what aspect does the nozzle make changes?
Explanation: Nozzle makes changes in terms of pressure variation. And rest all factors/terms are unaffected. By decreasing the pressure and increasing the velocity at other end through convergent-divergent nozzle, the required force or pace can be achieved to run the blades of turbine.
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