Multiple choice question for engineering
1. What is the storage used to hold the condensed water?
c) Hot well
Answer: c [Reason:] 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
Answer: d [Reason:] 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 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
Answer: b [Reason:] 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 950oF and carbon molybdenum steel for operating at steam temperature of 1050oF and stainless steel for operating temperature of 1200oF. 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
Answer: c [Reason:] 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 is spins and it drives electric generator connected to it, which generates electricity.
5. Chemicals are added in the feed water.
Answer: a [Reason:] 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
Answer: b [Reason:] The main objective to treat feed water is to prevent damage by scaling and exchange heat without scaling to produce high quality steam. Since 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 boiler is alkalized?
Answer: a [Reason:] 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
Answer: c [Reason:] 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
Answer: c [Reason:] 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 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
Answer: a [Reason:] 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 boilers 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
Answer: c [Reason:] 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
Answer: b [Reason:] 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
Answer: d [Reason:] 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?
Answer: b [Reason:] 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?
Answer: c [Reason:] 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.
1. What is the most important factor that is essential for economical working of a power plant?
a) Abundant fuel input
b) Rotational speed of turbines
c) Efficient transfer of heat energy to water
d) Proper maintenance Ash and other waste handling systems
Answer: c [Reason:] The economical working of power plant depends upon factors such as efficient transfer of heat energy to water for generation of steam and efficient combustion of fuel in combustion chamber. Many improvements have been made in design of the furnace to increase the rate of combustion.
2. What type of reaction is burning?
a) Endothermic reaction
b) Exothermic reaction
c) Synthesis reaction
d) Decomposition reaction
Answer: b [Reason:] Burning is an exothermic reaction. A fuel is a store of chemical energy that we convert into useful energy to our purposes. For example, we can use the energy stored in natural gas to cook our food. To release this energy, we usually burn the fuel. Burning is a chemical reaction in which the fuel reacts with oxygen gas in air and gives out energy in terms of heat. We call this type of reaction as exothermic reaction.
3. Which type of furnace cannot be used in the modern era plants?
a) Hand fired furnace
b) Electric arc furnace
c) Solar furnace
d) Central warm air furnace
Answer: a [Reason:] A hand fired furnace is simple in design, but it cannot be used in modern power plants because of its lower combustion efficiency. It does not respond quickly to fluctuating loads and control of draught is very difficult.
4. How much pounds of CO2 is emitted per million BTU (British thermal unit- common thermal unit) when coal is burnt?
Answer: d [Reason:] 205 million BTU is the pounds of CO2 that is emitted when coal is burnt. The amount of CO2 produced when a fuel is burned is a function of carbon content of fuel. The heat content, or the amount of energy produced when a fuel is burned, is mainly determined by the carbon(C) and hydrogen (H) content of the fuel.
5. A combustion equipment is a component of ____________
b) Steam generator
c) Flue gas system
d) Ash handling system
Answer: b [Reason:] A combustion equipment is a component of steam generator. It receives the fuel and air proportionals to each other and to the boiler steam demand, mix, ignites and performs other function such as distillation of volatile matter of coal.
6. What was the reason for the poor efficiency of boiler in earlier time?
a) Boilers were set close to grates
b) Poor design of exhaust system
c) Impurities contamination the fuels
d) Lack of proper maintenance
Answer: a [Reason:] In earlier times boilers were set very close to the grates and combustion space was limited and hence resulted in smoke and poor efficiency. Later, furnaces were made larger and the boilers were set at higher level above the grates. The hand fired furnace with large combustion space was used to burn a wide variety of coals.
7. Which was first combustion system used for solid fuels?
a) Firing stoker
b) Tangential stoker
c) Grate firing
d) Pulverized fuel firing
Answer: c [Reason:] Grate firing was the first combustion system used for solid fuels. It now is used mainly for burning waste and biomass, but also for smaller coal furnaces. Fuel fired per grate area is 1-2 MW/m2, ad maximum grate area is 100m2.
8. The amount of fuel burned depends on ____________
a) Design of burner
b) Depends on air inlet and exhaust system
c) Depends on bed movement velocity
d) Depends on amount of supply of combustion supportive air
Answer: c [Reason:] The amount of fuel burned depends on the amount of fuel burned and on the bed velocity movement. The grate area is the total area of grate (a frame of iron bars). The large the grate area, the more fuel can be burned per hour.
9. Which device is used for feeding the fuel automatically to boiler or furnace in power plants?
b) Mechanical stoker
c) Master controller
d) Feed pump
Answer: b [Reason:] Mechanical stoker is the device which automatically feeds a solid fuel (such as coal) into combustion chamber of a boiler or furnace, and provides air for the proper combustion; may include a means for automatically removing solid products of combustion.
10. What is used in case, to throw coal into furnace that is set off far from the supply?
a) Speed convey belt
b) Bucket chain
d) Steam jet
Answer: d [Reason:] Steam jet from the boiler or a mechanical catapult may also be used to throw coal into far reach of the furnace. The mechanical means used in the system depend on the design, combinations of screw feed, the conveyor belt, the bucket chain, the paddle and the ram.
11. Where exactly are mechanical stokers used?
a) In transportation of fuels
b) In small capacity plants
c) In large capacity plants
d) For domestic usage
Answer: c [Reason:] Mechanical stokers are usually used in large and medium capacity plants. Mechanical stokers are used to fire almost all kinds of coal. This produces less smoke than hand firing. A stoker consists of a power feeding machine and a grate.
12. Which type of stokers has more demand in the market?
a) Spreader stoker
b) Vibrating stoker
c) Travelling stoker
d) Underfeed stoker system
Answer: a [Reason:] Spreader stoker systems are receiving the greatest interest and sales in the market. Depending upon the method of introducing the coal into furnace, stokers are mainly classified into spreader stokers, underfeed stokers, vibrating grate stokers and travelling grate stokers.
1. What is the function of coal burners?
a) To burn pulverized coal by using secondary air
b) To burn pulverized coal in presence of Primary and secondary air
c) To burn pulverized coal by using induced draught
d) To burn the pulverized coal in short amount of time
Answer: b [Reason:] Function of the coal burner is to burn pulverized coal in the presence of primary and secondary air in a boiler furnace. Coal burners are classified according to their design and arrangement in the furnace.
2. Which coal burner is called Long-flame burner?
a) Tangential burner
b) Turbulent burner
c) Stream line burner
d) Cyclone burner
Answer: c [Reason:] Stream line burner is called as Long-flame burner, also known as U-flame burner. It is designed to fire downwards in the furnace without any turbulence. Thin flat streams of air and fuel mixture is discharged in the furnace which travels considerably long distance producing long flame.
3. The secondary air in the stream-liner coal burner is fed flames from which direction?
a) At straight angle
b) Opposite to the fuel flow
c) At Right angle
d) Along the fuel
Answer: c [Reason:] Heated secondary air in the stream-liner coal burners fed at right angles to the flame. It ensures proper mixing of air and fuel. This type of burner is suitable for burning fuels with low volatile matter as fuel flows at low velocity.
4. Which coal burner has the circular discharge orifices?
a) Tangential burner
b) Stream-line burner
c) Turbulent burner
d) Cyclone burner
Answer: c [Reason:] Turbulent is made up of circular discharge orifices or with straight narrow outlets. It is placed in the wall of water cooled furnaces. The fuel and air mixture pass through the burner such that they mix properly at furnace entrance.
5. In which coal burners are fuel and air streams ejected in horizontal direction?
a) Tangential burner
b) Cyclone burner
c) Stream-line burner
d) Turbulent burner
Answer: a [Reason:] In tangential burners, fuel and air streams are ejected in horizontal direction tangent to an imaginary circle at the centre of the furnace. The burners are placed at the corners of the furnace to ensure intense turbulence and thorough mixing of fuel and air.
6. Which coal burner is used to burn crushed coal instead of pulverized coal?
a) Cyclone burner
b) Tangential burner
c) Turbulent burner
d) Stream-line burner
Answer: a [Reason:] Cyclone burners are used to burn crushed coal instead of pulverized coal. This is to eliminate fly ash handling problems. It consists of a cyclone furnace. Crushed coal of about 8mm size is fed from the feeder to the centre of the cyclone along with primary air.
7. In which form does the coal burned rapidly in cyclone burner drains down the inner wall of furnace?
b) In form of small chips
c) Metal slag
d Gaseous form
Answer: c [Reason:] The ash formed due to rapid burning of coal drains down the inner wall of the furnace as molten slag. Hot flue gases along with 10 to 20% of fly ash enter the furnace. Due to centrifugal action most of the fly ash is thrown against the furnace wall and is drained out along with molten slag.
8. Which type of oil burners are used for domestic purposes?
a) Atomizing burner
b) Vaporizing burner
c) Steam jet atomization burner
d) Mechanical atomization burner
Answer: b [Reason:] The vaporizing burners are used for domestic purpose especially in portable air heaters, cooking stoves etc. petromax stove which burns kerosene is a classical example of a vaporizing burner. Here an upward moving high velocity fuel jet is allowed to strike against hot moving plate. The vapor burns with a short intense flame.
9. Which type of oil burners are commonly used in oil-fired furnaces of steam generators?
a) Vaporizing burner
b) Mechanical burner
c) Atomizing burner
d) Air jet burner
Answer: c [Reason:] Atomizing burners are very commonly used in oil-fired furnaces of steam generators. The oil is divided into fine particles to increase the surface area of contact with the combustion air. Due to atomization a homogeneous mixture of oil and air is produced which is fired in the furnace.
10. How is oil pressurized in mechanical atomization of atomizing burner of oil burners?
a) By positive displacement pumps
b) By centrifugal pumps
c) Helicon-axial pumps
d) Electric submersible
Answer: a [Reason:] In mechanical atomization of atomizing burner of oil burners, the oil is pressurized by using a positive displacement pump. It is used in high capacity steam generating furnaces. In order to improve efficiency and flow conditions the viscosity of the oil is reduced by heating it to about 120oC.
11. How does atomization of fuel occur in an atomizing burner of oil burner?
a) High pressure movement of fuels
b) By spraying the fuel at high pressure
c) By impinging two streams of fuel
d) By spark ignition method
Answer: c [Reason:] In the atomizing burner, oil is delivered under pressure through a central tube. Steam or air is supplied along the annular space between the oil pipe and the concentric outer tube. Near the tip of the burners the two streams impinge resulting in atomization of fuel.
12. Which type of gas burner is used to control flame length?
a) Ring burner
b) Sealed burner
c) Electric burner
d) Standing pilot burner
Answer: a [Reason:] Ring burners are used to control the flame length. The rate of gas flow can be controlled by using dampers. The gas flows through an annular ring, whereas air is induced both around and within the annular ring.
1. How is the fuel handled generally outside the plant?
c) Robotic technology
Answer: a [Reason:] It is absolutely essential to have an efficient fuel handling system in power plants. Since majority of the plants operate using coal as a fuel, it is necessary to study about coal handling system. Coal can be handled either manually or mechanically. But, citing the capacity of modern power plants it is almost impossible to handle coal manually. That means mechanical handling of coal is inevitable.
2. Why is fuel need to be stocked in steam power plant?
a) To supply to nearby other steam plants
b) For overusing when plant is run for extra periods
c) For emergency possible cases
d) For Non-stop work of power plant
Answer: c [Reason:] With more and more number of commissioning of large capacity steam power plants, it is very essential to have an effective means of transporting coal from coal mines to the plant site and subsequently store it to meet the emergencies.
3. What is the ideal site for power plant?
a) In hilly regions
b) On islands
c) Near water resources
d) In center lands
Answer: c [Reason:] An ideal site for power plant is near water source. If the plant is situated near the sea or river, coal can be economically transported in bulk quantity by ships or boats or barges. After unloading the coal by mechanical means, coal is either stored in the plants site or conveyed to the plant.
4. Which type of transportation system is ideal for transporting coal directly to the point of consumption?
a) Road transportation
b) Sea or river transportation
c) Transportation by rail
d) Transportation by air
Answer: a [Reason:] Road transportation is ideal for transporting coal directly to the point of consumption. Such a means is suitable for supplying coal to a small capacity plant. Trucks or tippers are used to supply coal for this purpose.
5. What is in plant coal handling system?
a) Maintenance of coal during emergencies
b) Maintenance of coal inside the boiler
c) Maintenance of coal inside the power production area
d) Maintenance of coal while transporting/moving it
Answer: c [Reason:] For easy, smooth and rapid operation mechanical handling system is embraced for inplant handling of coal. Inplant handling begins right from the coal delivery point unto the furnace firing system.
6. What is the main characteristic of in plant coal handling system?
a) It should be easy to handle
b) Should be simple in construction
c) Free from repetitive handling
d) Free from corrosion problems
Answer: c [Reason:] It should have minimum handling operations and should be free from repetitive handling. For easy inspection and maintenance it should have centralized handling units. Its capacity should be well above the requirement of coal during peak hours.
7. Why is it necessary to have a coal storage yard near the plant?
a) To supply to other nearby power plants
b) To cut down on varying transportation rates
c) To face any emergencies
d) Due to higher rate of deterioration due to reduction
Answer: c [Reason:] To meet the continuous demand of coal and to face any emergencies due to the short supply of coal, it is always desirable to have a coal storage yard near the plant. Capacity of such yard would be about 10% of annual consumption to a maximum of 25% of annual consumption.
8. Where should coal be dumped?
a) On solid ground
b) In the water
c) By mixing with other form of fuels
d) Near the plant
Answer: a [Reason:] Coal should be dumped on a solid ground completely free from standing water. It should be protected from direct sunlight preferably and should be done so in order to reduce chances of oxidation and combustion.
9. What is the advantage of stocking the coal in huge heaps?
a) Prevents from coal being oxidized
b) Provides grip for the storage
c) Prevents air circulation in the interior of heap
d) The moisture content will be eliminated
Answer: c [Reason:] Coal is piled in heaps of 10 to 12m height on a concrete floor, by compacting it in the layers of 20 to 30cm thickness using bulldozers. This prevents air circulation in the interior of the heap. The heap top is given a gentle slope to drain off rain water immediately without washing the coal.
10. How the oxidation of coal is eliminated?
a) By exposing it to the sunlight
b) By turning the entire coal heap upside down periodically
c) By circulating air uniformly
d) By burning coal at very high temperatures
Answer: c [Reason:] The heat of oxidation is removed by circulating air uniformly through layers. Air thus circulated carries away the excess heat, maintaining coal below its combustion temperature of 343K. Oxidation can also be avoided by sealing the coal heap asphalt, fine coal dust or bituminous powder.
11. Why is it necessary to use noncandescent materials in place of coal storage area?
a) To avoid it from catching fire
b) To act as a fire resistor during the cause of fire
c) To avoid it from acting as a supporter of fire
d) To provide a cool environment
Answer: a [Reason:] Coal is susceptible to spontaneous combustion due to heating during natural oxidation of new coal surfaces. Second, coal dust is highly combustible and explosion hazard. If a coal dust cloud is generated inside an enclosed space, and an ignition source is present, an explosion can ensure.
1. Which among the following are of great importance in a diesel power plant?
a) Tight pipe joints
c) Air compressors
d) High grade filters
Answer: d [Reason:] Due importance should be given for cleanliness in handling bulk fuel oil. Dirt particles will ruin lap of injection pumps or plug the injection nozzle orifices. Thus, high grade filters are of great importance to the diesel oil supply system.
2. Fuel injection system is the _______ of the diesel engine?
a) sole part
c) main part
Answer: b [Reason:] Function of fuel injection system are:
1) Filter the fuel.
2) Measure the correct quantity of fuel to be injected.
3) Proper time the fuel injection.
4) Control the rate of fuel injection.
5) Break up the fuel into fine particles.
6) Properly distribute the fuel in the combustion chamber.
3. How much amount of fuel must be measured out in a fuel injection system?
a) Very high
b) Very Small
Answer: b [Reason:] Fuel injection system is the heart of diesel engine. In an injection system very small quantity of fuel must be measured out, injected, atomized, and mixed with combustion air. The mixing problem becomes more difficult. The larger the cylinder and faster is the rotational speed. However, special combustion arrangements such as pre-combustion chambers, air cells etc, are necessary to ensure good mixture.
4. Injection systems are cheap.
Answer: b [Reason:] The injection systems, especially the parts that actually are manufactured with great accuracy meter and inject the fuel. Some of the tolerances between the moving parts are so small that they require some special attention during manufacture. Hence the injection systems are costly.
5. How many are the number of commonly used fuel injection systems in diesel power stations?
Answer: c [Reason:] There are three most commonly used fuel injection systems in diesel power station, they are: 1) Common rail injection system.
2) Individual pump injection system.
6. Atomization of fuel can be done in how many ways?
Answer: a [Reason:] Atomization of fuel can be done by (i) Air blast (ii) Pressure spray. In the olden days engines used air fuel injection at about 70bar which is sufficient not only to inject the oil, but also to atomize it for rapid and thorough combustion. The expense of providing an air compressor tank leads to the development of “solid” injection.
7. How many types of common rail injection systems are there?
Answer: b [Reason:] There are basically two types of common rail injection systems which are by using single pump and using controlled pressure system. In case of single pump, it supplies high pressure fuel to header. In the controlled pressure system, it has a pump which maintains a set head pressure.
8. Common rail system prototype was first developed in year?
Answer: c [Reason:] The common rail system prototype was developed in late 1960s by Robert Huber of Switzerland and the technology further developed by Dr. Marco Ganser at the Swiss federal institute of technology in Zurich, later of Ganser-Hydromag AG (est. 1995) Oberageri.