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The correct option is (a) Forced circulation BOILER

Explanation: Velox boiler is a forced circulation boiler. It has gas turbine driven AIR compressor, which compresses the air. This compressed air enters into the vertical combustion chamber; as a result, high rate of heat is released from the fuel, which INCREASES the flue gas velocity up to the sound velocity. In this boiler pump is used to circulate water inside tube.

The correct CHOICE is (c) Due to circulation of impure water

To ELABORATE: The salts are deposited in the evaporator drum (steam generator) due to the circulation of impure water can be EASILY cleaned by blowing off the water with pressure or by REMOVING the submerged COIL from the drum.

The CORRECT ANSWER is (c) To decrease the PRESSURE DROP

For explanation: Exhaust steam from turbine is admitted to a steam header in order to minimize the pressure drop. Steam gets condensed as it PASSES down through the finned tubes arranged in parallel rows.

The correct choice is (a) electric motors

Explanation: Rotary pumps are DRIVEN by electric motors. Water is pumped due to rotary ACTION of the IMPELLER. Rotary pumps are invented by Charles C Barnes. It is a positive DISPLACEMENT pump. The efficiency of these pumps depends on the percentage of slip to the total quantity DISPLACED.

Right option is (a) Finned TUBES

Best explanation: In DRY cooling tower circulating water is PASSED through finned tubes over which cooling air is passed. Heat is rejected to air in the form of sensible heat. A dry cooling tower may be either natural draft TYPE or forced draft type. These types are cheap than wet types of cooling tower.

Correct option is (a) ONE way valve

To explain I would say: Feed CHECK valve regulates the flow of feed water under pressure to the boiler drum. It is essentially a one way valve and allows water to flow only in one DIRECTION i.e., towards the boiler drum. No water flows back to the boiler drum.

Correct CHOICE is (c) COOLING towers

To explain I would SAY: In large power plants cooling towers are used in the place of cooling ponds. A cooling tower is a wooden or metallic RECTANGULAR structure, with packed baffling devices. The hot water is delivered to the top of tower and is made to fall down the tower and is broken into SMALL particles while passing over the baffling devices.

Correct CHOICE is (B) LOUVERS

Explanation: Air and WATER are thoroughly mixed by fill as water splashes down from one fill LEVEL to the next due to gravity outside air enters the tower through louvers from the side of the tower. The heat and mass transfer between water and air is enhanced due to intimate mixing.

Right ANSWER is (a) Spray COOLING pond

Best explanation: Spray cooling pond is the simplest METHOD of all. The hot water coming out of the condenser is SPRAYED through the nozzles to expose MAXIMUM surface area of water to air for effective cooling. The spray ponds are surrounded with wooden walls to prevent the wind from carrying the water particles.

Correct answer is (a) Nodulisation

To explain: Sintered light WEIGHT aggregates are produced by nodulisation of fly ash and sintering them at 1000^oc to 1300^oC. Unburnt fuel in the fly ash MODULES supports ignition. Sintered weight aggregate substitute’s chips in CONCRETE reducing dead weight.

Correct ANSWER is (a) SO2<25%

Best explanation: Although SULFUR dioxide is caused by ARTIFICIAL causes, it is primary CONCERN since it contributes <25% of all sulfur in the atmosphere. It is estimated that more than 90 million tons of sulfur dioxide are discharged into the atmosphere every year.

Right option is (a) recuperative AIR preheater

Best explanation: Tubular air preheater is also called as recuperative air preheater. This type of air preheater is composed of steel tubes through which HOT flue GASES flow. Air is made to circulate over these steel tubes and THUS gains heat.

Right answer is (b) 2

The explanation: SUPER heaters are COMMONLY CLASSIFIED into two types: Radiant superheater and convective superheater. If superheater absorbs heat from the BURNING fuel through radiation than it is known as Radiant Superheater. If the superheater that RECEIVES its heat entirely from the gases through convective heat transfer is called Convective superheater.

The CORRECT choice is (b) Propeller fans

Explanation: In mechanical draught COOLING tower the draught of air id PRODUCED mechanically by means of propeller fans. This increases the cooling rate by increasing the air velocity over the WET surfaces and through the tower. These two towers give higher EFFICIENCY; reduce spray and windage losses and less ground area.

The correct OPTION is (a) To prevent excessive steam pressure

Easy explanation: The function of safety valve is to prevent the excessive steam pressure inside the boiler drum EXCEEDING the DESIGN pressure. When the pressure inside the boiler drum exceeds the rated pressure, safety valve automatically opens and discharges the steam to the atmosphere till normal working pressure is RETAINED.

The correct option is (c) 8.13%

To explain I WOULD say: GIVEN: Draught in mm of WATER = 15mm

Height of chimney = 30m

Ambient temperature, Ta = 27 + 273 = 300K

Flue GAS temperature, Tg = 300 + 273 = 573K

% of carbon = 81%

The correct option is (d) By installing air preheater and ECONOMIZER along the gas path

For explanation I would say: The HEAT in exhaust gases can be recovered as much as possible by installing an air preheater and economizer along the gas flow path. As the draught PRODUCED in this system is independent of flue gas temperature care should be taken such that the fan handles gas at its lowest possible temperature.

The correct option is (d) Velox boiler

The explanation: Velox boiler is a forced circulation water tube boiler. In this boiler, the velocity of the flue gas is greater than the velocity of sound, which causes more heat transfer from gas to the water, which increases the steam generation rate. It is MOSTLY USED in gas turbine. DUE to this REASON it is ONE of the important boilers.

Correct choice is (a) D = 1.128\(\sqrt{\frac{Mg}{ρg V}}\)

The explanation: The MASS of GASES flowing through any cross SECTION of the CHIMNEY is given by

The correct option is (a) HT = Hv + Hb + Hc + Hcd

Easy explanation: The TOTAL draught required to PRODUCE the current of the air and to expel the flue gases is given as follows.

Total draught loss = Velocity head loss at the chimney exit + fuel bed RESISTANCE + head loss in

Equipment’s like economizer, air heater ETC. + head loss in chimney and ducts

i.e.,Ht = Hv + Hb + Hc + Hcd

Correct answer is (b) 8

Easiest explanation: There are eight METHODS of superheater temperature control. They are:

Bypassing the furnace

Tilting burners in the furnace

Auxiliary burners

De-superheater USING WATER supply

Pre CONDENSING control

Gas circulation

Twin furnace arrangement

Coil IMMERSION in boiler drum.

Correct OPTION is (b) Forced convection boilers

To elaborate: In these boilers water is CIRCULATED by using an additional pump. These boilers often use ORIFICES to control the flow circulation. Orifices are located at the bottom of the tubes that ensure even distribution of flow through water wall tubes. These boilers can generate steam upto about 200 bar.

Correct option is (d) Thermal DISCHARGE index

Explanation: To compare power generating systems with respect to the amount of thermal energy discharged to the environment a term is introduced, known as thermal discharge index (TDI). The thermal discharge index of any power SYSTEM is the number of thermal energy units discharged to the environment of each unit of electrical energy PRODUCED by PLANT.

The correct answer is (a) Regenerative heater

To EXPLAIN I would say: In the regenerative heater same SURFACE is alternately heated and cooled by the air and GAS steams through respective operating cycles. These are OFTEN preferred in thermal station DUE to its compactness, accessibility and reduced weight.

Right CHOICE is (a) PLATE air heater

Explanation: The plate type air heater consist a bunch of hollow leaves of sheet METAL electrically WELDED and ASSEMBLED in housing. The spacing between the adjustment leaves and the width of the opening of leaves are such that air and gas passages are of different widths.

Right choice is (c) sulfur dioxide

Easy EXPLANATION: ACID rain and acid snow are caused by mainly by sulfur dioxide and also oxides of nitrogen and other sulfur oxides contribute fewer amounts to it. These gasses carried ALONG wind currents combine with water molecules in the water vapor of the atmosphere, forming tiny DROPS. These drops when ENCOUNTERED by snow or rain producing clouds, results in acid rain.

The correct ANSWER is (a) 22.66m

The EXPLANATION is: Temperature of FUEL GASES Tg = 237 + 273 = 510K

Temperature of ambient air Ta = 32 + 273 = 305K

Drought in MM of water Hw = 9.5mm

Mass of air mg = 15kg

We have,

Right answer is (c) H = 32.77m

To explain I WOULD say: Given: D = 1.75m,

Draught in mm of water = 1.8cm = 18mm

Flue gas temperature = Tg = 290^oC = 563K

Ambient temperature = Ta = 20^oC = 293k

Flue gases formed PER KG of fuel burnt: (ma + 1) = 23kg

The correct answer is (b) Base of the chimney

The explanation is: In induced DRAUGHT system the blower is installed near the base of the chimney so as to facilitate sucking of flue gas from the FURNACE. Thus pressure inside the furnace is reduced below atmospheric pressure INDUCING outside AIR into the furnace.

Correct choice is (a) Air blower

To explain I would say: In FORCE draught SYSTEM an air blower is installed near the boiler which blows into the furnace. The PRESSURE of air throughout its path is above atmospheric pressure. This system also USES chimney to discharge hot flue gases into the atmosphere.

Correct choice is (b) 2

The explanation: There are 2 circuits in S-H boiler, in the primary CIRCUIT DISTILLED water from the water drum passes through the primary EVAPORATOR and steam produced is passed over drum and in secondary circuit, FEED pump supplies impure water from hot well to the evaporator drum through feed PREHEATER.

The correct choice is (d) Combustion gases are circulated through tubes with supersonic SPEED

The best explanation: This boiler USES oil or gaseous fuel INSIDE FURNACE for its combustion. The combustion gases are circulated through the tubes with supersonic speed velocity to increase the heat TRANSFER rate between the hot gases and feed water.

The correct choice is (a) By using high pressure and high TEMPERATURE steam

Explanation: The PLANT efficiency can be increased by using high pressure and high temperature steam. This also reduces the cost of electricity production. The development of newer materials permitted the USE of HIGHER operating pressure and temperature of the boiler.

The correct ANSWER is (b) 220 bar

To explain I WOULD say: Single boiler per unit turbines is designed to OPERATE at average critical temperature of 220bar. If the boilers are designed to operate above or below the critical pressure, than they are known as SUPER critical boilers are once through boilers. If the boilers are designed to operate below the critical pressure than they are known as sub critical or drum boilers.

Correct choice is (a) INTERNALLY fired boiler

For explanation I would say: If the furnace REGION is PLACED in the region of boiling WATER, the boilers are termed as internally fired boilers. EX: Lancashire boiler. If the furnace is placed outside the boiling water region, the boilers are known as externally fired boilers. Ex: Babcock-Wilcox boiler.

Correct answer is (a) 3 – 4%

Easiest EXPLANATION: About 20% of COAL ash in the coal is converted into bottom ash and 80% fly ash. INDIA utilizes only 3 – 4% of fly ash generated as compared to 40% UTILIZATION in France and U.K. The government 5t of India is imposing to achieve about 50% of fly ash in the upcoming years.

The correct CHOICE is (a) Close to the engine

The explanation is: Function of the steam separator is to SEPARATE the water particles in suspension that are carried by the steam coming from the BOILER. It is always installed as close to the engine or turbine as possible on the main PIPELINE.

The correct answer is (a) Rotor

The best explanation: This type of air PREHEATER consists of a rotor which TURNS about 2 to 3rpm. The rotor is FILLED with thin corrugated metal elements. Hot GASES PASS through one half of the heater and air through the other half. As the rotor turns, the heat storage elements transfer the heat absorbed from the hot gases to the incoming air.

The correct option is (d) Outside of boiler

The best I can EXPLAIN: The STEAM SEPARATOR is situated outside of the boiler. In this the MIXTURE of water and steam from the evaporator tube is sent, where it SEPARATES the steam and sends it to the super heater. The remaining water is again sent to the economizer.

The correct choice is (a) Carbon dioxide

Easy EXPLANATION: CO2 causes green house effect. The concentration of CO2 has INCREASED to a level beyond the capacity of plant life and the OCEANS to completely remove it. 50% of CO2 added is RETAINED in the atmosphere. And this retained CO2 causes green house effect.

The correct choice is (c) Safe guard against leakage accidents

To EXPLAIN I would say: In normal circumstances, REPLENISHMENT of DISTILLED water in the primary circuit is not required as every care is taken in the design and construction to prevent leakages. But as a safeguard against leakage ACCIDENTAL loss, a pressure gauge and safety valve are fitted in the Schmidt-Hartmann BOILER’s circuit.