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The correct OPTION is (c) Deposition of salts

To explain I WOULD say: The major DISADVANTAGE of the Benson boiler is that when water transforms into steam in the convective section of the EVAPORATOR, salts are DEPOSITED in the transformation zone. Hence periodic flashing of evaporator tubes in the convective section is necessary.

The CORRECT OPTION is (a) Nozzles

Easy explanation: An even circulation of FEED water in Lamont boiler TAKES place with the help of nozzles provided at the inlet of the tubes which create the differential pressure adequate to cover the variations OCCURRING at fluctuating loads or uneven firing conditions.

The correct OPTION is (b) Centrifugal pump

The best explanation: A centrifugal pump which forms the heart of the Lamont boiler is responsible to circulate water WITHIN the boiler system. It receives water from the DRUM and DELIVERS it to the distribution header. The numbers of headers may DIFFER in numbers and depends on the size and design of each boiler.

Correct choice is (a) Yes

For explanation: Boilers can be classified based on fuel used for COMBUSTION or heat generation SOURCE. Various heat sources are: heat generated by the combustion of fuel in SOLID, liquid or gaseous form. Heat generated by hot waste gases as BYPRODUCTS of other chemical processes. Heat generated by electrical energy and NUCLEAR energy.

Correct choice is (c) 540^oC

Best explanation: The modern high pressure BOILERS have steam capacities of 30 to 650 tonnes/hour and with pressure of UPTO 160 BAR & maximum steam temperature of about 540^oC. Also the furnace shape is not limited to cylindrical FORM; hence furnace shape can be changed to suit wide range of situations.

Right ANSWER is (a) Fire tube boiler

To ELABORATE: Cornish boiler is an EXAMPLE of fire tube boiler and also includes COCHRAN, Lancashire, and Locomotive and scotch marine boilers. Fire tube boilers are those in which the products of combustion pass through the TUBES and water lies around the outside of tubes. These boilers operate at moderate pressure (16-20bar) and more suitable to generate 3-8 tons of steam per hour which is used in process heating.

The correct option is (d) Cement

The explanation: Ash is widely used in the PRODUCTION of cement. Fly ash is POZZOLANIC and develops self hardening characteristics. Concrete MADE of ash can yield improved workability and strength greater than all cement based concrete. The pozzolanic quality of ash lime MIXTURE creates a healing of cracks in the pavement themselves.

The CORRECT option is (d) Balanced draught

The EXPLANATION is: A balanced draught system combines the features of forced draught and induced draught. In case of forced draught, when the furnace doors are OPENED high pressure air rushes outside and even blow out the fire entirely. In case of induced draught, when the furnace doors are opened to atmosphere air enters the furnace and causes IMBALANCE in the draught. This difficulty is overcome by using balanced draught.

Right answer is (a) Endothermic reaction

Best explanation: Production of nitrogen OXIDES is an endothermic reaction and its concentration is temperature dependent. NOx emissions can be REDUCED by LOWERING the combustion temperature and by ELIMINATING hotspots in the FURNACE.

Right option is (c) To generate steam at constant pressure

For explanation I would say: FUNCTION of boiler is to generate steam at constant pressure as per the process REQUIREMENT. The steam generated MAY be nearly dry saturated or superheated steam. Constant pressure in the boiler is MAINTAINED by GENERATING the steam equal to the steam flowing out of the boiler.

Correct choice is (C) Locomotive BOILER

To elaborate: The boilers, if they are portable, i.e., if they can be MOVED from one place to other place those are known as mobile boilers. Such boilers are used in locomotives and ships to GET the engine moving. And also small units are used for TEMPORARY at working sites. Ex: Locomotive boiler, Marine boiler etc.

Correct OPTION is (a) Because power requirement is high for forced draught

The EXPLANATION: Induced draught is considered to be better than forced draught because, the power requirement is high for forced draught and the maintenance of fan is COSTLIER. The induced draught occupies less space ass the fan drives are placed at the top of the tower, the cooling EFFECT is distributed across the entire cross section of the tower.

The correct CHOICE is (b) Double deck system

For explanation I would say: In double system of cooling ponds the spray NOZZLES are arranged at different elevations. Cooling effect is more than single deck cooling system as water COMES in contact with air at LOWER TEMPERATURES.

Right OPTION is (d) Shell boiler

To elaborate: The use of shell BOILERS are considered to be cheaper when the boilers are required to raise less than 30 tonnes of steam per hour and at pressures 30bar. Above these limits, i.e. for HIGH pressure and high output, water tube boilers are PREFERRED.

The CORRECT ANSWER is (a) Increase the temperature of steam

To EXPLAIN: Function of the superheater is to increase the temperature of steam above its saturation temperature. As HEAT contained in unit MASS of superheated steam is more than dry saturated or wet steam, it is extensively used in steam power plants.

Correct answer is (b) 42.55m

For explanation I would SAY: Density of air at 290K ρg = P/RT = [1.033 * 10^4 / 29.26 * 290]

= 1.217Kg/m^3

Density of fuel GAS at 563K, ρg = [1.033 * 10^4 / 26.2 * 563]

= 0.7 Kg/m^3

Static Draught, p = H (ρa– ρg)

22 = H (1.217 – 0.7)

H = 42.55m

The correct ANSWER is (b) Chimney

For explanation I would say: Natural draught is produced by using a chimney. A chimney is a vertical tubular structure made up of brick, STEEL or REINFORCED concrete. The draught produced by the chimney is due to the difference in TEMPERATURE of hot flue gases inside the chimney and the ATMOSPHERIC air.

Correct choice is (a) Evaporating water by SUPER heated steam

Easiest explanation: The novel feature of the Loffler boiler is to evaporate water solely by means of SUPERHEATED steam. The FURNACE heat is supplied only to ECONOMIZER and super heater. In other words, steam is used as a heat absorbing MEDIUM.

The correct choice is (d) 1922

To explain: Benson boiler is high pressure, drum less, water tube boiler with forced CIRCULATION. This was invented by Mark Benson in YEAR 1922. It was Mark Benson who first proposed the IDEA to COMPRESS the water eat supercritical pressure before heating in boiler.

The correct choice is (b) 180bar

To elaborate: Water is PURELY circulated by DENSITY difference with most of the heat from the fuel flame being radiated to the water walls directly. The steam pressure of such boilers is limited to about 180bar, with water and steam being separated in the BOILER DRUM.

Correct answer is (a) Increased thermal efficiency

The EXPLANATION: Increased thermal efficiency is one of the benefits and also other benefits are

i) Improved combustion

ii) Efficient use of low grade FUEL

iii) Saving in fuel consumption

iv) Increased STEAM generation CAPACITY.

Right choice is (a) 6

The BEST I can explain: There are SIX TYPES of economizers:

i) Steaming

ii) Independent

iii) Non-steaming

iv) Integral

v) Condensing

vi) Non-condensing.

The correct answer is (c) Chromium Molybdenum

For explanation I WOULD say: Superheater is made of coils of tubes forming parallel tube circuits connected between HEATERS. The superheater tubes are made of high temperature strengths SPECIAL alloy STEELS such of chromium molybdenum. The coils are HEATED by the heat of combustion gas during their passage from furnace to the chimney.

The correct choice is (C) Fuel consumption decreases

The explanation: Function of the economizer is to recover a portion of heat of the EXHAUST gases before the flue gases enter the chimney and discharged to the atmosphere. Due to the high TEMPERATURE of FEED water, fuel consumption reduces. This increases the overall efficiency of the boiler.

The correct answer is (c) INCREASING levels of CO2

To ELABORATE: The growing levels of CONCENTRATION of CO2 INCREASE the surface temperature of earth. This may result in climatic changes with disastrous consequences, such as MELTING of polar ice caps and rising of sea levels.

The correct answer is (c) 29.93

Explanation: Density of AIR at NORMAL temperature = 1/0.7734

= 1.293Kg/m^3

Density of air at 298K, ρa = 1.293 × 273/298

= 1.1845 Kg/m^3

Density of gases at 573K, ρg = 1.293 × ((18+1)/18) × 273/573

= 0.65 Kg/m^3

But, P = 12 + 4

= 16 mm of water

P = H (ρa – ρg)

16 = H (1.1845 – 0.65)

H = 29.93m

Correct option is (a) Forced steam draught

The explanation is: The high velocity steam coming out from the nozzle drags the air column along with it creating suction. The KINETIC energy of air and steam mixture is converted into PRESSURE energy forcing air through the coal BED to the furnace. So, Forced steam draught is used as a booster in conjunction with chimney draught.

Right CHOICE is (b) By induced fan

Explanation: In balanced draught system, a forced draught fan is installed near the BOILER which helps in overcoming the RESISTANCE of fuel bed by supplying sufficient air for combustion. An induced draught fan is installed near the chimney base removes the flue gases COMING from the furnace and maintains PRESSURE in the furnace slightly below the atmospheric pressure.

The correct answer is (c) Re-super HEAT PARTLY EXPANDED steam

Easy explanation: The function of Re-heater is to re-superheat the partly expanded steam from the turbine so that the steam remains DRY as far as possible through the last STAGE of turbine. Modern plants have reheaters as well as super heaters in the same gas passage of the boiler.

The correct choice is (b) 2

Explanation: The function of the WATER level INDICATOR is to indicate the level of water INSIDE the boiler drum at any given instant. Two water level indicators (one as a standby) are fitted at the front of the boiler drum. The boiler operator keeps TRACK of water level in the drum and OPERATES the feed pump as per the requirement to maintain a constant level of water inside the drum.

Correct choice is (a) To remove sludge

Explanation: Blow down valve is also called as Blow-off-cock. The FUNCTION of this valve is to remove the sludge or sediments collected at the bottom of the boiler DRUM from time to time. Whenever boiler cleaning and inspection is due, WATER inside the tubes and in the boiler drum can be completely DRAINED by operating the blow down valve.

The correct CHOICE is (a) Protect the fire tube

For explanation: The function of the fusible PLUG is to protect the fire tube from burning due to excessive heating. This usually happens when the water level INSIDE the drum BECOMES too low and the shell and CROWN plate are directly exposed to steam space.

The correct ANSWER is (c) Atmospheric cooling TOWER

The best explanation: In atmospheric cooling tower, the hot water is DELIVERED at the top most trays and it falls down from one tray to another until it REACHES the tank below the tower. The water is cooled by air FLOWING across the tower.

Right answer is (a) ENVIRONMENT

Explanation: The design, location, construction and operation of electrical power generation facilities have been affected by the concern for the environment. Hence power engineer MUST have concern for the environment while producing enough power to meet public demand at LOW cost. Government has passed environmental legislation that limits amount of pollutants that can be DISCHARGED to the environment.

The correct answer is (b) power plants

For explanation: Carbon dioxide is largely contributed by power plants. CO2 added to NATURE by natural causes viz., decay of organic matter contributes more than that by artificial causes. Also CO2 contaminants in ATMOSPHERE are not considered as pollutants as it is ESSENTIAL for plants.

The correct answer is (a) Boiler operation

To elaborate: The DRAUGHT PRODUCED in the chimney is DUE to the temperature difference of the hot flue gases. In addition to this, height of the above the furnaces grate, WHETHER conditions and boiler operations also have CONSIDERABLE effect on the amount of natural draught.

Right choice is (a) True

Explanation: Acid RAIN does affect trees and plants. It RESULTS in LEACHING of essential plants NUTRIENTS from the soil and reduces nitrogen fixation by microorganism. This makes soil less fertile. Also dissolve aluminum and cadmium out of soil minerals, ALLOWING them to enter roots and kill trees.

Correct OPTION is (b) Density

Easiest explanation: As the steam pressure INCREASES, its density ALSO increases while the corresponding increase in TEMPERATURE causes density of water to DECREASE. This makes the pressure difference causing water flow to decrease.

The correct option is (c) parallel in horizontal

For explanation: The boiler heating surface includes a number of TUBES arranged in a parallel form and the inlet ends are welded to the distributors or the headers. A CIRCULATION pressure is to be PROVIDED during the installation of the pump as per the boiler DESIGN and it should be sufficient to overcome the RESISTANCE offered by the tubes.

Right answer is (b) False

The explanation: There is a rare chance of overheating or the burning of the highly heated components of theprimary circuits there is no danger of SALT DEPOSITION as well as there is no chance of interruption to the circulation either by rust or any other material. The highly heated PARTS run safe THROUGHOUT the life of the boiler.