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Correct answer is (a) Mechanical ash handling system

Explanation: The mechanical ash handling system consumes less amount of power. Since the power is REQUIRED by the conveyor belt to transfer the ash from boiler furnace to over HEAD bunker which is located at END of the conveyor belt.And in case of pneumatic there is high power requirement to draw and blow the air at high velocities and high pressures.

The correct option is (a) Gaseous fuels

Easiest explanation: Gaseous fuels are either NATURAL fuels or artificial fuels. Natural fuels occur in the FORM of natural gas near oil bearing areas under earth’s surface. Artificial fuels prepared are coal gas COKE oven gas, blast furnace gas, producer gas, water gas and mond gas.

Correct choice is (a) True

Best explanation: A SOOT fire can be damaging to a boiler because it can cause localized hotspots to occur in the TUBES. These hotspots may reach temperatures that weaken the MATERIALS of the tubes. Soot blowers reduce the risk of soot FIRES and their RESULTING damage.

Right CHOICE is (b) Protects from high temperatures when not in USE

Explanation: Retractable blower, though more expensive initially, have the advantage of PROTECTION from high temperature when not in use. Also, using only two travelling nozzles, the jet can be larger without excessive steam drain, and the projected blast distance is greater.

Right answer is (B) RETRACTABLE blower

For explanation: Soot blower consists of a set of TUBES fitted with nozzles carrying high velocity jet of STEAM or air. In the hotter parts of the boiler, the blower advances into the furnace, cleans the heat transfer surfaces and comes back. This type of soot blower is known as retractable soot blower.

Correct choice is (a) To AVOID net loss

To explain: It is necessary to observe TEMPERATURE drops routinely. OBVIOUSLY if the temperature drops 24°C after BLOWING, the interval might well be decreased, where as if 12°C were observed; it could represent a net loss because the VALUE of the steam used was more than that of the increment of flue gas heat.

Right option is (b) Dry and uncooled

Best explanation: When not in use the soot BLOWER tube of the system would be dry and uncooled, and subject to gas TEMPERATURES. Even with alloy tubes the DETERIORATION is relatively rapid on units NORMALLY experiencing high gas temperatures.

Right choice is (a) Because they are tedious to operate manually

The best I can explain: Soot blowers are tedious to operate manually, and since must not all be operated simultaneously, the OPERATING heads are electric MOTOR powered and operated by remote control on an AUTOMATIC SEQUENTIAL BASIS.

The correct choice is (b) To admit HIGH PRESSURE steam

To EXPLAIN: The usual form for the smaller boilers is a dead-end tube projecting through the setting and extending into the tube banks. A number of small lateral nozzles are provided and the external HEAD is arranged so that high pressure steam can be admitted to the tube and at the same time the tube is rotated around its AXIS.

Correct option is (d) Bioleaching

The explanation is: The products of combustion cling to the water tubes, economizer tubes, air preheater tubes and super heater tubes. This LOWERS the efficiency of the plant by reducing heat transfer. So, regular REMOVAL of SOOT or DUST is necessary this method is known as soot BLOWING.

Right option is (C) To clean adequately

To elaborate: Steam jets clean soot from heating surface in their PROXIMITY, but the ACTION is limited in extent in a close array such as tube banks; HENCE several units may be NEEDED to clean the boiler adequately. It is quite common to see 8 to 16 units in a large boiler.

Right choice is (c) To REMOVE dust particles from flue GAS

Easy explanation: BAGHOUSE filters are used to remove dust particles from the flue gas produced from the combustion in boiler. These are also called as fabric filters or fabric dust collectors, designed to use fabric filter tubes, ENVELOPES or cartridges to capture or separate dust and particulate MATTER when the gas is made to pass through the voids.

Correct ANSWER is (d) 500m

For explanation: Belt conveyors can handle upto 50 to 100t/h of load can be CARRIED over a distance of about 500m. These conveyors can be USED with inclination upto 20° to the horizontal moving at an average speed of 60 to 90 m/min. However it cannot be used for carrying COAL at GREATER heights.

Correct choice is (c) To move COAL from one PLACE to another

To elaborate: Grab bucket CONVEYOR can grab as well as convey coal from one place to another. It is used with a crane or tower and it has different capacities. It is very essential when all other means of TRANSPORTING coal is not viable. It has HIGH initial cost but low operating cost.

The CORRECT answer is (a) Coal is reduced to fine granular state

To ELABORATE: The primary AIR fan induces flow of air through the pulverizer carrying the coal to the primary stage of grinding. In the primary stage of grinding, the coal is reduced to fine granular state by impact with a series of HAMMERS and then into the final stage where pulverization is completed by attrition.

Correct option is (a) 10 TONS of coal per hour

The best explanation: A ball has the capacity of pulverizing 10 tons of coal per hour containing4% of moisture requires 28 tons of steelballs and consumes 20 to 25 KW hr ENERGY per ton of coal. A wide range of fuels including anthracite and bituminous coal which are difficult pulverize, can still be used.

The CORRECT choice is (a) By ROTATING the CYLINDER

To explain I would say: The pulverization in ball mill takes place as a result of action between the balls and coal, as the cylinder they are put in is made to rotate. The cylinder is partly filled with VARIOUS sized steel balls. The cylinder is ROTATED at a velocity of 130 m/min periphery.

The CORRECT option is (b) Thinner fuel bed

Easy explanation: The primary air is SUPPLIED from the main wind box to the fuel bed situated below the stoker. The partly BURNT coal moves on to the extension grate. The low PRESSURE air entering into the extension grate, wind from main wind box is supplied to the thinner fuel bed on the extension grate. The quantity supplied can be regulated by air damper.

Right option is (c) Cyclone separator

Easiest explanation: Cyclones are mostly used for removing INDUSTRIAL dust from AIR or process gases. They are the principal type of gas-solid separator. The particulate is made to spin rapidly, heavier particle settle down and all the dust is REMOVED out from the ducts. To also remove dust from the pulverized COAL cyclone separator are used.

Correct choice is (c) Same direction

To ELABORATE: In under feed type of stokers, the fuel and air move in the same direction. In this stoker air after PASSING through the holes in the GRATE comes in CONTACT with the raw coal. As air DIFFUSES through the bed of raw coal, it mixes with the volatile matter generated by the raw coal.

Correct answer is (b) Multi-CYCLONE

For explanation I would say: When several cyclone operators are operated parallely, when this system is setup it is called multi-cyclone. It is important to note that cyclones can VARY drastically in their size. The size of the cyclone DEPENDS largely on how much flue gas must be filtered, and thus larger OPERATIONS tend to NEED larger cyclones.

The CORRECT answer is (a) Pneumatic WEIGHERS

The explanation: The pneumatic weighers use a pneumatic TRANSMITTER weigh head and the corresponding air pressure determined by the load applied and is transmitted to the weight indicating receiver may be used where electronic system is not permitted for use.

Right answer is (c) Inertia

The best I can explain: Cyclone separators or SIMPLY cyclones work on the principle of inertia to MOVE particulate matter from flue gases. In these high velocity dusts carrying gas is MADE to pass through CONICAL separator in tangential direction. This results in centrifugal action, throwing away the HEAVIER dust particles to the sides of conical chamber.

Right CHOICE is (a) To the shaft

The best explanation: SCREW conveyor is used to transmit COAL. It consists of an endless helicoids screw of diameter 150 mm to 500 mm wound around a ROTATING shaft. One end of the shaft is connected to the DRIVE whereas the other end is supported by a bearing.

Right choice is (c) On the type of coal used

For EXPLANATION I would say: DEPENDING on type of coal burned, the grate has air OPENINGS in the range of 20-40 percent of the total area. The air supply to different parts of the stoker is regulated to meet the CHANGING demand through these sections.

Correct choice is (c) Opposite direction

For EXPLANATION I WOULD say: FUEL, coke and ash in the fuel bed move in the direction opposite to that of air and GASES. The primary air entering from the bottom cools the ash until it finally rests in a plane immediately adjacent to the grate.

Right choice is (a) The volatile matter will be cooler at initial

To explain I would say: In case of over-feed burning, the volatile matter will be considerably cooler than the FURNACE gases and therefore it requires longer TIME for complete burning and also the AIR passes though incandescent zone and then enters ignition zone. This may CREATE a tendency to form smoke.

The correct answer is (c) When there is variation in STEAM pressure

To explain I would SAY: The master controller comes into action when there is variation in steam pressure and it goes down below the required level. This activates the SERVO motor COUPLED to the vanes of induced draught fan which opens the air damper slightly. Simultaneously the SECONDARY fan air damper also opens proportionately.

The correct CHOICE is (b) To settle the dust by letting them to strike

The best explanation: BAFFLES are placed in the direction of flow of flue gases. The dust particle strike down and settle. Heavier dust particles settle at the bottom by STRIKING on to the baffles and lighter dust particles are EXHAUST into ATMOSPHERE.

The correct choice is (a) Flight conveyor

Easy explanation: Flight conveyor is used for filling LARGE number of storage bins situated under the conveyor. It consists of a STEEL scrapers attached to CHAIN mechanism. Steel scrapers scrap the COAL through a trough and DISCHARGE it at the bottom.

Right option is (a) Ring burner

Easy explanation: 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.

The correct ANSWER is (C) At Right angle

Explanation: 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.

Right answer is (d) Direct firing system

To explain I WOULD say: The unit system is also called as the direct firing system. Most of the power plants with pulverized COAL as the FUEL are being installed with unit PULVERIZER. In this system each burner or a group of burner and pulverizer CONSTITUTE a unit. The over head bunker supplies raw coal by gravity into a feeder where it is dried with the help of hot air.

Correct answer is (a) Higher thermal EFFICIENCY

The best I can explain: Most of the large power plants use PULVERIZED fuel firing system since it is higher in its thermal efficiency. And selection of it mainly depends upon the size of BOILER unit, TYPE of the coal available, nature of load on the plant, load factor, cost of the fuel and availability of skilled labors.

The correct option is (c) Pre-cleaners

The explanation: CYCLONE separators are a part of a group of air pollution CONTROL devices known as pre-cleaners as they generally USED to roughly remove large pieces of PARTICULATE matter. This prevents finer filtration methods from having to deal with large, more abrasive particles LATER on.

The correct OPTION is (a) Below the raw fuel undergoing distillation

Explanation: The ignition zone lies directly below the raw fuel undergoing distillation. The GASES leaving the upper surface of the fuel BED CONTAIN combustible volatile matter formed from the raw fuel N2, CO2, O2, H2O and CO if the burning is incomplete.