Answer: c [Reason:] Charcoal is produced by slow pyrolysis. It is prepared by heating wood with limited supply of air below 280oC. It contains 80-90% of carbon. It is used for domestic purpose namely cooking, heating and metallurgical purpose. Charcoal is the light weight black carbon and ash residue produced by removing water and other volatile constituents from animal and vegetation substances. There are different types of coal namely sugar charcoal, activated charcoal, lump charcoal etc.

Answer: c [Reason:] Coal is prepared by heating bituminous coal continuously for 15 to 18 hours in closed chamber in the absence of air 500^oC to 700^oC. During this process the volatile matter is removed from the coal, leaving a dull black color to coke. It is hard porous structure and smokeless. It contains 85 to 95% carbon. When the bituminous coal is heated between 900^oC to 1000^oC, hard coke is produced. It is used in gas producing plants and blast furnaces.

Answer: c [Reason:] Briquette coal is prepared by moulding finely ground coal under pressure with or without the addition of binding material. Most commonly used binding materials are coal tar, crude oil and clay. By using briquetted coal, the fuel loss through boiler grates can be avoided.

Answer: b [Reason:] Pulverized coal is prepared by powdering low grade coal with high ash content. Dry coal is pulverized in pulverizing mills. It burns most efficiently when mixed with air and hence it is used in most of the power plants.

Answer: a [Reason:] They have low ignition temperature’. Ignition temperature is the minimum temperature at which a substance starts to burn. Different fuels have different ignition temperature. Some fuels have low ignition temperature and some have high ignition temperature. The fuels that have low ignition temperature are highly inflammable and burn quickly at the spark of fire. While some fuels that have high ignition temperature do not burn quickly. They require heating to burn. For e.g., kerosene oil does not burn unless it is heated up to its ignition temperature.

Answer: a [Reason:] Solid fuels tend to produce lot of smoke because they have large percentage of ash content. They are also brittle in nature and they contain some amount of ash in it when they are in ground. Due to their brittleness, it is common nature of solid fuels that they break into pieces while mining and transporting and form ash.

Answer: d [Reason:] Liquid fuels are available in nature in form of crude petroleum. All commercial liquid fuels are derived from crude petroleum or crude oil. The crude oil, as it comes out from oil wells contains 83-87% carbon, 10-14% hydrogen and small percentages of sulfur, nitrogen, oxygen and gases containing mainly ethane and methane.

Answer: a [Reason:] The impurities present in the crude oil are eliminated by the process of refining oil by distillation. It is based on the principle that boiling points of various hydrocarbons increase with an increase in molecular weight and when distilled, the crude oil is separated into gasoline, kerosene, fuel oil or reduced crude oil.

Answer: b [Reason:] Petrol has the lightest liquid petroleum fraction and highly volatile in nature. It is also called gasoline. It has specific gravity ranging from 0.70 to 0.78. It is obtained between 65 to 200^oC and it is a mixture of a number of hydrocarbons. It is light yellow in color and it is used as a fuel in automobiles and aero planes.

Answer: c [Reason:] Kerosene is heavier than gasoline but less volatile than it. It has specific gravity ranging from 0.78 to 0.85. It is obtained between 150 to 300^oC. It is mainly used in aviation gas turbines as jet fuel and also in lams and stoves. It is miscible in petroleum solvents but immiscible in water.

Answer: d [Reason:] Distillate is slightly heavier than kerosene and is used as fuel and domestic fuel. It is liquid fuel usually distilled from crude petroleum and produced in fractions. Distillate fuel is a type of fuel for internal combustion vehicles with either mechanical transmissions or electric transmissions. They are used in automobiles locomotives and agricultural machinery as well as space heaters and power generators.

Answer: a [Reason:] Diesel is heavier than kerosene. It has specific gravity ranging from 0.86 to 0.95. It is obtained between 200 to 370^oC. It is used in diesel engine. Diesel engines have found broad use as a result of higher thermodynamic efficiency and fuel efficiency.

Answer: a [Reason:] Fuel oil is similar to diesel but has wider composition than diesel. It is used in furnaces of oil fired boilers. Broadly speaking, fuel oil is any liquid fuel that is burned in furnace or boiler for the generation of power, except oil is having a flash point of approximately 42^oC and oils burned in cotton or wool-wick burners.

Answer: b [Reason:] Alcohol is an artificial fuel obtained from vegetable matter by fermentation process. It is used in many chemical processes. The first four aliphatic alcohols (methanol, propanol, ethanol and butanol) are of interest as fuels because they can be synthesized chemically or biologically. The general chemical formula for alcohol fuel is C_nH_2n+1OH.

Answer: d [Reason:] Artificial solid fuels need excess amount of air for complete combustion because they have low calorific value compared to liquid fuels and the rate of combustion of solid fuels cannot be easily controlled. They have tendency to form clinkers at high temperatures.

Answer: c [Reason:] With the acute shortage of other sources of energy viz. fossil based fuels and hydel sources the use of nuclear energy has become an inevitable option for the both developed and developing country.

Answer: a [Reason:] The amount of heat generated by burning one kg of nuclear fuel is equivalent to the energy generated by burning 3000 tonnes of coal or 1600 tonnes of oil. The production of Nuclear energy is carried out by two methods which are nuclear fission and nuclear fusion.

Answer: b [Reason:] Most attractive part of nuclear energy is that it has no combustion products and under safe working conditions contributes no pollutant to air. Site selection is completely independent of geographical area.

Answer: b [Reason:] Atom consists of a relatively heavy, positively charged nucleus and a number of much lighter negatively charged electrons. Electrons exist in various orbits around the nucleus. The nucleus consists of two sub-particles known as nucleons.

Answer: b [Reason:] The atom as a whole is not electrically charged it is actually electrically neutral in its state. The electric charge on the proton is equal in magnitude but opposite in sign to that of electron, the number of protons is equal to the number of electrons in the orbit.

Answer: a [Reason:] The nuclear energy is explained the basis of Einstein’s law, one atom may be transformed into another by losing or acquiring some of the above sub-particles. This results in mass change Δm and enormous amount of energy is released (or absorbed). According to Einstein’s law,
ΔE = Δmc²
Where, c=light of speed.

Answer: b

Most of the mass of the atom is in nucleus. The red dot is a proton it has positive charge of 1 unit, and black one is an electron, which has a negative charge of -1. There is only one orbital for hydrogen.

Answer: b

The masses of three atomic sub-particles are,
Neutron mass, mn = 1.008665 amu
Proton mass, mp = 1.007277 amu
Electron mass, me = 0.0005486 amu.

Answer: a [Reason:] Number of protons in the nucleus is called atomic number Z. it is unique for each chemical element, and represents both the number of positive charges on the central massive nucleus of the atom and the number of electrons in orbits around the nucleus.

Answer: b [Reason:] The total number of nucleons in the nucleus is called the mass number A. Nuclear symbols are written as zXA Where X is chemical symbol. The masses of atoms are compared on a scale in which an isotope of 6C12 has a mass of exactly 12.

Answer: c [Reason:] To disrupt a nucleus and separate in into its component nucleons, energy must be supplied from outside and this energy is called Binding energy. The nuclear force acts only when the nucleons are very close to each other and binds them into compact stable structure.

Answer: c [Reason:] The net neutrons produced per initial neutron accounting for all possible losses is called multiplication factor (K). If: K < 1 = system is subcritical. K = 1 = System is critical. K > 1 = system is super critical.

Answer: a [Reason:] Half life is the time during which one half of a number of radioactive species decays or one half of their activity ceases. It is also used to characterize any type of exponential and Non-exponential decay.

Answer: a [Reason:] Electrons that orbit outermost shell of an atom are called Valence electrons. The outermost shell is called valence shell. The presence of valence electron can determine the element’s chemical properties.

Answer: c [Reason:] A covalent bond is also called as molecular bond, which involves sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, when these share an electron than it is called as covalent bonding.

Answer: d [Reason:] Based on the contents of the tubular heating surface, boilers are primarily classified as fire tube boiler and water tube boiler. Fire tube boilers those in which production of combustion pass through the tubes and water tube boilers are those in which the products of combustion surround the water tubes from outside.

Answer: a [Reason:] 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.

Answer: d [Reason:] Water tube boilers are those in which the products of combustion (Hot flue gas) surround the water tubes from outside. Cold water enters the tubes and leaves hot. These boilers operate at very high pressures and are used for power generation.
Ex: Babcock-Wilcox boiler, Stirling boiler.

Answer: d [Reason:] If the boilers are used at one place only they are termed as stationary boilers. These boilers are used for either process heating in industries or for power generation in steam power plants. These are used at central station utility power plants, for plant process etc. Ex: Babcock-Wilcox boiler, Fluidized Bed Combustion (FBC) boiler.

Answer: c [Reason:] 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.

Answer: a [Reason:] 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.

Answer: a [Reason:] 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.

Answer: b [Reason:] 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.

Answer: b [Reason:] 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.

Answer: c [Reason:] Once-through boilers operate above critical pressure i.e., above 221.2bar. As the density of water and steam are same above the critical pressure there will be no recirculation. These types of boilers are also called as positive forced circulation boilers.

Answer: c [Reason:] In positive forced boilers, water enters the bottom of the tubes and completely transforms into steam as it passes through the tubes and reaches at the top. Thus, these boilers do not need a steam drum and hence often referred as drum-less boilers. These boilers work at very high pressures.

Answer: a [Reason:] Rate of evaporation is more as area of heating surface is more due to presence of large small diameter tubes. Due to that smaller water ratio is allowed to steam space where in the steam can be generated as a faster rate even if the boiler is cold. As the rate of evaporation is more, it is preferred in steam power plants for power generation.

Answer: d [Reason:] Due to high working pressure and positive circulation of water, chances of sediments depositing inside water tubes in the shell is less. This high working pressure of boiler in the shell can withstand high temperature or thermal stresses.

Answer: c [Reason:] Water circulation is limited inside the boiler shell. Water need not be that much pure and needs minimum treatment like passing through a pressure filter. Cleaning and repairing is not easy due to inaccessible parts, furnace cannot be altered and is used for one fuel only.

Answer: d [Reason:] The once through boiler has higher load response characteristics due to the fact that it does not have drum and has much lower water inventory. Many times load change response is dictated by the firing system and its controls rather than the boiler, per-say.

Answer: b [Reason:] 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.

Answer: a [Reason:] The function of the pressure gauge is to indicate the steam pressure inside the boiler drum in bar or in Kgf in cm² or in KN/m² in gauge pressure. If the boiler is fitted with a superheater, one more pressure gauge fitted to the superheater header indicates the superheated steam pressure at any given instant.

Answer: d [Reason:] Stop valve and junction valve are essentially same. Conventionally stop valves are smaller in size whereas, junction valves are larger. When the valve is mounted on the top most portion of the steam drum, normally the valve is called junction valve. If it is connected in the steam pipe to regulate the flow of steam, the valve is known as stop valve.

Answer: a [Reason:] 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.

Answer: a [Reason:] 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.

Answer: a [Reason:] 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.

Answer: a [Reason:] 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.

Answer: b [Reason:] Two types of safety valves are used in practice
A) Spring loaded safety valve
B) Dead weight safety valve

Answer: c [Reason:] 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.

Answer: a [Reason:] 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.

Answer: b [Reason:] Function of air preheater is to recover the heat of a portion of exhaust flue gases before the flue gases enter the chimney. It is places along the passage of the exhaust flue gases in between the economizer and the chimney.

Answer: a [Reason:] 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.

Answer: a [Reason:] 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.

Answer: a [Reason:] Function of feed water pump is to pump water at high pressure to the water space of the boiler drum. There are many types of feed pumps, in which they are mainly classified into rotary and reciprocating pumps.

Answer: a [Reason:] 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.

Answer: c [Reason:] when fuels are burnt, heat is produced. It can also be defined as the amount of heat produced on complete burning of 1gm of fuel. SI unit of calorific value is kJ/g. The chemical reaction is typically hydrocarbon or other organic molecule reacting with oxygen to form carbon dioxide and water and release heat.

Answer: a [Reason:] The different fuels have different calorific values, i.e. different fuels produce different amount of heat in heat on burning. The calorific value of fuel helps us to decide that which fuel is good for us. This is done by comparing the calorific values of fuels with each other. Usually, a fuel having higher calorific value is considered to be a good fuel.

Answer: c [Reason:] Hydrogen gas has the highest calorific value of 150KJ/g among all. So, hydrogen gas is considered is considered to be an extremely good fuel. However, hydrogen gas is not used as a fuel in homes and industries. Reason is hydrogen is highly combustible and it burns with explosion when lighted, its transportation from place to place is very difficult, and the cost of production of hydrogen is very high.

Answer: a [Reason:] Methane contains 25% of hydrogen. Since, the calorific value of fuels depends on the percentage of hydrogen present in them. So the fuels which have higher percentage of hydrogen will have higher calorific value as compared to those fuels which have lower percentage of hydrogen.

Answer: b [Reason:] The calorific value of solid of solid and liquid fuel is defined as the amount of heat liberated by complete combustion of unit mass of fuel. In SI unit s it is expressed in kJ/kg. A bomb calorimeter is a type of constant volume calorimeter used in measuring heat of combustion of particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured.

Answer: b [Reason:] The calorific values of gaseous fuel are defined as the amount of heat liberated by complete combustion of unit volume of fuel. SI unit is KJ/m3. This calorimeter works on principle of burning of a known volume of gas an imparting the heat with maximum efficiency to steadily flowing water and finding out the rise in temperature of a measured volume of water.

Answer: a [Reason:] The calorific value of all organic compounds has the sign corresponding to an exothermic reaction. Because the double bond in molecular oxygen is much weaker than other double bonds or pairs of single bonds, particularly those in combustion products carbon dioxide and water, conversion of the weak bonds in o2 to the stronger bonds in CO2 and H2O releases energy as heat.

Answer: a [Reason:] Energy value (heating value or calorific value) of a substance, usually a fuel or food is the amount of heat released during the combustion of a specified amount of it. The energy value is characteristic for each substance. It is measured in units of energy per unit of the substance, usually mass, such as Kj/Kg, KJ/mol, and kcal/kg.

Answer: a [Reason:] Gross heating value accounts for water in the exhaust leaving as vapor, and includes liquid water in the fuel prior to combustion. This value is important for fuels like wood and coal, which will usually contain some amount of water prior to burning.

Answer: c [Reason:] The difference between the two heating values depends on the chemical composition of the fuel. In the case of pure carbon or carbon monoxide, the two heating values are almost identical, the difference being the sensible heat content of carbon dioxide between 150^oC to 25^oC.