Define fuels.
Ans. Fuels defined as “a combustible substance containing carbon as the main constituent, which on proper burning liberates large amount of heat, which can be used economically for domestic as well as industrial purposes.”
2. Arrange wood, peat, lignite, bituminous coal and anthracite in decreasing order of their calorific values and in increasing order of their moisture contents.
Ans. Decreasing order of their calorific values:
Anthracite < bituminous coal < lignite < peat < wood. Increasing order of their moisture content : Authracite < bituminous coal < Lignite < peat < wood.
3. Distinguish between proximate and ultimate analysis of coal.
| No | Proximate Analysis of coal | Ultimate Analysis of coal |
| (i) | It involves the determinations of physical constituents like moisture, volatile, ash and fixed carbon contents in coal. | It involves the determination of chemical constituents like carbon, hydrogen, nitrogen, sulphur and oxygen contents in coal. |
| (ii) | It gives the approximate composition of the main constituents of coal. | It gives the exact composition of the elementary constituents of coal. |
4. Water gas is superior than producer gas How ?
Ans. Water-gas is a mixture of combustible CO and H2 gases with little non combustible CO2 and N2 gases but producer gas contains large amount of non-combustible N2 and CO2 gases.
Water gas produces a blue, short and hot flame, but producer gas produces long and low hot flame. So, the water gas is superior than producer gas.
5. Define octane number. How can it be improved?
Ans. Octane number of a gasoline is the percentage of iso-octane in a mixture of iso-octane and n-heptane which matches the fuel under test in knocking characteristics.
The octane number of many fuels can be improved by the addition of extremely poisonous materials like tetraethyllead (TEL) and diethyl telluride.
6. Define cetane number. How can it be improved?
Ans. Cetane Number is defined as, “the percentage of cetane present in a mixture of cetane and a-methyl Naphthalene.” The cetane number of a diesel oil can be improved by adding dopes like Ethyl nitrate.
7. Why the gaseous fuels preferred over kinds of fuels?
Ans. Gaseous fuels have high calorific value than solid fuels, because
(i) During burning they do not produce any ash or smoke.
(ii) Compared to solid and liquid fuels, they have high thermal efficiency.
8. What are the advantages and disadvantages of solid fuels?
(i) Solid fuels are easily available and they are cheap.
(ii) Handling and transportation are easy.
Disadvantages of solid fuels are,
(i) They form large amount of ash during burning and its disposal is a big problem.
(ii) A large space is required for storage.
9. What are advantages and disadvantages of liquid fuels?
Ans. Advantages of liquid fuels are,
(i) They can be stored in containers of different shape.
(ii) Easily transported through pipes.
(iii) No ash content.
(iv) Easily ignited and emissions can be easily controlled.
Disadvantages of Liquid fuels are,
(ii) It is more expensive than solid fuels.
(iii) It’s produce impleasant odours especially when the combustion is incomplete.
(iv) Risk of fire hazards is greater particularly in case of inflammable and volatile liquid fuels.
10. Water gas is used as reducing agent in industries why?
Ans. The average composition of water gas is CO= 41% , H2 = 51% and CO2 = 4% . It has high percentage of reducing gases such as CO and H2 . Hence it is used as a source of hydrogen in many industries.
11. What is water gas ? State its uses.
Ans. Water gas is a mixture of combutible gases CO and H2 with little non-combustible gases like CO2 and N2 . This average composition is H2 = 51% , CO = 41% , N2 = 4% , CO2 = 4% . Its calorific value is 2800Kcal/m3 . It is used as a source of hydrogen gas and an illuminating gas.
12. Why is octane number of 2, 3-dimethly heptane higher than that of n-heptane ?
Ans. The structure of 2, 3-dimethyl heptane is
CH3 -CH2– CH2-CH2-CH2– CH2– CH3
The anti-knocking tendency (octane number) of branched chain alkane is greater than straight chain alkane. So, the octane number of 2, 3-dimethyl heptane is higher than that of n-heptane.
13. Why is producer gas used immediately after production?
Ans. Producer gas exiting from as producer is quit hot (400 – 800°C) . In order to utilize the heat contained in the freshly produced producer gas is used immediately. This procedure also avoids the requirements of storage tanks. Hence producer gas is used immediately after its production.
14. Why is calorific value of coal gas higher than that of producer gas?
Ans. Coal gas contains higher percentage (about 90%) of combustible gases (CH4 + H2 + CO + C2H2 + C2H4) . So, its calorific value is quite high (about 4,900Kcal/m3). On the other hand, producer gas contains low percentage (about 30-40 %) of combustible gases (CO +H2). So, its calorific value is low (about 1,300 Kcal/m3 ).
15. Why is coke preferred to coal in metallurigical processes?
Ans. Coke possesses,
(i) Higher strength and porosity
(ii) Lesser sulphur content.
(iii) Short flame burning characteristics.
So, it is preferred to coal in metellurgical purposes.
16. Define Cracking.
Ans. The process of decomposition of less volatile heavier compounds into highly volatile lower fractions by the application of heat and pressure or by using catalysts is known as cracking.
17. What is diesel index ?
Ans. The quality of a diesel oil is indicated by diesel index number using the following formula.
Diesel index number
= Specific gravity (API) Aniline point in °F/100
API- American Petroleum Institute
18. Water gas is superior to producer gas. How?
Ans. It has higher calorific value ( 2800 K cals/m3 ) than producer gas.
It is a good source of hydrogen. So water gas can be used for the manufacture of Ammonia.
Since water gas contains about 48% of hydrogen, it can be used as reducing agent in metallurgical industries.
Water gas can be used for the manufacture of synthetic petrol.
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