1. C=70%, O=10%, N=1%, S=5% and ash=4%.The NCV of the fuel was found to be 9210cal/g. percentage of hydrogen be x and HCV of the fuel be y. Find out y/x.
a) 747.7
b) 768
c) 777
d) 676.9
Explanation: Apply the dulong’s formula that is: HCV = 1/100[8080C + 34500(H-O/8) + 22400S], here the C, S, O, H are the percentages of carbon, sulphur, oxygen and hydrogen. So, substitute all the given values in the formula and calculate so that you will get HCV. As we don’t know the value of H, you will get HCV=[5336.75+345H]Cal/g. Let it be eauatin-1 and then we know that NCV = (GCV-0.09H*587), here 587cal/g is the latent heat of steam. NCV is given then you will get GCV=[9210+52.83H]Cal/g and let it be equation-2. So equate both the equations to get the value of H. you will get H=13.25% and let it be x and substitute in equation-1 to get the value of HCV=9908cal/g. Now let be y and divide y with x to get 747.7.
2. A formula giving the gross heating value of coal in terms of the weight fractions of carbon, hydrogen, oxygen and sulphur from the _________
a) ultimate analysis
b) proximate analysis
c) distillation
d) filtration
Explanation: The percentages of the coal components are given by ultimate analysis and the proximate analysis is used to know the percentages of volatile matter, moisture, etc.
3. The dulong’s formula is not applicable for __________
a) solid fuel
b) gaseous fuel
c) liquid fuel
d) any fuel
Explanation: For calculating the components of coal and the petroleum the dulong’s formula is applied. So, the dulong’s formula is applied for both solids and liquids and not for gaseous.
4. Modification of the dulong’s formula can be done by considering the ___________
a) latent heat
b) heat
c) fuel state
d) liquid fuels
Explanation: The modification of the formula is done by considering the latent heat. It may be of water or vapour or steam accordingly. It represents the heating value of the fuels.
5. Calculate the HCV of the coal from the given data:
Weight of the fuel burnt=0.92
Initial temperature=120C
Final temperature=19.20C
Weight of the water in calorimeter is 1458g
Water equivalent of calorimeter = 14g.
a) 11520k.cal/m3
b) 11560k.cal/m3
c) 11000k.cal/m3
d) 11590k.cal/m3
Explanation: Use the formula HCV = [(W + w)(t2-t1)]/x, where W = Weight of the water in calorimeter, w = Water equivalent of calorimeter, t2 = Final temperature, t1 = Initial temperature, x = Weight of the fuel burnt. By substituting, you will get 11520k.cal/m3 as the final answer.
6. While calculating HCV, if we need to apply the fuse wire, acid and cooling corrections then what is the formula for HCV?
a) HCV = [(W + w)(t2-t1 + cooling correction)-(acid correction + fuse correction)]/weight of fuel
b) HCV = [(W + w)(t2+t1 + cooling correction)-(acid correction + fuse correction)]/weight of fuel
c) HCV = [(W + w)(t2-t1 + acid correction)-(cooling correction + fuse correction)]/weight of fuel
d) HCV = [(W + w)(t2+t1 + acid correction)-(cooling correction + fuse correction)]/weight of fuel
Explanation: The cooling correction must be added to the temperature difference because the heat loss is may be conduction, convection or radiation. The sum of acid and fuse corrections are subtracted because the heat produced by exothermic reactions is already included in the change in temperature. So, it is to be subtracted to get HCV.
7. One of the advantages of solid fuel is _________
a) low calorific value
b) requirement of excess air
c) ash formation
d) ease of transport
Explanation: Solid fuels can be transported very easily when compared to liquids and gaseous. Gaseous fuels are very difficult to carry as they escape easily and highly inflammable.
8. One of the disadvantages of solid fuel is _________
a) clinker formation
b) moderate ignition temperature
c) storage
d) transportation
Explanation: The clinker formation is the main disadvantage of solid fuels. They can be stored easily and transportation is also easy and having the moderate ignition temperature is also an advantage as we can control the rate of combustion.
9. _______ are used as rocket propellants in olden days.
a) solid fuels
b) liquid fuels
c) petroleum
d) gaseous fuels
Explanation: Solid fuels are used in rocket fuels. Gun powder is the main solid fuels that is mostly used in the rockets in the early stages but now we are using mostly liquid fuels as they have more efficiency than solid fuels.
10. Most available form of solid fuel is _________
a) coal
b) wood
c) petrol
d) lignite
Explanation: The most available form of solid fuel is wood. Wood is obtained from the trees and when trees die and decomposed for years through is called coal.