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A comprehensive overview of fuel, its classification, combustion principles, and the determination of calorific value. It delves into the concepts of gross and net calorific values, proximate and ultimate analysis of coal, and various types of fuels such as lpg, water gas, producer gas, and cng. The document also discusses the characteristics of a good fuel, the determination of calorific value by bomb calorimeter, and the importance of moisture, volatile matter, and ash content in coal.
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Calorific value of a fuel is โthe total quantity of heat liberated, when a unit mass (or volume) of the fuel is burnt completelyโ Units of Heat: ( 1 ) Calorie- is the amount of heat required to raise the temperature of one gram of water through one degree centigrade ( 15 - 16 ยฐ C). ( 2 ) Kilocalorie โ is equal to 1 , 000 calories. This is the unit of metric system and may be defined as โthe quantity of heat required to raise the temperature of one kilogram of water through one degree centigrade. Thus, 1 kcal = 1 , 000 calories. ( 3 ) British Thermal Unit (BTU)- is defined as โthe quantity of heat required to raise the temperature of one pound of water through one degree Fahrenheit ( 60 - 61 ยฐ F). This is the English system unit. 1 BTU = 252 cal = 0. 252 kcal and 1 kcal = 3. 968 BTU ( 4 ) Centigrade heat unit (CHU)-is โthe quantity of heat required to raise the temperature of 1 pound of water through one degree centigradeโ. Thus, 1 kcal = 3. 968 BTU = 2. 2 CHU
Description: Bomb Calorimeter consists of a strong stainless steel bomb where the fuel sample is burnt. The bomb has oxygen inlet valve and two stainless steel electrodes. A small ring is attached to one of the electrodes. In this ring, a nickel or stainless steel crucible is placed. Determination of calorific value by bomb calorimeter The bomb is placed in a copper calorimeter containing a known weight of water sample. The copper calorimeter is provided with a thermometer and stirrer for stirring water. The copper calorimeter is covered by an air jacket and water jacket.
A known weight of the fuel sample is taken into the crucible. The fine magnesium wire is touching the fuel sample and then stretched across the electrodes. The bomb lid is tightly closed with the help of screw. The bomb is filled with oxygen at 25 atmospheric pressure. The bomb is now placed in a copper calorimeter which containing known weight of water. Initial temperature of the water in the calorimeter is noted (t 1 ยฐC) after stirring. The electrodes are connected to a battery ( 6 v). The current is now supplied to the fuel sample which undergoes burning with the evolution of heat. The liberated heat increases the temperature of water in the calorimeter. The maximum temperature of the water during experiment is finally noted (t 2 ยฐC). From the temperature difference, calorific value of the fuel can be calculated as follows:
Coal is a highly carbonaceous matter. Coal was formed when dead plant matter decayed into peat and is converted into coal by the heat and pressure of deep burial over millions of years. It is chiefly composed of C, H, N and O besides non- combustible inorganic matter. The stages in the transformation of vegetable matter into coal are wood, peat, lignite, bituminous coal, and anthracite. Anthracite is the purest form of coal and contains 95 % carbon.
๐ฟ๐๐ ๐ ๐๐ ๐ค๐๐๐โ๐ก ๐๐ ๐๐๐๐ ๐๐๐๐โ๐ก ๐๐ ๐๐๐๐ ๐ก๐๐๐๐ ๐๐๐๐ก๐๐๐๐๐ฆ
Significance of Moisture: High moisture content of the coal is undesirable for the following reasons: Reduces the calorific value of coal, Increases the consumption of coal for heating purpose. Lengthens the time of heating.
(iii) Determination of ash in coal: It is the weight of residue obtained after burning a known weight of coal in an open crucible in the presence of air at 750 ยฐC for 30 minutes. % of ash content = (๐ฟ๐๐ ๐ ๐๐ ๐ค๐๐๐โ๐ก ๐๐ ๐๐๐๐)/(๐๐๐๐โ๐ก ๐๐ ๐๐๐๐ ๐ก๐๐๐๐ ) ร 100 Significance of ash content: Ash in the combination product of mineral matter in the coal. It consists mainly SiO 2 , Al 2 O 3 and Fe 2 O 3 with varying number of other oxides such as Na 2 O, CaO, MgO etc. Ash containing the oxides of Na, Ca and Mg melt easily. High ash content in coal is undesirable because it increases transporting, handling and storage costs is harder and stronger has lower calorific value.
(iv) Determination of fixed carbon: It is determined indirectly by deducting the sum total of moisture, volatile matter and ash percentage from 100. % of fixed carbon in coal = 100 - % (moisture + volatile matter + ash) Significance of Fixed carbon: It is the pure carbon present in coal. Higher the fixed carbon content of the coal, higher will be the calorific value of the sample.
Determination of carbon & hydrogen About 0.2g of accurately weighed coal is burnt in oxygen in apparatus shown above. C + O 2 CO 2 2H + ยฝ O 2 H 2 O
Mol. Wt. of CO 2 Mol. Wt. of C Mol. Wt. of H 2 O Mol. Wt. of H 2
Determination of carbon & hydrogen
