This PPT will let you know the basic information about the fuels, Types of fuel, Analysis of fuel and analysis of fuel gases.

1. Dr. Manoj Vora
Fuel

2. Dr. Manoj Vora
 A fuel is a combustible substance containing carbon as the main constituent which on proper
burning gives large amount of heat that can be used economically for domestic and industrial
purposes.
 During the process of combustion of a fuel, the atoms of carbon, hydrogen, etc combine with
oxygen with simultaneous liberation of heat. The calorific value of a fuel depends mainly on the
two elements.
Fuel + O2(Combustion) Product + Heat (Chemical Fuel)
C + O2 CO2 + 94 kcals
2H2 + O2 2H2O + 68.5 kcals
 So, carbon compounds have been used for many centuries as the source of heat and energy.
 The main source of fuel is coal and petroleum. These are stored fuels available in earth's crust
and are generally called fossil fuels because they were formed from the fossilised remains of plants
and animals.
Introduction of Fuel

3. Dr. Manoj Vora
 Coal is a highly carbonaceous matter that has been formed as a result of alteration of
vegetable matter (eg., plants) under certain favourable conditions. It is chiefly
composed of C, H, N and O besides non-combustible inorganic matter.
 The successive stages in the transformation of vegetable matter into coal are-wood,
peat, lignite, bituminous coal, steam coal and anthracite. Anthracite is probably the
purest form of coal and contains 95% carbon.
Coal

4. Dr. Manoj Vora
c) Bituminous Coal
Bituminous coal is further sub-classified on the basis
of its carbon content into three types as:
1. Sub-bituminous coal (70-80% C, 7000 kcal/kg)
2. Bituminous coal (78-90 %C, 8000-8500 kcal/kg)
3. Super-bituminous coal (90-93%, 8750 kcal/kg)
d) Anthracite
1. Anthracite is the superior grade of coal (95-98
%C).
2. Its volatile, moisture and ash contents are very
less.
3. Its calorific value is about 9000 kcal/kg
a) Peat
1. Peat is the first stage in the formation of coal.
2. Its calorific value is about 4000-5400 k cal/kg.
3. It is an uneconomical fuel due to its high proportion
of (80 -90%) moisture and lower calorific value.
4. It is a brown fibrous mass.
b) Lignite
1. Lignite is an intermediate stage in the process of coal
formation.
2. Its calorific value is about 6500-7100 kcal/kg
3. Due to the presence of high volatile content, it burns
with long smoky flame. (20-80% water)

5. Dr. Manoj Vora
Rank of Coal

6. Dr. Manoj Vora
 Primary Fuels (Natural fuels)
Fuels which occur naturally such as coal, crude petroleum and natural gas. Coal and crude
petroleum formed from organic matter many millions of years ago, are referred to as fossil
fuels.
 Secondary fuels (Artificial fuels)
Fuels which are derived from primary fuels by a treatment process such as coke, gasoline,
coal gas etc.
Both primary and secondary fuels may be further classified based upon their physical state as
(i) solid fuels
(ii) liquid fuels and
(iii) gaseous fuels.
Classification of Fuels

7. Dr. Manoj Vora
Chemical
Fuels
Primary Fuels
Solid
Liquid
Gaseous
Secondary Fuels
Solid
Liquid
Gaseous
Based on
Occurrence
Based on Physical State
Wood, peat, lignite, bituminous, anthracite etc
Mineral oils (Petroleum)
Natural gases
Coal, Charcoal, cock etc
Gasoline, Diesel, kerosene, coal tar, synthetic spirits etc
Coal gas, water gas, biogas, Oil gas, LPG, CNG etc..

8. Dr. Manoj Vora
Characteristics of a Good Fuel
1. Suitability
2. Cost
3. Calorific value
4. Ignition temperature
5. Flame temperature
6. Moisture
7. Non combustible matter content
8. Velocity of combustion
9. Control of the process
10.Ash
11.Sulphur and oxygen
12.Safety
13.Production of side products

9. Dr. Manoj Vora
Calorific value
CALORIFIC VALUE
Calorific value of a fuel is "the total quantity of heat liberated, when a unit mass (or volume) of the fuel is burnt
completely."
Units of Calorific value :
(1) 'Calorie' is the amount of heat required to raise the temperature of one gram of water through one degree Centigrade
(15-16°C).
(2) "Kilocalorie" is equal to 1,000 calories. It may be defined as 'the quantity of heat required to raise the temperature
of one kilogram of water through one degree Centigrade. Thus: 1 kcal = 1,000 cal
(3) "British Thermal unit" (B.T.U.) is defined as "the quantity of heat required to raise the temperature of one pound
of water through one degree Fahrenheit (60-61°F). This is the English system unit.
1 B.T.U. = 252 cal = 0.252 kcal
(4) Centigrade Heat Unit (C.H.U.) is defined as “the amount of heat required to raise the temperature of 1 pound of
water through 1 °C (15-16°C)”. 1 kcal = 3.968 B.T.U. = 2.2 C.H.U.

10. Dr. Manoj Vora
Higher or gross calorific value:
 Usually, all fuels contain some hydrogen and when the calorific value of hydrogen-containing fuel is determined
experimentally, the hydrogen is converted into steam. If the products of combustion are condensed to the room
temperature (15°C or 60°F), the latent heat of condensation of steam also gets included in the measured heat, which is
then called "higher or gross calorific value". So, gross or higher calorific value (HCV) is "the total amount of heat
produced, when unit mass/volume of the fuel has been burnt completely and the products of combustion have
been cooled to room temperature"(i.e., 15°C or 60°F ).
Lower or net calorific value (LCV)
 In actual use of any fuel, the water vapour and moisture, etc., are not condensed and escape as such along-with hot
combustion gases. Hence, a lesser amount of heat is available. So, net or lower calorific value (LCV) is "the net
heat produced, when unit mass /volume of the fuel is burnt completely and the products are permitted to
escape".
 Net calorific value= Gross calorific value - Latent heat of condensation of water vapour produced
= GCV - Mass of hydrogen per unit weight of the fuel burnt x 9 x Latent heat of condensation of
water vapour

11. Dr. Manoj Vora
• Dulong's formula for calorific value from the chemical composition of fuel is :
• HCV/GCV = 1/100 [8,080 C + 34,500 (H – O/8)+ 2,240 S] kcal/kg
• where C, H, O, and S are the percentages of carbon, hydrogen, oxygen and sulphur in the fuel respectively.
In this formula, oxygen is assumed to be present in combination with hydrogen as water, and
• LCV/NCV = [ HCV - 9H/100 x 587] kcal/kg
= [HCV - 0.09 H x 587] kcal/kg
• This is based on the fact that 1 part of H by mass gives 9 parts of H2O, and latent heat of steam is 587
kcal/kg.
Dulong's formula

12. Dr. Manoj Vora
Ex. 1 : A sample of coal contains C = 60%, O = 33%, H = 6%, S = 0.5% and N = 0.5%.
Calculate higher and lower calorific value of coal.
GCV = 1/100 [8,080 C + 34,500 (H – O/8)+ 2,240 S] kcal/kg
Ex. 2 : A sample of coal has the following composition C = 90%, O = 3.0%, S = 0.5%
and N = 0.5% and ash = 2.5%. Low calorific value of the coal was found to be 8400
Kcal/kg. Calculate percentage of hydrogen and gross calorific value of coal.
GCV= [LCV + 0.09 H x 587] kcal/kg ………..1
GCV = 1/100 [8,080 C + 34,500 (H – O/8)+ 2,240 S] kcal/kg……….2
1=2 ……3

13. Dr. Manoj Vora
Proximate analysis is a empirical rather than true analysis.
It includes the determination of the following:
1. Moisture content
2. Volatile matter
3. Ash
4. Fixed carbon
This gives quick and valuable information regarding commercial
classification and determination of suitability for a particular industrial
use.
Proximate Analysis

14. Dr. Manoj Vora
(1) Moisture: About 1 g of finely powered air-dried coal sample is weighed in a crucible. The crucible is
placed inside an electric hot air-oven, maintained at 105°-110°C. The crucible is allowed to remain in oven for
1 hour and then taken out, cooled in a desiccator and weighed. Loss in weight is reported as moisture (on
percentage-basis).
Percentage of moisture =
𝑳𝒐𝒔𝒔 𝒊𝒏 𝒘𝒆𝒊𝒈𝒉𝒕
𝑾𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒄𝒐𝒂𝒍 𝒔𝒂𝒎𝒑𝒍𝒆 𝒕𝒂𝒌𝒆𝒏
x 100
Significance
• Excess of moisture is undesirable in coal.
• For every percent of moisture present 1% of heat is lost.
• Moisture also increases the transport costs.
• However presence of about 5-10% moisture is desirable as it produces a uniform fuel bed and less of fly-ash.
Proximate Analysis

15. Dr. Manoj Vora
(2) Volatile matter:
 Consists of a complex mixture of gaseous and liquid products resulting from the thermal decomposition of
the coal.
 It consists of mainly of combustible gases (such as methane, hydrogen, carbon monoxide and other
hydrocarbons) or non-combustible gases (like CO2 and N2).
 The dried sample of coal left in the crucible then covered with a lid and placed in an electric furnace
(muffle furnace), maintained at 925°± 20°C. The crucible is taken out of the oven after 7 minutes of
heating. The crucible is cooled first in air, then inside a desiccator and weighed again. Loss in weight is
reported as volatile matter on percentage-basis.
Percentage of Volatile matt𝒆𝒓 =
𝑳𝒐𝒔𝒔 𝒊𝒏 𝒘𝒆𝒊𝒈𝒉𝒕 𝒅𝒖𝒆 𝒕𝒐 𝒓𝒆𝒎𝒐𝒗𝒂𝒍 𝒐𝒇 𝒗𝒐𝒍𝒂𝒕𝒊𝒍𝒆 𝒎𝒂𝒕𝒕𝒆𝒓
𝑾𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒄𝒐𝒂𝒍 𝒔𝒂𝒎𝒑𝒍𝒆 𝒕𝒂𝒌𝒆𝒏
x 100

16. Dr. Manoj Vora
Significance:
 A high volatile matter containing coal burns with a long flame, high smoke and has low calorific
value. Hence, lesser the volatile matter, better the rank of the coal. Higher volatile content in coal is
undesirable.
 A high volatile matter content means that high-proportion of fuel is burnt as a gas or vapour or may
escape unburnt.
 The high volatile coals do not cake well, where as medium volatile coals containing 20-30% of volatile
matter are capable forming hard and strong coke on carbonization.
 Coals containing less than 14% of volatile matter do not cake at all and are thus not suitable the
manufacturing coke.

17. Dr. Manoj Vora
(3) Ash content:
 Coal contains inorganic mineral substances which are converted into ash by chemical reactions during the
combustion of coal.
 Ash usually consists of silica, alumina, iron oxide and small quantities of lime, magnesia etc.
 Ash is determined by heating at 400 ℃ a known quantity of the powdered sample until most of the carbonaceous
matter is burnt off and then heating for 1 hour at 750 ℃ to complete the combustion. The cooled mass is weighed.
From the weight of the residue, the percentage of ash is calculated as,
Percentage of moisture =
𝑾𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒂𝒔𝒉 𝒍𝒆𝒇𝒕
𝑾𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒄𝒐𝒂𝒍 𝒔𝒂𝒎𝒑𝒍𝒆 𝒕𝒂𝒌𝒆𝒏
x 100
Two types:
1. Intrinsic Ash : minerals in vegetables. Oxides of Na, K, Mg, Ca and Si.
2. Extrinsic Ash: clay, gypsum, dirt mixed up during mining. Anhydrous CaSO4, CaCO3, Fe2O3.

18. Dr. Manoj Vora
Significance:
 A high percentage of ash is undesirable. It reduces the calorific value.
 In furnace grate, the ash may restrict the passage of air and lower the rate of combustion.
 High ash leads to large heat losses and leads to formation of ash lumps.
 The composition of ash and fusion range also influence the efficiency of coal.
 When coal is used in boiler, the fusion temperature of ash is very significant. Generally fusion
temperature lies in the range of 1000-1700 ℃. Ash having fusion temperature below 1200 ℃ is called
fusible ash and above 1430 ℃ is called refractory ash. If ash fuses at working temperature it leads to
clinker formation.
Clinker

19. Dr. Manoj Vora
(4) Fixed carbon:
Fixed carbon content increases from low ranking coals such as lignite to high ranking coal such as anthracite. Higher
the percentage of fixed carbon, greater is its calorific value and better the quality coal. Greater the percentage of fixed
carbon, smaller is the percentage of volatile matter. This also represents the quantity of carbon (in coal) that can be
burnt by a primary current of air drawn through the hot bed of a fuel,
Percentage of fixed carbon = 100 - % of (moisture + volatile matter + ash)
Significance:
• Higher the percentage of fixed carbon, greater is its calorific value.

20. Dr. Manoj Vora
Coal sample
A gm
Heat around 105 oC
For 1 hour
Take as a sample for VM %
B gm
%Moisture = A-B/A x 100
Heat around 950 oC
For 7min % VM= (B-C)/A X 100
Take as a sample for Ash %
C gm
Heat around 750 oC
For 1 hour % Ash= D/A X 100
Percentage of fixed carbon = 100 – [% moisture + %volatile matter + %ash]
Overview of Proximate Analysis
C= wt after heating at 950 oC
B = wt after heating at 110 oC
D= wt of final residue upon heating at 750 oC

21. Dr. Manoj Vora
 It includes the determination of carbon, hydrogen, nitrogen, sulphur and oxygen in coal.
 Since it is used for the determination of elements present in the coal, it is also called
elemental analysis.
 This analysis gives exact results and are useful in calculating the calorific value of coal
using Dulong's formula.
Ultimate Analysis

22. Dr. Manoj Vora
1. Carbon and Hydrogen (Liebig’s method)
A known amount of coal is taken in a combustion tube and is burnt in excess of pure oxygen. C and H of
coal are converted in to CO2 and H2O respectively.
The other oxidation products sulfur (S) and chlorine (Cl) are also obtained which are trapped by silver gauze
heated at 800-850 ℃ while CO2 and H2O are absorbed in pre-weighed KOH solution and anhydrous CaCl2
respectively.
C(s) + O2(g) CO2(g)
12gm 2(16)gm 44gm
H2(g) + 1/2O2(g) H2O
2gm 2(8)gm 18gm
1. Carbon and Hydrogen (Liebig’s method)

23. Dr. Manoj Vora
The chemical reactions involved are as under:
KOH + CO2 K2CO3 + H2O
CaCl2 + 7H2O CaCl2
.7H2O
Let,
Weight of coal sample= a gm
Increase in weight of CaCl2= b gm
Increase in weight of KOH= c gm
44 gm of CO2 = 12 gm of C
c gm of CO2 =(12/44) X c gm of carbon
Therefore, % carbon=(12/44) X (c X 100)/a
Similarly, % hydrogen= (2/18) X (b X100)/a

24. Dr. Manoj Vora
• Greater the percentage of carbon, greater the calorific value
• Higher percentage of carbon reduces the size of the combustion chamber
required.
• Higher percentage of hydrogen also increases the calorific value of the
fuel.
Significance of analysis of carbon and Hydrogen

25. Dr. Manoj Vora
2. Determination of Nitrogen

26. Dr. Manoj Vora

27. Dr. Manoj Vora
The nitrogen content present in coal is estimated by Kjeldahl’s method.
Procedure:
 A known weight of coal sample along with K2SO4 + HgSO4 is taken which acts as a
catalyst is heated with conc. H2SO4.
Nitrogen present gets converted into (NH4)2SO4.
The contents are then transferred into a round bottom flask and the contents are
then heated with excess NaOH.
The NH3 gas thus liberated is absorbed in a known volume of standard acid.
The unused acid is then determined b titrating with NaOH.
From volume of acid used by NH3 , nitrogen content can be calculated.

28. Dr. Manoj Vora
(NH4)2SO4 + 2NaOH → Na2SO4 + 2NH3 + 2H2O
NH3 + H2SO4 →(NH4)2SO4
Let, weight of coal sample = A gm
Volume of acid used= V1 ml
Normality of the acid = N1
V1 ml of N1 acid= V2 ml of N2 NH3
V2 ml of 1N NH3= V1 X N1 ml of acid
But 1000 ml of 1 N ammonia solution= 17g of NH3 = 14g of nitrogen
Therefore, V2 ml of 1 N NH3 solution = (14 X N1 X V1)/1000
% N=(1.4 x N1 x V1)/W

29. Dr. Manoj Vora
 Significance
 Nitrogen content in most of coals is between 1 and 2 percent.
 Is has no calorific value and hence its present is undesirable.
 In carbonization industries which recover a part of it as valuable by-product like
NH3, (NH4)3SO4 and pyridine bases.

30. Dr. Manoj Vora
There are two methods to determine Sulphur percentage
a) Oxygen bomb method: coal sample in Pt-crucible → placed in bomb of 300ml capacity → pure
oxygen is passed → bomb is placed in water → ignite by electric current → S coverts in to SO4 →
treat with BaCl2 → BaSO4 precipitates formed and calculate as per formula.
b) Eschka method: S oxidized by fuming Nitric acid in sulfuric acid → treat with BaCl2 → BaSO4
precipitates formed and calculate as per formula
 Percentage of S =
Weight of BaSO4 obtained x 32
Weight of coal sample taken x 233
x 100
Significance:
 Sulfur contribute to CV of coal
 SO2 and SO3 emits during combustion and H2S during carbonization and cause atmospheric pollution.
3. Determination of Sulphur content

31. Dr. Manoj Vora
5. Determination of Oxygen content : It is obtained by difference.
Percentage of O = 100 - Percentage of (C + H + S + N + ash)
Significance
• Less is the oxygen content better is the coal.
• O2 is in combined form with H2. H2 for combustion is lesser than total H2 present.
4. Ash determination is carried out as in proximate analysis.

32. Dr. Manoj Vora
 The mixture of gases such as CO2, O2, CO, etc., coming out from the combustion chamber is
called flue gases. The analysis of a flue gas would give idea about the complete or incomplete
combustion process. If the flue gases contain considerable amount of CO, it indicates that incomplete
combustion and it contain a considerable amount of oxygen indicates, complete combustion. The
analysis of flue gas is carried out by using Orsat's apparatus.
 Description of Orsat's Apparatus
 It consists of a horizontal tube, having 3 way stopcock. At one end of this tube, U-tube containing
fused CaCl2 is connected. The other end of this tube is connected with a graduated burette. The
burette is surrounded by a water-jacket to keep the temperature of gas constant. The lower end of the
burette is connected to a water reservoir by means of a rubber tube. The level of water in the burette
can be raised or lowered by raising or lowering the reservoir. The horizontal tube is also connected
with three different absorption bulbs I, II and III for absorbing CO2, O2 , CO.
Flue Gas Analysis (Orsat's method)

33. Dr. Manoj Vora
Bulb- I : contains KOH solution, and it absorbs only CO2
Bulb - II: contains 'alkaline pyrogallic acid' solution, and it
absorbs only CO2 and O2
Bulb- III: contains 'ammoniacal cuprous chloride' solution,
and it absorbs CO2, O2 and CO.

34. Dr. Manoj Vora
 Bulb- I : It contains 'potassium hydroxide' solution, and it absorbs only CO2
 Bulb - II: It contains 'alkaline pyrogallic acid' solution, and it absorbs only CO2 and
O2
 Bulb.:III : It contains 'ammoniacal cuprous chloride' solution, and it absorbs only
CO2, O2 and CO.
 Working
 The 3-way stopcock is opened to the atmosphere and the reservoir is raised, till the
burette is completely filled with water and air is excluded from the burette. The 3-
way stopcock is now connected to the flue gas supply, the flue gas is sucked into the
burette, and the volume of flue gas is adjusted to 100 cc by raising and lowering the
reservoir. Then the 3-way stop cock is closed.

35. Dr. Manoj Vora
 a) Absorption of CO2
 The stopper of the bulb-1 containing KOH solution is opened and all the gas is passed into the bulb-1 by
raising the level of water in the burette. The gas enters into the bulb-I, where CO2 present in the flue gas
is absorbed by KOH. The gas is again sent to the burette. This process is repeated several times to ensure
complete absorption of CO2.The decrease in volume of the flue gas in the burette indicates the volume of
CO2 in 100 cc of the flue gas.
b) Absorption of O2
 Stopcock of bulb-I is closed and stopcock of bulb-II is opened. The gas is again sent into the absorption
bulb-II, where O2 present in the flue gas is absorbed by alkaline pyrogallol (925 g of pyrogallol + 200g of
KOH in 500 ml distilled water). The decrease in volume of the flue gas in the burette indicates the volume
of O2.
c) Absorption of CO
 Now stopcock of bulb-II is closed and stopcock of bulb-Ill is opened. The remaining gas is sent into the
absorption bulb-III, where CO present in the flue gas is absorbed by ammoniacal cuprous chloride (100 g
CuCl2 + 125 mL liquor ammonia + 375 mL distilled water). The decrease in volume of the flue gas in the
burette indicates the volume of CO. The remaining gas in the burette after the absorption of CO2, O2 and
CO is taken as nitrogen.

36. Dr. Manoj Vora
References
 Engineering Chemistry by Jain and Jain
 A text book of Chemistry in Engineering by S. G. Pillai