FUELS AND COMBUSTION
1 Definition
1.1 Characteristics for good fuel
2.1 Calorific value
2.2 Gross or high calorific value (gcv)
2.3 Net or lower calorific value(ncv)
2.4 Theoretical calculation of calorific value (
dulong‟s formula)
3 Solid fuel
3.1 Advantages of solid fuels
3.2 Disadvantages of solid fuels
4 Coal
4.1 Proximate analysis
4.2 significance of proximate analysis
5 Carbonization of metallurgical coke
5.1 Metallurgical coke
5.2 Otto-Hoffman‟s method
5.3 Recovery of by-products
5.4 Advantages of otto hoffman‟s process
6 Liquid fuels
6.1 Advantages of liquid fuels, disadvantages of
liquid fuels
6.2 Petroleum
6.3 Refining of petroleum or crude oils
6.7. Knocking
7.1 Causes of knocking in S.I (petrol) engines
7.2 Improvement of anti knock characteristics
7.3 Octane number or octane rating
7.4Anti-knock agent
7.5Causes of knocking in C.I (diesel) engines
7.6 Cetane number or cetane rating
7.8 Diesel index
8. Hydrogenation of coal
8.1 Bergius process (indirect method)
8.2 Fischer-tropics process (indirect method)
9 Gaseous fuels
9.1. Compressed natural gas (CNG)
9.2 Producer gas
9.3. Water gas
9.4 LPG- liquefied petroleum gas
10 GLOSSARY
1 DEFINITION
Fuel is a combustible substance ,during combustion of it the atoms of C,H,S and N etc are combine with oxygen with simultaneous liberation of heat and light.
2. CHARACTERISTICS FOR GOOD FUEL
High calorific value.
Moderate ignition temperature.
Low moisture content.
Low contents of non-combustible matters.
Combustion should be controllable.
Easy to transport and readily available at low
cost.
2.1 Calorific value:
. It is
defined as the amount of heat liberated by the complete combustion of a unit
mass of the fuel.
2.2 Gross or high calorific value (GCV)
It is defined as the total heat generated when a unit quantity of fuel
is completely burnt and the products of combustion are cooled to room
temperature.
2.3 Net or Lower Calorific Value(NCV)
It is
defined as the “net heat produced when a unit quantity o f fuel is completely
burnt and the products of combustion are allowed to escape.
NCV =
GCV- latent heat of condensation of steam produced.
2.4 Theoretical calculation of calorific value (
Dulong‟s formula)
According to Dulong, the calorific value of a fuel
is the sum of the calorific values of its constituent elements.
The calorific values of C, H&S are found to be
8080, 34500 and 2240kcals when 1kg of the fuel is burnt completely.
Thus,Dulong‟s formulae for GCV is written as
GCV=1/100
[8080(C)+34500(H-O/8)+2240(S)]Cals/kg.
NCV =[
GCV-9/100( H)x 587] Kcals/kg.
The latent heat of steam is 587Kcals/kg.
In Dulong‟s formula C, H, O&S represent the
percentage of the corresponding elements.
3 SOLID FUEL
ADVANTAGES OF SOLID FUELS:
Solid fuels are easily available and they are
cheap.
Handling and transportation are easy.
They can be stored conveniently without any risk.
They have a moderate ignition temperature.
DISADVANTAGES OF SOLID FUELS:
Combustion process cannot be easily controlled.
The calorific value is comparatively lower.
They form large amount of ash and its disposal is a
big problem.
A large space is required for storage.
4 COAL
Analysis of coal
4.1 Proximate Analysis:
It
involves the determination of percentage of following in coal
a. Moisture content
b. Volatile matter
c. Ash content
d. Fixed carbon
Moisture content
1gm
of powdered and air-dried coal sample in crucible is heated at 100-150⁰C in an electric air oven for 1 hour.
The
loss in weight of the sample is found out and percentage of moisture is
calculated as
% of moisture = (Loss in weight of coal / Weight of
air-dried coal) ×100
(b) Volatile matter:
In this
the crucible with residual coal sample is covered with a lid and heated at 950±
20⁰C for
7mins in a muffle furnace. The loss in weight is found out.
(c) Ash
Content:
The
crucible with residual coal sample is heated without lid at 700 ± 50 ⁰C for ½hour in a muffle furnace.
The loss in weight is found out.
(d) Fixed
Carbon:
of fixed carbon = percentage of (a+b+c)
4.2 Significance of proximate analysis:
High percentage of moisture content is undesirable because
High percentage of volatile matter is undesirable because
High percentage of ash content is
undesirable because
High percentage of fixed carbon
content is desirable because
5 CARBONISATION OFMETALLURGICAL COKE
When coal
is heated strongly in the absence of air , it is converted into lustrous,
dense, porous and coherent mass known as coke. This process of converting coal
is known as carbonization.
5.1 METALLURGICAL COKE
When
bituminous coal is heated strongly in the absence of air, the volatile matter
escapes out and the mass becomes hard, porous and coherent which is called
Metallurgical coke.
PREPARATION
5.2 Otto-Hoffman’s method
Significance
of Otto-Hoffman‟s method
(i) To
increases the thermal efficiency of the carbonization process and,
(ii) To
recover the valuable by products (like coal gas, ammonia, benzyl oil, etc).
. The
oven consists of a number of silica chambers , each chamber is provided with a
charging hole at the top, it is also provided with a gas off take valve and
iron door at each end for discharging coke.
Coal is
introduced into the silica chamber and the chambers are closed.
The
chambers are heated to 1200 o C by burning the preheated air and the
producer gas mixture in the interspaces between the chambers.
The air
and gas are preheated by sending them through 2nd and 3rd
hot regenerator.
Hot flue
gases produced during carbonization are allowed to pass through 1st
and 4th regenerators until the temperature has been raised to 1000ċ.
While 1st
and 4th regenerated are heated by hot flue gases, the 2nd
and 3rd regenerators are used for heating the incoming air and gas
mixture.
When the
process is complete, the coke is removed and quenched with water.
The yield
of coke is about 70%.
The
valuable by products like coal gas, tar, ammonia, H2S and benzyl,
etc. can be recovered from flue gas.
5.3 Recovery of by-products
(i) Tar
The flue
gases are first passed through a tower in which liquor ammonia is sprayed. Tar and dust get dissolved and collected
in a tank below
(ii)
Ammonia
The gases
are then passed through another tower in which water is sprayed. Here ammonia gets converted to NH4OH.
(iii)
Naphthalene
The gases
are again passed through a tower, in which cooled
water is sprayed, naphthalene gets condensed.
(iv)
Benzene
The gases
are passed through another tower, where petroleum
is sprayed, benzene gets condensed to liquid.
(v)
Hydrogen Sulphide
The
remaining gases are then passed through a purifier packed with moist Fe2O3.
Here H2S is retained.
The final
gas left out is called coal gas
which is used as a gaseous fuel.
5.4 Advantages of Otto Hoffman’s process
Valuable by products like ammonia, coal gas,
Naphthalene etc. are recovered.
The carbonization time is less.
Heating is done externally by producer gas.
6 LIQUID FUELS
ADVANTAGES OF LIQUID FUELS:
They have higher calorific value than solid fuel.
They occupy less storage space than solid fuels.
Their combustion is uniform and easily
controllable.
Liquid fuels do not yield any ash after burning.
DISADVANTAGES OF LIQUID FUELS:
Liquid fuels are more costly than the solid fuels.
Liquid fuels give unpleasant odor during incomplete
combustion.
Special type of burners is required for effective
combustion.
Some amount of liquid fuels will escape due to
evaporation during storage.
6.2 PETROLEUM
It is
naturally occurring liquid fuel.
It is
dark brown or black coloured viscous oil
Crude oil
is a mixture of paraffinic, olefinic and aromatic hydrocarbons with small
amounts of organic compounds like N, O and S.
The
average composition of crude oil is as follows
C = 80-87%
H = 11-15%
S =
0.1-3.5%
N+O =
0.1-0.5% It is classified into three types
1.
Paraffinic-Base type crude oil
It
contains saturated hydrocarbons from CH4 to C35H72
with a smaller amount of naphthenes and aromatics.
2.
Naphthenic or Asphaltic Base type crude oil
It
contains Cycloparaffins or naphthenes with a smaller amount of paraffin and
aromatics
3. Mixed
base type crude oil
It
contains both paraffinic and asphaltic hydrocarbons.
6.3 REFINING OF PETROLEUM OR CRUDE OIL
The crude
oil obtained from the earth is a mixture of oil, water, unwanted impurities and
its subjected to fractional distillation.
During
fractional distillation, the crude oil is Thus, the process of removing
impurities and separating the crude oil into various fractions having different
boiling points is called Refining of Petroleum.
The
process of refining involves the following steps.
Step 1: Separation of water (Cottrell‟s
process)
The crude
oil well is an extremely stable emulsion. The crude oil is allowed to flow
between two highly charged electrodes, where colloidal water droplets combine
to form large drops, which is then separated out form the oil.
Step 2: Removal of harmful sulphur
compounds
Sulphur
compounds are removed by treating the crude oil with copper oxide. The copper
sulphide formed is separated out by filtration.
Step: 3 Fractional distillation
The
purified crude oil is then heated to about 400ċ in an iron retort, where the
oil gets vaporized.
The hot
vapors are then passed into the bottom of a “fractionating column”.
The
fractionating column is a tall cylindrical tower containing a number of
horizontal stainless steel trays at short distances.
Each tray
is provided with small chimney covered with a loose cap.
When the
vapors of the oil go up in the fractionating column, they become and get
condensed at different trays.
The
fractions having higher boiling
points condense at lower trays
whereas the fractions having lower
boiling points condense at higher
trays.
The
gasoline obtained by this fractional distillation is called straight-run gasoline.
Various
fractions obtained at different trays are given in table.
7. KNOCKING
The rate
of ignition of the fuel gradually increases and the final portion of the
fuel-air mixture gets ignited instantaneously producing an explosive sound
known as “Knocking”.
7.1 Causes of knocking in S.I (Petrol) engines
In a
petrol engine fuel used as a mixture of gasoline vapor and air at 1:17 ratio
The
mixture is compressed and ignited by an electric spark.
The
products of combustion increase the pressure and push the piston down the
cylinder.
If the
combustion proceeds in a regular way, there is no problem in knocking.
But in
some cases, the rate of combustion (oxidation) will not be uniform due to
unwanted chemical constituents of gasoline.
Knocking
property of the fuel reduces the efficiency of engine. So a good gasoline
should resist knocking.
7.2Improvement of anti knock characteristics
Blending petrol of high octane number with petrol
of low octane number, so that the octane number of the latter can be improved.
The addition of anti-knock agents like Tetra-Ethyl
Lead (TEL).
7.3 OCTANE NUMBER OR OCTANE RATING
Thus octane number is defined as „the percentage of
iso-octane present in a mixture of iso-octane and n-heptanes.‟Octane number is
introduced to express the knocking characteristics of petrol. On the other
hand, iso-octane gives very little knocking and so, its anti-knock value has
been given 100.
7.4 ANTI-KNOCK AGENT
Tetraethyl
lead (TEL) (C2H5)4 Pb is an important additive added to petrol. Thus the petrol
containing tetra ethyl lead is called leaded petrol. TEL reduces the knocking tendency
of hydrocarbon.
Mechanism of Knocking
.
Knocking follows a free radical mechanism, leading to a chain growth which
results in an explosion.
If the
chains are terminated before their growth, knocking will cease.
TEL
decomposes thermally to form ethyl free radicals which combine with the growing
free radicals of knocking process and thus the chain growth is stopped.
Disadvantages of using TEL
When the
leaded petrol is used as a fuel, the TEL is converted to lead oxide and
metallic lead.
To avoid
this, small amount of ethylene dibromide is added along with TEL.
This
ethylene dibromide reacts with Pb and PbO to give volatile lead bromide, which
goes out along with exhaust gases and creates atmospheric pollution.
But now a
day‟s aromatic phosphates are used instead of TEL.
7.5Causes of knocking in CI (Diesel) engines
In a
diesel engine, first air is compressed and raises the temperature of the
cylinder to about 500ċ then the oil is sprayed.
The
expanding gases push the piston and power stroke begins.
The
combustion of a fuel in a diesel engine is not instantaneous and the time
between injection of the fuel and its ignition is called Ignition lag or
Ignition delay and raising the temperature of vapour to its ignition
temperature.
.
Which undergo explosion during ignition ,this is
responsible for diesel knock.
7.6 CETANE
NUMBER OR CETANE RATING
Thus the
cetane number is defined as “the percentage of cetane present in a mixture of
cetane and 2-methyl naphthalene which has the same ignition lag as the fuel
under test”.
Cetane
number is introduced to express the knocking characteristics of diesel.
Cetane (C16H34)
has a very short ignition lag and hence its cetane number is taken as 100.
On the
other hand 2-methyl naphthalene has a long ignition lag and hence its cetane
number is taken zero.
The
cetane number decreases in the following order.
Straight
chain paraffin‟s >Cycloparaffins >Olefins >Branched
paraffin‟s.
The
cetane number of diesel oil can be increased by adding additives called dopes.
Ex: Ethyl nitrate, Iso-amyl nitrate.
7.8 DIESEL INDEX
The
quality of diesel oil is indicated by diesel index number using the following.
Aniline
point and specific gravity is noted from API
(American Petroleum Institute)
Comparison
of gasoline oil and diesel oil
Gasoline
oil
1. Low boiling fraction of petroleum contains
C5-C9 hydrocarbons.
2. Fuel for SI engine
3. Knocking tendency is measured in octane
rating
4. Knocking is due to premature ignition
5. Antiknocking is improved by the addition of
TEL
6. Its exhaust gases contain higher amount of
pollutants
7. More consumption, lower thermal efficiency
Diesel
oil
1. High boiling fraction of petroleum contains
C15-C18 hydrocarbons.
2. Fuel for Cl engine.
3. Knocking tendency is measured in cetin
rating.
4. Knocking is due to ignition lag.
5. Anti knocking is improved by doping with
ethyl nitrate.
6. Its exhaust gases contain lesser amount of
pollutants.
7. Less consumption, higher thermal efficiency.
8. Hydrogenation of coal
The
preparation of liquid fuels from solid coal is called Hydrogenation of coal.
Coal
contains about 4.5% of hydrogen compared to about 18% of in petroleum. So, coal
is a hydrogen deficient compound.
If coal
is heated with hydrogen to high temperature under high pressure, it is
converted to gasoline.
There are
two methods available for the hydrogenation of coal.
Bergius process (or direct method)
Fischer- Tropsch Process (or indirect method)
8.1(a)Bergius process (indirect method)
Finely
powdered coal + heavy oil+ catalyst powder (tin or nickel) is made into a paste
The paste
is pumped along with hydrogen gas into the converter, where the paste is heated
to 400-450ċ under a pressure of 200-250atm.
During
this process hydrogen combine with coal to form saturated higher hydrocarbons,
which undergo further decomposition at higher temperature to yield mixture of
lower hydrocarbons.
The
mixture is led to a condenser, where the crude oil is obtained.
The crude
oil is then fractionated to yield.
Gasoline (ii) Middle oil (iii) heavy oil
The
middle oil is further hydrogenated in vapour phase to yield more gasoline.
The heavy
oil is recycled for making paste with fresh coal dust.
The yield
of gasoline is about 60% of the coal.
8.2 (b) Fischer-tropics process (indirect method)
In this
process coal is first converted into coke. Then water gas is produced by
passing steam over red hot coke
The water
gas is mixed with hydrogen and the mixture is purified by passing through Fe 2O3
+Na2CO 3 (to remove sulphur compounds).
The
purified gas is compressed to 5 to 25 atm and then led through a converter,
which is maintained at a temperature of 200-300⁰C.
The
converter is provided with a catalyst bed consisting of a mixture of 100 parts
cobalt, 5 parts thoria, 8 parts magnesia and 200 parts kieselgurh earth.
A mixture
of saturated and unsaturated hydrocarbon is produced as a result
polymerization.
The out
coming gaseous mixture is led to condenser, where the liquid crude oil is
obtained.
The crude
oil is fractionated to yield (i) Gasoline and (ii) Heavy oil.
The heavy
oil is used for cracking to get more gasoline.
9 GASEOUS FUELS
ADVANTAGES
OF GASEOUS FUELS:
Gaseous fuels have high calorific value than solid
fuels.
During burning they do not produce any ash or
smoke.
Compared to solid and liquid fuels, they have high
thermal efficiency.
They can be easily transported through the pipes.
DISADVANTAGES
OF GASEOUS FUELS:
They are highly inflammable and hence the chances
for fire hazards are high.
Since gases occupy a large volume, they require
large storage tanks.
9.1COMPRESSED NATURAL GAS (CNG)
When the natural gas is compressed, it is called
compresses natural gas (CNG). The primary component present in CNG is methane.
It is mainly derived from natural gas.
Properties
1. CNG is
the cheapest, cleanest and least environmentally vehicle impacting alternative
fuel.
Vehicles powered by CNG produce less carbon
monoxide and hydrocarbon (HC) emission.
It is less expensive than and diesel.
The ignition temperature of CNG is about 55ċ.
CNG requires more air for ignition.
Uses:
CNG is
used to run an automotive vehicle just like LPG.
Comparison
of emission levels between CNG- driven vehicles and petrol driven vehicles
9.2 PRODUCER GAS
It is a
mixture of CO&N2 with small amount
of H2. Its average composition is as follows.
It is
calorific value is about 1300 kcal/m3.
Manufacture
The reactor used for the manufacture of producer
gas is known as gas producer.
It consists of a tall steel vessel inside of which
is lined with refractory bricks.
It is provided with cup and cone feeder at the top
and a side opening for producer gas exists.
At the bottom, it is provided with an inlet pipe
for passing air and steam.
When a mixture of air and steam is passes over a
red hot coke maintained at about
1100ċ in
a reactor, the producer gas is produced.
1. Ash
Zone
This is the lowest zone consists mainly of ash. The
incoming air and steam mixture is preheated in this zone.
2.
Combustion or oxidation zone
This is
the zone next to ash zone. Both the reactions are exothermic. Hence, the
temperature of the bed reaches around 1,100ċ.
3.
Reduction Zone
This is
the middle zone. Here both CO2 and steam are reduced.
The above
reactions are endothermic. Hence the temperature of the coke bed falls to
1000ċ.
4.
Distillation or Drying Zone
This is the upper most of the coke bed. In this
zone (400-800ċ) the incoming coke is heated by the outgoing gases.
Uses
It is used as a reducing agent in metallurgical
operations.
It is also used for heating muffle furnaces,
open-hearth furnaces etc.
9.3 WATER GAS
It is
mixture of CO and H2 with small amount of N2. The average
composition of water gas is as follows.
The above
reactions are endothermic. Hence the temperature of the coke bed falls to
1000ċ.
4.
Distillation or Drying Zone
This is the upper most of the coke bed. In this
zone (400-800ċ) the incoming coke is heated by the outgoing gases.
Uses
It is used as a reducing agent in metallurgical
operations.
It is also used for heating muffle furnaces,
open-hearth furnaces etc.
WATER GAS
It is
mixture of CO and H2 with small amount of N2. The average
composition of water gas is as follows.
Constituents Percentage
CO 41
H2 51
N2 4
CO2+CH4 rest
Its
calorific value is about 2800kcal/m3
Manufacture
It is provide with cup and cone feeder at the top
and a side opening of water gas exist.
At the bottom on it is provide with two inlet pipes
for passing air and steam.
When steam and little air is passed alternatively
over a red hot coke maintained at about 900-1000ċ in a reactor, water gas is
produced.
Step-I
In the
first stage, steam is passed through the red hot coke, where CO &H2 are
produced. The reaction is endothermic. Hence, the temperature of the coke bed
falls.
In the
second stage, in order to raise the temperature of the coke bed to 1000ċ, the
steam
supply is
temporarily cut off and air blown in; the reaction is
Thus the
steam-run and air blow are repeated alternatively to maintain proper
temperature.
Uses
It is used for the production of H2 and
in the synthesis of ammonia.
It is used to synthesis gasoline in Fischer-Tropics
process.
It is also used in the manufacture of power alcohol
and carbureted water gas (water gas oil
gas).
9.4LPG- Liquefied Petroleum gas
It is also known as bottled gas or refinery gas.
It is obtained by a by-product during the
fractional distillation of heavy oil or cracking of higher hydrocarbons.
It can easily be liquefied under pressure, but
exist as gas at atmospheric pressure.
LPG consists of the following hydrocarbons
containing carbons atoms up to 4(C4).
The
average composition of LPG is
Propane - 24.7%
Butane - 38.5%
Isobutene - 37.7%
LPG has
the calorific value of about 2500 Kcals/m3.
Uses
LPG is
supplied with the trade name like indene bharath gas etc. It is mainly used as
domestic and industrial fuel.
It is
also used as motor fuel, because it easily mixes with air and burns without any
pollution creating residue.
Advantages
It
possesses high efficiency and heating rate.
Burns
completely without smoke.
Needs
only little care in maintenance.
Easily
transported using steel cylinder to any places.
It is
very cheaper than gasoline.
Disadvantages
Handling should be only under pressure.
User of LPG in engines is possible only if it works
under high compression ratio.
Its response to blending is poor and so its uses
are selective.
Nitrogen Content:
Kjeldahl’s method:
Reactions :
From the
volume of HCl consumed % of Nitrogen is calculated
i) Sulphur
Content :
Burnt in
From the
weight of BaSO4, % of Sulphur is calculated
of Sulphur = 32 x weight of BaSO4 obtained / 233 x
weight of coal sample x 100
Ash content :
Draw backs of presence of S in Coal:
The combustion products of sulphur, SO2 and SO3 are harmful and have corrosion effects on equipments.
The coal containing sulphur is not suitable for the
preparation of etallurgical coke as it affects the properties of the metal.
Description of Orsat's apparatus
It
consists of a horizontal tube having three way stop cock at one end. The end of
three way stop cock is connected to a U tube containing fused CaCl2 to remove
moisture in the gas. The another end of the tube is connected with a graduated
burette. The burette is surrounded by a water jacket in order to keep the
temperature of gas constantly. The lower end of the burette is connected by a
water reservoir by means of Rubber tube. The level of the water in burette can
be raised or loweredby raising or lowering the reservoir. The middle of the
horizontal tube is connected with 3 bulbs(A, B and C) for absorbing flue gases
as follows:
Bulb 'A' containing KOH solution and it absorbs only CO2
Bulb 'B' containing alkaline pyrogallol solution
and it absorbs only O
Bulb 'C' containing ammoniacal cuprous chloride
solution and it absorbs CO.
Working of Orsat apparatus
The bulbs
A, B and C are cleaned and filled by respective solutions. Now, the three way
stop cock is opened and the burette is filled with water, by raising the water
reservoir to remove air from the burette. Then, the flue gas is taken in the
burette up to 100 cc by raising and lowering the reservoir. The 3 way stop cock
is now closed.
Absorption of gases in bulbs i) Absorption of CO2
The
stopper of the bulb 'A' is opened and the flue gas is allowed to pass by
raising the water reservoir. CO2 present in flue gas is absorbed by KOH. This
process is repeated several times by raising and lowering the water reservoir
until the volume of burette becomes constant. The decrease in volume of burette
indicates the volume of CO2 in 100 cc of the flue gas. Now the stopper of the
bulb „A' is closed.
ii) Absorption of O2
The
stopper of the bulb 'B' is opened and the flue gas is allowed to pass. O2
present in the flue gas is absorbed by alkaline pyrogallol. This process is
repeated several times until the volume of burette becomes constant. The
decrease in volume of flue gas in burette indicates the volume of O2 . Now the
stopper is closed.
c) Absorption of CO
The
stopper of the bulb 'C' is opened and the flue gas is allowed to pass. 'CO'
present in the flue gas is absorbed by ammoniacal cuprous chloride solution.
This process is repeated several times until the volume of burette becomes
constant. The decrease in volume of flue gas in burette indicates the volume of
CO. The remaining gas in the burette after the absorption of CO2 , O2 and CO is
taken as nitrogen. The % of N2 = [100 (% of CO2 + % of O2 + % of CO)]
10 Glossary
Fuel
Fuel is a
combustible substance, containing carbon as the main constituent, which on
burning gives large amount of heat that can be used for domestic and industrial
purposes.
Calorific value
Is the
total quantity of heat liberated when a unit mass of the furel is burnt
completely
Calorie
Is the
amount of heat required to raise the temperature of one gram of water through
one degree centigrade.
Cracking
Is
defined as “ the decomposition of higher boiling hydrocarbons of high molecular
weight into simpler, lower boiling hydrocarbons of lower molecular weight”.
Synthetic petrol
The
preparation of liquid fuels from solid coal is called hydrogenation of coal
(or) synthetic
petrol.
Knocking
Is a kind
of explosion due to rapid pressure rise occurring in an IC engine.
Octane number
Is
defined as “ the percentage of iso-octane present in a mixture of iso-octane
and n-heptanes, which matches the fuel under test in knocking characteristics”.
Cetane number
Is
defined as “ the percentage of hexadecane present in a mixture of hexadecane
and alpha methyl naphthalene, which has the same ignition characteristics as
the diesel under test”.
Water gas
Is a
mixture of combustible gases (CO and H2) with small amount of non
combustible gases
(CO2,
N2).
Producer gas
Is a
mixture of combustible gases ( CO & N2 ) with small amount of
non-combustible gases
( N2,
CO2 etc).
Power alcohol
Is known
as power alcohol. It is used as additive to motors fuels, when blended with
petrol at concentration of 5-10%, it is called power alcohol.
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