fuel - bakhtiyarpur college of engineering · solid and liquid fuel. (ii) oy’s gas calorimeter is...

FUEL

Dr. Anant Kumar

H.O.D.

Department of Chemistry

B.C.E. Bakhtiyarpur

Dr.Anant Kumar, HOD Chemistry, B.C.E.

Bakhtiyarpur

1. DEFINITION

A substance that produces useful energy when it undergoes

a chemical or nuclear reaction.

Examples:

• Coal, Wood, Oil, or Gas provides energy when burnt.

•Compounds in the body such as glucose are broken down

into compounds to provide energy for metabolic

processes

• Some radioactive substances, such

as plutonium and tritium, provide energy by

undergoing nuclear fission or fusion.

Dr.Anant Kumar, HOD Chemistry, B.C.E. Bakhtiyarpur

2. CLASSIFICATION

2.1 Based on Occurrence

(i) Natural or Primary Fuel

e.g. Wood, coal, peat, Petroleum etc

(i) Artificial or secondary Fuel

e.g. Coke, kerosene oil, petrol, coal Gas et


2. CLASSIFICATION

2.2 Based on the basis of Physical state of aggregation

Solid, Liquid and Gas

Type of Fuel

Natural or Primary Artificial or Secondary

Solid Wood, Peat, Lignite, Dung, Bituminous and Anthracite coal

Charcoal, coke etc

Liquid Crude Oil Petrol, Diesel and other fractions of Petroleum

Gas Natural gas Coal gas, Oil gas, Bio Gas, Water Gas.


3. CHARECTERISTICS OF A GOOD FUEL

An ideal fuel should have the following properties:

High calorific value.

Moderate ignition temperature.

Low moisture content.

Low non -combustible matter.

Moderate velocity of combustion.

Products of combustion should not be harmful.

Low cost including storage cost

Easy to transport.

Uniform size

Should burn in air without much smoke


4. RELATIVES MERITS OF SOLID, LIQUID AND GASEOUS FUEL

S.N. FUEL CHARECTERISTICS

SOLID FUELS

LIQUID FUELS

GASEOUS FUELS

1. Cost Cheap More costly than solid fuel

Costly

2. Storage Easy In Closed Container only

In Leak proof voluminous storage tanks

3. Risk of Fire Hazards Lowest Greater Very high Dr.Anant Kumar, HOD Chemistry, B.C.E.

Bakhtiyarpur

CONTD................

S.N. FUEL

CHARECTERISTICS SOLID FUELS

LIQUID FUELS

GASEOUS FUELS

4. Combustion Rate Slow Fast Very fast

5. Combustion Control

Not easy Easy Possible by controlling air supply

6. Handling Cost High Low Low

7. W/W Calorific Value

Least Higher Highest

8. Thermal Efficiency Least Higher Highest

9. Ash Yes No No


CONTD..............

S.N. FUEL CHARECTERISTICS

SOLID FUELS LIQUID FUELS

GASEOUS FUELS

10 Smoke Invariably produced

High Carbon and aromatic liquid fuels may produce smoke

Not produced

11. Thermal Efficiency Least Higher Highest


5. COMBUSTION

Combustion is an exothermic chemical reaction.

C(s) + O2(g) = CO2(g) + 97 Kcal

Ignition Temp: Minimum temperature required for ignition.

Calculation of air quantities

(i) Air contains 23% O2 by mass 21% by volume

(ii) PV = nRT is used as per requirement

(iii) Nitrogen, Ash and CO2 present in the fuel or air are incombustible. They do not consume any oxygen in combustion.


6. NUMERICALS (Q 1. & 2.)

A gas has the following composition by volume in percentage

N2 H2 CH4 CO CO2 O2

34 30 5 20 6 5

If 50% excess air is used find the wt. of air actually supplied per m3 of this gas. The molar wt. of air is 29. (Ans: 2771gm)

45 20 5 20 5

If 50% excess air is used find the wt. of air actually supplied per m3 of this gas. (Ans: 2768.4gm)


7. CALORIFIC VALUE

The amount of heat released by a unit weight or unit volume of a substance during complete combustion.

Table of calorific value of fuels

Serial No. Fuel Calorific value

1. Hydrogen 150KJ/g

2. Methane 55 KJ/g

3. LPG 50 KJ/g

4. Kerosene oil 48 KJ/g

5. Charcoal 33 KJ/g

6. Wood 17KJ/g


8. UNITS OF HEAT

B.Th.U - British Thermal Unit The amount of heat required to raise the temperature of one pound of water through 1oF (58.5oF - 59.5oF) at sea level (30 inches of mercury). 1 Btu (British thermal unit) = 1055.06 J = 0.252 kcal =252 cal Calorie The amount of heat required to raise the temperature of one gram of water 1oC

kilocalorie or Kilogram Centigrade Unit The amount of energy required to raise the temperature of one kilogram of water by one degree Celsius Centigrade Heat Unit (C.H.U.) The amount of energy required to raise the temperature of one pound of water by one degree Celsius. 1 kcal = 4186.8 J =3.9683 B.Th.U = 1000 cal = 2.2 C.H.U.


HIGHER AND LOWER CALORIFIC VALUE

Higher calorific value (HCV) of a fuel portion is defined as the amount of heat evolved when a unit weight (or volume in the case of gaseous fuels) of the fuel is completely burnt and the products of combustion cooled to the normal conditions (with water vapour condensed as a result).

If water vapour, as a product of combustion, is not condensed in water form, the net energy obtained by complete combustion of unit quantity of fuel is called lower calorific (LCV) or net calorific value.

LCV = HCV- Latent heat of water vapour formed

= HCV- mass of hydrogen x 9x Latent heat of steam

Latent heat of steam = 587 kcal/kg or 1060 B.Th.U/lb of of water vapour formed at room temp. (i.e. 150C)


UNITS OF CALORIFIC VALUE

For solid or liquid fuel :

• cal/gm 0r k.cal/kg

• B.Th.U./lb

For gaseous fuel:

• k.cal/cubic meter (kcal/m3)

• B.Th.U./lb

Relation between various units

1 kcal/kg = 1.8 x B.Th.U./lb

1 kcal/m3 = .1077 x B.Th.U./ft3

1 B.Th.U./ft3 = 9.3 kcal/m3


Bakhtiyarpur

TO DETERMINE CALORIFIC VALUE

(i) Bomb Calorimeter for determination of Calorific Value of solid and liquid fuel.

(ii) Boy’s Gas Calorimeter is an apparatus to determine the calorific value of gaseous fuel and those liquid fuels which vaporize easily.

(ii) Junker’s Calorimeter is used to determine calorific value of gaseous fuel.


9. DETERMINATION OF CALORIFIC VALUE

(I) Bomb Calorimeter for determination of Calorific Value of solid and liquid fuel

Used to measure the calorific value (CV) of solid as well as liquid fuel. To determine the CV of gas Junker's calorimeter is used Calorimeter contain thick walled cylindrical vessel with a lid which supports two electrodes which are in contact with fuse and fuel sample of known weight. Lid contains oxygen inlet valve through which high pressure oxygen gas (at about 25 to 30 atm) is supplied. Entire lid with fuel sample is now held in a copper calorimeter containing known weight of water. Mechanical stirrer is provided to stirred well for uniform heating of water. A thermometer is also provided to measure the change in temperature of water due to combustion of fuel in Lid.


(ii) BOMB CALORIMETER


(iii) BOMB CALORIMETER EXPERIMENT

A known quantity of fuel sample is taken in crucible.

Note the initial temperature of water.

Start the stirrer

Start current through crucible to burn fuel sample in presence of O2.

Heat released during combustion of fuel is absorbed by water and temperature of water rises.

Note final steady state temperature of water.


(iv) CALCULATION

W = Mass of water in calorimeter (gm)

w = Water equivalent in gms of calorimeter, stirrer, thermometer, bomb, etc

= Wt. Of apparatus x sp. Heat = W’ x S

T1 = Initial temp. of water in calorimeter;

T2 = Final temp. of water in calorimeter;

L = Higher (Gross) Calorific value of fuel in cal/gm

So, Heat liberated by burning of fuel = x L Cal.

And, Heat absorbed by water = { W x S x (T2-T1)}

And heat absorbed by apparatus = { W’ x S x (T2-T1)} = w(T2-T1)

Hence, total heat absorbed by apparatus water etc

= { Wx 1 x (T2-T1) + w x1 x (T2-T1) } = {(W+w) x1x (T2-T1)} cal


Bakhtiyarpur

Contd.........

Sp. Heat of water = 1cal/gm0C and 1cal = 4.186J

The water equivalent of the calorimeter(w) is determined by burning a fuel of known calorific value.

Fuel used for this purpose are benzoic acid (HCV= 6,325 kcal/kg)

and naphthalene (HCV = 9,688 kcal/kg)

Heat taken by water in forming steam (or latent heat of water vapour formed) = 0.09 H x 587 cal

LCV = (HCV – 0.09 H x 587) cal/gm


Contd............ Corrections to be made for accurate result • Fuse wire correction

Heat liberated by ignition of fuse wire should be subtracted • Acid correction

S + H2 + 2O2 = H2SO4 + Heat 2N + H2 + 3O2 = 2HNO3 + Heat The correction for 1mg of S = 2.25 cal 1mL of N/10 HNO3 = 1.43 cal Thus, these amount is also subtracted

• Cooling correction (i) Time taken by water of calorimeter from maxm. to room temp is noted (ii) From the rate of cooling(dT0/min) and the actual time taken for cooling , the cooling correction , dT x t is added to the rise in temp. So, HCV = [(W+w)(T2-T1+cooling correction)]-(Acid + Fuse) correction/Mass of

fuel (x) Dr.Anant Kumar, HOD Chemistry, B.C.E.

Bakhtiyarpur

BOY’S CALORIMETER • A gas burner with an arrangement to

measure gas flow at uniform rate

• The burner burns inside a specially designed calorimeter container containing a cooling coil with flowing water.

• The water is provided with a rotameter to measure flow of cooling water.

• Two thermometers are provided - one at the inlet and one at the outlet of the water flow through the coil.

• The heat from the burner flows up through the center of the calorimeter container and back down again inside the container and back up again before exhausting to ensure maximum heat transfer to the cooling liquid and hence accurate measurement of calorific value of gas.


CALCULATION

(i) Circulation of water and burning of gaseous fuel are continued for 15 minutes to warm up the calorimeter.

(ii) Now, the rate of fuel burning and water circulation are adjusted so that the exit water leaves the apparatus nearly at atm. pressure.

(iii) Heat produced by burning of gaseous fuel is transferred to water and the steam formed is condensed back into water which is collected.

(iv) The readings are taken as:

(a) Vol. of gas burnt at STP in time “t” = V m3

(b) Wt. of water passed through the coil in time “t” = W kg

(c) Temp. of incoming water = T1 0C

(d) Temp. of outgoing water = T2 0C

(e) Wt. Of condensed steam = W kg

(f) Let, HCV of fuel = C kcal/m3


Contd............ (g) Heat absorbed by circulating water= W(T2-T1) x 1kg 0C kcal/kg0C

(h) Heat produced by the combustion of fuel = V x C m3 x kcal/m3

(i) Heat produced = Heat absorbed

So, V x C = W(T2-T1)

C = W(T2-T1) kcal/m3

V

(j) Latent Heat of Water vapour = 587 cal/gm or k.cal/kg

(k) Wt. of water condensed from 1m3 of gas = W’/V kg/m3

So, Latent Heat of steam per m3 of gas

=587 kcal/kg x W’kg/Vm3

= 587W’ kcal /m3 V

(l) LCV of fuel = HCV- Latent Heat of steam per m3 of gas LCV= C- 587W’ V


JUNKER’S CALORIMETER

PRINCIPLE OF OPERATION It works on the Junker's principle of burning of a known volume of gas and imparting the heat with maximum efficiency to steadily flowing water and finding out of the rise in temperature of a measured volume of water.

The formula, Calorific Value of Gas X Volume of Gas = Volume of water X Rise in Temperature, is then used to determine the Calorific Value of the Gas (assuming that heat capacity of water is unity).


Contd................

The Calorimeter is fixed on a tripod stand having levelling screws to keep the Calorimeter in perfectly vertical position. The Calorimeter mainly consists of a gas combustion chamber, heat exchanger and water flow system. Heat exchanger is designed for maximum efficiency of heat transfer. The outer housing is of powder coated stainless steel. The constant water level attachment has an over flow device through which excess water drains out. Water, while going up, absorbs the heat generated by burning the gas in the burner located at the bottom of the central chamber of the Calorimeter. Two thermometers are provided in the water inlet and outlets ports. Temperature of the effluent gas can be measured from the thermometer fixed at the exhaust gas outlet. Provision for fixing the burner is provided at the Calorimeter base. An outlet for collection of condensate is provided at the bottom. Pressure Governor has been provided to regulate the pressure of gas before it enters the flow meter.


Bakhtiyarpur

Contd............

Let V = vol. of gas collected at S.T.P. In certain time ‘t’

W = Wt. of water collected in that time ‘t’

T1 = Temp. of incoming water

T1 = Temp. of outgoing water

HCV = W(T2-T1)/ V kcal/m3

m = Mass of steam condensed in certain time ‘t’ in

graduated cylinder from V m3 of gas.

Latent heat of steam = 587 kcal/kg

Thus, L.C.V. = [HCV –m x 587] kcal/m3

V


THEORETICAL CALCULATION OF CALORIFIC VALUE OF A FUEL BY DULONG FORMULA

Calorific value of a fuel is the sum of the calorific values due to all the components present in the given fuel.

So, GCV = 1 [ 8080C + 34500 ( H- O ) + 2240S] cal/gm

100 8

Constituent (in percentage) C H S

GCV 8080 34500 2240


Contd...........

The oxygen, present in the fuel, is assumed to be present in the combined form with hydrogen i.e in form of H2O.

2H2 + O2 = 2H2O

1 8 9

Fixed Hydrogen = Mass of oxygen in the fuel/8

Thus, amount of hydrogen available for combustion

= H- O/8

Wt. Of H2O produced from 1gm H2 = 9gm

Wt. Of H2O produced from H/100 gm H2 = 9 x H/100 gm =0.09Hgm

Latent heat (LH) of steam = 587 cal/gm

So, LH of water vapour formed = 0.09 H x 587 cal.

And, LCV = HCV – 0.09H x 587 cal/gm


Bakhtiyarpur

NUMERICALS (Q. No. 3-5) 3. Calculate the gross and net calorific value of a coal sample having the

composition in percentage:

C= 80,H=7, O= 3, S= 3.5, N= 2.1, Ash= 4.4 (Ans: 8458kcal/kg)

4. A sample of coal containing 89% C: 8% H; 3% Ash. When this coal was burnt in the laboratory for its calorific value in the bomb calorimeter , the following data were obtained:

Wt. Of burnt = 0.85g

Wt. Of water taken = 650g

Wt. Of equivalent of Bomb and calorimeter =2500g

Rise in temp. = 2.50C

Cooling correction = 0.030C

Fuse wire correction = 10 cal

Acid correction = 50 cal

Latent heat of condensation of steam = 580cal/g

Calculate the GCV and NCV of the coal in cal/gm?

(Ans: 9205.2 and 8787.6 cal/g Dr.Anant Kumar, HOD Chemistry, B.C.E.

Bakhtiyarpur

Contd..........

5. A sample of coal contains 75% C: 5.2%H; 12.1% O; 3.2% N and 4.5% Ash.

(i) Calculate the minimum amount of O2 and air by wt. necessary for complete combustion of 1kg of coal.

(i) Wt. of air required if 40% excess air is supplied.

(i) GCV and NCV of coal sample using Dulong’s formula

(Ans: 7332.2 and 7057.5 kcal/kg)


CLASSIFICATION OF GASEOUS FUELS

(A) Fuels naturally found in nature:

– Natural gas

– Methane from coal mines

(B) Fuel gases made from solid fuel:

-Gases derived from Coal

-Gases derived from waste and Biomass

-Other industrial processes (Blast furnace gas)

(C) Gases made from petroleum

-Liquefied Petroleum gas (LPG)

-Refinery gases

-Gases from oil gasification

(D) Gases from some fermentation process


TYPES OF GASEOUS FUEL

Primary Fuels

• Natural gas

Secondary Fuels

• Producer Gas

• Water Gas

• Carburetted Gas

• Coal gas


Natural Gas

• Naturally occurring gas found in oil fields and coal fields (Fire damp).

• It is also called ‘Marsh Gas’.

• The quantities of the constituents vary but the principal component is methane. Other components include higher hydrocarbons. Some gases also contain hydrogen sulphide.

• Terms used to describe gases:

dry or lean - high methane content (less condensate)

wet - high concentration of higher hydrocarbons (C5 - C10)

sour - High concentration of H2S

sweet - low conc. of H2S

residue gas - gas remaining after the condensing process

casing head gas - gas extracted from an oil well by extraction at the surface.

Calorific value is 8000-14000 kcal/m3


Contd………..

• H2S can be removed by scrubbing with monoethanolamine

HO-CH2-CH2-NH2 + H2S = {HO-CH2-CH2-NH2}2.H2S

• Natural gases can be liquefied for distribution by tanker. Liquefied natural gas (LNG) contains mostly methane, LPG (Liquefied petroleum gas) mostly butane and propane.

• It is used as a raw material for manufacture of:

(i) Carbon Black and Hydrogen which in turn are used as filler for rubber and ammonia.

(ii) Methanol, formaldehyde and chemicals

(iii) Synthetic proteins from microbiological fermentation of methane


Synthetic Gases

• These are gases which are chemically made by some process.

• Main methods of synthesis:

(i) Producer gas:

• A mixture 55% Nitrogen (from air), 30% CO (incomplete combustion) and 3% CO2, 12% H2

• CO is combustible and nitrogen is incombustible.

• It is insoluble in water and is poisonous in nature.

• The gas is produced by blowing air and little steam over a bed of red hot coal or coke in gas producer at ~ 11000C.

• The reaction with air is exothermic but insufficient air is added hence CO is produced.

• Steam addition results in the formation of hydrogen by the water gas reaction. This is endothermic and hence balances out the exothermic air reaction.


• Ash zone: At the bottom. Ash will be there and a disposal of ash is there at the bottom

• Combustion zone:

This is the middle zone of gas producer. The steam and CO2 (produced in the combustion zone) moves up through the red hot fuel bed and liberates free hydrogen and CO.

C + O2 = CO2 + 97 kcal

C+ ½ O2 = CO2 + 53 kcal

Temp: 11000C

• Reduction zone:

C + CO2 = 2CO -36 kcal

C+ H2O = CO + H2 -29 kcal

C+ 2H2O = CO2 + 2H2 -19 kcal

Temp: As these are endothermic reactions, so temp. falls to 10000C


Bakhtiyarpur

• Distillation zone

Upper part of the fuel bed

As the producer gas moves upward, it transfer some of the heat to the down coming coal. This along with the heat radiated from the lower part help to distil the fuel and as a result volatile matter of coal is removed and comes out with outgoing gas.

When steam is introduced with the air, the final gaseous product contains hydrogen also.

• Features

Producer gas has a low heating value because it is about 60% inert nitrogen.

• Applications:

It is widely used in industry because it can be made with cheap fuel.

When producer gas contains hydrogen, it is also a source material for the manufacture of synthetic ammonia.

Used as reducing agent in metallurgical process


(ii) BLUE or WATER GAS OR SYNTHESIS GAS

• The bed of red hot coke or coal is blasted with air followed by steam. • Air reaction is exothermic so the bed heats up C + O2 = CO2 + 97kcal 2C + O2 = 2CO + 59kcal • Steam reaction is endothermic so the bed cools down again. C + H2O = CO + H2

- 29kcal • The temp. is maintained at about 900-10000 by blowing the steam

and air alternatively.

• Calorific value is 2800kcal/m3

• Mixture of gas produced is higher in quality. • Typical composition: H2 = 49%; CO = 41%; CO2 = 4.7%; N2 = 4.5%; CH4 = 0.8%


• Applications:

(i) As a source of hydrogen gas

(ii) As a fuel gas

(iii) As a raw material for Fischer-tropsch process

(iv) As an illuminating gas


(iii) Oil Gas Features • Golden Colour • Burns with smoke • The main constituents are CH4, H2 and CO. • Calorific value is 4500-5400 kcal/m3. Preparation: • Formed by the thermal cracking of crude oil. • If oil is sprayed onto heated checker work (refractory) it

cracks to form lower gaseous hydrocarbons. Applications: • Used as laboratory gas • Used to improve the calorific value of water gas • Mixture of water gas and oil gas is called carburetted

water gas.


(iv) Carbureted Water Gas -

Features

• The main constituents are H2 and CO and other components are saturated and unsaturated hydrocarbons, N2, CO.

• Calorific value is 4500 kcal/m3.

Preparation:

• Formed by mixing the water gas and gaseous hydrocarbons produced due to thermal cracking of crude oil.

Applications:

• Used for illumination and heating papooses.


(v) Coal and Coke Oven Gas

• Features

It contains mainly H2 and CH4. The other components are CO, C2H2, C2H4, N2 and CO2.

Colorless and burns with smoky flame

The calorific value is 4900 kcal/m3.

• Preparation:

From slury of

• Applications

As a fuel

As a reducing agent in many metallurgical processes

As illuminant in cities and town


(VI) Bio Gas

• Features

The most easily available bio gas is Gober gas

It mainly contains Methane

Colorless and burns with blue flame

The calorific value is 5300 kcal/m3.

• Preparation:

From cattle dung in form of slurry

Slurry is made by mixing equal part of water and cattle dung

Unaerobic fermentation of slurry by bacteria present in the dung at 34-48OC.

• Applications

As a fuel

For and power purposes

As a manure because it contains 2% nitrogen as against 0.75% in farm manure.


• Advantages:

One kg dry cattle dung produces 23.4 kcal but its bio gas produces 188 kcal

It does not contain poisonous gas

Free from smoke and dirt

Utensils and environment remain comparatively clean

Optimum utilization of waste


COAL

Features • Coal is the most abundant fossil fuel found on the planet. • Fossil fuels are energy sources and considered as non-renewable

resources of energy. • Coal is formed as: Wood → Peat→Lignite → Bituminous → Anthracite • Formed from ancient swamps and bogs. The vegetation found in these

areas eventually become buried beneath sediment and rock called overburden.

• As more and more overburden is added, the buried vegetation becomes compressed. The temperature and pressure are also increasing as a result of the overburden. Under these conditions, the buried vegetation is kept free of oxygen by the presence of mud and acidic water. Slowly over time, the buried vegetation is 'cooked' to coal. The process of turning dead carbon-rich vegetation to coal is called carbonization.

• This is where the stages of coal formation begin, starting with peat and moving up to anthracite. It takes millions of years for this process to occur about 325 million years ago.


TYPES OF COAL The four types of coal are peat, lignite, bituminous, and

anthracite. • Peat is the first step in coal formation. Peat is composed of

over 60% organic matter; typically, ferns and vegetation found in swamps or bogs. As a result of the high water content of this environment, peat contains a lot of water, which limits its heat content or the amount of energy it contains. It's a very soft brown coal. Its caolorific value is 4125- 5400 kcal/kg

• Eventually over time, with increasing pressures and temperatures, peat is 'cooked' into coal's next stage, lignite. Lignite is a soft brown coal that still contains a high amount of water. Lignite has a higher heat content than peat but is still not the most desired form of coal. However, lignite makes up almost half of our known coal reserves. Its caolorific value is 6500- 7100 kcal/kg


• Bituminous coal is formed as more pressure is applied to lignite coal. The greater the pressure applied, the more water is expelled, which increases the amount of pure carbon present and increases the heat content of the coal. Bituminous coal is often classified as sub-bituminous or bituminous. The difference is that sub-bituminous is the transition stage from lignite to bituminous coal. Its calolrific is 8000- 8500 kcal/kg

• Anthracite coal is a metamorphic rock and is considered the highest grade coal. It's hard and dark black in color. It has a very light weight when compared to other forms of coal, as there is very little water present in anthracite. As a result, anthracite has the highest heat content. Anthracite is formed when bituminous coal is subjected to great pressures, such as those associated with the folding of rock during the creation of mountain ranges. Its caolorific value is 8650- 8700 kcal/kg


Bakhtiyarpur

FLUE GAS ANANLYSIS

• The mixture of gases, CO2, CO and O2 passing out of the combustion chamber is called flue gas

• The analysis of flue gas indicates the efficiency of the combustion.

• Excess CO gas indicates incomplete combustion.

• Excess O2 indicates too much air supply which causes loss of heat.

• Normally, 50-100 % excess air is supplied

• Analysis of flue gas is done by Orsat’s apparatus Dr.Anant Kumar, HOD Chemistry, B.C.E.

Bakhtiyarpur

ORSAT APPARATUS


• Fused CaCl2 and Glass Wool:

For drying flue gas and avoiding incoming of any smoke particle

• KOH solution

Absorbs CO2 gas

• Alkaline Pyrogallic acid

Absorbs O2 and CO2.

• Ammonical Cuprous Chloride

Absorbs CO, O2 and CO2.


NUMERICALS (Q. No. 6-8)

From the following data:

Components

C H O S N CO CO2 N2 CH4 H2

Moisture

Ash

% for Q. 6 75.4 4.5 12.5 1.4 3.1 - - - - - - Y

Calculate the minimum weight of air necessary for complete combustion of 1 kg of coal and percentage composition of the dry products of combustion by weights? Ans: 9824.6 g air; CO2: 26.6% ; N2: 73.1%; SO2: 0.27%; Wt. Of dry products: 10388.6g

% for Q. 7

76.0 5.2 12.8 1.2 2.7 - - - - - - Y

Calculate the minimum weight and volume of air at NTP necessary for complete combustion of 1 kg of coal. Also percentage composition of the dry products of combustion by weight if 50% excess air is supplied? (Ans: Air=10.116kg and 7.83m3; %CO2,SO2,N2,O2=17.77,0.153,74.7, 7.417

% for Q. 8

81 5.0 8.5 1.0 1.0 - - - - - - Y

(Ans: Air & O2=10.8 & 2485g; %CO2,SO2,N2,O2=26.02,0.177,73.6; Total wt. Of dry products: 11319.4g Dr.Anant Kumar, HOD Chemistry, B.C.E.

Bakhtiyarpur

ANALYSIS OF COAL

(i) Proximate analysis

(ii) Ultimate analysis


PROXIMATE ANANLYSIS

Involves following determinations:

(i) Moisture Content

(i) Volatile Matter

(i) Ash

(i) Fixed Carbon


MOISTURE CONTENT

Moisture causes:

(i) Increase in cost

(ii) Quenches the fire in furnace

(iii) Moisture carries away latent heat in form of vapour

Estimation of moisture

(i) Known wt. of finely divided coal taken in silica crucible and heated in an electric hot air oven at 105-110OC for about 1 hr.

(ii) Cooled in dessicator and weighed.

(iii) Process repeated till wt. Becomes costant

(iv) Loss in wt is calculated as:

% of moisture = Loss in wt X 100/Wt. of coal taken


Bakhtiyarpur

VOLATILE MATTER

Volatile matters

(i) Combustible matters

Hydrogen, CO, Methane and Lower hydrocarbons

(ii) Non- Combustible matters

CO2 and N2

Volatile matters cause

(i) No addition toward value of heat

(ii) To occupy large volume in the furnace

(iii) Large amount of volatile matters distil over and escapes unburnt.

(iv) A long flame, high smoke and low calorific value


Estimation of Volatile matters

(i) Known wt. of moisture free coal taken in silica crucible covered with lid.

(ii) Heated in muffle furnace at about 950OC for about 7 min.

(iii) Cooled inside indicator in open air and weighed.

(iv) Process repeated till wt. Becomes constant

(v) Loss in wt is calculated as:

% of volatile matter = Loss in wt X 100/Wt. of coal


Bakhtiyarpur

ASH Ash (i) Combustible matters

Ash causes (i) Reduction in calorific value (ii) Decrease in efficiency of fuel as it hinders flow of air and heat (iii) Additional cause in its disposal (iv) A long flame, high smoke and low calorific value Estimation of Volatile matters (i) Known wt. of moisture free coal taken in silica crucible covered with lid. (ii) Heated in muffle furnace at about 950OC for about 7 min. (iii) Cooled inside indicator in open air and weighed. (iv) Process repeated till wt. Becomes constant (v) Loss in wt is calculated as:

(vi) % of ash = Loss of ash formed X 100/Wt. of dry coal taken


FIXED CARBON

It is the quantity of carbon , in coal, that can be burnt by a primary current of air drawn through the hot bed of fuel.

After determination of moisture, volatile matter and ash contents, the remaining material is fixed carbon.

The % of fixed carbon helps in designing the furnace.

Higher the % of fixed carbon better the quality of coal

% of fixed ‘C’ = 100 - % of (moisture + volatile matter + ash)


ULTIMATE ANALYSIS

Determination of: (i) Carbon

(i) Hydrogen

(i) Nitrogen

(i) Sulphur

(i) Oxygen


ESTIMATION OF CARBON AND HYDROGEN

• Known quantity of coal is burnt in presence of dry O2.

• C & H are oxidized as:

CxHy + (y/4)O2 = xCO2 + (y/2) H2O

• H2O is absorbed in U-tube containing anhydrous CaCl2 and CO2 is absorbed in another tube containing KOH solution.

• From increase in wt. of CaCl2 and KOH solution the percentage of carbon and hydrogen are calculated.


ESTIMATION OF NITROGEN BY KJELDAHL’S METHOD

• Known wt of powdered coal , conc. H2SO4, K2SO4 and CuSO4

heated in kjeldahl’s flask to convert nitrogen of O.C. into (NH4)2SO4.

O.C. + H2SO4 = (NH4)2SO4

• Resulting acid mixture is the heated with excess of NaOH and liberated NH3 gas is absorbed in excess standard soln of H2SO4.

• Unreacted H2SO4 is titrated with standard solution of NaOH soln.

• Now, amt. of acid reacted with NH3 is determined and then % of ‘N’ is calculated.


ESTIMATION OF SULPHUR

• Known amt. of coal is burnt in a current of oxygen to oxidize ‘S’ to sulphate.

• The ash from the bomb calorimeter is extracted with dil. HCl. The acid extract is then treated with BaCl2 solution to precipitate BaSO4.

• The precipitate is then filtered, washed, dried and heated to constant wt.

• From the wt. of BaSO4, the % of ‘S’ is determined


ESTIMATION OF OXYGEN

Features

• Oxygen is present in combined form with hydrogen in coal thus hydrogen available for combustion is lesser.

• More the oxygen content, lower the calorific value.

• An increase in 1% oxygen content decreases the calorific value by 1.7%

• Good quality coal should have low % of oxygen

Determination

% of oxygen = 100 - % of (C + H+ N + S + Ash)


NUMERICALS (Q. No. 9-11)

9. On complete combustion, 0.246 g of an organic compound(O.C) gave 0.198 g of CO2 and 0.1014 g of of H2O. Determine the percentage composition of carbon and hydrogen?

(Ans: 21.95 & 4.58%)

10. During estimation of nitrogen present in an O.C. by Kjeldahl’s method, the ammonia evolved from 0.5 g of the compound neutralized 10mL of 1M H2SO4. Find out the percentage of nitrogen in the compound? (Ans: 56%)

11. In sulphur estimation, 0.157g of an O.C. gave 0.4813g of BaSO4. Find the percentage of sulphur in given compound.

(Ans: 42.10%) Dr.Anant Kumar, HOD Chemistry, B.C.E.

Bakhtiyarpur

ANY QUESTION


Thank You


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