Aula-3 Fuels and Combustion (2)

7/28/2019 Aula-3 Fuels and Combustion (2)

1/47

1

Training Session on Energy

Equipment

Fuels & Combustion

Presentation from the

Energy Efficiency Guide for Industry in Asia

www.energyefficiencyasia.org

UNEP 2006


2/47

2

UNEP 2006

Training Agenda: Fuels &

Combustion

Introduction

Type of fuels

Performance evaluation

Energy efficiency opportunities


3/47

3

UNEP 2006

Introduction

Solar energy is converted to

chemical energy through photo-synthesis in plants

Energy produced by burning wood or

fossil fuels

Fossil fuels: coal, oil and natural gas

The Formation of Fue

ls


4/47

4

UNEP 2006


Combustion

Introduction

Type of fuels




5/47

5

UNEP 2006

Type of Fuels

Liquid Fuels

Usage

Used extensively in industrial applications

Examples

Furnace oil

Light diesel oil

Petrol

Kerosine

Ethanol

LSHS (low sulphur heavy stock)


6/47

6

UNEP 2006

Type of Fuels

Liquid Fuels

Density

Ratio of the fuels mass to its volume at 15 oC,

kg/m3

Useful for determining fuel quantity and quality


7/47

7

UNEP 2006

Type of Fuels

Liquid Fuels

Specific gravity

Ratio of weight of oil volume to weight of same

water volume at a given temperature

Specific gravity of water is 1

Hydrometer used to measure

Fuel oil

type

LDO

(Light Diesel Oil)

Furnace oil LSHS (Low Sulphur

Heavy Stock)

Specific

Gravity

0.85-0.87 0.89-0.95 0.88-0.98

Table 1. Specific gravity of various fuel oils (adapted

from Thermax India Ltd.)


8/47

8

UNEP 2006

Type of Fuels

Liquid Fuels

Viscosity

Measure of fuels internal resistance to flow

Most important characteristic for storage and use

Decreases as temperature increases

Flash point Lowest temperature at which a fuel can be

heated so that the vapour gives off flashes when

an open flame is passes over it

Flash point of furnace oil: 66o

C


9/47

9

UNEP 2006

Type of Fuels

Liquid Fuels

Pour point

Lowest temperature at which fuel will flow Indication of temperature at which fuel can be

pumped

Specific heat

kCal needed to raise temperature of 1 kg oil by

1oC (kcal/kgoC)

Indicates how much steam/electricity it takes to

heat oil to a desired temperature


10/47

10

UNEP 2006

Type of Fuels

Liquid Fuels

Calorific value

Heat or energy produced

Gross calorific value (GCV): vapour is fully

condensed

Net calorific value (NCV): water is not fully

condensed

Fuel Oil Gross Calorific Value (kCal/kg)

Kerosene 11,100

Diesel Oil 10,800

L.D.O 10,700

Furnace Oil 10,500

LSHS 10,600


11/47

11

UNEP 2006

Type of Fuels

Liquid Fuels

Sulphur content

Depends on source of crude oil and less on the

refining process

Furnace oil: 2-4 % sulphur

Sulphuric acid causes corrosion

Ash content Inorganic material in fuel

Typically 0.03 - 0.07%

Corrosion of burner tips and damage to materials

/equipments at high temperatures


12/47

12 UNEP 2006

Type of Fuels

Liquid Fuels

Carbon residue

Tendency of oil to deposit a carbonaceous solidresidue on a hot surface

Residual oil: >1% carbon residue

Water content

Normally low in furnace oil supplied (


13/47

13 UNEP 2006

Type of Fuels

Liquid Fuels

Storage of fuels

Store in cylindrical tanks above or belowthe ground

Recommended storage: >10 days of

normal consumption

Cleaning at regular intervals


14/47

14 UNEP 2006

Type of Fuels

Liquid Fuels

Properties Fuel OilsFurnace Oil L.S.H.S L.D.O

Density (Approx.

g/cc at 150C)

0.89-0.95 0.88-0.98 0.85-0.87

Flash Point (0C) 66 93 66

Pour Point (0C) 20 72 18

G.C.V. (Kcal/kg) 10500 10600 10700Sediment, % Wt.

Max.

0.25 0.25 0.1

Sulphur Total, %

Wt. Max.

< 4.0 < 0.5 < 1.8

Water Content, %

Vol. Max.

1.0 1.0 0.25

Ash % Wt. Max. 0.1 0.1 0.02

Typical specifications of fuel oils(adapted from Thermax India Ltd.)


15/47

15 UNEP 2006

Type of Fuels

Solid Fuels

Coal classification

Anthracite: hard and geologically theoldest

Bituminous

Lignite: soft coal and the youngest

Further classification: semi- anthracite,

semi-bituminous, and sub-bituminous


16/47

16 UNEP 2006

Type of Fuels

Solid Fuels

Physical properties

Heating or calorific value (GCV) Moisture content

Volatile matter

Ash

Chemical properties

Chemical constituents: carbon, hydrogen,

oxygen, sulphur


17/47

17 UNEP 2006

Type of Fuels

Solid Fuels (Physical properties)

Heating or calorific value

The typical GVCs for various coals are:

Parameter Lignite(Dry

Basis)IndianCoal IndonesianCoal SouthAfrican

Coal

GCV(kCal/kg)

4,500 4,000 5,500 6,000


18/47

18 UNEP 2006

Type of Fuels


Moisture content

% of moisture in fuel (0.5 10%)

Reduces heating value of fuel

Weight loss from heated and then cooled powdered

raw coal

Volatile matter

Methane, hydrocarbons, hydrogen, CO, other

Typically 25-35%

Easy ignition with high volatile matter

Weight loss from heated then cooled crushed coal


19/47

19 UNEP 2006

Type of Fuels


Ash

Impurity that will not burn (5-40%) Important for design of furnace

Ash = residue after combustion

Fixed carbon

Fixed carbon = 100 (moisture + volatile matter + ash)

Carbon + hydrogen, oxygen, sulphur, nitrogen

residues

Heat generator during combustion


20/47

20 UNEP 2006

Type of Fuels

Solid Fuels (Physical properties) Proximate analysis of coal

Determines only fixed carbon, volatile matter,

moisture and ash

Useful to find out heating value (GCV)

Simple analysis equipment

Ultimate analysis of coal

Determines all coal component elements: carbon,

hydrogen, oxygen, sulphur, other

Useful for furnace design (e.g flame temperature,

flue duct design)

Laboratory analysis


21/47

21 UNEP 2006

Type of Fuels


Proximate analysis

Typical proximate analysis of various coals (%)

IndianCoal IndonesianCoal South AfricanCoal

Moisture 5.98 9.43 8.5

Ash 38.63 13.99 17

Volatile

matter

20.70 29.79 23.28

Fixed Carbon 34.69 46.79 51.22


22/47

22 UNEP 2006

Type of Fuels

Solid Fuels (Chemical Properties)

Ultimate analysis

Typical ultimate analysis of coal (%)

Parameter Indian Coal, % Indonesian Coal, %

Moisture 5.98 9.43

Mineral Matter (1.1 x Ash) 38.63 13.99

Carbon 41.11 58.96Hydrogen 2.76 4.16

Nitrogen 1.22 1.02

Sulphur 0.41 0.56

Oxygen 9.89 11.88

GCV (kCal/kg) 4000 5500


23/47

23 UNEP 2006

Type of Fuels

Solid Fuels (Chemical Properties)

Storage, Handling & Preparation

Storage to minimize carpet loss and loss dueto spontaneous combustion

Reduce carpet loss: a) a hard surface b)

standard concrete/brick storage bays

Coal preparation before use is important for

good combustion


24/47

24 UNEP 2006

Type of Fuels

Gaseous Fuels

Advantages of gaseous fuels

Least amount of handling

Simplest burners systems

Burner systems require least

maintenance

Environmental benefits: lowest GHG

and other emissions


25/47

25 UNEP 2006

Type of Fuels

Gaseous Fuels

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

-From other industrial processes(C) Gases made from petroleum-Liquefied Petroleum gas (LPG)

-Refinery gases

-Gases from oil gasification

(D) Gases from some fermentation


26/47

26 UNEP 2006

Type of Fuels

Gaseous Fuels

Calorific value

Fuel should be compared based on the netcalorific value (NCV), especially natural gas

Typical physical and chemical properties of various gaseous fuels

FuelGas

RelativeDensity

Higher HeatingValue kCal/Nm3 Air/Fuelratio m3/m3 FlameTemp oC Flamespeed m/s

Natural

Gas

0.6 9350 10 1954 0.290

Propane 1.52 22200 25 1967 0.460

Butane 1.96 28500 32 1973 0.870


27/47

27 UNEP 2006

Type of Fuels

Gaseous Fuels

Liquefied Petroleum Gas (LPG)

Propane, butane and unsaturates, lighter C2and heavier C5 fractions

Hydrocarbons are gaseous at atmospheric

pressure but can be condensed to liquid state

LPG vapour is denser than air: leaking gases

can flow long distances from the source


28/47

28 UNEP 2006

Type of Fuels

Gaseous Fuels

Natural gas

Methane: 95%

Remaing 5%: ethane, propane, butane, pentane,

nitrogen, carbon dioxide, other gases

High calorific value fuel

Does not require storage facilities

No sulphur

Mixes readily with air without producing smoke or

soot


29/47

29 UNEP 2006

Type of Fuels

Comparing Fuels

Fuel Oil Coal Natural

Gas

Carbon 84 41.11 74

Hydrogen 12 2.76 25

Sulphur 3 0.41 -

Oxygen 1 9.89 Trace

Nitrogen Trace 1.22 0.75

Ash Trace 38.63 -

Water Trace 5.98 -


30/47

30 UNEP 2006


Combustion

Introduction

Type of fuels




31/47

31 UNEP 2006

Performance Evaluation

Combustion: rapid oxidation of a fuel

Complete combustion: total oxidation of

fuel (adequate supply of oxygen needed)

Air: 20.9% oxygen, 79% nitrogen and other

Nitrogen: (a) reduces the combustion

efficiency (b) forms NOx at high

temperatures

Carbon forms (a) CO2 (b) CO resulting in

less heat production

Principles of Combustion


32/47

32 UNEP 2006


Control the 3 Ts to optimize combustion:

Water vapor is a by-product of burning fuel

that contains hydrogen and this robs heat

from the flue gases

Principles of Combustion

1T) Temperature

2T) Turbulence

3T) Time


33/47

33 UNEP 2006


Oxygen is the key to combustion

Principle of Combustion

Bureau of Energy Efficiency, India, 2004


34/47

34 UNEP 2006


Stochiometric calculation of airrequired

Stochiometric air needed for combustion of

furnace oil

Theoretical CO2 content in the flue gases

Actual CO2 content and % excess air

Constituents of flue gas with excess air

Theoretical CO2 and O2 in dry flue gas by

volume


35/47

35 UNEP 2006


Measure CO2 in flue gases to estimate

excess air level and stack losses

Concept of Excess Air

Carbon dioxide (%)

Exces

sair(%)

Source: Bureau of Energy Efficiency, India, 2004


36/47

36 UNEP 2006


Concept of Excess Air

Residual oxygen (%)

Excessair(%)

Bureau of Energy Efficiency, India, 2004

Measure O2 in flue gases to estimate

excess air level and stack losses


37/47

37 UNEP 2006


To exhaust combustion products to

atmosphere

Natural draft:

Caused by weight difference between the hot gases

inside the chimney and outside air

No fans or blowers are used

Mechanical draft:

Artificially produced by fans

Three types a) balanced draft, b) induced draft and c)

forced draft

Draft System


38/47

38 UNEP 2006


Combustion

Introduction

Type of fuels




39/47

39 UNEP 2006

Energy Efficiency Opportunities

Preheating of combustion oil

Temperature control of combustionoil

Preparation of solid fuels

Combustion controls

Four main areas


40/47

40 UNEP 2006


Purpose: to make furnace oil easier

to pump Two methods:

Preheating the entire tank

Preheating through an outflow heater asthe oil flows out

Preheating of Combustion Oil


41/47

41 UNEP 2006


To prevent overheating

With reduced or stopped oil flow

Especially electric heaters

Using thermostats

Temperature Control of

Combustion Oil


42/47

42 UNEP 2006


Sizing and screening of coal

Important for efficient combustion

Size reduction through crushing and

pulverizing (< 4 - 6 mm)

Screen to separate fines and small particles Magnetic separator for iron pieces in coal

Preparation of Solid Fuels


43/47

43 UNEP 2006


Conditioning of coal:

Coal fines cause combustion problems

Segregation can be reduced by

conditioning coal with water

Decrease % unburnt carbon

Decrease excess air level required

Preparation of Solid Fuels


44/47

44

UNEP 2006


Blending of coal

Used with excessive coal fines

Blending of lumped coal with coal

containing fines

Limits fines in coal being fired to


45/47

45

UNEP 2006


Assist burner to achieve optimum boiler

efficiencythrough the regulation of fuel

supply, air supply, and removal ofcombustion gases

Three controls:

On/Off control: burner is firing at full rate or it is

turned off

High/Low/Off control: burners with two firing rates

Modulating control: matches steam pressure

demand by altering the firing rate

Combustion Controls

T i i S i E


46/47

46

Training Session on Energy

Equipment

Fuels & Combustion

THANK YOU

FOR YOUR ATTENTION

UNEP GERIAP


47/47

47

Disclaimer and References

This PowerPoint training session was prepared as part ofthe project Greenhouse Gas Emission Reduction from

Industry in Asia and the Pacific (GERIAP). While

reasonable efforts have been made to ensure that thecontents of this publication are factually correct andproperly referenced, UNEP does not accept responsibility forthe accuracy or completeness of the contents, and shall notbe liable for any loss or damage that may be occasioneddirectly or indirectly through the use of, or reliance on, the

contents of this publication. UNEP, 2006. The GERIAP project was funded by the Swedish

International Development Cooperation Agency (Sida)

Full references are included in the textbook chapter that is

Documents

Aula-3 Fuels and Combustion (2)