• What information does basic fuel characterisation provide?

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      espadmin

1. Background

The
concepts of fuel characterisation are outlined in Combustion File 48 “What is pulverised fuel characterisation?”.

Two levels of pulverisation fuel characterisation are identified:

  • Basic pulverised fuel characterisation
  • Advanced pulverised fuel characterisation

This combustion file develops information on the former and commences to provide examples for a range of solid fuels for pulverised fuel firing.

2. Basic Fuels Characterisation

The basic fuel characterisation techniques, described in details in Combustion File 24 How do I make a basic combustion characterisation of a Biofuel?, focuses on the following main physical-chemical and combustion characteristics:

  • [GLOSS]proximate analysis[/GLOSS]: moisture, volatile matter, fixed carbon and ash content
  • [GLOSS]ultimate analysis[/GLOSS]: carbon, hydrogen, nitrogen, sulphur and oxygen
  • chlorine content: important where plastic wastes and some biomass, such as straw, are included
  • [GLOSS]higher calorific value[/GLOSS]
  • bulk density
  • particle size distribution
  • ash composition
  • [GLOSS]ash fusibility[/GLOSS] defined by ash fusion temperatures: [GLOSS]initial deformation temperature[/GLOSS], [GLOSS]hemisphere temperature[/GLOSS] and [GLOSS]flow temperature[/GLOSS],
  • [GLOSS]heavy metals analyses[/GLOSS].

3. Basic fuel characterisation example

An example of the basic fuel characterisation can be seen on Table 1, from [1].

Table 1a. Proximate analysis.

%wt
as received

Bituminous
coal

Pine
sawdust

Dry
sewage sludge

RDF-Refuse
derived fuel
Moisture

1.7

7.3

4.0

4.66
Volatile
matter

34.0

76.2

52.0

72.78
Fixed
carbon

59.3

13.9

13.0

13.66
Ash

5.0

2.6

31.0

8.9

 

Table 1b. Ultimate analysis.

%wt
dry basis (incl.ash)

Bituminous
coal

Pine
sawdust

Dry
sewage sludge

RDF-Refuse
derived fuel
Carbon

79.2

50.6

30.9

43.19
Hydrogen

4.7

5.6

4.6

6.75
Nitrogen

1.8

0.1

4.5

0.63
Sulphur

0.9

0.04

1.1

trace
Oxygen

7.6

40.84

26.5

38.79
Chlorine

0.7

0.02

0.1

1.3

 

Table 1c. Calorific value.

 

Bituminous
coal

Pine
sawdust

Dry
sewage sludge

RDF-Refuse
derived fuel
MJ/kg

79.2

50.6

30.9

43.19

Higher
calorific  value:

  • British Standard Methods (BS:1016:part 5: 1977) using bomb calorimeter
  • Calculated based on the ultimate analysis as an example [MJ/kg] = 109.6*(C/3+H+S/8-O/8)-0.8817

Table 1d. Bulk density.

 

Bituminous
coal

Pine
sawdust

Dry
sewage sludge

RDF-Refuse
derived fuel
Kg/m3

603.3

182

610

64.1

 

Table 1d. Particle size distribution.

 

Particle
size

Percentage

Bituminous
coal

<188 mm
<87 mm
<54 mm
<38 mm
<22 mm

100
95.4
79.3
63.2
39.3
Pine
sawdust

<1.78 mm
<1.38 mm
<0.78 mm

100
75
25
Dry
sewage sludge

<300 mm
<106 mm
<53 mm
<38 mm
<25 mm

100
94.0
80.6
68.2
50.4
RDF-Refuse
derived fuel

<564 mm
<203 mm
<84 mm
<50 mm
<24 mm

 100
90
67
49
25

 

Table 1e. Ash composition.

%wt
as oxide

Bituminous
coal

Pine
sawdust

Dry
sewage sludge

Refuse
derived fuel
SiO2

34.1

18.1

33.6

39.8
Al2O3

24.9

2.5

15.6

23.7
CaO

8.1

55.7

22.2

22.9
P2O5

1.2

2.1

16.7

1.0
Fe2O3

21.1

2.4

3.6

2.3
TiO2

0.7

0.3

1.3

2.1
MgO

1.9

6.3

2.3

2.7
Na2O

2.1

1.9

0.5

2.0
K2O

1.0

8.3

1.1

1.9
SO3

4.9

2.4

3.1

1.6

 

Table 1f. Ash fusion temperature.

oC

Bituminous
coal

Pine
sawdust

Dry
sewage sludge

Refuse
derived fuel
IDT

1080

1060

1110

1150
HDT

1170

1150

1220

1170
FT

1300

1230

1270

1220

IDT
– Initial Deformation Temperature, HDT – Hemisphere Temperature, FT – Flow Temperature

Table 1g. Heavy metals – trace element concentration.

ppm
by weight

Bituminous
coal

Pine
sawdust

Dry
sewage sludge

Refuse
derived fuel
Pb

20

<3

211

50
Cd

<1

<1

2

<1
Hg

<2

<2

<2

<2
V

7

<1

12

4
Zn

15

9

567

85
Ni

3

<2

32

2
Mn

53

93

209

57
Fe

2940

<6

5400

768
As

5

14

10

5
Mo

<2

<2

5

<2
Al

146

15

11700

1600
Cu

23

3

829

35
Co

<2

<2

3

<2
Cr 

<2

3

62

8
SO-24 

10300

209

28800

3450

 

Sources

[1] Abbas, T., Costen, P. Glaser, K., Hassan S. Lockwood, F. Ou, J.-J. Combined
Combustion of Biomass, Municipal Sewage Sludge and Coal in a Pulverised Fuel
Plant. In Hein, K.R.G. (ed.), Clean Coal Technology Programme 1992-1994 Vol. II,
Combined Combustion of Biomass/Sewage Sludge and Coals: Final Reports,
EC-Research Project: APAS-Contract COAL-CT92-0002, Institute for Process
Engineering and Power Plant. (1994).

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