Self-heating in biofuel pellets

Anders Lönnermark, SP Fire Research Adjunct Prof. at Mälardalen University

Seminar on handling of biofuel pellets at large facilities, Teknologisk Institut, Taastrup, Denmark, 2014-04-08

SP Technical Research Institute of Sweden

The SP group Fire Research >1300 employees Approx 90 employees

Fire Research

Certification

Glass

Electronics

Energy Technology

Chemistry, Materials and Surfaces

Food and Biotechnology

Calibration and Verifications

MeasurementTechnology

Wood Technology

Process Development

Active Safety

Structuraland Solid Mechanics Machinery

Testing andInspection

Agriculture and environment

Bioeconomy

Swedish-Norwegian fire cooperation: SP Fire Research SP Fire Technology SINTEF NBL

≈ 120 employees in total

SP Fuel Storage Safety

An international Center of Expertise for fire safety during storage and handling of gaseous, liquid and solid fuels and recycling of waste material involving research, innovation and knowledge transfer.

Fuel storage self-heating problems in focus Self-heating properties and risk for

spontaneous ignition Fire development and risk for escalation Difficult to detect Often limited access Difficult and time consuming

extinguishing process Silo fires often result in total damage Improved guidelines

Self-heating

• Microbiological activity generally not significant (as in e.g. piles of wood chips) • Heat from oxidation of wood constituents • Oxidation of unsaturated fatty acids proposed to be major heat source • Self-heating often seen shortly after production • Some fuel qualities show higher heating activity and can during unfavorable conditions lead to

spontaneous ignition

0

50

100

150

200

250

300

350

Time

Temp

eratu

re (º

C)

LUBA

• LUBA – Large scale utilization of Biopellets for energy Applications – WP1 :Import of sustainably produced biomass for energy application – WP2: Development of new sampling techniques for suspended biofuels – WP3: Quantification of important factors causing self-heating, oxygen depletion and off-

gassing • 3.3 Measurements characterizing the self-heating of wood pellets

– Self-heating properties: micro calorimeter – Self-heating properties: oven-basket tests – Simulation and extrapolation of data towards full-scale – Thermal properties – Medium-scale verification tests

Description of pellets tested in LUBA

Pellet Pellet origin Type of pellet

A Swedish fresh pellets Pine

B Scottish pellets , 3 months storage in Denmark Pine

C Swedish fresh pellets Spruce/pine/energy wood

D Pellets from torrefied material+tar additive Spruce (torrefied)

E Russian pellets from harbour in Denmark Spruce/pine

F Portuguese pellets from harbour in Denmark Pine

G Swedish fresh pellets Spruce/pine/energy wood

H Scottish fresh pellets (10 days) Pine

I Scottish pellets from harbour in Denmark Pine

J Scottish fresh pellets Pine

K Swedish fresh pellets Spruce/pine/energy wood

L Swedish fresh pellets Spruce/pine/energy wood

M Scottish pellets stored in 16 kg plastic bags Pine

Self-heating properties of various materials in different scales

0.00

0.20

0.40

0.60

0.80

1.00

0 5 10 15 20 25

Heat

rele

ase

rate

, mW

/g

Time, h

60°C

Pellets L, sample 1Pellets L, sample 2Pellets M, sample 1Pellets M, sample 2

Micro calorimeter method

• Isothermal calorimetry • Very accurate (mW-scale) measure of the heat of reaction • 20 mL ampoule • 2 g, 4 g, 6 g, 8 g • 40 °C, 60 °C, 80 °C

Basket-heating test (Crossing-point)

0102030405060708090

100110120130140150160170180190200210220230240

0 1 2 3 4 5 6

Tem

p (

C)

Distance from centre (cm)

5 min

10 min

30 min

60 min

90 min

120 min

150 min

180 min

210 min

240 min

270 min

300 min

330 min

𝑙𝑙𝑙𝑙 �𝜕𝜕𝜕𝜕𝜕𝜕𝜕𝜕� = 𝑙𝑙𝑙𝑙 �

𝑄𝑄𝑄𝑄𝐶𝐶𝑃𝑃� −

𝐸𝐸𝑅𝑅𝜕𝜕𝐶𝐶𝑃𝑃

Transient plain source (TPS)

8 mm

Sample 1

Sample 2

X

Y

Z

Approx. 25 mm

Medium-scale tests (1 m3)

Label of pellets

Pellet type Bulk density (kg/m3)

Pellet diameter (mm)

L Agro Energi, Sweden Sampled relatively fresh from production

715 8

M Verdoe, Scotland Transported and stored for 3 months before sampled

719 8

Medium-scale tests – Test set-up

YX

Z

400

1100

420

360

3600

2495

1100 Ø600

95+10

2

Pre-heating inflow

95+10

TC_54

V3160 Ø 100

3000

V2

2500

X

Z

FanHeater

Pellets160 Ø

250

Ø

2500

600

1016

24

25

40

Outflow

All

duct

sin

sula

ted

A.

B.

C.

100 Ø

TC 52

V1

600

250

TC 46-48

TC 49-51

TC 53

V2

Medium-scale tests: Measurements Rear side

Front side (with hatch)

P1

P2 P8

P9

P3

P7

P6

P4

P5

Z

X

1500 1100

1100

550

Thermocouple (0.5 mm type K)

Thermocouple + gas sampling

10050

17.16.

15.

14.

13.

12.

10.

9.

8.

7.

6.5.

18.

21.

20.

23.

30.

27.

24.

26.

32.33.

29.

11. 25. 28.31. 19. 22.

2001504.

P1 P2 P3 P4 P5

200 200 200 150

270

Results – Micro calorimeter

0.00

0.20

0.40

0.60

0.80

1.00

0 5 10 15 20 25

Heat

rele

ase

rate

, mW

/g

Time, h

60°C

Pellets L, sample 1Pellets L, sample 2Pellets M, sample 1Pellets M, sample 2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 5 10 15 20

Hea

t rel

ease

rate

(mW

/g)

Time (h)

60°C A, pellets

A, pellets

B, pellets

B, pellets

C, pellets

C, pellets

C, powder

C, powder

Effect of temperature

0.00

0.50

1.00

1.50

2.00

0 5 10 15 20 25

Hea

t rel

ease

rate

(mW

/g)

Time (h)

80 °C, L Sample 1

80 °C, L Sample 2

60 °C, L Sample 1

60 °C, L Sample 2

40 °C, L Sample 1

40 °C, L Sample 2

Variation in heat release rate

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25

Heat

rele

ase

rate

(mW

/g)

Pellets id

Fresh pine 4g

Fresh S/P/EW 4g

Fresh pine 8g

Fresh S/P/EW 8g

Stored pine 4g

Stored spruce/pine 4g

Stored S/P/EW 4g

Stored pine 8g

Other 4g

Results – Medium-scale tests

0

50

100

150

200

250

300

350

400

450

0 10 20 30 40 50

Tem

pera

ture

(°C)

Time (h)

Test 1

Test 2

Test 3

Test 4

0

20

40

60

80

100

120

140

0 10 20 30 40 50

Tem

pera

ture

(°C)

Time (h)

Test 1

Test 2

Test 3

Test 4

Test Pellet type Air temperature in enclosure (ºC)

1 L 90 2 L 105 3 M 90 4 M 105

Results – Medium-scale tests (2): Increase in temperature

Test Pellet type

Air temperature in enclosure (ºC)

Pre-heating + 5h

+ 10h + 20h + 30h + 35h

1 L 90 16.1 18.9 23.4 26.5 27.8

2 L 105 20.8 24.7 34.4 55.4 304.6

3 M 90 4.2 7.2 11.6 12.6 12.3

4 M 105 5.8 10.2 17.1 21.4 23.4

Modelling: Calculated heat production

0

100

200

300

400

500

600

700

800

900

1000

0 50 100 150 200

Heat

pro

duct

ion

rate

J/m

3 s

Temperature (°C)

Pellet M - CP

Pellet L - CP

Pellet M - µ-cal

Pellet L - µ-cal

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 120

Heat

pro

duct

ion

rate

J/m

3 s

Temperature (°C)

Pellet M - CP

Pellet L - CP

Pellet M - µ-cal

Pellet L - µ-cal

Conclusions from the self-heating studies within LUBA (1)

• Micro calorimeter tests – In total 21 different samples (13 different batches) were tested

• type of pellets • physical form (whole pellets or crushed into powder) • storage time (fresh or stored for several months) • one sample after being involved in a 1 m3 self-heating test

– Significant differences in propensity for self-heating • difference between different types of pellets • fresh pellets more active than stored pellets • Increase in activity with increased temperature

– Good repeatability in the micro calorimeter tests – Micro calorimetry and crossing-point gave approximately the same overall ranking

Conclusions from the self-heating studies within LUBA (2)

• 1 m3 tests – Effective in separating the self-heating activity of the two types of pellets investigated

• Type M had a very moderate activity • Type L showed much higher activity, resulting in spontaneous ignition • The gas production was also higher for Type L

– Possibilities for development of test method • Modelling

– Small differences in heat production rate and critical ambient temperature (1 m3) between type L and type M based on crossing-point data.

– The calculation based on micro calorimeter data gave lower critical ambient temperature and larger difference between type L and type M.

– big silo > normal silo > flat storage > tower silo

SafePellets: Characterization of the self-heating of wood pellets

Screening and classification Determination of reaction kinetics

(small scale) – Isothermal calorimetry – Oven-basket experiments – TGA/DSC Analysis of thermal and other

relevant physical properties of pellets Mathematical simulations Medium-scale tests Real-scale tests

www.safepellets.eu

Reports from the LUBA project on self-heating

SP Report 2012:49

SP Report 2012:50 www.sp.se

Examples of other reports and recommendations of interest

www.ieabioenergy.com

Self-heating in biofuel pellets

Anders Lönnermark, SP Fire Research Adjunct Prof. at Mälardalen University

Seminar on handling of biofuel pellets at large facilities, Teknologisk Institut, Taastrup, Denmark, 2014-04-08

Thank you for the attention!

www.sp.se anders.lonnermark@sp.se