Solid biofuels - Determination of self-heating of pelletized biofuels - Part 2: Basket heating tests (ISO/TS 20049-2:2020)

This document provides information on basket heating tests for characterisation of self-heating properties of solid biofuel pellet.
This document includes:
— A compilation of basket heating test methods.
— Guidance on the applicability and use of basket heating tests for solid biofuel pellets.
— Information on the application of basket heating test data for calculations of critical conditions in storages.
Data on spontaneous heat generation determined using this document is only associated with the specific quality and age of the sample material.
This document is applicable to solid biofuel pellets only.
NOTE    The information derived using this document is for use in quality control and in hazard and risk assessments related to the procedures given in ISO/DIS 20024:2019.

Biogene Festbrennstoffe - Bestimmung der Selbsterhitzung von pelletierten biogenen Brennstoffen - Teil 2: Warmlagerungsprüfungen im Drahtnetzkorb (ISO/TS 20049-2:2020)

Biocombustibles solides - Détermination de l'auto-échauffement des granulés de biocombustibles - Partie 2: Essais utilisant la méthode du point de croisement (ISO/TS 20049-2:2020)

Le présent document spécifie les essais utilisant la méthode du point de croisement pour la caractérisation des propriétés d'auto-échauffement des granulés de biocombustibles solides.
Le présent document comprend les parties suivantes:
a)    une compilation des méthodes d'essai utilisant la méthode du point de croisement;
b)    des recommandations sur l'applicabilité et l'utilisation des essais utilisant la méthode du point de croisement pour les granulés de biocombustibles solides;
c)    des informations relatives à l'application des données d'essais utilisant la méthode du point de croisement pour le calcul des conditions critiques dans les lieux de stockages.
Les données relatives à la production spontanée de chaleur déterminées à l'aide du présent document sont uniquement associées à la qualité et à l'âge spécifiques de l'échantillon de matériau.
Les informations déduites à l'aide du présent document sont destinées à être utilisées dans le contrôle qualité et dans l'identification des dangers et l'évaluation des risques associés aux procédures fournies dans l'ISO 20024.
Les méthodes décrites peuvent être utilisées pour d'autres substances que les granulés de biocombustibles solides (par exemple: les plaquettes de bois).

Trdna biogoriva - Določanje samosegrevanja peletiziranih biogoriv - 2. del: Preskusi ogrevanja košare (ISO/TS 20049-2:2020)

General Information

Status
Published
Public Enquiry End Date
28-Feb-2022
Publication Date
08-May-2022
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
20-Apr-2022
Due Date
25-Jun-2022
Completion Date
09-May-2022

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SLOVENSKI STANDARD
SIST-TS CEN ISO/TS 20049-2:2022
01-junij-2022
Trdna biogoriva - Določanje samosegrevanja peletiziranih biogoriv - 2. del:
Preskusi ogrevanja košare (ISO/TS 20049-2:2020)

Solid biofuels - Determination of self-heating of pelletized biofuels - Part 2: Basket

heating tests (ISO/TS 20049-2:2020)

Biogene Festbrennstoffe - Bestimmung der Selbsterhitzung von pelletierten biogenen

Brennstoffen - Teil 2: Warmlagerungsprüfungen im Drahtnetzkorb (ISO/TS 20049-
2:2020)
Biocombustibles solides - Détermination de l'auto-échauffement des granulés de

biocombustibles - Partie 2: Essais utilisant la méthode du point de croisement (ISO/TS

20049-2:2020)
Ta slovenski standard je istoveten z: CEN ISO/TS 20049-2:2022
ICS:
75.160.40 Biogoriva Biofuels
SIST-TS CEN ISO/TS 20049-2:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST-TS CEN ISO/TS 20049-2:2022
---------------------- Page: 2 ----------------------
SIST-TS CEN ISO/TS 20049-2:2022
CEN ISO/TS 20049-2
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
April 2022
TECHNISCHE SPEZIFIKATION
ICS 27.190; 75.160.40
English Version
Solid biofuels - Determination of self-heating of pelletized
biofuels - Part 2: Basket heating tests (ISO/TS 20049-
2:2020)

Biocombustibles solides - Détermination de l'auto- Biogene Festbrennstoffe - Bestimmung der

échauffement des granulés de biocombustibles - Partie Selbsterhitzung von pelletierten biogenen

2: Essais utilisant la méthode du point de croisement Brennstoffen - Teil 2: Warmlagerungsprüfungen im

(ISO/TS 20049-2:2020) Drahtnetzkorb (ISO/TS 20049-2:2020)

This Technical Specification (CEN/TS) was approved by CEN on 27 March 2022 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to

submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS

available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in

parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TS 20049-2:2022 E

worldwide for CEN national Members.
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SIST-TS CEN ISO/TS 20049-2:2022
CEN ISO/TS 20049-2:2022 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST-TS CEN ISO/TS 20049-2:2022
CEN ISO/TS 20049-2:2022 (E)
European foreword

The text of ISO/TS 20049-2:2020 has been prepared by Technical Committee ISO/TC 238 "Solid

biofuels” of the International Organization for Standardization (ISO) and has been taken over as

CEN ISO/TS 20049-2:2022 by Technical Committee CEN/TC 335 “Solid biofuels” the secretariat of

which is held by SIS.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

Any feedback and questions on this document should be directed to the users’ national standards body.

A complete listing of these bodies can be found on the CEN website.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO/TS 20049-2:2020 has been approved by CEN as CEN ISO/TS 20049-2:2022 without any

modification.
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SIST-TS CEN ISO/TS 20049-2:2022
---------------------- Page: 6 ----------------------
SIST-TS CEN ISO/TS 20049-2:2022
TECHNICAL ISO/TS
SPECIFICATION 20049-2
First edition
2020-12
Solid biofuels — Determination of
self-heating of pelletized biofuels —
Part 2:
Basket heating tests
Biocombustibles solides — Détermination de l'auto-échauffement des
granulés de biocombustibles —
Partie 2: Essais utilisant la méthode du point de croisement
Reference number
ISO/TS 20049-2:2020(E)
ISO 2020
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SIST-TS CEN ISO/TS 20049-2:2022
ISO/TS 20049-2:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
SIST-TS CEN ISO/TS 20049-2:2022
ISO/TS 20049-2:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols .......................................................................................................................................................................................................................... 3

5 Basket heating tests .......................................................................................................................................................................................... 3

6 Tests for product classification ............................................................................................................................................................. 4

6.1 UN classification .................................................................................................................................................................................... 4

6.1.1 General...................................................................................................................................................................................... 4

6.1.2 Test method for self-heating substances — UN MTC Test N.4 ................................................. 4

6.1.3 Classification criteria — GHS ................................................................................................................................ 5

6.2 Classification criteria — IMO ...................................................................................................................................................... 5

6.3 Applicability of UN MTC Test N.4 for pelletized biofuels .................................................................................... 5

7 Tests for determination of reaction kinetics ........................................................................................................................... 6

7.1 General ........................................................................................................................................................................................................... 6

7.2 Isoperibolic test methods .............................................................................................................................................................. 6

7.2.1 General...................................................................................................................................................................................... 6

7.2.2 Test procedure ................................................................................................................................................................... 7

7.2.3 Determination of reaction kinetics .................................................................................................................. 7

7.2.4 Applicability for pelletized biofuels ................................................................................................................ 7

7.3 Crossing-point method .................................................................................................................................................................... 8

7.3.1 General...................................................................................................................................................................................... 8

7.3.2 Test procedure ................................................................................................................................................................... 8

7.3.3 Determination of reaction kinetics .................................................................................................................. 9

7.3.4 Applicability for pelletized biofuels ................................................................................................................ 9

7.4 Adiabatic hot storage tests ........................................................................................................................................................10

7.4.1 General...................................................................................................................................................................................10

7.4.2 Test procedure ................................................................................................................................................................10

7.4.3 Determination of reaction kinetics ...............................................................................................................11

7.4.4 Applicability for pelletized biofuels .............................................................................................................12

8 Sample handling ................................................................................................................................................................................................12

8.1 General ........................................................................................................................................................................................................12

8.2 Sampling ....................................................................................................................................................................................................12

8.3 Sample transport and storage .................................................................................................................................................13

8.4 Sample preparation .........................................................................................................................................................................13

8.5 Sample disposal ...................................................................................................................................................................................13

9 Test report ................................................................................................................................................................................................................13

Annex A (informative) Example of calculating kinetic parameters from crossing-point

method tests ...........................................................................................................................................................................................................15

Annex B (informative) Use of data for calculations of critical conditions in storages ...................................18

Bibliography .............................................................................................................................................................................................................................23

© ISO 2020 – All rights reserved iii
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SIST-TS CEN ISO/TS 20049-2:2022
ISO/TS 20049-2:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 238, Solid biofuels.
A list of all parts in the ISO 20049 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
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SIST-TS CEN ISO/TS 20049-2:2022
ISO/TS 20049-2:2020(E)
Introduction

There is a continuous global growth in production, storage, handling, bulk transport and use of solid

biofuels especially in the form of pelletized biofuels.

The specific physical and chemical characteristics of solid biofuels, their handling and storage can lead

to a risk of fire and/or explosion, as well as health risks such as intoxication due to exposure to carbon-

monoxide, asphyxiation due to oxygen depletion or allergic reactions.

Heat can be generated in solid biofuel by exothermic biological, chemical and physical processes.

Biological processes include the metabolism of fungus and bacteria and occur at lower temperatures;

the oxidation of wood constituents increases with temperature and dominates at higher temperatures;

the heat production from biological and chemical processes leads to transport of moisture in the bulk

material, with associated sorption and condensation of water, which both are exothermic processes.

In, for example, a heap of stored forest fuel or a heap of moist wood chips, all of these processes can be

present and contribute to heat production.
[6]

Solid biofuels such as wood pellets, however, are intrinsically sterile due to the conditions during

manufacturing (exposure to severe heat during drying, fragmentation during hammermilling and

pressure during extrusion) but can attract microbes if becoming wet during handling and storage

resulting in metabolism and generation of heat. Leakage of water into a storage of wood pellets can

also lead to the physical processes mentioned above. Non-compressed wood like feedstock and chips

typically have a fauna of microbes which under certain circumstances will result in heating. All the

processes mentioned above contribute to what is called self-heating although oxidation is likely to be

one of the main contributing factors in the temperature range under which most biofuels are stored.

The heat build-up can be significant in large bulk stores as the heat conduction in the material is low.

Under certain conditions the heat generation can lead to thermal runaway and spontaneous ignition.

The potential for self-heating seems to vary considerably for different types of solid biofuel pellets. The

raw material used, and the properties of these raw materials have proven to influence the propensity

for self-heating of the produced wood pellets. However, the production process (e.g. the drying process)

also influences the potential for self-heating. It is therefore important to be able to identify solid biofuel

pellets with high heat generation potential to avoid fires in stored materials.

Two intrinsically different types of tests methods can be used to estimate the potential of self-heating:

a) in the isothermal calorimetry method described in ISO 20049-1, the heat flow generated from the

test portion is measured directly;

b) in the basket heating tests described in this document, the temperature of the test portion is being

monitored and the critical ambient temperature (CAT), where the temperature of the test portion

just does not increase significantly due to self-heating, is used for indirect assessment of self-

heating.

These two methods are applied at different analysis temperature regimes. The operating temperature

for an isothermal calorimeter is normally in the range 5 °C to 90 °C whereas basket heating tests are

conducted at higher analysis (oven) temperatures. For basket heating tests with wood pellets, the CAT

is found for a 1 l sample portion in the range 150 °C to 200 °C.

NOTE 1 The two types of test methods referred to above do not measure heat production from physical

processes such as transport of moisture.

NOTE 2 It is likely that oxidation reactions taking place in the low respective high temperature regimes for

solid biofuel pellets are of different character and thus have different reaction rates and heat production rates.

In such a case, extrapolation of the data from a high temperature test series can lead to non-conservative results

and might not be applicable without taking the low temperature reactions into account. In the general case of

two reactions with different activation energies, the high activation energy is “frozen out” at low temperatures

[7]
and the low activation energy reaction is “swamped” at higher temperatures .
© ISO 2020 – All rights reserved v
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SIST-TS CEN ISO/TS 20049-2:2022
ISO/TS 20049-2:2020(E)

NOTE 3 It has been shown for a limited number of different types of wood pellets that the reaction rates in the

lower temperature regime measured by isothermal calorimetry were higher compared to the reaction rate data

[8]
determined from basket heating tests in the higher temperature regime .

Basket heating tests have been used traditionally for characterization of the tendency for spontaneous

ignition of predominantly coals, but also for other reactive organic materials such as, for example,

[9]

cottonseed meal, bagasse and milk powder . The principle used in this type of tests is to find the CAT

for a self-heating sample material of specific size and geometry.

There are several different methods described in the literature with different degrees of sophistication.

The variations span from simple pass and fail tests to more advanced tests from which data on reaction

[10]
rates can be extracted .

Basket heating tests are useful for assessment of self-heating of solid biofuel pellets. The test method

selected can be evaluated for its applicability based on the information given in this document.

A compilation of available basket heating test methods is given in this document. Guidance on the

suitability for application of these methods for tests with pelletized biofuels is provided.

Basic theory of the use of basket heating test data for calculations of critical conditions in storages is

provided in Annex B.
vi © ISO 2020 – All rights reserved
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SIST-TS CEN ISO/TS 20049-2:2022
TECHNICAL SPECIFICATION ISO/TS 20049-2:2020(E)
Solid biofuels — Determination of self-heating of pelletized
biofuels —
Part 2:
Basket heating tests
1 Scope

This document specifies basket heating tests for the characterization of self-heating properties of solid

biofuel pellets.
This document includes:
a) a compilation of basket heating test methods;

b) guidance on the applicability and use of basket heating tests for solid biofuel pellets;

c) information on the application of basket heating test data for calculations of critical conditions in

storages.

Data on spontaneous heat generation determined using this document is only associated with the

specific quality and age of the sample material.

The information derived using this document is for use in quality control and in hazard and risk

assessments related to the procedures given in ISO 20024.

The described methods can be used for other substances than solid biofuel pellets (e.g. wood chips).

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Terminology, definitions and descriptions
ISO 18135, Solid Biofuels — Sampling
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 16559 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
analysis temperature
temperature of the analysis environment, i.e. the oven temperature
© ISO 2020 – All rights reserved 1
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SIST-TS CEN ISO/TS 20049-2:2022
ISO/TS 20049-2:2020(E)
3.2
Biot number

quotient of the convective heat transfer coefficient (between the sample boundary and the

surrounding air) and the conduction in the sample material normalized by the characteristic

dimension of the test basket
3.3
critical ambient temperature
CAT

ambient temperature [the analysis temperature (3.1) or the temperature of a storage] where the

internal temperature of the test portion (3.6) or the stored material increases significantly (due to self-

heating (3.4))
3.4
self-heating

rise in temperature in a material resulting from an exothermic reaction within the material

[SOURCE: ISO 13943:2017, 3.341, modified — “” has been deleted from the beginning of the

definition.]
3.5
spontaneous ignition
ignition caused by an internal exothermic reaction
Note 1 to entry: See the definitions of ignition in ISO 13943.

[SOURCE: ISO 13943:2017, 3.24, modified — “spontaneous ignition” has replaced auto-ignition” has the

preferred term and the other terms have been deleted. Notes 1 to 3 have been deleted and a new Note 1

to entry has been added.]
3.6
test portion
sub-sample either of a laboratory sample (3.8) or a test sample (3.7)
3.7
test sample
laboratory sample (3.8) after an appropriate preparation made by the laboratory

Note 1 to entry: In this document, the test sample is typically a representative sample from a batch of solid biofuel

pellets.
3.8
laboratory sample
combined sample or a sub-sample of a combined sample for use in a laboratory
[SOURCE: ISO 16559:2014, 4.124]
2 © ISO 2020 – All rights reserved
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SIST-TS CEN ISO/TS 20049-2:2022
ISO/TS 20049-2:2020(E)
4 Symbols
Symbol Quantity Typical unit
A pre-exponential factor in Arrhenius expression s
B dimensionless adiabatic temperature rise dimensionless
Bi dimensionless
Biot number, (Bi= )
c ambient oxygen concentration by volume fraction dimensionless
−1 −1
C specific heat capacity of the reaction products J kg K
−1 −1
C specific heat capacity of the bulk material J kg K
d diameter of body m
2 −1
D diffusion coefficient m s
E activation energy J mol
H gross calorific value J kg
−2 −1
h heat transfer coefficient W m K
−2 −1
h radiative amount on heat transfer coefficient W m K
−2 −1
h convective amount on heat transfer coefficient W m K
L characteristic length m
n order of reaction dimensionless
P constant, see Formulae (2) and (3) dimensionless
heat generation term, see Formula (B.1) W m
Q heat of reaction J kg
Q heat of reaction by volume of oxygen J m
−1 −1
R universal gas constant J mol K
Ra Rayleigh number dimensionless
t time s
T temperature K
T ambient temperature K
T crossing point temperature K
x length coordinate m
δ Frank-Kamenetskii parameter, see Formula (B.4) dimensionless
δ critical value of δ dimensionless
ε dimensionless
activation energy parameter, (ε = )
Ф oxygen diffusion parameter, see Formula (B.13) dimensionless
−1 −1
λ thermal conductivity of sample W m K
−1 −1
λ thermal conductivity of air W m K
air
ρ bulk density kg m
−2 −4
σ Stefan-Boltzmann coefficient W m K
5 Basket heating tests

The detailed test procedure varies between different isoperibolic and adiabatic methods. Isoperibolic

methods include that the test portion is put in a wire-mesh basket, which is placed in an oven heated to

a fixed elevated temperature. The oven is equipped with a fan to keep the temperature uniform and to

[9][10]

give a relatively large convective heat transfer coefficient to the test specimen . For adiabatic tests,

[5]

the oven temperature is adjusted to the temperature at the centre of the sample .

© ISO 2020 – All rights reserved 3
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SIST-TS CEN ISO/TS 20049-2:2022
ISO/TS 20049-2:2020(E)

Basket heating tests are based on the Frank-Kamenetskii theory of criticality of a self-heating isotropic

slab (see Annex B) and have been developed to determine the reaction kinetics of the global reaction

responsible for heat production in a self-heating material.

NOTE 1 The large gap volume of pelletized material can lead to convective heat transport in the bulk if the

furnace is equipped with a fan. In this case, it is recommended to keep the air flow in the vicinity of the sample at

a low level and to correct the critical Frank-Kamenetskii parameter (see B.1.3) or to prevent convective transport

within the sample by further measures (e.g. finer mesh wire of the basket).

NOTE 2 The CAT for the test portion in a basket heating tests is not equal to the CAT for spontaneous ignition in,

for example, large-scale storage. The critical size for spontaneous ignition (if only heat transfer is considered) is

directly related to the surface area-volume ratio of the self-heating specimen where heat is produced distributed

in the volume and heat is dissipated from the surf
...

SLOVENSKI STANDARD
kSIST FprEN ISO 20049-2:2022
01-februar-2022

Trda biogoriva - Določanje samosegrevanja peletiziranih biogoriv - 2. del: Preskusi

ogrevanja košare (ISO/TS 20049-2:2020)

Solid biofuels - Determination of self-heating of pelletized biofuels - Part 2: Basket

heating tests (ISO/TS 20049-2:2020)

Biogene Festbrennstoffe - Bestimmung der Selbsterhitzung von pelletierten biogenen

Brennstoffen - Teil 2: Warmlagerungsprüfungen im Drahtnetzkorb (ISO/TS 20049-
2:2020)
Biocombustibles solides - Détermination de l'auto-échauffement des granulés de

biocombustibles - Partie 2: Essais utilisant la méthode du point de croisement (ISO/TS

20049-2:2020)
Ta slovenski standard je istoveten z: FprCEN ISO/TS 20049-2
ICS:
75.160.40 Biogoriva Biofuels
kSIST FprEN ISO 20049-2:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
kSIST FprEN ISO 20049-2:2022
---------------------- Page: 2 ----------------------
kSIST FprEN ISO 20049-2:2022
TECHNICAL ISO/TS
SPECIFICATION 20049-2
First edition
2020-12
Solid biofuels — Determination of
self-heating of pelletized biofuels —
Part 2:
Basket heating tests
Biocombustibles solides — Détermination de l'auto-échauffement des
granulés de biocombustibles —
Partie 2: Essais utilisant la méthode du point de croisement
Reference number
ISO/TS 20049-2:2020(E)
ISO 2020
---------------------- Page: 3 ----------------------
kSIST FprEN ISO 20049-2:2022
ISO/TS 20049-2:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
kSIST FprEN ISO 20049-2:2022
ISO/TS 20049-2:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols .......................................................................................................................................................................................................................... 3

5 Basket heating tests .......................................................................................................................................................................................... 3

6 Tests for product classification ............................................................................................................................................................. 4

6.1 UN classification .................................................................................................................................................................................... 4

6.1.1 General...................................................................................................................................................................................... 4

6.1.2 Test method for self-heating substances — UN MTC Test N.4 ................................................. 4

6.1.3 Classification criteria — GHS ................................................................................................................................ 5

6.2 Classification criteria — IMO ...................................................................................................................................................... 5

6.3 Applicability of UN MTC Test N.4 for pelletized biofuels .................................................................................... 5

7 Tests for determination of reaction kinetics ........................................................................................................................... 6

7.1 General ........................................................................................................................................................................................................... 6

7.2 Isoperibolic test methods .............................................................................................................................................................. 6

7.2.1 General...................................................................................................................................................................................... 6

7.2.2 Test procedure ................................................................................................................................................................... 7

7.2.3 Determination of reaction kinetics .................................................................................................................. 7

7.2.4 Applicability for pelletized biofuels ................................................................................................................ 7

7.3 Crossing-point method .................................................................................................................................................................... 8

7.3.1 General...................................................................................................................................................................................... 8

7.3.2 Test procedure ................................................................................................................................................................... 8

7.3.3 Determination of reaction kinetics .................................................................................................................. 9

7.3.4 Applicability for pelletized biofuels ................................................................................................................ 9

7.4 Adiabatic hot storage tests ........................................................................................................................................................10

7.4.1 General...................................................................................................................................................................................10

7.4.2 Test procedure ................................................................................................................................................................10

7.4.3 Determination of reaction kinetics ...............................................................................................................11

7.4.4 Applicability for pelletized biofuels .............................................................................................................12

8 Sample handling ................................................................................................................................................................................................12

8.1 General ........................................................................................................................................................................................................12

8.2 Sampling ....................................................................................................................................................................................................12

8.3 Sample transport and storage .................................................................................................................................................13

8.4 Sample preparation .........................................................................................................................................................................13

8.5 Sample disposal ...................................................................................................................................................................................13

9 Test report ................................................................................................................................................................................................................13

Annex A (informative) Example of calculating kinetic parameters from crossing-point

method tests ...........................................................................................................................................................................................................15

Annex B (informative) Use of data for calculations of critical conditions in storages ...................................18

Bibliography .............................................................................................................................................................................................................................23

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kSIST FprEN ISO 20049-2:2022
ISO/TS 20049-2:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 238, Solid biofuels.
A list of all parts in the ISO 20049 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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kSIST FprEN ISO 20049-2:2022
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Introduction

There is a continuous global growth in production, storage, handling, bulk transport and use of solid

biofuels especially in the form of pelletized biofuels.

The specific physical and chemical characteristics of solid biofuels, their handling and storage can lead

to a risk of fire and/or explosion, as well as health risks such as intoxication due to exposure to carbon-

monoxide, asphyxiation due to oxygen depletion or allergic reactions.

Heat can be generated in solid biofuel by exothermic biological, chemical and physical processes.

Biological processes include the metabolism of fungus and bacteria and occur at lower temperatures;

the oxidation of wood constituents increases with temperature and dominates at higher temperatures;

the heat production from biological and chemical processes leads to transport of moisture in the bulk

material, with associated sorption and condensation of water, which both are exothermic processes.

In, for example, a heap of stored forest fuel or a heap of moist wood chips, all of these processes can be

present and contribute to heat production.
[6]

Solid biofuels such as wood pellets, however, are intrinsically sterile due to the conditions during

manufacturing (exposure to severe heat during drying, fragmentation during hammermilling and

pressure during extrusion) but can attract microbes if becoming wet during handling and storage

resulting in metabolism and generation of heat. Leakage of water into a storage of wood pellets can

also lead to the physical processes mentioned above. Non-compressed wood like feedstock and chips

typically have a fauna of microbes which under certain circumstances will result in heating. All the

processes mentioned above contribute to what is called self-heating although oxidation is likely to be

one of the main contributing factors in the temperature range under which most biofuels are stored.

The heat build-up can be significant in large bulk stores as the heat conduction in the material is low.

Under certain conditions the heat generation can lead to thermal runaway and spontaneous ignition.

The potential for self-heating seems to vary considerably for different types of solid biofuel pellets. The

raw material used, and the properties of these raw materials have proven to influence the propensity

for self-heating of the produced wood pellets. However, the production process (e.g. the drying process)

also influences the potential for self-heating. It is therefore important to be able to identify solid biofuel

pellets with high heat generation potential to avoid fires in stored materials.

Two intrinsically different types of tests methods can be used to estimate the potential of self-heating:

a) in the isothermal calorimetry method described in ISO 20049-1, the heat flow generated from the

test portion is measured directly;

b) in the basket heating tests described in this document, the temperature of the test portion is being

monitored and the critical ambient temperature (CAT), where the temperature of the test portion

just does not increase significantly due to self-heating, is used for indirect assessment of self-

heating.

These two methods are applied at different analysis temperature regimes. The operating temperature

for an isothermal calorimeter is normally in the range 5 °C to 90 °C whereas basket heating tests are

conducted at higher analysis (oven) temperatures. For basket heating tests with wood pellets, the CAT

is found for a 1 l sample portion in the range 150 °C to 200 °C.

NOTE 1 The two types of test methods referred to above do not measure heat production from physical

processes such as transport of moisture.

NOTE 2 It is likely that oxidation reactions taking place in the low respective high temperature regimes for

solid biofuel pellets are of different character and thus have different reaction rates and heat production rates.

In such a case, extrapolation of the data from a high temperature test series can lead to non-conservative results

and might not be applicable without taking the low temperature reactions into account. In the general case of

two reactions with different activation energies, the high activation energy is “frozen out” at low temperatures

[7]
and the low activation energy reaction is “swamped” at higher temperatures .
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kSIST FprEN ISO 20049-2:2022
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NOTE 3 It has been shown for a limited number of different types of wood pellets that the reaction rates in the

lower temperature regime measured by isothermal calorimetry were higher compared to the reaction rate data

[8]
determined from basket heating tests in the higher temperature regime .

Basket heating tests have been used traditionally for characterization of the tendency for spontaneous

ignition of predominantly coals, but also for other reactive organic materials such as, for example,

[9]

cottonseed meal, bagasse and milk powder . The principle used in this type of tests is to find the CAT

for a self-heating sample material of specific size and geometry.

There are several different methods described in the literature with different degrees of sophistication.

The variations span from simple pass and fail tests to more advanced tests from which data on reaction

[10]
rates can be extracted .

Basket heating tests are useful for assessment of self-heating of solid biofuel pellets. The test method

selected can be evaluated for its applicability based on the information given in this document.

A compilation of available basket heating test methods is given in this document. Guidance on the

suitability for application of these methods for tests with pelletized biofuels is provided.

Basic theory of the use of basket heating test data for calculations of critical conditions in storages is

provided in Annex B.
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kSIST FprEN ISO 20049-2:2022
TECHNICAL SPECIFICATION ISO/TS 20049-2:2020(E)
Solid biofuels — Determination of self-heating of pelletized
biofuels —
Part 2:
Basket heating tests
1 Scope

This document specifies basket heating tests for the characterization of self-heating properties of solid

biofuel pellets.
This document includes:
a) a compilation of basket heating test methods;

b) guidance on the applicability and use of basket heating tests for solid biofuel pellets;

c) information on the application of basket heating test data for calculations of critical conditions in

storages.

Data on spontaneous heat generation determined using this document is only associated with the

specific quality and age of the sample material.

The information derived using this document is for use in quality control and in hazard and risk

assessments related to the procedures given in ISO 20024.

The described methods can be used for other substances than solid biofuel pellets (e.g. wood chips).

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 14780, Solid biofuels — Sample preparation
ISO 16559, Solid biofuels — Terminology, definitions and descriptions
ISO 18135, Solid Biofuels — Sampling
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 16559 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
analysis temperature
temperature of the analysis environment, i.e. the oven temperature
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3.2
Biot number

quotient of the convective heat transfer coefficient (between the sample boundary and the

surrounding air) and the conduction in the sample material normalized by the characteristic

dimension of the test basket
3.3
critical ambient temperature
CAT

ambient temperature [the analysis temperature (3.1) or the temperature of a storage] where the

internal temperature of the test portion (3.6) or the stored material increases significantly (due to self-

heating (3.4))
3.4
self-heating

rise in temperature in a material resulting from an exothermic reaction within the material

[SOURCE: ISO 13943:2017, 3.341, modified — “” has been deleted from the beginning of the

definition.]
3.5
spontaneous ignition
ignition caused by an internal exothermic reaction
Note 1 to entry: See the definitions of ignition in ISO 13943.

[SOURCE: ISO 13943:2017, 3.24, modified — “spontaneous ignition” has replaced auto-ignition” has the

preferred term and the other terms have been deleted. Notes 1 to 3 have been deleted and a new Note 1

to entry has been added.]
3.6
test portion
sub-sample either of a laboratory sample (3.8) or a test sample (3.7)
3.7
test sample
laboratory sample (3.8) after an appropriate preparation made by the laboratory

Note 1 to entry: In this document, the test sample is typically a representative sample from a batch of solid biofuel

pellets.
3.8
laboratory sample
combined sample or a sub-sample of a combined sample for use in a laboratory
[SOURCE: ISO 16559:2014, 4.124]
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4 Symbols
Symbol Quantity Typical unit
A pre-exponential factor in Arrhenius expression s
B dimensionless adiabatic temperature rise dimensionless
Bi dimensionless
Biot number, (Bi= )
c ambient oxygen concentration by volume fraction dimensionless
−1 −1
C specific heat capacity of the reaction products J kg K
−1 −1
C specific heat capacity of the bulk material J kg K
d diameter of body m
2 −1
D diffusion coefficient m s
E activation energy J mol
H gross calorific value J kg
−2 −1
h heat transfer coefficient W m K
−2 −1
h radiative amount on heat transfer coefficient W m K
−2 −1
h convective amount on heat transfer coefficient W m K
L characteristic length m
n order of reaction dimensionless
P constant, see Formulae (2) and (3) dimensionless
heat generation term, see Formula (B.1) W m
Q heat of reaction J kg
Q heat of reaction by volume of oxygen J m
−1 −1
R universal gas constant J mol K
Ra Rayleigh number dimensionless
t time s
T temperature K
T ambient temperature K
T crossing point temperature K
x length coordinate m
δ Frank-Kamenetskii parameter, see Formula (B.4) dimensionless
δ critical value of δ dimensionless
ε dimensionless
activation energy parameter, (ε = )
Ф oxygen diffusion parameter, see Formula (B.13) dimensionless
−1 −1
λ thermal conductivity of sample W m K
−1 −1
λ thermal conductivity of air W m K
air
ρ bulk density kg m
−2 −4
σ Stefan-Boltzmann coefficient W m K
5 Basket heating tests

The detailed test procedure varies between different isoperibolic and adiabatic methods. Isoperibolic

methods include that the test portion is put in a wire-mesh basket, which is placed in an oven heated to

a fixed elevated temperature. The oven is equipped with a fan to keep the temperature uniform and to

[9][10]

give a relatively large convective heat transfer coefficient to the test specimen . For adiabatic tests,

[5]

the oven temperature is adjusted to the temperature at the centre of the sample .

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Basket heating tests are based on the Frank-Kamenetskii theory of criticality of a self-heating isotropic

slab (see Annex B) and have been developed to determine the reaction kinetics of the global reaction

responsible for heat production in a self-heating material.

NOTE 1 The large gap volume of pelletized material can lead to convective heat transport in the bulk if the

furnace is equipped with a fan. In this case, it is recommended to keep the air flow in the vicinity of the sample at

a low level and to correct the critical Frank-Kamenetskii parameter (see B.1.3) or to prevent convective transport

within the sample by further measures (e.g. finer mesh wire of the basket).

NOTE 2 The CAT for the test portion in a basket heating tests is not equal to the CAT for spontaneous ignition in,

for example, large-scale storage. The critical size for spontaneous ignition (if only heat transfer is considered) is

directly related to the surface area-volume ratio of the self-heating specimen where heat is produced distributed

in the volume and heat is dissipated from the surface area only. The test sample in laboratory size basket heating

test has a very high surface area-volume ratio and has consequently a high CAT compared to a larger specimen.

6 Tests for product classification
6.1 UN classification
6.1.1 General

The United Nations (UN) Globally Harmonized System of Classification and Labelling of Chemicals

[11]

(GHS) is the international convention for hazard communication and labelling of gases, vapours,

solid and liquid substances, and mixtures. The GHS defines limit values, classes and categories and

related measures in relation to the level of hazards during transportation, handling and storage.

[12]

The UN Manual of Tests and Criteria (MTC) prescribes specific test procedures in support of the GHS.

6.1.2 Test method for self-heating substances — UN MTC Test N.4
[12]

Test N.4 is described in the UN MTC Part III, 33.3.1.6 , sometimes called the “basket test”.

This basket heating test determines the ability of a substance to undergo oxidative self-heating with

exposure of it to air at temperatures of 100 °C, 120 °C or 140 °C in a 25 mm or 100 mm wire mesh cube.

The Test N.4 basket heating test is not intended for determination of self-heating kinetics but rather

prescribed to classify a material (e.g. solid biofuels) as meeting the criteria for self-heating set out by

[11]
the GHS for hazard communication and labelling purposes.

The test set-up consists of a hot-air circulating oven, cubic sample containers of 25 mm and 100 mm

sides made of stainless-steel net with a mesh opening of 0,05 mm, and thermocouples of 0,3 mm

diameter for the measurement of the oven temperature and the temperature of the centre of the

sample. The sample container is housed in a cubic container cover made from stainless-steel net with

a mesh opening of 0,60 mm, and is slightly larger than the test container. To avoid the effect of air

circulation, this cover is installed in a second steel cage, made from a net with a mesh size of 0,595 mm

and 150 mm × 150 mm × 250 mm in size.

The normal procedure is to start with a test at 140 °C with a 100 mm cube sample. The container is

housed in the cover and hung at the centre of the oven. The oven temperature is raised to 140 °C and

kept there for 24 h. A positive result is obtained if spontaneous ignition occurs or if the temperature

of the sample exceeds the oven temperature by 60 °C. If a negative result is obtained, no further test is

necessary.

If a positive result is obtained at 140 °C with a 100 mm cube sample, the substance is classified as a self-

heating substance and further testing shall be made to find the correct classification (see 6.1.3).

NOTE The bulk density tested can influence the test results. prEN 15188 suggests adjusting the bulk density

of the sample to the respective practical conditions (if known) and recording the tested bulk density. The UN

MTC contains no information on the bulk density to be tested.
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6.1.3 Classification criteria — GHS
[11]

The classification criteria are given in chapter 2.11.2 of the GHS . The criteria are summarized in

Table 1.
Table 1 — Criteria in the GHS for self-heating substances and mixtures
Category Criteria
1 A positive result is obtained in a test using 25 mm sample cube at 140 °C.

2 a) A positive result is obtained in a test using a 100 mm sample cube at 140 °C and a negative

result is obtained in a test using a 25 mm cube sample at 140 °C and the substance or mixture

is to be packed in packages with a volume of more than 3 m ; or

b) A positive result is obtained in a test using a 100 mm sample cube at 140 °C and a negative

result is obtained in a test using a 25 mm cube sample at 140 °C, a positive result is obtained

in a test using a 100 mm cube sample at 120 °C and the substance or mixture is to be packed

in packages with a volume of more than 450 litres; or

c) A positive result is obtained in a test using a 100 mm sample cube at 140 °C and a negative

result is
...

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