CEN/TS 14918:2005

SLOVENSKI STANDARD
01-september-2005
7UGQDELRJRULYD±0HWRGD]DXJRWDYOMDQMHNDORULþQHYUHGQRVWL
Solid Biofuels - Method for the determination of calorific value
Feste Biobrennstoffe - Verfahren Zur Bestimmung des Heizwertes
Biocombustibles solides - Méthode pour la détermination du pouvoir calorifique
Ta slovenski standard je istoveten z: CEN/TS 14918:2005
ICS:
75.160.10 Trda goriva Solid fuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION
CEN/TS 14918
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
May 2005
ICS 75.160.10
English version
Solid Biofuels - Method for the determination of calorific value
Biocombustibles solides - Méthode pour la détermination Feste Biobrennstoffe - Verfahren Zur Bestimmung des
du pouvoir calorifique Heizwertes
This Technical Specification (CEN/TS) was approved by CEN on 16 August 2004 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, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 14918:2005: E
worldwide for CEN national Members.

Contents
page
Contents .2
Foreword.3
1 Scope .5
2 Normative references .5
3 Terms and definitions .6
4 Principle.7
5 Reagents.7
6 Apparatus .8
7 Preparation of test sample.11
8 Calorimetric procedure .12
9 Calibration .18
10 Gross calorific value .24
11 Precision.28
12 Calculation of net calorific value at constant pressure.29
13 Test report .30
Annex A (normative)  Adiabatic bomb calorimeters.32
Annex B (normative)  Isoperibol and static-jacket bomb calorimeters.36
Annex C (normative)  Automated bomb calorimeters .42
Annex D (informative)  Checklists for the design and procedures of combustion experiments.45
Annex E (informative)  Examples to illustrate the main calculations used in this Technical
Specification when an automated (adiabatic) bomb calorimeter is used for determinations.50
Annex F (informative)  List of symbols used in this Technical Specification.54
Annex G (informative)  Key-word index .57
Annex H (informative)  Default values of most used biofuels for the calculations of calorific
values.61
Annex I (informative)  Flow chart for a routine calorific value determination.62

Foreword
This document (CEN/TS 14918:2005) has been prepared by Technical Committee CEN/TC 335 “Solid
Biofuels”, the secretariat of which is held by SIS.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this CEN Technical Specification: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
Introduction
WARNING - Strict adherence to all of the provisions prescribed in this Technical Specification should
ensure against explosive rupture of the bomb, or a blow-out, provided that the bomb is of proper
design and construction and in good mechanical condition.

1 Scope
This document specifies a method for the determination of the gross calorific value of a solid biofuel at
constant volume and at the reference temperature 25 °C in a bomb calorimeter calibrated by combustion of
certified benzoic acid.
The result obtained is the gross calorific value of the analysis sample at constant volume with all the water of
the combustion products as liquid water. In practice, biofuels are burned at constant (atmospheric) pressure
and the water is either not condensed (removed as vapour with the flue gases) or condensed. Under both
conditions, the operative heat of combustion to be used is the net calorific value of the fuel at constant
pressure. The net calorific value at constant volume may also be used; formulae are given for calculating both
values.
General principles and procedures for the calibrations and the biofuel experiments are presented in the main
text, whereas those pertaining to the use of a particular type of calorimetric instrument are described in
Annexes A to C. Annex D contains checklists for performing calibration and fuel experiments using specified
types of calorimeters. Annex E gives examples to illustrate some of the calculations.
2 Normative references
The following referenced documents are indispensable for the application 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.
prCEN/TS 15234, Solid biofuels – Fuel quality assurance
CEN/TS 14774-1:2004, Solid biofuels – Methods for determination of moisture content – Oven dry method –
Part 1: Total moisture – Reference method
CEN/TS 14774-2, Solid biofuels – Methods for determination of moisture content – Oven dry method – Part 2:
Total moisture – Simplified method
CEN/TS 14774-3, Solid biofuels – Methods for determination of moisture content – Oven dry method – Part 3:
Moisture in general analysis sample
prCEN/TS 14780, Solid biofuels – Methods of sample preparation
prCEN/TS XXX , Solid biofuels - Calculation of analyses to different bases
00335026, Solid biofuels –Determination of total content of sulfur and chlorine
EN ISO 10304-1:1995 Water quality – Determination of dissolved fluoride, chloride, nitrite, ortophosphate,
bromide, nitrate, and sulfate ions, using liquid chromatography of ions – Part 1: Method for water with low
contamination (ISO 10304-1:1992).
ISO 651:1975, Solid-stem calorimeter thermometers.
ISO 652:1975, Enclosed-scale calorimeter thermometers.
ISO 1770:1981, Solid-stem general purpose thermometers.

1) Currently being worked on.
ISO 1771:1981, Enclosed-scale general purpose thermometers.
3 Terms and definitions
For the purposes of this Technical Specification, the following terms and definitions apply.
3.1
gross calorific value at constant volume
absolute value of the specific energy of combustion, in joules, for unit mass of a solid biofuel burned in oxygen
in a calorimetric bomb under the conditions specified. The products of combustion are assumed to consist of
gaseous oxygen, nitrogen, carbon dioxide and sulfur dioxide, of liquid water (in equilibrium with its vapour)
saturated with carbon dioxide under the conditions of the bomb reaction, and of solid ash, all at the reference
temperature
3.2
net calorific value at constant volume
absolute value of the specific energy of combustion, in joules, for unit mass of the biofuel burned in oxygen
under conditions of constant volume and such that all the water of the reaction products remains as water
vapour (in a hypothetical state at 0,1 Mpa), the other products being as for the gross calorific value, all at the
reference temperature
3.3
net calorific value at constant pressure
absolute value of the specific heat (enthalpy) of combustion, in joules, for unit mass of the biofuel burned in
oxygen at constant pressure under such conditions that all the water of the reaction products remains as
water vapour (at 0,1 MPa), the other products being as for the gross calorific value, all at the reference
temperature
3.4
reference temperature
international reference temperature for thermochemistry of 25 °C is adopted as the reference temperature for
calorific values (see 8.7)
NOTE The temperature dependence of the calorific value of biofuels is small [less than 1 J/(g x K)].
3.5
effective heat capacity of the calorimeter
amount of energy required to cause unit change in temperature of the calorimeter
3.6
corrected temperature rise
change in calorimeter temperature caused solely by the processes taking place within the combustion bomb.
It is the total observed temperature rise corrected for heat exchange, stirring power, etc. (8.6).
NOTE The change in temperature may be expressed in terms of other units: resistance of a platinum or thermistor
thermometer, frequency of a quartz crystal resonator, etc., provided that a functional relationship is established between
this quantity and a change in temperature. The effective heat capacity of the calorimeter may be expressed in units of
energy per such an arbitrary unit. Criteria for the required linearity and closeness in conditions between calibrations and
fuel experiments are given in 9.3.
A list of the symbols used and their definitions is given in Annex F
4 Principle
4.1 Gross calorific value
A weighed portion of the analysis sample of the solid biofuel is burned in high-pressure oxygen in a bomb
calorimeter under specified conditions. The effective heat capacity of the calorimeter is determined in
calibration experiments by combustion of certified benzoic acid under similar conditions, accounted for in the
certificate. The corrected temperature rise is established from observations of temperature before, during and
after the combustion reaction takes place. The duration and frequency of the temperature observations
depend on the type of calorimeter used. Water is added to the bomb initially to give a saturated vapour phase
prior to combustion (see 8.2.1 and 9.2.2), thereby allowing all the water formed, from the hydrogen and
moisture in the sample, to be regarded as liquid water.
The gross calorific value is calculated from the corrected temperature rise and the effective heat capacity of
the calorimeter, with allowances made for contributions from ignition energy, combustion of the fuse(s) and for
thermal effects from side reactions such as the formation of nitric acid. Furthermore, a correction is applied to
account for the difference in energy between the aqueous sulfuric acid formed in the bomb reaction and
gaseous sulfur dioxide, i.e. the required reaction product of sulfur in the biofuel. The corresponding energy
effect between aqueous and gaseous hydrochloric acid can be neglected due to the usually low chlorine
content of most biofuels.
NOTE The typical chlorine content of solid biofuels is below 0,5 % (m/m) in dry matter.
4.2 Net calorific value
The net calorific value at constant volume and the net calorific value at constant pressure of the biofuel are
obtained by calculation from the gross calorific value at constant volume determined on the analysis sample.
The calculation of the net calorific value at constant v
...