SIST-TS CEN/TS 14918:2005
(Main)Solid Biofuels - Method for the determination of calorific value
Solid Biofuels - Method for the determination of calorific value
This Technical Specification 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.
Feste Biobrennstoffe - Verfahren Zur Bestimmung des Heizwertes
Diese Technische Spezifikation legt für feste Biobrennstoffe ein Verfahren zur Bestimmung des Heizwertes bei konstantem Volumen und bei einer Referenztemperatur von 25 °C fest, wozu ein Bombenkalorimeter verwendet wird, das durch die Verbrennung zertifizierter Benzoesäure kalibriert wird.
Bei der Verbrennung des zu untersuchenden Biobrennstoffes wird als Prüfergebnis der Heizwert einer Analysenprobe bei konstantem Volumen ermittelt, der dadurch gekennzeichnet ist, dass das gesamte Wasser in den Verbrennungsprodukten in flüssigem Zustand vorliegt. In der Praxis werden Biobrennstoffe bei konstantem (atmosphärischem) Druck verbrannt, wobei eine Kondensation des Wassers entweder stattfindet oder nicht stattfindet (d. h. Wasser wird als Wasserdampf zusammen mit den Abgasen abgeführt). In beiden Fällen ist aus der wirksamen Verbrennungswärme der Heizwert des Brennstoffes bei konstantem Druck zu errechnen. Der Heizwert bei konstantem Volumen darf ebenfalls errechnet werden; in der vorliegenden Spezifikation werden Gleichungen zur Berechnung des Brenn und Heizwertes angegeben.
Die zur Kalibrierung und zur Verbrennung des Biobrennstoffes allgemein anzuwendenden Prinzipien und Verfahren werden im Hauptteil dieser Norm dargelegt, während Prinzipien und Verfahren im Zusammenhang mit der Anwendung spezieller Kalorimeter Typen in den Anhängen A bis C beschrieben werden. Anhang D enthält eine Checkliste zur Durchführung der Kalibrierungen und Brennstoffprüfungen unter Anwendung bestimmter Kalorimeter Typen. Im Anhang E werden Berechnungsbeispiele angegeben.
Biocombustibles solides - Méthode pour la détermination du pouvoir calorifique
Trdna biogoriva – Metoda za ugotavljanje kalorične vrednosti
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TS CEN/TS 14918:2005
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
SIST-TS CEN/TS 14918:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TS CEN/TS 14918:2005
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.
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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
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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.
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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.
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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
1
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.
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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
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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 volume requires information about the moisture and
hydrogen contents of the analysis sample. In principle, the calculation of the net calorific value at constant
pressure also requires information about the oxygen and nitrogen contents of the sample.
5 Reagents
5.1 Oxygen, at a pressure high enough to fill the bomb to 3 MPa, pure with an assay of at least 99,5 % (V/V),
and free from combustible matter.
NOTE Oxygen made by the electrolytic process may contain up to 4 % (V/V) of hydrogen.
5.2 Fuse
5.2.1 Ignition wire, of nickel-chromium 0,16 mm to 0,20 mm in diameter, platinum 0,05 mm to 0,10 mm in
diameter, or another suitable conducting wire with well-characterized thermal behaviour during combustion.
5.2.2 Cotton fuse, of white cellulose cotton, or equivalent, if required (see Note 8 to 8.2.1).
5.3 Combustion aids of known gross calorific value, composition and purity, like benzoic acid, n-dodecane,
paraffin oil, combustion bags or capsules may be used.
5.4 Standard volumetric solutions and indicators, only for use when analysis of final bomb solutions is
required.
5.4.1 Barium hydroxide solution, c[Ba(OH) ] = 0,05 mol/l.
2
5.4.2 Sodium carbonate solution, c(Na C0 ) = 0,05 mol/I.
2 3
5.4.3 Sodium hydroxide solution, c(NaOH) = 0,1 mol/I.
5.4.4 Hydrochloric acid solution, c(HCI) = 0,1 mol/I.
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5.4.5 Screened methyl orange indicator, 1 g/I solution.
Dissolve 0,25 g of methyl orange and 0,15 g of xylene cyanole FF in 50 ml of 95 % (V/V ethanol and dilute to
250 ml with water.
5.4.6 Phenolphthalein, 10 g/I solution.
Dissolve 2,5 g of phenolphthalein in 250 ml of 95 % (V/V) ethanol.
5.5 Benzoic acid, of calorimetric-standard quality, certified by (or with certification unambiguously traceable
to) a recognized standardizing authority.
NOTE Benzoic acid is the sole substance recommended for calibration of an oxygen-bomb calorimeter. For the
purpose of checking the overall reliability of the calorimetric measurements, test substances, e.g. n-dodecane, are used.
Test substances are mainly used to prove that certain characteristics of a sample, e.g. burning rate or chemical
composition, do not introduce bias in the results. A test substance shall have a certified purity and a well-established
energy of combustion.
The benzoic acid is burned in the form of pellets. It is normally used without drying or any treatment other than
pelletizing; consult the sample certificate. It does not absorb moisture from the atmosphere at relative
humidities below 90 %.
The benzoic acid shall be used as close to certification conditions as is feasible; significant departures from
these conditions shall be accounted for in accordance with the directions in the certificate. The energy of
combustion of the benzoic acid, as defined by the certificate for the conditions utilized, shall be adopted in
calculating the effective heat capacity of the calorimeter (see 9.2).
6 Apparatus
6.1 General
The calorimeter (see Figure 1), consists of the assembled combustion bomb, the calorimeter can (with or
without a lid), the calorimeter stirrer, water, temperature sensor, and leads with connectors inside the
calorimeter can required for ignition of the sample or as part of temperature measurement or control circuits.
During measurements the calorimeter is enclosed in a thermostat. The manner in which the thermostat
temperature is controlled defines the working principle of the instrument and hence the strategy for evaluation
of the corrected temperature rise.
In aneroid systems (systems without a fluid) the calorimeter can, stirrer and water are replaced by a metal
block. The combustion bomb itself constitutes the calorimeter in some aneroid systems.
In combustion calorimetric instruments with a high degree of automation, especially in the evaluation of the
results, the calorimeter is in a few cases not as well-defined as the traditional, classical-type calorimeter.
Using such an automated calorimeter is, however, within the scope of this Technical Specification as long as
the basic requirements are met with respect to calibration conditions, comparability between calibration and
fuel experiments, ratio of sample mass to bomb volume, oxygen pressure, bomb liquid, reference temperature
of the measurements and repeatability of the results. A print-out of some specified parameters from the
individual measurements is essential. Details are given in Annex C.
As the room conditions (temperature fluctuation, ventilation etc.) may have an influence on the precision of the
determination, the manufacturers instructions for the placing of the instrument shall always be followed.
Equipment, adequate for determinations of calorific value in accordance with this Technical Specification, is
specified below.
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6.2 Calorimeter with thermostat
6.2.1 Combustion bomb, capable of withstanding safely the pressures developed during combustion. The
design shall permit complete recovery of all liquid products. The material of construction shall resist corrosion
by the acids produced in the combustion of biofuels. A suitable internal volume of the bomb would be from
250 ml to 350 ml.
WARNING - Bomb parts shall be inspected regularly for wear and corrosion; particular attention shall
be paid to the condition of the threads of the main closure. Manufacturers' instructions and any local
regulations regarding the safe handling and use of the bomb shall be observed. When more than one
bomb of the same design is used, it is imperative to use each bomb as a complete unit. Swapping of
parts may lead to a serious accident.
Key
1 Stirrer 4 Thermometer
2 Thermostat lid 5 Calorimeter can
3 Ignition leads 6 Thermostat
Figure 1 - Classical-type bomb combustion calorimeter with thermostat
6.2.2 Calorimeter can, made of metal, highly polished on the outside and capable of holding an amount of
water sufficient to completely cover the flat upper surface of the bomb while the water is being stirred. A lid
generally helps reduce evaporation of calorimeter water, but unless it is in good thermal contact with the can it
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lags behind in temperature during combustion, giving rise to undefined heat exchange with the thermostat and
a prolonged main period.
6.2.3 Stirrer, working at constant speed. The stirrer shaft should have a low-heat-conduction and/or a
low-mass section below the cover of the surrounding thermostat to minimize transmission of heat to or from
the system; this is of particular importance when the stirrer shaft is in direct contact with the stirrer motor.
When a lid is used for the calorimeter can, this section of the shaft should be above the lid.
NOTE The rate of stirring for a stirred-water type calorimeter should be large enough to make sure that hot spots do
not develop during the rapid part of the change in temperature of the calorimeter. A rate of stirring such that the length of
the main period can be limited to 10 min or less is usually adequate (see Annexes A and B).
6.2.4 Thermostat (water jacket), completely surrounding the calorimeter, with an air gap of approximately
10 mm separating calorimeter and thermostat.
The mass of water of a thermostat intended for isothermal operation shall be sufficiently large to outbalance
thermal disturbances from the outside. The temperature should be controlled to within ± 0,1 K or better
throughout the experiment. A passive constant temperature ("static") thermostat shall have a heat capacity
large enough to restrict the change in temperature of its water. Criteria for satisfactory behaviour of this type of
water jacket are given in Annex B.
NOTE 1 For an insulated metal static jacket, satisfactory properties are usually ensured by making a wide annular jacket
with a capacity for water of at least 12,5 I.
NOTE 2 Calorimeters surrounded by insulating material, creating a thermal barrier, are regarded as static-jacket
calorimeters.
When the thermostat (water jacket) is required to follow closely the temperature of the calorimeter, it should be of low
mass and preferably have immersion heaters. Energy shall be supplied at a rate sufficient to maintain the temperature of
the water in the thermostat to within 0,1 K of that of the calorimeter water after the charge has been fired. When in a
steady state at 25 °C, the calculated mean drift in temperature of the calorimeter shall not exceed 0,000 5 K/min
(see A.3.2).
6.2.5 Temperature measuring instrument, capable of indicating temperature with a resolution of at least
0,001 K so that temperature intervals of 2 K to 3 K can be determined with a resolution of 0,002 K or better.
The absolute temperature shall be known to the nearest 0,1 K at the reference temperature of the calorimetric
measurements. The temperature measuring device should be linear, or linearized, in its response to changes
in temperature over the interval it is used.
As alternatives to the traditional mercury-in-glass thermometers, suitable temperature sensors are platinum
resistance thermometers, thermistors, quartz crystal resonators, etc. which together with a suitable resistance
bridge, null detector, frequency counter or other electronic equipment provide the required resolution. The
short-term repeatability of this type of device shall be 0,001 K or better. Long-term drift shall not exceed the
equivalent of 0,05 K for a period of six months. For sensors with linear response (in terms of temperature),
drift is less likely to cause bias in the calorimetric measurements than are non-linear sensors.
Mercury-in-glass thermometers shall conform to ISO 651, ISO 652, ISO 1770 or ISO 1771. A viewer with
magnification about 5× is needed for reading the temperature with the resolution required.
A mechanical vibrator to tap the thermometer is suitable for preventing the mercury column from sticking (see
8.4). If this is not available, the thermometer shall be tapped manually before reading the temperature.
6.2.6 Ignition circuit
The electrical supply shall be 6 V to 12 V alternating current from a step-down transformer or direct current
from batteries. It is desirable to include a pilot light in the circuit to indicate when current is flowing.
Where the firing is done manually, the firing switch shall be of the spring-loaded, normally open type, located
in such a manner that any undue risk to the operator is avoided (see warning in 8.4).
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6.3 Crucible, of silica, nickel-chromium, platinum or similar unreactive material.
The crucible should be 15 - 25 mm in diameter, flat based and about 20 mm deep. Silica crucibles should be
about 1,5 mm thick and metal crucibles about 0,5 mm thick.
If smears of unburned carbon occur, a small low-mass platinum or nickel-chromium crucible, for example 0,25
mm thick, 15 mm in diameter and 7 mm deep, may be used.
6.4 Ancillary pressure equipment
6.4.1 Pressure regulator, to control the filling of the bomb with oxygen.
6.4.2 Pressure gauge (e.g. 0 MPa to 5 MPa), to indicate the pressure in the bomb with a resolution of
0,05 MPa.
6.4.3 Relief valve or bursting disk, operating at 3,5 MPa, and installed in the filling line, to prevent
overfilling the bomb.
CAUTION - Equipment for high-pressure oxygen shall be kept free from oil and grease (high vacuum
grease recommended by the manufacturer can be used according to the operating manual of the
instrument). Do not test or calibrate the pressure gauge with hydrocarbon fluid.
6.5 Timer, indicating minutes and seconds.
6.6 Balances
6.6.1 Balance for weighing the sample, fuse, etc., with a resolution of at least 0,1 mg; 0,01 mg is
preferable and is recommended when the sample mass is of the order of 0,5 g or less (see 8.2.1).
6.6.2 Balance for weighing the calorimeter water, with a resolution of 0,5 g (unless water can be
dispensed into the calorimeter by volume with the required accuracy, see 8.3).
6.7 Thermostat (optional), for equilibrating the calorimeter water before each experiment to a predetermined
initial temperature, within about ± 0,3 K.
6.8 Pellet press, capable of applying a force of about 10 tonnes, either hydraulically or mechanically, and
having a die suitable to press a pellet having a diameter about 13 mm and a mass of (1,0 ± 0,1) g.
7 Preparation of test sample
The biofuel sample used for the determination of calorific value shall be the general analysis sample (ground
to pass a test sieve with an aperture of 1,0 mm) prepared according to the procedure given in
prCEN/TS 14780, Solid biofuels –Methods of sample preparation. Sieve with an aperture less than 1,0 mm
(0,5 mm or 0,25 mm) might be necessary for many biofuels to ensure the requisite repeatability and a
complete combustion.
Due to the low density of solid biofuels they shall be tested in a pellet form. A pellet of mass (1 ± 0,1) g is
pressed with a suitable force to produce a compact, unbreakable test piece. Alternatively the test may be
carried out in powder form, closed in a combustion bag or capsule.
The sample shall be well-mixed and in reasonable moisture equilibrium with the laboratory atmosphere. The
moisture content shall either be determined simultaneously with the weighing of the samples for the
determination of calorific value, or the sample shall be kept in a small, effectively closed container until
moisture analyses are performed, to allow appropriate corrections for moisture in the analysis sample.
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Determination of the moisture content of the analysis sample shall be carried out by the method specified in
CEN/TS 14774-3, Solid biofuels – Determination of moisture content – Oven dry method – Part 3: Moisture in
general analysis sample.
8 Calorimetric procedure
8.1 General
The calorimetric determination consists of two separate experiments, combustion of the calibrant (benzoic
acid) and combustion of the biofuel, both under same specified conditions. The calorimetric procedure for the
two types of experiment is essentially the same. In fact, the overall similarity is a requirement for proper
cancellation of systematic errors caused, for example, by uncontrolled heat leaks not accounted for in the
evaluation of the corrected temperature rise θ .
The experiment consists of carrying out quantitatively a combustion reaction (in high-pressure oxygen in the
bomb) to defined products of combustion and of measuring the change in temperature caused by the
...
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