Solid recovered fuels - Determination of calorific value

This European Standard specifies a method for the determination of gross calorific value of solid recovered fuels at constant volume and at the reference temperature 25 °C in a bomb calorimeter calibrated by combustion of certified benzoic acid.

Feste Sekundärbrennstoffe - Bestimmung des Brennwertes

Diese Europäische Norm legt für feste Sekundärbrennstoffe ein Verfahren zur Bestimmung des Brennwertes bei konstantem Volumen und einer Referenztemperatur von 25 °C fest, wozu ein Bombenkalorimeter verwendet wird, das durch die Verbrennung zertifizierter Benzoesäure kalibriert ist.

Combustibles solides de récupération - Méthodes de détermination du pouvoir calorifique

Le présent document spécifie une méthode de détermination du pouvoir calorifique supérieur de combustibles
solides de récupération à volume constant et à une température de référence de 25 °C dans une bombe
calorimétrique étalonnée par combustion d'acide benzoïque certifié.

Trdna alternativna goriva - Določevanje kalorične vrednosti

Ta evropski standard opredeljuje metodo za določevanje bruto kalorične vrednosti trdnih alternativnih goriv pri konstantni prostornini in pri referenčni temperaturi 25 °C v komori - kalorimetru, kalibriranem s sežiganjem certificirane benzojeve kisline.

General Information

Status
Published
Public Enquiry End Date
09-Nov-2009
Publication Date
07-Apr-2011
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
16-Mar-2011
Due Date
21-May-2011
Completion Date
08-Apr-2011

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Feste Sekundärbrennstoffe - Bestimmung des BrennwertesCombustibles solides de récupération - Méthodes de détermination du pouvoir calorifiqueSolid recovered fuels - Determination of calorific value75.160.10Trda gorivaSolid fuelsICS:Ta slovenski standard je istoveten z:EN 15400:2011SIST EN 15400:2011en,de01-maj-2011SIST EN 15400:2011SLOVENSKI

STANDARDSIST-TS CEN/TS 15400:20071DGRPHãþD
SIST EN 15400:2011
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 15400
March 2011 ICS 75.160.10 Supersedes CEN/TS 15400:2006English Version
Solid recovered fuels - Determination of calorific value
Combustibles solides de récupération - Détermination du pouvoir calorifique

Feste Sekundärbrennstoffe - Bestimmung des BrennwertesThis European Standard was approved by CEN on 22 January 2011.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.

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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,

B-1000 Brussels © 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 15400:2011: ESIST EN 15400:2011

EN 15400:2011 (E) 2 Contents Page Foreword ..............................................................................................................................................................3Introduction .........................................................................................................................................................41Scope ......................................................................................................................................................52Normative references ............................................................................................................................53Terms and definitions ...........................................................................................................................54Principle ..................................................................................................................................................65Reagents .................................................................................................................................................76Apparatus ...............................................................................................................................................77Preparation of test sample ................................................................................................................. 108Calorimetric procedure ...................................................................................................................... 119Calibration ........................................................................................................................................... 1710Gross calorific value .......................................................................................................................... 2211Precision .............................................................................................................................................. 2612Calculation of net calorific value at constant pressure .................................................................. 2713Test report ........................................................................................................................................... 28Annex A (normative)

Adiabatic bomb calorimeters ..................................................................................... 29Annex B (normative)

Isoperibol and static-jacket bomb calorimeters ....................................................... 33Annex C (normative)

Automated bomb calorimeters ................................................................................... 38Annex D (informative)

Checklists for the design and procedures of combustion experiments .............. 41Annex E (informative)

Examples to illustrate the main calculations used in this European Standard if an automated (adiabatic) bomb calorimeter is used for determinations .................. 46Annex F (informative)

List of symbols used in this European Standard .................................................... 49Annex G (informative)

Key-word index .......................................................................................................... 52Annex H (informative)

Flow chart for a routine calorific value determination ........................................... 55Annex I (informative)

Interlaboratory test results ......................................................................................... 56Bibliography ..................................................................................................................................................... 58 SIST EN 15400:2011

EN 15400:2011 (E) 3 Foreword This document (EN 15400:2011) has been prepared by Technical Committee CEN/TC 343 “Solid recovered fuels”, the secretariat of which is held by SFS. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 2011, and conflicting national standards shall be withdrawn at the latest by September 2011. This document supersedes CEN/TS 15400:2006. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association. This document differs from CEN/TS 15400:2006 mainly as follows: a) specification respectively recommendation regarding repeatability and reproducibility limits deleted; b) results of interlaboratory tests informatively added in Annex I; c) whole document editorially revised. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: 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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

SIST EN 15400:2011

EN 15400:2011 (E) 4 Introduction WARNING — Strict adherence to all of the provisions specified in this document 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. This European Standard is based on ISO 1928 and EN 14918 and modified to solid recovered fuels with some additions and alterations specific to solid recovered fuels properties. The result obtained is the gross calorific value of the sample analysed at constant volume with all the water of the combustion products as liquid water. In practice, solid recovered fuels are burned at a 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 can also be used; equations are given for calculating both values. General principles and procedures for the calibrations and the solid recovered fuels experiments are presented in the normative text, whereas those pertaining to the use of a particular type of calorimetric instrument are specified 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. SIST EN 15400:2011

EN 15400:2011 (E) 5 1 Scope This European Standard specifies a method for the determination of gross calorific value of solid recovered fuels at constant volume and at the reference temperature 25 °C in a bomb calorimeter calibrated by combustion of certified benzoic acid. 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. EN 15296, Solid biofuels — Conversion of analytical results from one basis to another EN 15357:2011, Solid recovered fuels — Terminology, definitions and descriptions EN 15358, Solid recovered fuels — Quality management systems — Particular requirements for their application to the production of solid recovered fuels EN 15414-3, Solid recovered fuels — Determination of moisture content using the oven dry method — Part 3: Moisture in general analysis sample EN 15440, Solid recovered fuels — Methods for the determination of biomass content EN 15443, Solid recovered fuels — Methods for the preparation of the laboratory sample EN ISO 10304-1, Water quality — Determination of dissolved anions by liquid chromatography of ions —

Part 1: Determination of bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate (ISO 10304-1:2007) 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 15357:2011 and the following 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 recovered fuel burned in oxygen in a calorimetric bomb under the conditions specified NOTE The products of combustion are assumed to consist of gaseous oxygen, nitrogen, carbon dioxide and sulphur 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 a solid recovered fuel 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 a solid recovered fuel 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 SIST EN 15400:2011

EN 15400:2011 (E) 6 3.4 reference temperature international reference temperature for thermo-chemistry of 25 °C is adopted as the reference temperature for calorific values (see 8.7) NOTE The temperature dependence of the calorific value of solid recovered fuels is small [less than 1 J/(g ⋅ 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 NOTE 1 It is the total observed temperature rise corrected for heat exchange, stirring power etc. (see 8.6). NOTE 2 The change in temperature can 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 can 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. NOTE 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 a solid recovered fuel 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 the 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 sulphuric acid formed in the bomb reaction and gaseous sulphur dioxide, i.e. the required reaction product of sulphur in the solid recovered fuel. The corresponding energy effect between aqueous and gaseous hydrochloric acid is neglected for solid recovered fuels. NOTE The corresponding energy effect between aqueous and gaseous hydrochloric acid depends on the sample characteristics, e.g. the content of inorganic and organic chlorine, mineral composition and the actual pH-value in bomb liquid. At the present time no values are available for this chlorine correction. Attention should be paid to the extremely high chlorine content in the test sample because e.g. PVC fractions can affect the calorific value significantly. 4.2 Net calorific value The net calorific value at constant volume and the net calorific value at constant pressure of the solid recovered fuel 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. SIST EN 15400:2011

EN 15400:2011 (E) 7 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 % volume fraction, and free from combustible matter. NOTE Oxygen made by the electrolytic process can contain up to 4 % volume fraction 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 1 of 8.2.1). 5.3 Combustion aids, of known gross calorific value, composition and purity, e.g. benzoic acid, n-dodecane, paraffin oil, combustion bags or capsules. 5.4 Standard volumetric solutions and indicators, only for use if analysis of final bomb solutions is required. 5.4.1 Barium hydroxide solution, c[Ba(OH)2] = 0,05 mol/l. 5.4.2 Sodium carbonate solution, c(Na2C03) = 0,05 mol/I. 5.4.3 Sodium hydroxide solution, c(NaOH) = 0,1 mol/I. 5.4.4 Hydrochloric acid solution, c(HCI) = 0,1 mol/I. 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 ethanol with a volume fraction of 95 % and dilute to 250 ml with water. 5.4.6 Phenolphthalein, 10 g/I solution: Dissolve 2,5 g of phenolphthalein in 250 ml ethanol with a volume fraction of 95 %. 5.5 Benzoic acid, of calorimetric-standard quality, certified by (or with certification unambiguously traceable to) a recognized standardizing authority. NOTE 1 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. NOTE 2 The benzoic acid is burned in the form of pellets. It is usually used without drying or any treatment other than pelletizing; the sample certificate provides information. 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 (6.2.1), the calorimeter can (6.2.2) (with or without a lid), the calorimeter stirrer (6.2.3), water, temperature sensor, and leads with SIST EN 15400:2011

EN 15400:2011 (E) 8 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 (6.2.4). 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.

Key 1 stirrer (6.2.3) 4 thermometer 2 thermostat lid 5 calorimeter can (6.2.2) 3 ignition leads 6 thermostat (6.2.4) Figure 1 — Classical-type bomb combustion calorimeter with thermostat 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 European Standard 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.) can 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 European Standard, is specified in 6.2 to 6.8. 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 solid recovered fuels. A suitable internal volume of the bomb would be from 250 ml to 350 ml. SIST EN 15400:2011

EN 15400:2011 (E) 9 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. If more than one bomb of the same design is used, it is imperative to use each bomb as a complete unit. Swapping of parts can lead to a serious accident. 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 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 (6.2.4) to minimise transmission of heat to or from the system; this is of particular importance if the stirrer shaft is in direct contact with the stirrer motor. If a lid is used for the calorimeter can (6.2.2), 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. If 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. If 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 which conform to ISO 651, ISO 652, ISO 1770 or ISO 1771 satisfy the requirements. A viewer with magnification about 5× is needed for reading the temperature with the resolution required. SIST EN 15400:2011

EN 15400:2011 (E) 10 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 if current is flowing. Where the firing is done manually, the firing switch shall be of the spring-loaded, usually open type, located in such a manner that any undue risk to the operator is avoided (see warning in 8.4). 6.3 Crucible, of silica, nickel-chromium, platinum or similar unreactive material. The crucible should be 15 mm to 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 may 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, with a resolution of at least 0,1 mg; 0,01 mg is preferable and is recommended if 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 pressure resulting from a mass of about 103 kg, either hydraulically or mechanically, and having a die suitable to press a pellet having a diameter of about 13 mm and a mass of (1 ± 0,1) g. 7 Preparation of test sample The solid recovered fuel 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 EN 15443. SIST EN 15400:2011

EN 15400:2011 (E) 11 The preparation of test sample for determining calorific value of biomass/non-biomass part of SRF shall be carried out in accordance with EN 15440. Due to the low density of solid recovered fuels they shall be tested in a pellet form. Press a pellet with a mass of (1 ± 0,1) g with a suitable force to produce a compact test piece. Alternatively, the test may be carried out in powder form, closed in a combustion bag or capsule. NOTE 1 For sample materials containing high content of plastics or rubber, the mass of the sample should be reduced to a mass in the range from 0,4 g to 0,8 g. NOTE 2 For sample materials containing a mass fraction of ash ≥ 30 % on dry basis, it is recommended to use a combustion aid (see 8.2.2). 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. The moisture content of the analysis sample shall be determined in accordance with

EN 15414-3. 8 Calorimetric procedure 8.1 General The calorimetric determination consists of two separate experiments, combustion of the calibration reference (benzoic acid) and combustion of the solid recovered fuels, 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 deviations caused, for example, by uncontrolled heat leaks not accounted for in the evaluation of the corrected temperature rise θ. The experiment consists of quantitatively carrying out a combustion reaction (in high-pressure oxygen in the bomb) to

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