SIST-TS CEN/TS 16980-1:2017
(Main)Photocatalysis - Continuous flow test methods - Part 1: Determination of the degradation of nitric oxide (NO) in the air by photocatalytic materials
Photocatalysis - Continuous flow test methods - Part 1: Determination of the degradation of nitric oxide (NO) in the air by photocatalytic materials
This standard describes a method for assessing the performance of photocatalytic inorganic materials contained in cement mortars and/or limes or ceramic-based matrices, paints or materials deposited as thin films or coatings on a variety of substrates for the photocatalytic abatement of nitric oxide in the gas phase. This method is not suitable for the assessment of samples to be applied with flow perpendicular to the surface or flow permeating the surface itself as polymeric and paper filters, honeycomb structures and suchlike.
The performance for the photocatalytic sample under test is evaluated by measuring the degradation rate of nitric oxide (NO) using the method described herein. The photocatalytic abatement rate is calculated from the observed rate by eliminating the effects of mass transfer. The intrinsic photocatalytic abatement rate is an intrinsic property of the material tested and makes it possible to distinguish the photocatalytic activities of various products with an absolute scale defined with physical and engineering meaning.
For the measurements and calculations described in this standard the concentration of nitrogen oxides (NOx) is defined as the stoichiometric sum of nitric oxide (NO) and nitrogen dioxide (NO2).
Safety statement
Persons using this document should be familiar with the normal laboratory practice, if applicable. This document cannot address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any regulatory conditions.
Environmental statement
It is understood that some of the material permitted in this standard may have negative environmental impact. As technological advantages lead to better alternatives for these materials, they will be eliminated from this standard to the extent possible.
At the end of the test, the user of the standard will take care to carry out an appropriate disposal of the wastes, according to local regulation.
Photokatalyse - Durchlauftestverfahren - Teil 1: Bestimmung der Verminderung von Stickoxiden (NO) in Luft durch photokatalystische Materialien
Diese Norm beschreibt ein Verfahren zur Bewertung der Leistung von photokatalytischen anorganischen Werkstoffen in Zementmörtel und/oder Kalken oder aus Keramik bestehende Grundsubstanzen, Farben oder Werkstoffen, die als dünne Filme oder Beschichtungen auf einer Vielzahl von Trägerwerkstoffen für die photokatalytische Beseitigung von Stickstoffmonoxid in der Gasphase vorkommen. Dieses Verfahren eignet sich weder für die Bewertung von Anwendungen, bei denen die Beschichtung senkrecht zur Oberfläche aufgetragen wird, noch für Anwendungen, bei denen die Oberflächen als polymere Filter und Papierfilter, Wabenstrukturen und dergleichen durchdrungen werden.
Die Leistung für die photokatalytische Probe unter Prüfbedingungen wird durch die Messung der Abbaurate von Stickstoffmonoxid (NO) mit Hilfe des hier beschriebenen Verfahrens bewertet. Die photokatalytische Minderungsrate wird aus den beobachteten Werten berechnet, indem die Auswirkungen des Stoffübergangs abgezogen werden. Die innere photokatalytische Minderungsrate ist eine innere Eigenschaft des untersuchten Werkstoffs und macht es möglich, die photokatalytischen Aktivitäten verschiedener Produkte in einem absoluten Maßstab im Sinne von physikalischen und technischen Eigenschaften zu unterscheiden.
Für die in dieser Norm beschriebenen Messungen und Berechnungen, wird die Konzentration von Stickoxiden (NOx) als die stöchiometrische Summe von Stickstoffmonoxid (NO) und Stickstoffdioxid (NO2) definiert.
Photocatalyse - Méthodes d'essai en flux continu - Partie 1: Détermination de la dégradation du monoxyde d'azote (NO) dans l'air par des matériaux photocatalytiques
La présente norme décrit une méthode d’évaluation de la performance des matériaux inorganiques photocatalytiques contenus dans les mortiers de ciment et/ou les chaux ou dans les matrices à base de céramique, les peintures ou les matériaux déposés sous forme de films minces ou de revêtements sur une variété de substrats pour la dégradation photocatalytique du monoxyde d’azote en phase gazeuse. Cette méthode ne convient pas pour l’évaluation des échantillons devant être utilisés avec un flux perpendiculaire à la surface ou traversant la surface, comme les filtres polymères et papier, les structures en nid d’abeille et autres éléments similaires.
La performance de l’échantillon photocatalytique étudié est évaluée en mesurant le taux de dégradation du monoxyde d’azote (NO) à l’aide de la méthode décrite ici. Le taux de dégradation photocatalytique est calculé à partir du taux observé en éliminant les effets du transfert de masse. Le taux intrinsèque de dégradation photocatalytique est une propriété intrinsèque du matériau soumis à l’essai et il permet de distinguer les activités photocatalytiques de divers produits au moyen d’une échelle absolue définie par des caractéristiques physiques et mécaniques.
Pour les mesures et les calculs décrits dans la présente norme, la concentration en oxydes d’azote (NOx) est définie comme la somme stoechiométrique du monoxyde d’azote (NO) et du dioxyde d’azote (NO2).
Fotokataliza - Metode preskušanja kontinuiranega pretoka - 1. del: Ugotavljanje razgradnje dušikovega oksida (NO) v zraku z materiali fotokatalize
Ta standard opisuje metodo za ocenjevanje delovanja fotokatalitskih neorganskih materialov v cementnih maltah in/ali apnih ali matrikah, barvah ali materialih na osnovi keramike, ki so naneseni kot tanki filmi ali premazi na različne substrate za fotokatalitsko zmanjšanje dušikovega oksida v plinski fazi. Ta metoda ni primerna za ocenjevanje vzorcev, ki se nanašajo s pretokom, pravokotnim na površino, ali s pretokom, ki prodira skozi površino, kot so polimerni in papirnati filtri, sataste strukture in podobno.
Delovanje fotokatalitskega vzorca med preskusom se ugotavlja z merjenjem stopnje razgradnje dušikovega oksida (NO) z metodo, opisano tukaj. Stopnja fotokatalitskega zmanjšanja se izračuna iz ugotovljene stopnje z odstranitvijo učinkov prenosa mase. Intrinzična stopnja fotokatalitskega zmanjšanja je intrinzična lastnost preskušenega materiala, ki omogoča razlikovanje fotokatalitskih dejavnosti različnih proizvodov z absolutno lestvico, ki je določena v fizičnem in inženirskem smislu.
Za meritve in izračune, opisane v tem standardu, je koncentracija dušikovih oksidov (NOx) določena kot stehiometrična vsota dušikovega oksida (NO) in dušikovega dioksida (NO2).
Izjava o varnosti
Osebe, ki uporabljajo ta dokument, bi morale biti seznanjene z običajno laboratorijsko prakso, če je to potrebno. Ta dokument ne more obravnavati vseh morebitnih varnostnih težav, ki se nanašajo na njegovo uporabo. Za vzpostavitev ustreznih varnostnih in zdravstvenih praks ter za zagotovitev skladnosti z morebitnimi predpisanimi pogoji je odgovoren uporabnik.
Okoljska izjava
Nekateri materiali, uporabljeni v tem standardu, lahko negativno vplivajo na okolje. Ker tehnološke prednosti vodijo do boljših alternativ za te materiale, bodo ti materiali izločeni iz tega standarda v največji možni meri.
Ob koncu preskusa mora uporabnik standarda poskrbeti za ustrezno odlaganje odpadkov v skladu z lokalnimi predpisi.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TS CEN/TS 16980-1:2017
01-februar-2017
Fotokataliza - Metode preskušanja kontinuiranega pretoka - 1. del: Ugotavljanje
razgradnje dušikovega oksida (NO) v zraku z materiali fotokatalize
Photocatalysis - Continuous flow test methods - Part 1: Determination of the degradation
of nitric oxide (NO) in the air by photocatalytic materials
Photokatalyse - Durchlauftestverfahren - Teil 1: Bestimmung der Verminderung von
Stickoxiden (NO) in Luft durch photokatalystische Materialien
Photocatalyse - Méthodes d'essai en flux continu - Partie 1: Détermination de la
dégradation du monoxyde d'azote (NO) dans l'air par des matériaux photocatalytiques
Ta slovenski standard je istoveten z: CEN/TS 16980-1:2016
ICS:
25.220.20 Površinska obdelava Surface treatment
SIST-TS CEN/TS 16980-1:2017 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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CEN/TS 16980-1
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
December 2016
TECHNISCHE SPEZIFIKATION
ICS 25.220.20
English Version
Photocatalysis - Continuous flow test methods - Part 1:
Determination of the degradation of nitric oxide (NO) in
the air by photocatalytic materials
Photocatalyse - Méthodes d'essai en flux continu - Photokatalyse - Prüfverfahren mit kontinuierlichem
Partie 1 : Détermination de la dégradation du Durchfluss - Teil 1: Bestimmung des Abbaus von
monoxyde d'azote (NO) dans l'air par des matériaux Stickstoffmonoxid (NO) aus der Luft durch
photocatalytiques photokatalytische Werkstoffe
This Technical Specification (CEN/TS) was approved by CEN on 8 August 2016 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, 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: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 16980-1:2016 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms, definitions and abbreviations . 5
3.1 Terms and definitions . 5
3.2 Abbreviations . 5
4 Principle . 7
5 Interferences . 7
6 Apparatus . 7
7 Sample preparation . 13
7.1 Precaution. 13
7.2 Sample characteristics . 13
7.3 Conditioning . 13
8 Measurement of concentrations . 14
8.1 General . 14
8.2 Measurement of the initial concentration of nitrogen oxides before entering the
photochemical reactor . 14
8.3 Conversion without sample . 14
8.4 Conversion in the dark and in the presence of sample . 15
8.5 Conversion under illumination in the presence of sample . 15
9 Calculation of photocatalytic degradation rate . 17
9.1 The observed rate of photocatalytic degradation . 17
9.2 Intrinsic rate of photocatalytic transformation . 18
10 Acceptability ranges of main test parameters . 18
11 Test report . 19
Annex A (informative) Typical trend of NO, NO and NO concentrations during a
2 x
photocatalytic test . 21
Annex B (informative) Example of test for the control of mass transfer conditions . 22
Annex C (informative) Typical Ohmic response of the fan . 23
Bibliography . 24
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European foreword
This document (CEN/TS 16980-1:2016) has been prepared by Technical Committee CEN/TC 386
“Photocatalysis”, the secretariat of which is held by AFNOR.
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.
This document is part of the CEN/TS 16980 series that consists of the following parts:
— Part 1: Determination of the degradation of nitric oxide (NO) in the air by photocatalytic materials
— Part 2: [To be determined].
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom
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1 Scope
This standard describes a method for assessing the performance of photocatalytic inorganic materials
contained in cement mortars and/or limes or ceramic-based matrices, paints or materials deposited as
thin films or coatings on a variety of substrates for the photocatalytic abatement of nitric oxide in the
gas phase. This method is not suitable for the assessment of samples to be applied with flow
perpendicular to the surface or flow permeating the surface itself as polymeric and paper filters,
honeycomb structures and suchlike.
The performance for the photocatalytic sample under test is evaluated by measuring the degradation
rate of nitric oxide (NO) using the method described herein. The photocatalytic abatement rate is
calculated from the observed rate by eliminating the effects of mass transfer. The intrinsic
photocatalytic abatement rate is an intrinsic property of the material tested and makes it possible to
distinguish the photocatalytic activities of various products with an absolute scale defined with physical
and engineering meaning.
For the measurements and calculations described in this standard the concentration of nitrogen oxides
(NO ) is defined as the stoichiometric sum of nitric oxide (NO) and nitrogen dioxide (NO ).
x 2
Safety statement
Persons using this document should be familiar with the normal laboratory practice, if applicable. This
document cannot address all of the safety problems, if any, associated with its use. It is the
responsibility of the user to establish appropriate safety and health practices and to ensure compliance
with any regulatory conditions.
Environmental statement
It is understood that some of the material permitted in this standard may have negative environmental
impact. As technological advantages lead to better alternatives for these materials, they will be
eliminated from this standard to the extent possible.
At the end of the test, the user of the standard will take care to carry out an appropriate disposal of the
wastes, according to local regulation.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
CEN/TS 16599:2014, Photocatalysis - Irradiation conditions for testing photocatalytic properties of
semiconducting materials and the measurement of these conditions
EN ISO 9169, Air quality - Definition and determination of performance characteristics of an automatic
measuring system (ISO 9169)
ISO 7996, Ambient air — Determination of the mass concentration of nitrogen oxides —
Chemiluminescence method
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3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms, definitions and abbreviations apply.
3.1.1
concentration of nitrogen oxides
NO
x
stoichiometric sum of nitric oxide (NO) and nitrogen dioxide (NO )
2
Note 1 to entry: For grade 999 nitrogen or air: the purity of the gas should be equal at least to 99,9 %.
3.1.2
photocatalyst
Catalyst able to produce, upon absorption of light, chemical transformations of the reaction partners
Note 1 to entry: The excited state of the photocatalyst repeatedly interacts with the reaction partners forming
reaction intermediates and regenerates itself after each cycle of such interactions.
3.1.3
photocatalytic materials
materials in which or on which the photocatalyst is added by coating, impregnation, mixing, etc
3.2 Abbreviations
CSTR Continuous Stirred-Tank Reactor
IN
C concentration at reactor inlet
OUT,DARK
C concentration of NO and NO at reactor outlet under stable conditions in the dark (no
2
illumination)
OUT,light
concentration at reactor outlet under stable conditions with illumination (lamp on)
C
IN
concentration of NO at reactor inlet
C
NO
IN
concentration of NO at reactor inlet
2
C
NO
2
OUT,DARK
concentration of NO at reactor outlet under stable conditions in the dark (no
C
NO
illumination) without sample
OUT,DARK
concentration of NO at reactor outlet under stable conditions in the dark (no
2
C
NO
2
illumination) without sample
OUT,DARK
concentration of NO at reactor outlet under stable conditions in the dark (no
C
NO,S
illumination) in presence of sample
OUT,DARK
concentration of NO at reactor outlet under stable conditions in the dark (no
2
C
NO ,S
2
illumination) in presence of sample
OUT,LIGHT
concentration of NO at reactor outlet under stable conditions with illumination (lamp
C
NO
on) without sample
OUT,LIGHT
concentration of NO at reactor outlet under illumination of sample measured at fan
C
NO,0
speed at nominal voltage V
0
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OUT,LIGHT concentration NO at reactor outlet under illumination of sample measured at fan speed
2
C
NO ,0
2
nominal voltage V
0
F Flow
th
F fan flow at i potential
v,i
I irradiance
LED light emitting diodes
MM molecular mass
P pressure in atmosphere
PTFE Polytetrafluoroethylene
R ideal gas constant
RH gas relative humidity at 25 °C inside the reactor
dark
conversion of NO in the dark
η
NO
dark
conversion to NO in the dark
2
η
NO
2
PHOTO
conversion of NO under illumination without sample
η
NO,lamp
th
total
conversion of NO measured with fan speed at i potential
η
NO ,i
th
total
conversion to NO measured with fan speed at i potential
2
η
NO ,i
2
photo
NO abatement rate at each fan speed (i = 0.n)
r
NO,i
photo
NO photocatalytic production rate at each fan speed (i = 0.n)
2
r
NO ,i
2
photo
NO abatement rate correspond to NO abatement rate minus NO photocatalytic
x 2
r
NO ,i
x
production rate
photoCAT
NO photocatalytic degradation rate intrinsic to the surface of the material, after
r
NO
removing the mass transfer limitations
photoCAT
NO photocatalytic degradation rate intrinsic to the surface of the material, after
x
r
NO
X
removing the mass transfer limitations
UV-A ultraviolet with wavelength (λ) situated between 315 nm and 400 nm (IUPAC)
V fan nominal operating potential (in Volt)
0
V fan minimum operating potential (in Volt) set by the manufacturer
min
S Sample
T temperature in Kelvin
t time to reach the stability of NO concentration
stab
UV UltraViolet
Vr Reactor net volume
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4 Principle
The method consists in measuring the photocatalytic abatement of nitric oxide (NO) by photocatalytic
materials as specified in paragraph 1 using a Continuous Stirred-Tank Reactor (CSTR) with flow
tangential to the sample. Information on the theory is reported in the specialized literature (Minero et
al. 2013). The residual NO and NOx concentration at the CSTR outlet is measured by a
chemiluminescence analyser (ISO 7996).
The photocatalytic activity test is carried out using chromatographic grade air, also obtained by mixing
pure gases, to which NO is added in such an amount as to simulate a high degree of air pollution. The NO
concentration is set to (0,50 ± 0,05) ppmv.
5 Interferences
Any measurement interferences are reported in the technical specifications of the chemiluminescence
analyser. As what is measured are all species that can be converted by reduction to NO, NO
2
concentration is here defined as [NO ] = [NO ]-[NO]. For interferences on chemiluminescence detection,
2 x
see Winer et al. (1974).
6 Apparatus
The test apparatus shall consist of the following main components.
6.1 Gas mixture preparation system.
The system used for preparing the reaction mixture is shown in Figure 1.
The mass flow controllers, calibrated and traceable, shall ensure a maximum flow consistent with that
needed for a correct test execution. To ensure the necessary accuracy, the flow shall not exceed 90 % of
the rated full scale.
As an example, to obtain the gas mixture only gases of chromatographic grade or higher purity shall be
used. Instead of dry air cylinders, two separate cylinders of pure N and O can be used at the inlet of
2 2
mass-flow controllers, adjusted so as to produce a mixture consisting of 20,8 % of O and 79,2 % of N .
2 2
The NO concentration to flow #1 is set to (0,50 ± 0,05) ppmv.
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a) Relative humidity is set by regulating the b) Relative humidity is set by regulating the
flow to U, which is downstream to F pressure before U and F
Key
S source of nitric oxide NO diluted in N
1 2
S cylinder of air (chromatographic grade) or, alternatively, individual cylinders of N and O
2 2 2
(chromatographic grade)
F flow controller with mass-flow controllers (2 or 3)
P pressure regulators with low-pressure manometers
U humidifier maintained at controlled temperature
F#1 flow entering the reactor
Figure 1 — Gas mixture preparation system
The humidification of the gas mixture can be obtained with two different configurations:
a) using two mass flow controllers regulating the flow to U, as in Figure 1 left;
b) using one mass flow controller regulating the pressure on U, as in Figure 1 right.
The gas mixture preparation system shall ensure a relative humidity of (40 ± 5) % inside the CSTR
reactor. The relative humidity shall be measured either inside the reactor R (Figure 2) or immediately
at its outlet on flow 2 of Figure 2 by means of a hygro-thermometer.
6.2 Illumination and measuring system:
6.2.1 General:
The light source arrangement and the measuring system are shown in Figure 2.
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Key
R reaction chamber, Continuous Stirred-Tank Reactor (CSTR) type
V fan
A power supply of fan V
N NO/NO chemiluminescence analyser
2
E processing/logging unit
L illumination system
1, 2, 3, 4 flow paths, with valves and tubing
Figure 2 — Illumination, reaction and measuring system
All parts of the test apparatus, including connections and pipes, which come into contact with the nitric
oxide mixture shall be made of chemically inert materials. For pipes and connections PTFE is
recommended. The pipes of paths 1, 2, 3, 4 and the related connections shall have an outer diameter of
6 mm (1/4”) and inner clearance of at least 4 mm to avoid overpressures that may affect the gas
concentration inside the reactor.
Temperature shall be measured and recorded inside the reactor during the test or immediately at its
outlet on flow 2 by means of a hygro-thermometer. The gas temperature inside the reaction chamber
shall be (25 ± 5) °C.
6.2.2 Illumination system L:
The illumination source shall consist of any lamp able to excite the photocatalyst (quartz mercury vapor
lamps, UV-A fluorescent lamps, Xenon lamps, LEDs, lamps consisting of a metal vapor element
combined with tungsten incandescence elements, etc.) as specified in the Technical Specification
CEN/TS 16599.
The illumination system shall provide an average irradiance to the test sample surface within the range
2
of wavelengths that are mostly adsorbed by the photocatalyst, equal to (10,0 ± 5 %) W/m .
The geometry of the illumination system shall be such that uniform illumination of the sample surface is
ensured. The illumination is considered uniform if 5 independent measurements performed on the
surface (one in centre position and the other four in positions perpendicular to each other and next to
the edge of the sample) show a percentage variation compared to the average value of less than 10 %.
The control of the uniformity of illumination and average irradiance shall be repeated each time the
system geometry changes (position of the lamp or any filters or reflectors, sample position, etc.).
Irradiance shall be measured by placing a radiometric sensor inside the reaction chamber in the same
position occupied by the sample in order to measure real irradiance at its surface. A second measuring
sensor for the control of source stability can be positioned outside the reaction chamber, provided that
it has been calibrated with a reference radiometric sensor placed inside the reactor. Irradiance can be
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measured continuously during the test or, alternatively, just before the beginning of the test and
immediately after its conclusion. The irradiance values shall be measured only after the lamp intensity
has stabilized as a result of its warming-up (typically 10 min after being turned on). The irradiance
value as measured shall be recorded as average value in the test report.
The radiometer used for the measurement shall have been previously calibrated by means of a
spectroradiometer, which in turn has been previously calibrated by means of standard sources.
In order to avoid decomposition by direct photolysis of NO, the integrated irradiance at λ < 340 nm shall
2
be less than 0,5 W/m . The direct NO photolysis rate shall be checked by performing the test using the
empty reactor, where standard NO concentration (0,5 ppmv) is introduced and the reactor outlet
concentration is measured according to paragraph 8.3.a. For example, in the case of a photocatalyst
consisting of pure TiO , the illumination system that uses a mercury lamp shall be such as to ensure the
2
surface of the sample receives a UV irradiance (λ < 400 nm) mainly composed of the line at 365 nm of
2
mercury, and an integrated irradiance for λ < 340 nm of less than 0,5 W/m .
The spectrum of the lamp used shall be acquired and reported in the test report, because the analysis
result depends significantly on the lamp type used.
6.2.3 Reaction chamber R:
A schematic of the reaction chamber is given in Figure 3.
Dimensions in millimetres
Key
1, S sample 4 inflow
2 fan
3 outflow
3A gas output (alternative)
Figure 3 — Top view of the CSTR reaction chamber, with dimensional details and indication of
flows for thorough mixing and location of the sampling point
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Other dimensional details of the reaction chamber with related sample positions are also shown in the
Figures 4-5 below.
The reaction chamber shall be built with NO inert materials, i.e. glass, polymethylmethacrylate or other
inert plastic materials. The chamber shall be gas-tight. On top, the chamber shall be provided with a flat
window that is transparent to the light emitted by the illumination system and vertically incident to the
sample. This flat window, transparent to the wavelengths used (e.g. made up of borosilicate glass) shall
be (3-4) mm thick to ensure sufficient strength and also removable to allow for sample positioning.
Dimensions in millimetres
Key
HAC holes for air circulation
HF hole for a fan with Φ = 60 mm
1 top window
2 fan 60 mm nominal
3 gas outlet
4 gas inlet
Figure 4 — Side view (back of fan side) of the CSTR reactor
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Dimensions in millimetres
Key
3 gas outlet
h distance to the surface of the sample
S sample
th sample on the support, any thickness, max 50mm
max
Figure 5 — Side view (fan front side) of reactor CSTR, with indications of sample position
The reaction chamber shall comply with the dimensions shown in Figures 3 to 5. Considering the
volumes occupied by internal barriers, fan, sample and sample support, the total net volume is (2,8 to
3
3,5) dm . This volume is not critical. The gas flow is maintained constant throughout the whole test, and
3 −1
shall be equal to 1,6 dm min . It shall be at least 20 % higher than the sampling flow of the NO/NO
2
analyser. The max flow variation allowed is 10 %.
The fan ensures perfect mixing inside the reaction chamber. The fan is placed inside the reactor on a
support having a hole with diameter equal to the fan aperture and axial to the fan axis. The support has
lateral holes that ensure full air mixing inside the chamber. The fan shall provide nominal flows at the
3 −1
nominal supply voltage of 70 m h .
Fans with external dimensions of 60 mm × 60 mm and thickness from 25 mm to 35 mm are suitable for
this purpose. The fan flow shall be varied by varying the supply voltage by an appropriate power supply
of continuous variable output voltage (see A of Figure 2).
2
6.2.4 NO/NO analyser
The analyser shall be calibrated according to the procedures described in ISO 7996 or according to
EN ISO 9169. The instrument's calibration can be performed using NO and/or NO mixtures at a known
2
and certified concentration of either grade 999 nitrogen or air. For the measurement range adopted
during calibration, at least 4 standard gas mixtures shall be analysed, supported by the related
calibration certificates, with different NO contents in N (or in any other inert gas) with concentrations
2
equal to approx. 0,2 ppmv, 0,4 ppmv, 0,6 ppmv, 0,8 ppmv.
Alternatively, the concentrations needed to check the analyser calibration can be generated starting
from a single gas cylinder with certified NO concentration and with the help of a calibrated flow
controller provided with calibration certificates for mass-flow controllers.
Adjustments and calibrations shall be always carried out when the measuring device is under steady
conditions.
12
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By comparing the measured NO concentration values and the related certified values it is possible to
obtain, for each concentration level, the corresponding analyser calibration condition, which can be
expressed in table form, as a calibration curve or a response factor.
If calibration provides a linear response as nitrogen oxide concentrations vary within the calibration
range, then a single level measurement can be adopted during the control of the instrument calibration
condition. The frequency of such control operations depends on the accuracy level desired in
accordance with the time drift of the instrumental signal typical of each NOx-analyser.
7 Sample preparation
7.1 Precaution
Samples shall be preconditioned under supplier advices to ensure that the conversion is constant under
the test conditions.
7.2 Sample characteristics
2
The samples being analysed shall have a surface area of 64 ± 6 cm . For larger samples, use a mask. The
surface area value shall be carefully assessed being a parameter necessary for the normalization of the
test result.
The sample shall be positioned on a support made of borosilicate glass, polytetrafluoroethylene (PTFE)
or ceramic material that is not photocatalytically active, paying attention that its surface is as close as
possible to the level of the fan rotation axis and central to the free space between fan and reactor wall in
the lateral direction (see Figure 5). As to distance tolerances, the sample surface can be at a distance of
(30 to 50) mm from the internal base, that is (60 to 40) mm from the inner surface of the upper
transparent window of the reactor. This means that the sample shall have a maximum usable thickness
of 50 mm. Solid samples of 50 mm thickness can be positioned in the reaction chamber without any
support.
The geometric surface area exposed to the gas flow can be square, rectangular or circular, provided that
the illumination uniformity conditions are met (see paragraph 6.2.2). The sample width in axial
2
direction should not exceed 120 mm. Typically a cylindrical sample has a surface area of (64 ± 6) cm
(±10 %).
The required surface area can be achieved by combination of various samples, provided that they are
coplanar and the resulting surface meets the specifications above.
The surfaces of the tested sample other than those exposed orthogonally to the incident light flow, shall
be isolated from gas containing nitric oxide by means of a coating of commercial silicones, paraffin
waxes, inert polymer films or composite materials. The test shall be performed only after these
protective films have completely dried. All coatings shall withstand irradiance conditions for at least
6 h, should not release potentially interfering substances and should have no photocatalytic activity.
...
SLOVENSKI STANDARD
kSIST-TS FprCEN/TS 16980-1:2016
01-junij-2016
Fotokataliza - Preskusne metode kontinuiranega pretoka - 1. del: Ugotavljanje
razgradnje dušikovega oksida (NO) v zraku z materiali fotokatalize
Photocatalysis - Continuous flow test methods - Part 1: Determination of the degradation
of nitric oxide (NO) in the air by photocatalytic materials
Photokatalyse - Durchlauftestverfahren - Teil 1: Bestimmung der Verminderung von
Stickoxiden (NO) in Luft durch photokatalystische Materialien
Photocatalyse - Méthodes d'essai en flux continu - Partie 1: Détermination de la
dégradation du monoxyde d'azote (NO) dans l'air par des matériaux photocatalytiques
Ta slovenski standard je istoveten z: FprCEN/TS 16980-1
ICS:
25.220.20 Površinska obdelava Surface treatment
kSIST-TS FprCEN/TS 16980-1:2016 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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kSIST-TS FprCEN/TS 16980-1:2016
FINAL DRAFT
TECHNICAL SPECIFICATION
FprCEN/TS 16980-1
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
April 2016
ICS 25.220.20
English Version
Photocatalysis - Continuous flow test methods - Part 1:
Determination of the degradation of nitric oxide (NO) in
the air by photocatalytic materials
Photocatalyse - Méthodes d'essai en flux continu - Photokatalyse - Durchlauftestverfahren - Teil 1:
Partie 1: Détermination de la dégradation du Bestimmung der Verminderung von Stickoxiden (NO)
monoxyde d'azote (NO) dans l'air par des matériaux in Luft durch photokatalystische Materialien
photocatalytiques
This draft Technical Specification is submitted to CEN members for Vote. It has been drawn up by the Technical Committee
CEN/TC 386.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a Technical Specification. It is distributed for review and comments. It is subject to change
without notice and shall not be referred to as a Technical Specification.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TS 16980-1:2016 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 5
3.1 Definitions . 5
3.2 Abbreviations . 5
4 Principle . 7
5 Interferences . 7
6 Apparatus . 7
7 Sample preparation . 13
7.1 Precaution. 13
7.2 Sample characteristics . 13
7.3 Conditioning . 13
8 Measurement of concentrations . 13
8.1 General . 13
8.2 Measurement of the initial concentration of nitrogen oxides before entering the
photochemical reactor . 14
8.3 Conversion without sample . 14
8.4 Conversion in the dark and in the presence of sample . 15
8.5 Conversion under illumination in the presence of sample . 15
9 Calculation of photocatalytic degradation rate . 17
9.1 The observed rate of photocatalytic degradation . 17
9.2 Intrinsic rate of photocatalytic transformation . 18
10 Acceptability ranges of main test parameters . 18
11 Test report . 19
Annex A (informative) Typical trend of NO, NO and NO concentrations during a
2 x
photocatalytic test . 21
Annex B (informative) Example of test for the control of mass transfer conditions . 22
Annex C (informative) Ohmic response of the fan . 23
Bibliography . 24
2
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European foreword
This document (FprCEN/TS 16980-1:2016) has been prepared by Technical Committee CEN/TC 386
“Photocatalysis”, the secretariat of which is held by AFNOR.
This document is currently submitted to the vote on TS.
This document is part of the CEN/TS 16980 series that consists of the following parts:
— Part 1: Determination of the degradation of nitric oxide (NO) in the air by photocatalytic materials
— Part 2: [To be determined].
3
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1 Scope
This standard describes a method for assessing the performance of photocatalytic inorganic materials
contained in cement mortars and/or limes or ceramic-based matrices, paints or materials deposited as
thin films or coatings on a variety of substrates for the photocatalytic abatement of nitric oxide in the
gas phase. This method is not suitable for the assessment of samples to be applied with flow
perpendicular to the surface or flow permeating the surface itself as polymeric and paper filters,
honeycomb structures and suchlike.
The performance for the photocatalytic sample under test is evaluated by measuring the degradation
rate of nitric oxide (NO) using the method described herein. The photocatalytic abatement rate is
calculated from the observed rate by eliminating the effects of mass transfer. The intrinsic
photocatalytic abatement rate is an intrinsic property of the material tested and makes it possible to
distinguish the photocatalytic activities of various products with an absolute scale defined with physical
and engineering meaning.
For the measurements and calculations described in this standard the concentration of nitrogen oxides
(NO ) is defined as the stoichiometric sum of nitric oxide (NO) and nitrogen dioxide (NO ).
x 2
Safety statement
Persons using this document should be familiar with the normal laboratory practice, if applicable. This
document cannot address all of the safety problems, if any, associated with its use. It is the
responsibility of the user to establish appropriate safety and health practices and to ensure compliance
with any regulatory conditions.
Environmental statement
It is understood that some of the material permitted in this standard may have negative environmental
impact. As technological advantages lead to better alternatives for these materials, they will be
eliminated from this standard to the extent possible.
At the end of the test, the user of the standard will take care to carry out an appropriate disposal of the
wastes, according to local regulation.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
CEN/TS 16599:2014, Photocatalysis - Illumination conditions for testing photocatalytic properties of
semiconducting materials and the measurement of these conditions
EN ISO 9169, Air quality - Definition and determination of performance characteristics of an automatic
measuring system (ISO 9169)
ISO 7996, Ambient air — Determination of the mass concentration of nitrogen oxides —
Chemiluminescence method
4
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3 Terms and definitions
For the purposes of this document, the following terms, definitions and abbreviations apply.
3.1 Definitions
3.1.1
concentration of nitrogen oxides
NO
x
stoichiometric sum of nitric oxide (NO) and nitrogen dioxide (NO )
2
Note 1 to entry: For grade 999 nitrogen or air: the purity of the gas should be equal at least to 99,9 %.
3.1.2
photocatalyst
Catalyst able to produce, upon absorption of light, chemical transformations of the reaction partners
Note 1 to entry: The excited state of the photocatalyst repeatedly interacts with the reaction partners forming
reaction intermediates and regenerates itself after each cycle of such interactions.
3.1.3
photocatalytic materials
materials in which or on which the photocatalyst is added by coating, impregnation, mixing, etc
3.2 Abbreviations
CSTR Continuous Stirred-Tank Reactor
IN
concentration at reactor inlet
C
OUT,DARK
concentration of NO and NO at reactor outlet under stable conditions in the dark (no
2
C
illumination)
OUT,light
concentration at reactor outlet under stable conditions with illumination (lamp on)
C
IN
concentration of NO at reactor inlet
C
NO
IN
concentration of NO at reactor inlet
2
C
NO
2
OUT,DARK
concentration of NO at reactor outlet under stable conditions in the dark (no
C
NO
illumination) without sample
OUT,DARK
concentration of NO at reactor outlet under stable conditions in the dark (no
2
C
NO
2
illumination) without sample
OUT,DARK
concentration of NO at reactor outlet under stable conditions in the dark (no
C
NO,S
illumination) in presence of sample
OUT,DARK
concentration of NO at reactor outlet under stable conditions in the dark (no
2
C
NO ,S
2
illumination) in presence of sample
OUT,LIGHT concentration of NO at reactor outlet under stable conditions with illumination (lamp
C
NO
on) without sample
OUT,LIGHT
concentration of NO at reactor outlet under illumination of sample measured at fan
C
NO,0
speed at nominal voltage V
0
5
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OUT,LIGHT concentration NO at reactor outlet under illumination of sample measured at fan speed
2
C
NO ,0
2
nominal voltage V
0
F Flow
th
F fan flow at i potential
v,i
I irradiance
LED light emitting diodes
MM molecular mass
P pressure in atmosphere
PTFE Polytetrafluoroethylene
R ideal gas constant
RH gas relative humidity at 25 °C inside the reactor
dark
conversion of NO in the dark
η
NO
dark
conversion to NO in the dark
2
η
NO
2
PHOTO
conversion of NO under illumination without sample
η
NO,lamp
th
total
conversion of NO measured with fan speed at i potential
η
NO ,i
th
total
conversion to NO measured with fan speed at i potential
2
η
NO ,i
2
photo
NO abatement rate at each fan speed (i = 0.n)
r
NO,i
photo
NO photocatalytic production rate at each fan speed (i = 0.n)
2
r
NO ,i
2
photo
NO abatement rate correspond to NO abatement rate minus NO photocatalytic
x 2
r
NO ,i
x
production rate
photoCAT
NO photocatalytic degradation rate intrinsic to the surface of the material, after
r
NO
removing the mass transfer limitations
photoCAT
NO photocatalytic degradation rate intrinsic to the surface of the material, after
x
r
NO
X
removing the mass transfer limitations
UV-A ultraviolet with wavelength (λ) situated between 315 nm and 400 nm (IUPAC)
V fan nominal operating potential (in Volt)
0
V fan minimum operating potential (in Volt) set by the manufacturer
min
S Sample
T temperature in Kelvin
t time to reach the stability of NO concentration
stab
UV UltraViolet
Vr Reactor net volume
6
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4 Principle
The method consists in measuring the photocatalytic abatement of nitric oxide (NO) by photocatalytic
materials as specified in paragraph 1 using a Continuous Stirred-Tank Reactor (CSTR) with flow
tangential to the sample. Information on the theory is reported in the specialized literature (Minero et
al. 2013). The residual NO and NOx concentration at the CSTR outlet is measured by a
chemiluminescence analyser (EN ISO 7996).
The photocatalytic activity test is carried out using chromatographic grade air, also obtained by mixing
pure gases, to which NO is added in such an amount as to simulate a high degree of air pollution. The NO
concentration is set to (0,50 ± 0,05) ppmv.
5 Interferences
Any measurement interferences are reported in the technical specifications of the chemiluminescence
analyser. As what is measured are all species that can be converted by reduction to NO, NO
2
concentration is here defined as [NO ] = [NO ]-[NO]. For interferences on chemiluminescence detection,
2 x
see Winer et al (1974).
6 Apparatus
The test apparatus shall consist of the following main components.
6.1 Gas mixture preparation system.
The system used for preparing the reaction mixture is shown in Figure 1.
The mass flow controllers, calibrated and traceable, shall ensure a maximum flow consistent with that
needed for a correct test execution. To ensure the necessary accuracy, the flow shall not exceed 90 % of
the rated full scale.
As an example, to obtain the gas mixture only gases of chromatographic grade or higher purity shall be
used. Instead of dry air cylinders, two separate cylinders of pure N and O can be used at the inlet of
2 2
mass-flow controllers, adjusted so as to produce a mixture consisting of 20,8 % of O and 79,2 % of N .
2 2
The NO concentration to flow #1 is set to (0,50 ± 0,05) ppmv.
7
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a) Relative humidity is set by regulating the b) Relative humidity is set by regulating the
flow to U, which is downstream to F pressure before U and F
Key
S source of nitric oxide NO diluted in N
1 2
S cylinder of air (chromatographic grade) or, alternatively, individual cylinders of N and O
2 2 2
(chromatographic grade)
F flow controller with mass-flow controllers (2 or 3)
P pressure regulators with low-pressure manometers
U humidifier maintained at controlled temperature
F#1 flow entering the reactor
Figure 1 — Gas mixture preparation system
The humidification of the gas mixture can be obtained with two different configurations:
a) with use of two mass flow controllers regulating the flow to U, as in Figure 1 left;
b) with use of one mass flow controller regulating the pressure on U, as in Figure 1 right.
The gas mixture preparation system shall ensure a relative humidity of (40 ± 5) % inside the CSTR
reactor. The relative humidity shall be measured either inside the reactor R (Figure 2) or immediately
at its outlet on flow 2 of Figure 2 by means of a hygro-thermometer.
6.2 Illumination and measuring system:
6.2.1 General:
The light source arrangement and the measuring system are shown in Figure 2.
8
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Key
R reaction chamber, Continuous Stirred-Tank Reactor (CSTR) type
V fan
A power supply of fan V
N NO/NO chemiluminescence analyser
2
E processing/logging unit
L illumination system
1, 2, 3, 4 flow paths, with valves and tubing
Figure 2 — Illumination, reaction and measuring system
All parts of the test apparatus, including connections and pipes, which come into contact with the nitric
oxide mixture shall be made of chemically inert materials. For pipes and connections PTFE is
recommended. The pipes of paths 1, 2, 3, 4 and the related connections shall have an outer diameter of
6 mm (1/4”) and inner clearance of at least 4 mm to avoid overpressures that may affect the gas
concentration inside the reactor.
Temperature shall be measured and recorded inside the reactor during the test or immediately at its
outlet on flow 2 by means of a hygro-thermometer. The gas temperature inside the reaction chamber
shall be (25 ± 5) °C.
6.2.2 Illumination system L:
The illumination source shall consist of any lamp able to excite the photocatalyst (quartz mercury vapor
lamps, UV-A fluorescent lamps, Xenon lamps, LED, lamps consisting of a metal vapor element combined
with tungsten incandescence elements, etc.) as specified in the Technical Specification CEN/TS 16599.
The illumination system shall provide an average irradiance to the test sample surface within the range
2
of wavelengths that are mostly adsorbed by the photocatalyst, equal to (10,0 ± 5 %) W/m .
The geometry of the illumination system shall be such that uniform illumination of the sample surface is
ensured. The illumination is considered uniform if 5 independent measurements performed on the
surface (one in centre position and the other four in positions perpendicular to each other and next to
the edge of the sample) show a percentage variation compared to the average value of less than 10 %.
The control of the uniformity of illumination and average irradiance shall be repeated each time the
system geometry changes (position of the lamp or any filters or reflectors, sample position, etc.).
Irradiance shall be measured by placing a radiometric sensor inside the reaction chamber in the same
position occupied by the sample in order to measure real irradiance at its surface. A second measuring
sensor for the control of source stability can be positioned outside the reaction chamber, provided that
it has been calibrated with a reference radiometric sensor placed inside the reactor. Irradiance can be
measured continuously during the test or, alternatively, just before the beginning of the test and
9
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immediately after its conclusion. The irradiance values shall be measured only after the lamp intensity
has stabilized as a result of its warming-up (typically 10 min after being turned on). The irradiance
value as measured shall be recorded as average value in the test report.
The radiometer used for the measurement shall have been previously calibrated by means of a
spectroradiometer, which in turn has been previously calibrated by means of standard sources.
In order to avoid decomposition by direct photolysis of NO, the integrated irradiance at λ < 340 nm shall
2
be less than 0,5 W/m . The direct NO photolysis rate shall be checked by performing the test using the
empty reactor, where standard NO concentration (0,5 ppmv) is introduced and the reactor outlet
concentration is measured according to paragraph 8.3.a. For example, in the case of a photocatalyst
consisting of pure TiO , the illumination system that uses a mercury lamp shall be such as to ensure the
2
surface of the sample receives a UV irradiance (λ < 400 nm) mainly composed of the line at 365 nm of
2
mercury, and an integrated irradiance for λ < 340 nm of less than 0,5 W/m .
The spectrum of the lamp used shall be acquired and reported in the test report, because the analysis
result depends significantly on the lamp type used.
6.2.3 Reaction chamber R:
A schematic of the reaction chamber is given in Figure 3.
Dimensions in millimetres
1
Key
1 sample
2 fan
3 outflow
3A gas output (alternative)
4 inflow
S sample
Figure 3 — Top view of the CSTR reaction chamber, with dimensional details and indication of
flows for thorough mixing and location of the sampling point
10
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Other dimensional details of the reaction chamber with related sample positions are also shown in the
Figures 4-5 below.
The reaction chamber shall be built with NO inert materials, i.e. glass, polymethylmethacrylate or other
inert plastic materials. The chamber shall be gas-tight. On top, the chamber shall be provided with a flat
window that is transparent to the light emitted by the illumination system and vertically incident to the
sample. This flat window, transparent to the wavelengths used (e.g. made up of borosilicate glass) shall
be (3-4) mm thick to ensure sufficient strength and also removable to allow for sample positioning.
Dimensions in millimetres
Key
HAC holes for air circulation
HF hole for a fan with Φ = 60 mm
1 top window
2 fan 60 mm nominal
3 gas outlet
4 gas inlet
Figure 4 — Side view (back of fan side) of the CSTR reactor
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Dimensions in millimetres
Key
3 gas outlet
h distance to the surface of the sample
S sample
th sample on the support, any thickness, max 50mm
max
Figure 5 — Side view (fan front side) of reactor CSTR, with indications of sample position
The reaction chamber shall comply with the dimensions shown in Figures 3 to 5. Considering the
volumes occupied by internal barriers, fan, sample and sample support, the total net volume is (2,8 to
3
3,5) dm . This volume is not critical. The gas flow is maintained constant throughout the whole test, and
3 −1
shall be equal to 1,6 dm min . It shall be at least 20 % higher than the sampling flow of the NO/NO
2
analyser. The max flow variation allowed is 10 %.
The fan ensures perfect mixing inside the reaction chamber. The fan is placed inside the reactor on a
support having a hole with diameter equal to the fan aperture and axial to the fan axis. The support has
lateral holes that ensure full air mixing inside the chamber. The fan shall provide nominal flows at the
3 −1
nominal supply voltage of 70 m h .
Fans with external dimensions of 60 mm × 60 mm and thickness from 25 mm to 35 mm are suitable for
this purpose. The fan flow shall be varied by varying the supply voltage by an appropriate power supply
of continuous variable output voltage (see A of Figure 2).
2
6.2.4 NO/NO analyser
The analyser shall be calibrated according to the procedures described in ISO 7996 or according to
EN ISO 9169. The instrument's calibration can be performed using NO and/or NO mixtures at a known
2
and certified concentration of either grade 999 nitrogen or air. For the measurement range adopted
during calibration, at least 4 standard gas mixtures shall be analysed, supported by the related
calibration certificates, with different NO contents in N (or in any other inert gas) with concentrations
2
equal to approx. 0,2 ppmv, 0,4 ppmv, 0,6 ppmv, 0,8 ppmv.
Alternatively, the concentrations needed to check the analyser calibration can be generated starting
from a single gas cylinder with certified NO concentration and with the help of a calibrated flow
controller provided with calibration certificates for mass-flow controllers.
Adjustments and calibrations shall be always carried out when the measuring device is under steady
conditions.
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By comparing the measured NO concentration values and the related certified values it is possible to
obtain, for each concentration level, the corresponding analyser calibration condition, which can be
expressed in table form, as a calibration curve or a response factor.
If calibration provides a linear response as nitrogen oxide concentrations vary within the calibration
range, then a single level measurement can be adopted during the control of the instrument calibration
condition. The frequency of such control operations depends on the accuracy level desired in
accordance with the time drift of the instrumental signal typical of each NOx-analyser.
7 Sample preparation
7.1 Precaution
Samples shall be preconditioned under supplier advices to ensure that the conversion is constant under
the test conditions.
7.2 Sample characteristics
2
The samples being analysed shall have a surface area of 64 ± 6 cm . For larger samples, use a mask. The
surface area value shall be carefully assessed being a parameter necessary for the normalization of the
test result.
The sample shall be positioned on a support made of borosilicate glass, polytetrafluoroethylene (PTFE)
or ceramic material that is not photocatalytically active, paying attention that its surface is as close as
possible to the level of the fan rotation axis and central to the free space between fan and reactor wall in
the lateral direction (see Figure 5). As to distance tolerances, the sample surface can be at a distance of
(30 to 50) mm from the internal base, that is (60 to 40) mm from the inner surface of the upper
transparent window of the reactor. This means that the sample shall have a maximum usable thickness
of 50 mm. Solid samples of 50 mm thickness can be positioned in the reaction chamber without any
support.
The geometric surface area exposed to the gas flow can be square, rectangular or circular, provided that
the illumination uniformity conditions are met (see paragraph 6.2.2). The sample width in axial
2
direction should not exceed 120 mm. Typically a cylindrical sample has a surface area of (64 ± 6) cm
(±10 %).
The required surface area can be achieved by combination of various samples, provided that they are
coplanar and the resulting surface meets the specifications above.
The surfaces of the tested sample other than those exposed orthogonally to the incident light flow, shall
be isolated from gas containing nitric oxide by means of a coating of commercial silicones, paraffin
waxes, inert polymer films or composite materials. The test shall be performed only after these
protective films have completely dried. All coatings shall withstand irradiance conditions for at least
6 h, should not release potentially interfering substances and should have no photocatalytic activity.
The type of the used product shall be specified in the final report.
7.3 Conditioning
Samples can be conditioned according to the manufacturer before being testing.
8 Measurement of concentrations
8.1 General
−3
All concentrations can be expressed either in ppmv or μg m .
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−3
Assuming an ideal behaviour for the gases in question, the conversion from ppmv to μg m is given by
the following equation:
ppmv××MM P
−3 3
(1)
C(µ g m ) 10 ppmv×k
RT×
where
NO −1 NO2 –1
MM is the gas molecular mass (MM = 30,0061 g mol , MM = 46,0055 g mol );
3 –1 −1
R, P and T are, respectively, the ideal gas constant (0,0821 dm atm mol K ), the pressure
expressed in atm a
...
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