1、BRITISH STANDARD BS1747-9: 1987 ISO7996:1985 Methods for Measurement of air pollution Part 9: Determination of the mass concentration of nitrogen oxides in ambient air: chemiluminescence method ISO title: Ambient air Determination of the mass concentration of nitrogen oxidesChemiluminescence method
2、UDC551.510.42+614.72:543.272.32:535:379BS1747-9:1987 This British Standard, having been prepared under the directionof the Environment andPollution Standards Committee, was published underthe authority of the BoardofBSI and comes intoeffecton 30September1987 BSI 11-1999 The following BSI references
3、relate to the work on this standard: Committee reference EPC/35 Draft for comment84/50181DC ISBN 0 580 15501 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Environment and Pollution Standards Committee (EPC/-) to Technical Committee E
4、PC/35, upon which the following bodies were represented: British Coal British Gas British Steel Corporation Cement Makers Federation Department of Health and Social Security Department of Trade and Industry (Laboratory of the Government Chemist) Department of Trade and Industry (Warren Spring Labora
5、tory) Electricity Supply Industry in England and Wales GAMBICA (BEAMA Ltd.) Health and Safety Executive Institute of Petroleum Institution of Environmental Health Officers Institution of Gas Engineers Lead Development Association National Industrial Fuel Efficiency Service National Society for Clean
6、 Air Society of Chemical Industry The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Asbestosis Research Council Chartered Institution of Building Services Engineers Council of Environmental Conservation Department of the Environment Departm
7、ent of the Environment (Building Research Establishment) Engineering Equipment and Materials Users Association Fibre Cement Manufacturers Association Limited Institute of Energy Institute of Occupational Hygienists Institute of Occupational Medicine Institution of Electrical Engineers London Regiona
8、l Transport Amendments issued since publication Amd. No. Date of issue CommentsBS1747-9:1987 BSI 11-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 References 1 3 Principle 1 4 Reactions 1 5 Apparatus 1 6 Procedure 2 7 Expressi
9、on of results 5 8 Test report 5 Annex Typical performance characteristics 10 Figure 1a) Schematic representation of a dual type chemiluminescenceanalyser (two reaction chambers and photomultipliers) 6 Figure 1b) Schematic representation of a dual type chemiluminescenceanalyser utilizing a double rea
10、ction chamber and onephotomultiplier 6 Figure 1c) Schematic representation of a cyclic type chemiluminescenceanalyser 7 Figure 2 Schematic representation of arrangement for checking analyserconverter efficiency 8 Figure 3 Schematic representation of a typical calibration system using a nitrogendioxi
11、de permeation cell 9 Publications referred to Inside back coverBS1747-9:1987 ii BSI 11-1999 National foreword This Part of BS1747, which has been prepared under the direction of the Environment and Pollution Standards Committee, is identical with ISO7996:1985 “Ambient air Determination of the mass c
12、oncentration of nitrogen oxides chemiluminescence method” published by the International Organization for Standardization. It was prepared by Technical Committee146, Air quality, of the International Organization for Standardization (ISO) with the active participation and approval of the UK. This Pa
13、rt of BS1747 is one of a series relating to air quality arising from UK participation in the work of ISO/TC146. Methods for the determination of particular constituents of ambient air will be published as further Parts of this standard. Topics relating to air quality characteristics will be publishe
14、d as Parts of BS6069 “Methods for characterization of air quality”. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in
15、 British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. It is current practice in British Standards to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, they
16、 should be read as “Part of BS1747”. The symbol “l” has been used to denote litre (and in its submultiples). In British Standards it is current practice to use the symbol “L”. It is also current practice to use the spelling “sulphur”, instead of “sulfur”. The Technical Committee has reviewed the pro
17、visions of ISO6711 and ISO6879, to which reference is made in the main body of the standard and in the Annex respectively, and has decided that they are acceptable for use in conjunction with this standard. Textual errors. When adopting the text of the International Standard, the textual errors give
18、n below were discovered. They have been marked in the text with an asterisk and have been reported to ISO in a proposal to amend the text of the International Standard. In6.2.2.3, line3,“ 1 C” should be“ 0,1 C”. In6.3.1, equation(3), delete“+ (NO)” and the explanation of this term thereunder. In6.3.
19、2, lines7 and8, delete “and (NO) by (NO 2 ) or (NO x )”. In6.3.2, note3, the last sentence should be part of itemb). In Figure 2, the cylinder containing the NO source, should show“. 1” before “ppm(V/V)”. Cross-references International Standards Corresponding British Standards BS4559: Methods for pr
20、eparation of calibration gas mixtures ISO6142:1981 Section1.1:1983 Mixtures containing components fully vaporizable under ambient conditions (Identical) ISO6144:1981 Part3:1983 Static volumetric methods (Identical) ISO6349:1979 Part7:1981 Permeation method (Identical)BS1747-9:1987 BSI 11-1999 iii Ad
21、ditional information. For clarification, the term “zero air”, which is used in6.2.1 and subsequent clauses, refers to air containing no nitrogen oxides. In order to provide clarification notice is brought to users of this standard that the equations given in6.3.1 assume a converter efficiency of100%
22、 for nitrogen dioxide conversion to nitrogen oxide. For very accurate determinations, the appropriate conversion factor may have to be used and in such cases the attention of users is also drawn to note3 in6.3.2, which describes alternative calibration systems. A British Standard does not purport to
23、 include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover,
24、pagesitoiv, pages1to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS1747-9:1987 BSI 11-1999 1 1 Scope and field of application Th
25、is International Standard specifies a chemiluminescence method for the determination of the mass concentration of nitrogen oxides present in ambient air. The method is applicable to the determination of the mass concentration of nitrogen monoxide present in ambient air up to approximately12,5mg/m 3a
26、nd of nitrogen dioxide up to approximately19mg/m 3respectively 1)at25 C and101,3kPa. For interferents, see6.6. 2 References ISO6142, Gas analysis Preparation of calibration gas mixtures Weighing methods. ISO6144, Gas analysis Preparation of calibration gas mixtures Static volumetric methods. ISO6349
27、, Gas analysis Preparation of calibration gas mixtures Permeation method. ISO6711, Gas analysis Checking of calibration gas mixtures by a comparison method. 3 Principle Passage of the air sample through a filter (toprevent mal-operation of the chemiluminescence analyser) at a constant flow rate into
28、 the reaction chamber of the analyser, where it is mixed with an excess of ozone. Filtering of the emitted radiation, proportional to the amount of nitrogen monoxide present in the air sample, by means of a selective optical filter and conversion of the filtered radiation into an electric signal by
29、a photomultiplier tube. Measurement of nitrogen dioxide in the air sample by reducing it to nitrogen monoxide by passage through a converter before it enters the reaction chamber. The electric signal obtained is proportional to the total amount of nitrogen oxides, and the nitrogen dioxide contributi
30、on is calculated from the difference between this value and that obtained for nitrogen monoxide onlywhen the air sample does not pass through the converter. Analysers may be of the dual or cyclic type. In the dual type, the air flow is divided into two streams, one passing directly to the reaction c
31、hamber and the other via the converter. There are two reaction chambers and one or two detectors respectively monitoring the nitrogen monoxide and nitrogen oxides content of the air sample. In the cyclic type analyser, there is only one reaction chamber and detector and the output alternates between
32、 nitrogen monoxide and total nitrogen oxides measurements, i.e.the air sample alternately bypasses or passes through the converter. 4 Reactions Luminescence is a characteristic of many substances from which light is emitted when they are excited. This phenomenon is called chemiluminescence when prod
33、uced as a result of a chemical reaction. This chemiluminescence method is based on the reaction Excited nitrogen dioxide emits radiation centred around the near infra-red(1200nm). 5 Apparatus Schematic diagrams of typical analysers are given in Figure 1a) and Figure 1b) (dual type) and Figure 1c) (c
34、yclic type). An apparatus consists of the following principal components(5.1 to5.10). 5.1 Sample line The sample intake shall consist of a small inverted funnel connected to the sample line the latter being as short as practically possible. Both shall be made of material which is inert to nitrogen m
35、onoxide and nitrogen dioxide. It is very important not to use any materials made from copper based alloys. From experience, the best materials to use are polytetrafluoroethylene (PTFE) or perfluoro(ethylene/propylene) (FEP). In order to avoid disturbance of the nitrogen monoxide-nitrogen dioxide-ozo
36、ne equilibrium caused by reduced daylight intensity in the sample line, the residence time in the sample line should be as short as possible. The sample line may be moderately heated to avoid any condensation. 1) At the temperature and pressure given, the following conversion factors apply. NO: 1mg/
37、m 3 0,81ppm (V/V) 1ppm(V/V) 1,23mg/m 3 NO 2 : 1mg/m 3 0,53ppm(V/V) 1ppm(V/V) 1,88mg/m 3BS1747-9:1987 2 BSI 11-1999 5.2 Particle filter The particle filter shall retain all particles likely to alter the performance of the analyser. At the same time, it and its support shall be made from material whic
38、h will not retain nitrogen monoxide or nitrogen dioxide, for example PTFE or stainless steel. The particle filter shall be replaced or cleaned periodically as required by the dust loading at the sampling site. Overloading of this filter may cause loss of nitrogen dioxide by sorption on the particula
39、te matter. 5.3 Control and regulation of sample flow rate The sample flow rate shall be maintained to 2% of that specified by the manufacturer of the analyser. Flow rate control is usually maintained by a controlled pressure drop across restrictors. 5.4 Converter The converter shall consist of a hea
40、ted furnace maintained at a constant temperature and is made of stainless steel, copper, molybdenum, tungsten or spectroscopically pure carbon. It shall be capable of converting at least95% of the nitrogen dioxide to nitrogen monoxide at a temperature not exceeding400 C. The role of the converter is
41、 very important since it controls the determination of nitrogen dioxide. 5.5 Ozone generator Ozone is generated from oxygen by either ultra-violet radiation or by a high voltage silent electric discharge. If oxygen in ambient air is used for ozone generation by a high voltage silent electric dischar
42、ge, it is essential that the air be thoroughly dried and filtered before entering the generator. If the ozone is generated using oxygen of recognized analytical grade from a compressed gas cylinder, this oxygen can be fed directly into the generator. The concentration of ozone produced shall be grea
43、ter than the maximum concentration of nitrogen oxides being measured. The flow rate of air or oxygen to the ozone generator shall be kept constant. 5.6 Reaction chamber This shall be constructed of an inert material. Its dimensions determine the characteristics of the chemiluminescence reaction (res
44、idence time, speed of reaction). The reaction chamber may be heated slightly to avoid condensation. The reaction is generally carried out at reduced pressure to minimize quenching effects and increase sensitivity. 5.7 Optical filter This filter shall remove all radiation at wavelengths below600nm, t
45、hus avoiding any interference produced by the chemiluminescence reaction with unsaturated hydrocarbons which radiate at these wavelengths. 5.8 Photomultiplier tube The output of the analyser is closely affected by the characteristics of the photomultiplier tube. In order to reduce background noise a
46、nd the effect of temperature changes, the tube is usually housed in a thermostatically controlled refrigerated container. 5.9 Ozone filter The ozone shall be removed from the gas on leaving the reaction chamber by passage through activated charcoal. This prevents pollution of the immediate ambient a
47、ir and protects the sampling pump. 5.10 Sampling pump Situated at the end of the circuit, the sampling pump draws air through the apparatus. It shall be capable of operating under the pressure conditions required for the reaction chamber. 5.11 Apparatus for checking the analyser converter efficiency
48、 (see6.1) 5.11.1 Source of nitrogen monoxide, compressed gas cylinder containing nitrogen monoxide in nitrogen at a concentration of the order of1ppm(V/V). The actual concentration need not be known provided that it remains constant throughout the test. 5.11.2 Source of oxygen, compressed gas cylind
49、er containing oxygen or air. 5.11.3 Ultra-violet lamp, capable of varying the size of the lamp window for producing varying amounts of ozone from oxygen. 5.11.4 Chemiluminescence analyser in which the temperature of the converter furnace is controllable. 6 Procedure The operation of the apparatus will vary from one to another. Follow the manufacturers instructions regarding setting up operations, and flow rates of air sample and ozone. The frequency of calibration will vary from one apparatus to another, but th
