DIN EN ISO 6145-11-2008 Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 11 Electrochemical generation (ISO 6145-11 2005) English vers.pdf

1、November 2008DEUTSCHE NORM English price group 11No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 71.040.40!$Rx*“147850

2、7www.din.deDDIN EN ISO 6145-11Gas analysis Preparation of calibration gas mixtures using dynamic volumetricmethods Part 11: Electrochemical generation (ISO 6145-11:2005)English version of DIN EN ISO 6145-11:2008-11Gasanalyse Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-volumetrische

3、nVerfahren Teil 11: Elektrochemische Herstellung (ISO 6145-11:2005)Englische Fassung DIN EN ISO 6145-11:2008-11www.beuth.deDocument comprises 20 pagesDIN EN ISO 6145-11:2008-11 2 National foreword This standard has been prepared by Technical Committee ISO/TC 158 “Analysis of gases” (Secretariat: NEN

4、, Netherlands) and has been taken over as EN ISO 6145-11:2008 by Technical Committee CEN/SS N21 “Gaseous fuels and combustible gas” (Secretariat: CMC). The responsible German body involved in its preparation was the Normenausschuss Materialprfung (Materials Testing Standards Committee), Technical Co

5、mmittee NA 062-05-73 AA Gasanalyse und Gas-beschaffenheit. ISO 6145 consists of the following parts, under the general title Gas analysis Preparation of calibration gas mixtures using dynamic volumetric methods: Part 1: Methods of calibration Part 2: Volumetric pumps Part 4: Continuous injection met

6、hod Part 5: Capillary calibration devices Part 6: Critical orifices Part 7: Thermal mass-flow controllers Part 8: Diffusion method Part 9: Saturation method Part 10: Permeation method Part 11: Electrochemical generation The DIN Standards corresponding to the International Standards referred to in th

7、is document are as follows: ISO 6143 DIN EN ISO 6143 ISO 6145-1 DIN EN ISO 6145-1 ISO 7504 DIN V 51897 In addition, it should be noted that the “Guide to the expression of uncertainty in measurement (GUM)” has been published as DIN V ENV 13005. National Annex NA (informative) Bibliography DIN V 5189

8、7, Gas analysis Definitions and explanations DIN V ENV 13005, Guide to the expression of uncertainty in measurement DIN EN ISO 6143, Gas analysis Comparison methods for determining and checking the composition of calibration gas mixtures DIN EN ISO 6145-1, Gas analysis Preparation of calibration gas

9、 mixtures using dynamic volumetric methods Part 1: Methods of calibration EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 6145-11 August 2008 ICS 71.040.40 English Version Gas analysis - Preparation of calibration gas mixtures using dynamic volumetric methods - Part 11: Electrochemical gene

10、ration (ISO 6145-11:2005) Analyse des gaz - Prparation des mlanges de gaz pour talonnage laide de mthodes volumtriques dynamiques - Partie 11: Gnration lectrochimique (ISO 6145-11:2005) Gasanalyse - Herstellung von Kalibriergasgemischen mit Hilfe von dynamisch-volumetrischen Verfahren - Teil 11: Ele

11、ktrochemische Herstellung (ISO 6145-11:2005) This European Standard was approved by CEN on 30 July 2008. 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

12、. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN 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 translati

13、on under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Gr

14、eece, 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 COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Manage

15、ment Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 6145-11:2008: E2 Contents Page Foreword3 Introduction .4 1 Scope 5 2 Normative references 5 3 Procedure .6 3.1 Principle6 3.2

16、 Complementary gas 6 3.3 Electrolytic systems for gas generation .6 3.4 Apparatus .7 3.4.1 Cell construction7 3.4.2 Current supply and gas flow control .7 3.5 Gas mixture preparation .7 3.5.1 Complementary gas 7 3.5.2 Voltage supply .7 3.5.3 Calculation of gas mixture content8 4 Uncertainty evaluati

17、on . 10 4.1 Introduction. 10 4.2 Sources of uncertainty. 10 4.2.1 Complementary gas flow . 10 4.2.2 Gas generation 10 4.2.3 Absorption of generated gas in the cell electrolyte 10 4.2.4 Effect of moisture content . 10 4.2.5 Effect of temperature 10 4.2.6 Purity of electrolytic chemicals. 10 4.2.7 Imp

18、urities in complementary gas 11 4.3 Uncertainty of volume fraction 11 5 Electrochemical cell design. 11 Annex A (informative) Example of a commercial electrochemical cell 13 Annex B (informative) Schematics of electrolytic cells used for gas generation . 15 Annex C (informative) Schematic of electri

19、cal supply to gas generation cell . 16 Annex D (informative) Decomposition voltages of solutions between smooth platinum electrodes . 17 Bibliography. 18 DIN EN ISO 6145-11:2008-11 EN ISO 6145-11:2008 (E) Foreword 3 The text of ISO 6145-11:2005 has been prepared by Technical Committee ISO/TC 158 “An

20、alysis of gases” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 6145-11:2008 by Technical Committee CEN/TC N21 “Gaseous fuels and combustible gas” the secretariat of which is held by CMC. This European Standard shall be given the status of a national st

21、andard, either by publication of an identical text or by endorsement, at the latest by February 2009, and conflicting national standards shall be withdrawn at the latest by February 2009. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent ri

22、ghts. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. 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, Cyprus,

23、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 the United Kingdom. Endorsement notice The text of ISO 6145-1

24、1:2005 has been approved by CEN as a EN ISO 6145-11:2008 without any modification. EN ISO 6145-11:2008 (E) DIN EN ISO 6145-11:2008-11 Introduction This part of ISO 6145 is one of a series of standards dealing with the various dynamic volumetric methods used for the preparation of calibration gas mix

25、tures. Electrochemical gas generation can be used to produce calibration gas mixtures containing calibration components which, because of their corrosive nature or low content, are unlikely to be stable in high-pressure cylinders. 4 DIN EN ISO 6145-11:2008-11 EN ISO 6145-11:2008 (E) 1 Scope This par

26、t of ISO 6145 specifies a method for the preparation of calibration gas mixtures by using electrochemical generation of a calibration component and introduction into a complementary gas flow. By alteration of the gas flow or the charge passed through the cell electrolyte, it is possible to change th

27、e composition of the gas mixture. The relative expanded uncertainty of the calibration gas content, U, obtained by multiplying the relative combined standard uncertainties by a coverage factor, k = 2, is not greater than 5 %. The method described in this part of ISO 6145 is intended to be applied to

28、 the preparation of calibration gas mixtures in the volume fraction ranges (0,1 to 250) 106. NOTE 1 Gases that can be produced by electrochemical generation are oxygen (O2), hydrogen (H2), hydrogen cyanide (HCN), hydrogen sulfide (H2S), chlorine (Cl2), bromine (Br2), chlorine dioxide (ClO2), ammonia

29、 (NH3), nitric oxide (NO), nitrogen (N2), carbon dioxide (CO2), phosphine (PH3), arsine (AsH3) and ozone (O3). NOTE 2 The merits of the method are that a stable calibration gas mixture can be quickly prepared within minutes. NOTE 3 Gas blending systems based on electrochemical generation and thermal

30、 mass flow controllers, with the facility of computerization and automatic control, are commercially available. An example is given in Annex A. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cit

31、ed applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 6143, Gas analysis Comparison methods for determining and checking the composition of calibration gas mixtures ISO 6145-1, Gas analysis Preparation of calibration gas mixtures us

32、ing dynamic volumetric methods Part 1: Methods of calibration ISO 6145-7:2001, Gas analysis Preparation of calibration gas mixtures using dynamic volumetric methods Part 7: Thermal mass-flow controllers 5 EN ISO 6145-11:2008 (E) DIN EN ISO 6145-11:2008-11 3 Procedure 3.1 Principle Electrochemical ga

33、s generation is a fundamental method in which the quantity of the calibration gas component generated is proportional to the charge passed. The proportionality factor is the reciprocal of the Faraday constant the electrical charge carried by one mole of electrons (or singly charged ions), which is e

34、qual to the product of the Avogadro constant (NA) and the charge of an electron (e). F = NA e (1) where F is 96 485,341 5 C/mol with a relative uncertainty of 4,0 108(see References 1, 2 and 3). The passage of accurately determined electrical current through a cell determines the gas output provided

35、 the conditions given in Clause 5 are applied. 3.2 Complementary gas The flow rate of complementary gas shall be determined by one of the methods given in ISO 6145-1. 3.3 Electrolytic systems for gas generation Table 1 lists some examples of gases which can be prepared in quantitative yield by direc

36、t electrolysis, using platinum and other electrodes. Also included is an example of the suppression of an unwanted constituent by adsorption on activated carbon surrounding the appropriate electrode. Table 1 Electrolysis systems for gas generation Gas required Electrolysis system Gas liberated at ot

37、her electrode Yield mole of required gas per charge numerically equal to Faraday number O2or H2Pt, H2SO4, Pt Pt, K2SO4, Pt Pt, KOH, Pt H2or O21/4 (O2) 1/2 (H2) O2Pt, H2SO4, Hg2SO4, +C, Hg Pt, neutral solution, active C Pt, KOH, HgO, +C, Hg Pt, KOH, CdO, Cd nil 1/4 N2Pt, N2H4, H2SO4, Pt H21/4 Cl2Pt,

38、NaCl, Pt H21/2 CO2Pt, H2C2O4, Pt H21 NO Pt, (NOH)SO4, + H2SO4, Pt aO2aThis system has also been used for the generation of nitrogen dioxide 4.6 DIN EN ISO 6145-11:2008-11 EN ISO 6145-11:2008 (E) 3.4 Apparatus 3.4.1 Cell construction Cell construction shall be designed to ensure that the generated ca

39、librated component is transferred into the complementary gas stream at maximum efficiency suitable for calibration purposes. Some of the conditions that shall be fulfilled for the operation of an electrolytic cell used for this purpose are given in Clause 5. Examples of electrolytic cells are given

40、in Figures B.1 and B.2. 3.4.2 Current supply and gas flow control 3.4.2.1 The content of the calibration gas produced from the system is dependent on three factors: a) the current supplied through the cell which generates a volume flow rate of the calibration gas component; b) the (volume) flow rate

41、 of the complementary gas; and c) the cell efficiency. NOTE Cell efficiency is the fraction recovery of calibration component over the calculated quantity generated by the current supplied to the cell (see 4.2.3). It depends on the design of the cell. Practical hints on design are given in Clause 5

42、and an example is given in Annex C. 3.4.2.2 A battery, capable of supplying voltage in the range 0,5 V to 1,0 V, and a milliamperemeter with a measurement range of 0,5 mA to 5,0 mA with an uncertainty of 1,0 %, are suitable. DC generators are an alternative but may pass an AC ripple, which can affec

43、t the electrolysis process. 3.4.2.3 A flow measuring unit (e.g. a thermal mass-flow meter) that has been calibrated for the complementary gas between a volume flow rate of 0,2 l/min and 5,0 l/min with an uncertainty of 1 % is suitable. NOTE Methods for the measurement of the flow rate of the complem

44、entary gas are given in ISO 6145-1, which also describes the procedure for calibration of the thermal mass-flow meter. 3.5 Gas mixture preparation 3.5.1 Complementary gas The calibration gas mixture shall be prepared by passing the chosen complementary gas through the calibrated thermal mass flow co

45、ntroller, set at known flow, through the cell. If the complementary gas is air, the supply to the controller may be managed with a small air pump. Other complementary gases may be chosen by using a regulated supply from a high-pressure cylinder to the controller. The complementary gas shall be allow

46、ed to purge out the cell for 2 min and then the cell voltage supply required for the electrolysis shall be switched on. The purity of the complementary gas shall be established before use, particularly with regard to any impurities that may cross respond or react with the gas being generated. If pum

47、ped air is chosen as the complementary gas, then suitable purification shall be used to remove any interfering substances. 3.5.2 Voltage supply The applied voltage to the cell from the battery shall be slowly increased to the point at which gas bubbles appear at the electrode. The value at that poin

48、t is termed the decomposition potential. This is the point at which electrolysis occurs and the calibration component is produced at its electrode. The reading of the milliamperemeter is noted when the value has become stable. Decomposition potentials for various electrolytes are given in Table D.1.

49、 Different values of the content of the calibration gas mixture can now be obtained by variation of the flow rate of the complementary gas or the current passed through the cell. It would be advisable to select that parameter which is nearest to the middle of its range. 7 EN ISO 6145-11:2008 (E) DIN EN ISO 6145-11:2008-11 3.5.3 Calculation of gas mixture content The volume fraction of the calibration component, A, in the calibration gas mixture is calculated from the relation: AAABqqq =+(2) in which qAa