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IS 15641-1 (2006): Natural Gas - Determination of Water bythe karl fischer method, Part 1: Introduction [PCD 3:Petroleum, Lubricants and their Related Products]

IS 15641 (Part 1) :20061s010101-1:1993

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Indian Standard

NATURAL GAS — DETERMINATION OF WATERBY THE KARL FISCHER METHOD

PART 1 lNTROD~CTION

ICS 75.060

0 BIS 2006

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

January 2006 Price Group 2

Petroleum, Lubricants and Their Related Products Sectional Committee, PCD 3

NATIONAL FOREWORD

This Indian Standard (Part 1) which is identical with ISO 10101-1:1993 ‘Natural gas — Determination

of water by the Karl Fischer method — Part 1 : Introduction’ issued by the International Organization forStandardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of thePetroleum, Lubricants and Their Related Products Sectional Committee and approval of thePetroleum,Coal and Related Products Division Council.

The text of ISO Standard has been approv.ed as s-uitable for publication as-an Indian Standard withoutdeviations. Certain conventions are, however, not identical to those used in Indian Standards. Attentionis particularly d~awn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they shouldbe read as ‘Indian Standard’.

b) Comma (,) has been used as a decimal marker while in Indian Standards, the currentpractice is to use a point (.) as the decimal marker.

The technical committee responsible for the preparation of this standard has reviewed the provisionsof the following International Standards and has decided that they are acceptable for use in conjunctionwith this standard:

International Standard Title

ISO 6712:1982 Gas analysis — Sampling and transfer equipment for gases supplyingan analytical unit

Iso 10101-2:1993 Natural gas — Determination of water by the Karl Fischer method’-Part 2: Titration procedure

LSo 10101-3:1993 Natural gas — Determination of water by the Karl Fischer method -Part 3: Coulometric procedure

In reporting the results of a test or analysis made ir, accordance with this standard, if the final value,observed or calculated, is to be rounded off, it shall be done in accordance with IS 2:1960 ‘Rules forrounding off numerical values (revised)’.

lS 15641 (Part l) :20061s0 10101-1:1993

Indian Standard

NATURAL GAS — DETERMINATION OF WATERBY THE KARL FISCHER METHOD

PART 1 INTRODUCTION

WARNING — Local-safety regulations must be taken into account, when the equipment is locatedin hazardous areas. Due to the toxicity and odour of pyridine, the user should ensure that there isadequate ventilation.

1 Scope

This part of 1S0 10101 specifies general requirementsfor the determination of water in natural gas using theKarl Fischer method. ISO 10101-2 and ISO 10101-3specify two individual methods of determination, atitration procedure and a coulometric procedure, re-spectively.

2 Normative references

The followina standards contain movisions which,through refer;nce in this text, constitute provisionsof this part of ISO 10101. At the time of publication,the editions indicated were valid. All standards aresubject to revision, and parties to agreements basedon this part of ISO 10101 are encouraged to investi-gate the possibility of applying the most recent edi-tions of the standards indicated below. Members ofIEC and ISO maintain registers of currently validInternational Standards.

ISO 6712:1982, Gas arra/ysis — Sampling and transferequipment for gases supplying an analytical unit.

1S0 10101-2:1993, Natural gas — Determination ofwater by the Karl Fischer method — Part 2.” Titrationprocedure,

ISO 10101-3:1993, Natura/ gas — Determination ofwater by the Karl Fischer method — Part 3:Coulometric procedure.

3 Principle

Reaction of water present in the test sample withiodine and sulfur-dioxide in a pyridine/methanol’ mix-ture (Karl Fischer reagent).

3.1 Principle of the first-method(1s0 10101-2)

A measured volume of gas is passed through a cellcontaining a relatively small volume of absorbent sol-ution. Water in the gas is dissolved in the absorbentsolution and subsequently titrated with Karl Fischerreagent, the endpoint being detected voltametrically.

3.2 Principle of the second method(1s010101-3)

A measured volume of gas is passed through a cellcontaining anhydrous, previously titrated, anodic sol-ution. The iodine required for the titration of the dis-solved water is coulometriially produced from theiodide present in the solution by the reaction

21- + 12+2e-

4 Reactions and interferences

CH~OH + S02+ R3N~

[R3NH]S03CH3

IS 15641 (Part 1) :20061s0 10101-1:1993

H20 + 12+ [R3NH]S03CH3 + 2R3N-+ ter at 273,15 K (O “C) and

[R3NH]S04CH3+”2 [R3NH]I101,325 kPa (1 atm);

.Q(Sas H2S) is the measured sulfur as hydrogen

NOTE 1 Methanol may be replaced by 2-methoxyethanol sulfide, in milligrams per cubic meter(ethylene glycol monomethylether) and pyridine (R3N) may at 273,15 K (O “C) and 101,325 kPabe replaced by any other suitable basic nitrogen compound. (1 atm);

Various gas components react with the Karl Fischerreagent and can give rise to erroneous results. Suchcomponents are oxidizing and reducing agents, e.g.hydrogen sulfide, mercaptans and certain basicnitrogenous substances.

Hydrogen sulfide and mercaptans are present in somenatural gases. If their concentration is less than 20 YO

of the water content, interference due to their pres-ence shall be corrected as follows:

9Q(S as H2S)dH20), = dHJV - , ~

Q(S as 17SH) is the measured sulfur as mer-captans in the gas, in milligrams percubic meter at 273,15 K (O “C) and101,325 kPa (1 atm).

At higher contents of H2S and RSH this method is notapplicable.

NOTE 2 The sulfur present as hydrogen sulfide and mer-captans can be determined by potentiometric titration (see1S0 6362-3) or by any other suitable method.

5 Sampling9Q(S as RSH)

32Carry out sampling according to the general samplingguidelines given in ISO 6712. During sampling, ensure

where that the temperature of the gas stream is above thedew-point temperature. If necessary the sampling

e(H20)a is the actual water content, in milli- equipment should be heated.grams per cubic meter at 273,15 K(O “Cj and 101,325 kPa (1 atm); All parts in contact with the gas shall be of steel or

glass. The ends of pipes shall fit securely together and@i20) is the observed or measured water ~he connecting ~eces shall be made _&f fluoro-

content, in milligrams per cubic me- elastomers..,. ,

2

IS 15641 (Part 1): 20061s0 1-0101-1:1993

Annex A(informative)

Bibliography

[1] ISO 760:1978, Determination of water — KarlFischer method (General method).

[2] ISO 6326-3:1989, Natural gas — Determinationof sulfur compounds — Part 3: Determinationof hydrogen su/fide, mercaptan sulfur andcarbonyl sulfide sulfur by potentiometry.

[31 FISCHER, K. Neues Verfahren zur mas.s-analytischen Bestimmung des Wassergehaltes

von Flussigkeiten und festen Korpern.Angewandte Chemie 46 (1935), 26, p, 394.

[4] KAESLER,H. Direkte Bestimmung des Wasser-gehaltes in Gasen nach Karl Fischer.gwf-ga.sjerdgas 125 (1984),3, pp, 125-131.

[5] SCHOLZ,E. Karl Fischer Titration, Methoden zurWasserbestimmung. Springer-verslag, Berlin,Heidelberg, 1984.

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This Indian Standard has been developed from Dot: No. PCD 3 (2238).

Amendments Issued Since Publication

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