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1、INTERNATIONAL STANDARD IS0 157 Second edition 1996-06-01 Coal - Determination of forms of sulfur Charbon - DBtermination de la teneur en diffkentes formes de soufre Reference number IS0 157:1996(E) Copyright International Organization for Standardization Provided by IHS under license with ISO Licens
2、ee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 02:28:13 MDTNo reproduction or networking permitted without license from IHS -,-,- Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The wor
3、k of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be rep- resented on that committee. International organizations, governmental and non-govern
4、mental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for vot
5、ing. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 157 was prepared by Technical Committee ISOflC 27, Solid mineral fuels, Subcommittee SC 5, Methods of analysis. This second edition cancels and replaces th
6、e first edition (IS0 157:1975), of which it constitutes a technical revision. Annex A of this International Standard is for information only. 0 IS0 1996 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
7、or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 . CH-1211 Geneve 20 l Switzerland Printed in Switzerland ii Copyright International Organization for Standardization Provided by IHS u
8、nder license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 02:28:13 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 IS0 157:1996(E) Introduction For many purposes, a knowledge of the total sulfur content of a coal is sufficient, but
9、for certain work it is also necessary to know how the sulfur is distributed between the coal substance and the mineral matter. In particular, such information may be required in connection with coal classi- fication and cleaning. Sulfur is usually present in coal in three forms, viz: a) sulfate sulf
10、ur, i.e. the sulfur present in the form of inorganic sulfates; b) pyritic sulfur, i.e. the sulfur present in the form of pyrites and marca- site; c) organic sulfur, i.e. the sulfur present in the form of organic sulfur compounds. . III Copyright International Organization for Standardization Provide
11、d by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 02:28:13 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD IS0 IS0 157:1996(E) Coal - Determination of forms of sulfur Section 1: General 1.1 Scope
12、 This International Standard specifies methods of determining the sulfate and pyritic sulfur contents of coals, including brown coals and Iignites, and of calculating the amount of organic sulfur present. 1.2 Normative references The following standards contain provisions which, through reference in
13、 this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most re
14、cent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IS0 331 :I 983, Coal - Determination of moisture in the analysis sample - Direct gravimetric method. IS0 334:1993, So/id mineral fuels - Determination of total sulfur
15、 - Eschka method. IS0 351 :I 995, So/id mineral fuels - Determination of total sulfur - High temperature combustion method. IS0 1015:1992, Brown coals and /ignites - Determi- nation of moisture content - Direct volumetric method. IS0 1170:1977, Coal and coke - Calculation of analy- ses to different
16、bases. IS0 1988: 1975, Hard coal - Sampling. IS0 5068:1983, Brown coals and /ignites - Determi- nation of moisture content - Indirect gravimetric method. IS0 5069-2:1983, Brown coals and /ignites - Prin- ciples of sampling - Part 2: Sample preparation for determination of moisture content and for ge
17、nera/ analysis. 1.3 Principle The procedure described in this International Standard utilizes the differential solubilities of sulfates and pyrites in dilute hydrochloric and nitric acids under reflux conditions, such that each can be taken in solution successively and determined directly. A general
18、 schematic representation of the procedure is given in figure 1. 1.4 Preparation of the test sample The test sample is the general analysis test sample prepared in accordance with IS0 1988 or IS0 5069-2, as appropriate. Grind about 25 g of the sample to pass a sieve of aperture 75 urn and ensure tha
19、t its moisture content is in equilibrium with the laboratory atmosphere, exposing it if necessary in a thin layer for the mini- mum time required to achieve equilibrium. Before commencing the determination, thoroughly mix the test sample for at least 1 min, preferably by mechanical means. If the res
20、ults are to be calculated other than on an air- dried basis (see 6.1) then, after weighing the test portion (see 2.41, determine the moisture content using a further portion of the test sample by the method described in IS0 331, IS0 1015 or IS0 5068, as appropriate. 1 Copyright International Organiz
21、ation for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 02:28:13 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 157: 1996(E) Coal sample (2 g to 8 g) 1 Reflux in dilute hydrochloric acid
22、 (dissolves non-pyritic iron) 2 Filter I I Filtrate insoluble residue (Iron in + 2 and + 3 oxidation states) 1 Reflux in dilute nitric acid 2 Filter Add hydrogen peroxide 1 (Iron In + 3 oxidatlon state) Fittrate (contains Insoluble residue pyritic iron) (discard) 1 Add ammonia solution 2 Filter l-l
23、1 Addhydrogenperoxide 2 Boil Filtrate I Precipitate (discard) 3 Cool 1 Adjust pH 2 Add potassium sulfate solution 3 Boil 4 Add barium chloride solution 5 Filter Alternative finishes I I I Determination of Determination Determination pyritic iron by of pyritic iron of pyritic iron atomic absorption b
24、y titrimetry by calorimetry spectroscopy I I Filtrate (discard) Precipitate I Gravimetric determination of sulfate sulfur Calculate pyritic sulfur from pyritic iron NOTE - Organic sulfur = Total sulfur - (sulfate sulfur + pyritic sulfur) Figure 1 - General schematic representation of the procedure 2
25、 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 02:28:13 MDTNo reproduction or networking permitted without license from IHS -,-,- 0 IS0 IS0 157:1996(E) Section 2: Separation of
26、 sulfate and pyritic sulfur 2.1 Principle The test portion is extracted with dilute hydrochloric acid to bring both the sulfate sulfur and the non-pyritic iron into solution. The pyritic iron and sulfur remain in the residue which is separated by filtration. 2.2 Reagents WARNING - Care must be exerc
27、ised when handling the reagents, many of which are toxic and corrosive. During the analysis, unless otherwise stated, use only reagents of recognized analytical reagent grade and only distilled water or water of equivalent quality. 2.2.1 Hydrochloric acid, concentrated, approximately 36 % (m/m). 2.2
28、.2 Hydrochloric acid, dilute, approximately 15 % (m/m). Water inlet - c L 019 Dilute 420 ml of the hydrochloric acid (2.2.1) to 1 litre with water. 2.2.3 Nitric acid, dilute, approximately 9 % (m/m). Dilute 130 ml of concentrated nitric acid approximate- ly 70 % (m/m) to 1 litre with water. 2.3 Appa
29、ratus 2.3.1 Analytical balance, capable of weighing to the nearest 0,l mg. 2.3.2 Graduated glassware, conforming to the requirements for class A in the International Stan- dards prepared by ISO/TC 48, Laboratory glassware and related apparatus. 2.3.3 Cold-finger condenser, to fit loosely into the ne
30、ck of a 250 ml conical flask (see figure 2). Approximate dimensions in millimetres - Water outlet - 0 16 Figure 2 - Cold-finger condenser for the determination of sulfate and pyritic sulfur 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NAS
31、A Technical Standards 1/9972545001 Not for Resale, 04/20/2007 02:28:13 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 157:1996(E) IS0 2.4 Procedure 2.4.2 Extraction 2.4.1 Test portion Take a test portion of the mass given in table 1 for the expected total sulfur conten
32、t, weighing to the nearest 0,l mg. Table 1 - Test portion Transfer the test portion to a 250 ml conical flask, add 50 ml of the dilute hydrochloric acid (2.2.2) and fit the cold-finger condenser (2.3.3) into the neck of the flask. Boil for 30 min. ensuring that a slow stream of water is passing thro
33、ugh the cold finger. Remove the condenser and thoroughly rinse back into the flask. Filter the mixture through a medium-textured, doubly acid-washed filter paper into a tall-form beaker. Wash the residue three times with the dilute hydrochloric acid (2.2.2) and a further three times with hot distill
34、ed water, using a total volume of approximately 30 ml. Retain the filtrate for the determination of sulfate sulfur (see Section 3). Immediately transfer the washed, undissolved residue and filter paper to a 250 ml conical flask, add 50 ml of the dilute nitric acid (2.2.3) and retain for the determin
35、ation of pyritic sulfur (see Section 4). Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 02:28:13 MDTNo reproduction or networking permitted without license from IHS -,-,- Q IS0
36、IS0 157:1996(E) Section 3: Determination of sulfate sulfur 3.1 Principle The sulfate sulfur extracted by dilute hydrochloric acid from the test portion is determined gravimetrically by precipitation with barium chloride. 3.2 Reagents WARNING - Care must be exercised when handling the reagents, many
37、of which are toxic and corrosive. During the analysis, unless otherwise stated, use only reagents of recognized analytical reagent grade and only distilled water or water of equivalent purity. 3.2.1 Hydrogen peroxide, solution, approximately 30 % (m/m). 3.2.2 Methyl red, indicator solution. Dissolve
38、 1 g of 2-(4-dimethylaminophenylazo)benzoic acid, sodium salt (methyl red) in 1 litre of water. 3.2.3 Ammonia, concentrated, solution not less than 25 % h/m). 3.2.4 Hydrochloric acid, concentrated, approxi- mately 36 % (m/m). 3.2.5 Potassium sulfate, approximately 2 g/l sol- ution. Dissolve approxim
39、ately 2 g of potassium sulfate in water and dilute to 1 litre. 3.2.6 Barium chloride, approximately 85 g/l sol- ution. Dissolve 100 g of barium chloride dihydrate in water and dilute to 1 litre. Filter before use through a close- textured, doubly acid-washed filter-paper or filter-pad. 3.2.7 Silver
40、nitrate, approximately I7 g/l solution. Dissolve 17 g of silver nitrate in water and dilute to 1 litre. Store in a dark glass bottle. 3.3 Apparatus 3.3.1 Analytical balance, capable of weighing to the nearest 0,l mg. 3.3.2 Graduated glassware, conforming to the requirements for class A in the Intern
41、ational Stan- dards prepared by lSO/TC 48. 3.3.3 Electrically-heated muffle furnace, capable of being maintained at 800 “C + 25 “C, with an adequate ventilation rate. 3.3.4 Crucible, of platinum, silica or glazed por- celain, of capacity approximately 25 ml. 3.3.5 Flat plate, 6 mm thick, of silica o
42、r other suit- able refractory material, which fits easily into the muffle furnace (3.3.3). 3.3.6 Gooch crucible, of glazed porcelain or sin- tered glass. 3.3.7 Air oven, capable of being maintained at a temperature of 130 “C + IO “C. 3.3.8 Filter cone, made of porcelain, of diameter 25 mm. 3.4 Proce
43、dure To the filtrate from the hydrochloric acid extraction (see 2.4.21, add 5 ml of the hydrogen peroxide sol- ution (3.2.1) and boil for 5 min to convert all the sol- uble iron to the + 3 oxidation state. While still hot, add 2 or 3 drops of the methyl red indicator solution (3.2.2) followed by the
44、 ammonia solution (3.2.31, drop by drop, until the solution is just alkaline (yellow colour) and then add a further 5 drops in excess. Filter the resultant precipitate on a toughened fast filter paper into a 250 ml beaker. Wash thoroughly with hot water, discarding the precipitate. Cautiously add th
45、e concentrated hydrochloric acid (3.2.4) to the filtrate, drop by drop, until the colour of the solution changes to pink and then add a further 1 ml in excess. The volume of the solution shall be between 150 ml and 250 ml. Add 25,0 ml of the potassium sulfate solution (3.2.5) from a one-mark pipette
46、. Cover the beaker with a watch glass, heat the covered beaker until the solu- tion boils and then reduce the heating slightly until ebullition ceases. Add 10 ml of the cold barium chlo- ride solution (3.2.6) from a pipette with a delivery time of approximately 20 s, held so that the barium chloride
47、 falls into the centre of the hot solution, whilst this is being agitated. Keep the solution just below boiling point, without agitation, for 30 min. Filter the solution using one of the following tech- niques. a) By gravity through an ashless, close-textured, doubly acid-washed filter paper of diam
48、eter 100 mm to 125 mm. Carefully fold the filter paper and fit it into a fluted, long-stemmed 60” funnel, so that the stem remains full of liquid during the filtration. 5 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 02:28:13 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 b) By gravity through a filter-paper pad prepared from ashless, doubly acid-washed filter paper. To prepare t