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1、INTERNATIONAL STANDARD IS0 7215 Second edition 1995-l l-l 5 Iron ores - Determination of relative reducibility Minerais de fer - Determination de la rkductibilit6 relative Reference number IS0 7215:1995(E) Copyright International Organization for Standardization Provided by IHS under license with IS
2、O Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 22:03:33 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7215:1995(E) Foreword IS0 (the international Organization for Standardization) is a worldwide federation of national standards bodies (IS
3、0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, gove
4、rnmental and non-governmental, in liaison with KO, 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
5、 member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 7215 was prepared by Technical Committee lSO/rC 102, iron ores, Subcommittee SC 3, Physical testing. This second edition cancels and
6、replaces the first edition (IS0 7215:1985), clauses 6, 7 and 9 of which have been technically re- vised. Annexes A and B of this International Standard are for information only. 0 IS0 1995 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in a
7、ny form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case Postale 56 l CH-1211 Genbve 20 l Switzerland Printed in Switzerland ii Copyright International Organization f
8、or Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 22:03:33 MDTNo reproduction or networking permitted without license from IHS -,-,- I IS0 IS0 7215:1995(E) Introduction The relative reducibility test method is one of s
9、everal procedures used to evaluate the behaviour of natural and processed iron ores under specific conditions. The specific conditions involved in this test are: isothermal re- duction; reduction in a fixed bed; reduction by means of carbon monoxide; a sample having a specified size range. The resul
10、ts of this test should be considered in conjunction with the re- sults of other tests, particularly those showing the physical behaviour of materials during reduction. Annex A, giving mathematical derivations for formulae for relative reducibility, is included for information only. . . . III Copyrig
11、ht International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 22:03:33 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD 0 IS0 IS0 7215:1995(E) Iron ore
12、s - Determination of relative reducibility 1 Scope This International Standard specifies a method for determining the reducibility in relative terms of natural and processed iron ores. 2 Normative references The following standards contain provisions which, through reference in this text, constitute
13、 provisions of this International Standard. At the time of publi- cation, 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- cent editions of t
14、he standards indicated below. Members of IEC and IS0 maintain registers of cur- rently valid International Standards. IS0 2597-l :1994, Iron ores - Determination of total iron content - Part 1: Titrimetric method after tinM chloride reduction. IS0 3310-l :1990, Test sieves - Technical require- ments
15、 and testing - Part 1: Test sieves of metal wire cloth. IS0 33 1 O-2: 1990, Test sieves - Technical require- ments and testing - Part 2: Test sieves of perforated metal plate. IS0 9035:1989, Iron ores - Determination of acid- soluble iron(lll content - Titrimetric method. IS0 9507:1990, Iron ores -
16、Determination of total iron content - TitaniumfIll) chloride reduction meth- ods. IS0 9508:1990, Iron ores - Determination of total iron content - Silver reduction titrime tric method. IS0 10836:1994, iron ores - Method of sampling and sample preparation for physical testing. 3 Definitions For the p
17、urposes of this International Standard, the following definitions apply. 3.1 reducibility: The ease with which oxygen com- bined with iron can be removed from natural or pro- cessed ores. ISO 113231 3.2 degree of reduction: The extent to which oxy- gen has been removed from iron oxides, expressed as
18、 the ratio of oxygen removed to oxygen originally combined with the iron. 3.3 relative reducibility test: An isothermal re- duction test performed under specified conditions on a fixed bed of natural, processed or agglomerated ores to determine the final degree of reduction. 4 Principle Using carbon
19、 monoxide, isothermal reduction of the test portion placed on a balance in a fixed bed at 900 “C for 3 h. Heating and cooling in an inert atmos- phere. Calculation of the degree of reduction from the loss in mass and the total iron and iron contents of the test sample. 5 Reducing gas Volumes and flo
20、w rates of gases used in this Inter- national Standard are measured at a temperature of 0 “C and at atmospheric pressure (101,325 kPa). 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/
21、22/2007 22:03:33 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 7215:1995(E) 0 IS0 5.1 Composition d) a device to connect the reduction tube to the weighing device; The reducing gas shall consist of: co 30 % wvl f 1.0 % WN) N2 70 % (V/v) 12,5 mm; 16,O mm; 18.0 mm; 20,O
22、 mm 6.2 Electrically heated reduction furnace, with tube assembly, gas supply and flow rate regulating system (see figure 1). and equipped with a balance permitting the oxygen loss of the sample to be read at any time during the test. 6.2.1 The tube assembly (see figure 2) shall consist Of: a) b) c)
23、 a reduction tube made of non-scaling, heat- resistant metal capable of withstanding a tem- perature greater than 910 “C and having an internal diameter of 75 mm a perforated plate made of non-scaling, heat- resistant metal capable of withstanding a tem- perature greater than.910 “C, mounted within
24、the reduction tube to support the test portion; the plate shall be 4 mm thick; the holes shall be 2 mm to 3 mm in diameter and the pitch between holes shall be 4 mm to 5 mm; a frictionless connection between the gas supply and reduction tube which ensures linearity of weight loss determination; e) a
25、 heat exchange medium, for example alumina balls, placed in the bottom under the perforated plate of the reduction tube, to a depth of 100 mm, to preheat the gas. 6.2.2 The furnace, shall have a heating capacity sufficient to maintain the entire test portion and the gas entering the bed at 900 “C f
26、IO “C. 6.2.3 The weighing device, shall be capable of weighing the reduction tube assembly, including the test portion, to an accuracy of 0,5 g. The weighing device shall be checked for accuracy and sensitivity at regular intervals. 7 Sampling and samples 7.1 Sample for relative reducibility test Th
27、e test sample shall be prepared in accordance with IS0 10836. A quantity of sample sufficient to provide at least five 500 g portions shall be prepared. The sample shall be oven dried at 105 “C * 5 “C to constant mass. The gross sample taken for testing is repeatedly div- ided, extracting masses for
28、 the reserve sample, tum- ble test sample, etc., until a stage is reached where the mass retained just exceeds the minimum required for the preparation of the test sample for relative reducibility. 7.1.1 Pellets The division of the gross sample by riffle shall proceed until the mass retained just ex
29、ceeds 30 kg. This sample shall be dried at 105 “C f 5 “C, sieved on 12,5 mm and 10,O mm test sieves, discarding the + 12,5 mm - 10,O mm fractions and retaining the - 12,5 mm + 10,O mm fraction. A minimum of 2,5 kg shall be used for the relative reducibility test sample. From the test sample, four te
30、st portions and one chemical analysis sample, each having a mass of 0.5 kg shall be obtained. 7.1.2 Sinters and ores The size fraction required is - 20.0 mm + 18.0 mm to be obtained by increment division. One 62.5 kg sample is set aside as the reserve sample and the other 62.5 kg sample shall be dri
31、ed at 105 “C f 5 “C and then further divided. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 22:03:33 MDTNo reproduction or networking permitted without license from IHS -,-,- Q
32、 IS0 IS0 7215:1995(E) One sample (approximately 30 kg), to be used as the relative reducibility test sample, shall be sieved on 20,O mm and 18,0 mm test sieves, discarding the +20,0 mm - 160 mm fraction. The - 20,O mm + 18.0 mm fraction shall be further divided using the increment division method to
33、 give a minimum of 2.5 kg for the relative reducibility test sample. From this test sample, four test portions and one chemical analysis sample, each having a mass of 0,5 kg shall be prepared. 7.2 Sample for chemical analysis A 500 g test portion shall be reserved for the deter- mination of total ir
34、on content and iron content. 8 Test conditions 8.1 Flow rate of reducing gas The reducing gas (clause 5) flow rate shall, during the test period, be maintained at 15 I/min + 0,5 I/min. 8.2 Temperature of test The reducing gas shall be preheated before entering the test portion to maintain the test p
35、ortion at 900 “C + 10 “C during the entire test period. Close the top of the reduction tube (6.2.1) ensuring that the thermocouple is at the central position of the test portion. Insert the reduction tube into the furnace (6.2) and suspend it centrally from the weighing de- vice (6.2.3), ensuring th
36、at there is no contact with the furnace or heating elements. Connect the gas supply. Pass a flow of N, through the reduction tube at a flow rate of approximately 5 I/min and start heating. When the temperature of the test portion approaches 900 “C increase the flow rate to 15 l/min and continue heat
37、ing at 900 “C for 30 min. Record the mass of the test portion (mass m,). Introduce the reducing gas to replace the N, at a flow rate of 15 I/min. CAUTION - Carbon monoxide and the reducing gas, which contains carbon monoxide, are toxic and therefore hazardous. During the following procedure, the tes
38、ting shall be carried out in a well ventilated area or under a hood. Precautions, according to the safety codes of each country, should be taken for the safety of the operator. At the end of 3 h of reduction, determine the mass of the test portion (mass 5) and turn off the power. For safety reasons,
39、 introduce again, N2 at a flow rate of 5 I/min to replace the reducing gas in the tube. Maintain the N, gas flow until the test portion is cooled to below 100 “C. NOTES 9 Procedure 9.1 Number of determinations Carry out the test in duplicate on one ore sample. 9.2 Other determinations Simultaneously
40、 with the test, determine the total iron content in accordance with IS0 2597, IS0 9507 or IS0 9508 and the iron content in accordance with IS0 9035. 1 If reduction versus time curves are required, record the mass of the test portion every 10 min during the first hour and every 15 min during the last
41、 two hours. 2 In the case of lump ores, the temperature of the test portion should be raised to 900 “C over more than 60 min to reduce decrepitation of the lump ore. 3 If physical tests, such as crushing strength, are to be performed on the reduced test portion, the flow of N2 after reduction should
42、 be continued until the test portion reaches room temperature. 10 Expression of results 9.3 Test portion Weigh, to the nearest 1 g, approximately 500 g ( ml is the mass, in grams, of the test portion immediately before starting the reduction; m;! is the mass, in grams, of the test portion after 3 h
43、of reduction; w1 is the iron oxide content, as a percent- age by mass, of the test sample prior to the test and is calculated from the iron content by multiplying by a factor of 1,286, determined in accordance with IS0 9035; Y is the total iron content, as a percentage by mass, of the test sample pr
44、ior to the test, determined in accordance with IS0 2597, IS0 9507 or IS0 9508. Record the final degree of reduction to one place of decimals. 10.2 Number of tests and repeatability 10.2.1 Number of tests The reduction test shall be carried out in duplicate. If the difference between the paired resul
45、ts of Rf meets the repeatability limit given in 10.2.2, the test is ter- minated, if not, another duplicate test shall be carried out. 10.2.2 Repeatability For a paired result, the difference between the two individual results shall be less than 3 % absolute for pellets and less than 5 % absolute fo
46、r sinter. NOTE 4 A repeatability limit for lump ore is not specified, because of the inherent heterogeneity, which varies for dif- ferent ores. 10.3 CalcuIation of final results The final degree of reduction, Rf, expressed as a per- centage, shall be reported as the arithmetic mean of all test resul
47、ts, rounded to the nearest whole number. 11 Test report The test report shall include the following information: a) reference to this International Standard; b) description of the test sample; c) number of tests and final degree or reduction, R,; d) total iron and iron contents of the test sample; e
48、) type of sieve used. 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 22:03:33 MDTNo reproduction or networking permitted without license from IHS -,-,- J IS0 IS0 7215:1995(E)
49、Exit gas Test portion Heat exchange medium L Reducing gas Inert gas I Flow meter 1 ) Flow meter ) 1 1 1 y -+-I Pressure gauge inLet, Electric furnace Figure 1 - Schematic diagram of reduction test apparatus 5 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technica