BS-ISO-7215-1995.pdf

BRITISH STANDARD BS ISO 7215:1995 Implementation of ISO 7215:1995 Iron ores Determination of relative reducibility Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 7215:1995 This British Standard, having been prepared under the direction of the Engineering Sector Board, was published under the authority of the Standards Board and comes into effect on 15 March 1996 © BSI 12-1999 The following BSI references relate to the work on this standard: Committee Reference ISE/58 Draft for comment 93/310937 DC ISBN 0 580 25499 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee ISE/58, Iron ores, upon which the following bodies were represented: British Iron and Steel Producers Association Institution of Mining and Metallurgy Co-opted Member Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 7215:1995 © BSI 12-1999i Contents Page Committees responsibleInside front cover National forewordii Forewordiii Text of ISO 72151 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 7215:1995 ii © BSI 12-1999 National foreword This British Standard reproduces verbatim ISO 7215:1995 and implements it as the UK national standard. This British Standard is published under the direction of the Engineering Sector Board whose Technical Committee ISE58 has the responsibility to: aid enquirers to understand the text; present to the responsible international committee any enquiries on interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. NOTEInternational and European Standards, as well as overseas standards, are available from Customer Services, BSI, 389 Chiswick High Road, London W4 4AL. A British Standard does not purport to 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, pages i and ii, the ISO title page, pages ii to iv, pages 1 to 7 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. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7215:1995(E) ii © BSI 12-1999 Contents Page Forewordiii Introduction1 1Scope1 2Normative references1 3Definitions1 4Principle1 5Reducing gas1 6Apparatus2 7Sampling and samples2 8Test conditions2 9Procedure3 10Expression of results3 11 Test report4 Annex A (informative) Derivation of the equation for final degree of reduction6 Annex B (informative) Bibliography7 Figure 1 Schematic diagram of reduction test apparatus4 Figure 2 Schematic diagram of reduction tube assembly5 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7215:1995(E) © BSI 12-1999iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work 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 represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO 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 voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 7215 was prepared by Technical Committee ISO/TC 102, Iron ores, Subcommittee SC 3, Physical testing. This second edition cancels and replaces the first edition (ISO 7215:1985), clauses 6, 7 and 9 of which have been technically revised. Annex A and Annex B of this International Standard are for information only. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7215:1995(E) © BSI 12-19991 Introduction The relative reducibility test method is one of several procedures used to evaluate the behaviour of natural and processed iron ores under specific conditions. The specific conditions involved in this test are: isothermal reduction; reduction in a fixed bed; reduction by means of carbon monoxide; a sample having a specified size range. The results of this test should be considered in conjunction with the results 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. 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 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 recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 2597-1:1994, Iron ores Determination of total iron content Part 1: Titrimetric method after tin(II) chloride reduction. ISO 3310-1:1990, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth. ISO 3310-2:1990, Test sieves Technical requirements and testing Part 2: Test sieves of perforated metal plate. ISO 9035:1989, Iron ores Determination of acid-soluble iron(II) content Titrimetric method. ISO 9507:1990, Iron ores Determination of total iron content Titanium(III) chloride reduction methods. ISO 9508:1990, Iron ores Determination of total iron content Silver reduction titrimetric method. ISO 10836:1994, Iron ores Method of sampling and sample preparation for physical testing. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 reducibility the ease with which oxygen combined with iron can be removed from natural or processed ores ISO 11323 3.2 degree of reduction the extent to which oxygen has been removed from iron oxides, expressed as the ratio of oxygen removed to oxygen originally combined with the iron 3.3 relative reducibility test an isothermal reduction 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 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 atmosphere. Calculation of the degree of reduction from the loss in mass and the total iron and iron(II) contents of the test sample. 5 Reducing gas Volumes and flow rates of gases used in this International Standard are measured at a temperature of 0 °C and at atmospheric pressure (101,325 kPa). 5.1 Composition The reducing gas shall consist of: 5.2 Purity Impurities in the reducing gas shall not exceed: Impurities in the heating gas (N2) shall not exceed 0,1 % (V/V). CO30 % (V/V) ± 1,0 % (V/V) N270 % (V/V) ± 1,0 % (V/V) H20,2 % (V/V) CO20,2 % (V/V) O20,1 % (V/V) H2O0,2 % (V/V) Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7215:1995(E) 2 © BSI 12-1999 6 Apparatus Ordinary laboratory equipment and 6.1 Test sieves, having square mesh apertures of the following nominal sizes and conforming to ISO 3310-1 or ISO 3310-2: 10,0 mm; 12,5 mm; 16,0 mm; 18,0 mm; 20,0 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) a reduction tube made of non-scaling, heat-resistant metal capable of withstanding a temperature greater than 910 °C and having an internal diameter of 75 mm ± 1 mm; b) a perforated plate made of non-scaling, heat-resistant metal capable of withstanding a temperature greater than 910 °C, mounted within 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; c) a frictionless connection between the gas supply and reduction tube which ensures linearity of weight loss determination; d) a device to connect the reduction tube to the weighing device; e) a 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 ±10 °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 The test sample shall be prepared in accordance with ISO 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 divided, extracting masses for the reserve sample, tumble 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 exceeds 30 kg. This sample shall be dried at 105 °C ± 5 °C, sieved on 12,5 mm and 10,0 mm test sieves, discarding the + 12,5 mm 10,0 mm fractions and retaining the 12,5 mm + 10,0 mm fraction. A minimum of 2,5 kg shall be used for the relative reducibility test sample. From the test sample, four test 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 dried at 105 °C ± 5 °C and then further divided. One sample (approximately 30 kg), to be used as the relative reducibility test sample, shall be sieved on 20,0 mm and 18,0 mm test sieves, discarding the + 20,0 mm 18,0 mm fraction. The 20,0 mm + 18,0 mm fraction shall be further divided using the increment division method to 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 determination of total iron content and iron(II) 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 l/min ± 0,5 l/min. 8.2 Temperature of test The reducing gas shall be preheated before entering the test portion to maintain the test portion at 900 °C ± 10 °C during the entire test period. Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 05:46:24 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 7215:1995(E) © BSI 12-19993 9 Procedure 9.1 Number of determinations Carry out the test in duplicate on one ore sample. 9.2 Other determinations Simultaneously with the test, determine the total iron content in accordance with ISO 2597, ISO 9507 or ISO 9508 and the iron(II) content in accordance with ISO 9035. 9.3 Test portion Weigh, to the nearest 1 g, approximately 500 g (± 1 particle) of the test sample (mass m0). 9.4 Reduction Place the test portion in the reduction tube such that the surface is even. 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 device (6.2.3), ensuring that there is no contact with the furnace or heating elements. Connect the gas supply. Pass a flow of N2 through the reduction tube at a flow rate of approximately 5 l/min and start heating. When the temperature of the test portion approaches 900 °C increase the flow rate to 15 l/min and continue heating at 900 °C for 30 min. Record the mass of the test portion (mass m0). Introduce the reducing gas to replace the N2 at a flow rate of 15 l/min. CAUTION Carbon monoxide and the reducing gas, which contains carbon monoxide, are toxic and therefore hazardous. During the following procedure, the testing 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 m2) and turn off the power. For safety reasons, introduce again, N2 at a flow rate of 5 l/min to replace the reducing gas in the tube. Maintain the N2 gas flow until the test portion is cooled to below 100 °C. NOTE 1If 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 two hours. NOTE 2In 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. NOTE 3If physical tests, such as crushing strength, are to be performed on the reduced test portion, the flow of N2 after reduction should be continued until the test portion reaches room temperature. 10 Expression of results 10.1 Calculation of degree of reduction The degree of reduction attained after 3 h (referred to as the final degree of reducti