BS ISO 4695:2021 pdf download – Iron ores for blast furnace feedstocks — Determination of the reducibility by the rate of reduction index
This document specifies a method to provide a relative measure for evaluating the extent to and ease with which oxygen can be removed from iron ores, when reduced under conditions resembling those prevailing in the reduction zone of a blast furnace.
This document is applicable to lump ores, sinters and hot-bonded pellets.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2597-1, Iron ores — Determination of total iron content — Part 1: Titrimetric method after tin(II) chloride reduction
ISO 2597-2, Iron ores — Determination of total iron content — Part 2: Titrimetric methods after titanium(III) chloride reduction
ISO 3082, Iron ores — Sampling and sample preparation procedures
ISO 9035, Iron ores — Determination of acid-soluble iron(II) content — Titrimetric method
ISO 11323, Iron ore and direct reduced iron — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11323 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
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4 Principle
The test portion is isothermally reduced in a fixed bed, at 950 °C, using a reducing gas consisting of CO and N 2 , and the mass loss of the test portion is recorded continuously or at specified time intervals until its degree of reduction reaches 65 %. The rate of reduction is calculated at the oxygen/iron ratio of 0,9.
6.3 Furnace, having a heating capacity and temperature control able to maintain the entire test portion, as well as the gas entering the bed, at 950 °C ± 10 °C.
6.4 Balance, capable of weighing the reduction tube assembly, including the test portion, to an accuracy of 1 g. The balance shall have an appropriate device to suspend the reduction tube assembly.
6.5 Gas-supply system, capable of supplying the gases and regulating gas flow rates. It shall be ensured that a frictionless connection between the gas-supply system and the reduction tube does not
affect the weight loss determination during reduction.
6.6 Weighing device, capable of weighing the test sample and test portions to an accuracy of 1 g.
7 Test conditions
7.1 General
Volumes and flow rates of gases used are as measured at a reference temperature of 0 °C and at a reference atmospheric pressure of 101,325 kPa (1,013 25 bar).
7.2 Reducing gas
7.2.1 Composition
The reducing gas shall consist of
CO 40,0 % ± 0,5 % (volume fraction)
N 2 60,0 % ± 0,5 % (volume fraction)
7.2.2 Purity
Impurities in the reducing gas shall not exceed the following:
H 2 0,2 % (volume fraction)
CO 2 0,2 % (volume fraction)
O 2 0,1 % (volume fraction)
H 2 O 0,2 % (volume fraction)
7.2.3 Flow rate
The flow rate of the reducing gas, during the entire reducing period, shall be maintained at 50 l/min ± 0,5 l/min.
7.3 Heating and cooling gas
Nitrogen (N 2 ) shall be used as the heating and cooling gas. Impurities shall not exceed 0,1 % (volume fraction).
The flow rate of N 2 shall be maintained at 25 l/min until the test portion reaches 950 °C, and at 50 l/min during the temperature-equilibration period. During cooling, it shall be maintained at 5 l/min.
7.4 Temperature of the test portion
The temperature of the entire test portion shall be maintained at 950 °C ± 10 °C during the entire reducing period and, as such, the reducing gas shall be preheated before entering the test portion.
8 Procedure
8.1 Number of determinations for the test
Carry out the test as many times as required by the procedure in Annex A.
8.2 Chemical analysis
Take, at random, one of the test portions prepared in 5.2 and use it for the determination of the iron(II) oxide content (w 1 ) in accordance with ISO 9035 and the total iron content (w 2 ) in accordance with ISO 2597-1 or ISO 2597-2.BS ISO 4695 pdf download.