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GB/T 13241-2017 English PDF (GBT13241-2017)

GB/T 13241-2017 English PDF (GBT13241-2017)

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GB/T 13241-2017: Iron ores -- Determination of reducibility

This Standard specifies the test conditions, test equipment, specimen preparation, test steps, result calculation and test report for determination of reducibility of iron ores. This Method is applicable to the determination of the reducibility of iron ores (including natural iron ore, sintered ore, pellet ore, hereinafter referred to as iron ore) expressed in terms of reduction degree and reduction rate.
GB/T 13241-2017
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 73.060.10
D 31
Replacing GB/T 13241-1991
Iron ores - Determination of reducibility
ISSUED ON: SEPTEMBER 07, 2017
IMPLEMENTED ON: JUNE 01, 2018
Issued by: General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 5
4 Principle ... 5
5 Test conditions ... 6
6 Test equipment ... 6
7 Specimen preparation ... 10
8 Test steps ... 10
9 Result calculation ... 12
10 Test report ... 14
Annex A (informative) Carbon monoxide generator ... 16
Annex B (informative) Deduction of reduction formula ... 19
Annex C (normative) Repeatability and test times ... 21
Iron ores - Determination of reducibility
WARNING - The use of this Standard may involve certain hazardous
materials, operations, and equipment, but does not make
recommendations for all safety issues related to this. Before using this Standard, users are responsible for adopting appropriate safety and
protection measures and ensuring that they meet the conditions
stipulated by relevant national regulations.
1 Scope
This Standard specifies the test conditions, test equipment, specimen
preparation, test steps, result calculation and test report for determination of reducibility of iron ores.
NOTE: The characteristics of the specified test method are: In a fixed bed, use a mixed gas of CO and N2 to conduct isothermal reduction. The specimen has a certain size range. This Method is applicable to the determination of the reducibility of iron ores (including natural iron ore, sintered ore, pellet ore, hereinafter referred to as iron ore) expressed in terms of reduction degree and reduction rate.
2 Normative references
The following referenced documents are indispensable for the application 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.
GB/T 6003.1, Test sieves - Technical requirements and testing - Part 1: Test sieves of metal wire cloth
GB/T 6003.2, Test Sieves - Technical Requirements and Testing - Part 2: Test Sieves of Perforated Metal Plate
GB/T 6005, Test sieves - Metal wire cloth perforated metal plate and
electroformed sheet - Nominal sizes of openings
GB/T 6730.5, Iron ores - Determination of total iron content - Titanium (III) chloride reduction methods
GB/T 6730.8, Iron ores - Determination of iron (II) content - Potassium dichromate titrimetric method
5 Test conditions
5.1 General conditions
The gas volume and flow rate used in this Standard adopt the volume and flow rate in the standard state (0??C and 101.325kPa).
5.2 Reducing gas composition (volume fraction)
CO: 30%??0.5%
N2: 70%??0.5%
5.3 Purity of reducing gas (volume fraction)
CO???99.9%
N2???99.99%
5.4 Reduction gas flow
During the whole test period, the standard flow rate of the reducing gas shall be maintained at 15L/min??0.5L/min.
5.5 Test temperature
The iron ore sample is subjected to isothermal reduction at 900??C. During the entire test, the temperature of the gas entering the material layer is maintained at 900??C??5??C.
6 Test equipment
6.1 Gas purification and configuration system
The gas purification and configuration system include:
a) N2 mass flow controller: range is 20L/min, accuracy is not less than ??1.5%F.S.
b) CO mass flow controller: range is 5L/min, accuracy is not less than
??1.5%F.S.
c) Gas washing + gas distribution chamber volume: ???5L. (When the CO
generator is used to generate CO, the CO purification system is excluded.) The mass flow controller is calibrated at least once a year. Where there is no bottled CO, it can refer to the CO generator and purification system in Annex A 6.6.5 Counting machine: particle size range ??10.0mm~??12.5mm.
7 Specimen preparation
7.1 Sampling and preparation
Test specimen shall be sampled and prepared in accordance with the
provisions of GB/T 10322.1. Test specimen shall be dried at 105??C??5??C. Drying time is not less than 2h, then cooled to room temperature and stored in a desiccator.
7.2 Specimen for reduction test
7.2.1 Total amount of specimen
The total amount of test specimen is not less than 2.5kg, calculated on a dry basis.
7.2.2 Pellet mine
The specimen with a particle size range of 10.0mm~12.5mm obtained by
screening is not less than 2.5kg.
7.2.3 Natural iron ore and sinter
Sieve out specimens larger than 12.5mm. And carefully break the part larger than 12.5mm. Until all passes the 16.0mm sieve. Then combine the parts for screening. Screen out the parts larger than 12.5mm and less than 10.0mm from specimens. Then mix the obtained 10.0mm~12.5mm specimen. Ensure that the specimen of 10.0mm~12.5mm is not less than 2.5kg.
7.3 Division of test material
The specimen is divided into 4 parts by a divider. Take 100g of each part and mix them into a specimen, about 400g, as the specimen for measuring TFe and FeO. The rest are kept in separate seals and used as reducibility test
specimens.
8 Test steps
8.1 Experiment determination times
For the same specimen, it shall at least conduct the test twice.
8.2 Amount of test material
7 - Reducing gas regulator;
8 - Flowmeter;
9 - System control cabinet;
10 - Three-point temperature control thermocouple;
11 - Thermogravimetric balance;
12 - Lower heating section;
13 - Middle heating section;
14 - Upper heating section;
15 - Reduction furnace body;
16 - Electric lifting mechanism;
17 - Reaction tube.
Figure 4 -- Process flow chart of iron ore medium temperature reduction experiment
8.3.2 The reduction furnace starts to heat up. Heating rate shall not be greater than 10??C/min. At 200??C ~900??C, it is protected by nitrogen and the flow rate is 5L/min. At 900??C, increase the nitrogen flow to 15L/min. At a constant
temperature 30min. Weigh the total mass of the test material and reduction tube, to the nearest of 0.1g. Record as m1. Then, replace the protective nitrogen with 15L/min??0.5L/min reducing gas and reduce it for 180min. Use
thermogravimetric balance to continuously record the total mass of test material and reduction tube during the reduction process, to the nearest of 0.1. Record as mt. During the reduction process, ensure that the temperature of the gas entering the test material layer and the overall temperature of the test material layer are kept within 900??C??5??C.
8.3.3 After the reduction is completed, cut off the reducing gas. Access with nitrogen at a flowrate of 15L/min. Eliminate reducing gas in test equipment pipeline and reaction tube. After 5min, turn off the nitrogen, the reduction tube comes out, and the test is over.
9 Result calculation
9.1 Calculation of degree of reduction degree
Use formula (1) to calculate the degree of reduction Rt at time t. When calculating Rt, t is 180min. Based on the state of trivalent iron, express in mass fraction (%).
Where,
K - Constant that depends on y (%). When y is 50%, K = 20.0; when y is 55%, K = 26.5.
NOTE 1: Atomic ratio O/Fe=0.9, equivalent to a reduction degree of 40%. NOTE 2: See Annex B for the derivation of the formula.
9.3 Tolerance and test times
Tolerance of reduction index RI: For a pair of test results, the difference between the two results, not more than 5% (absolute value) for sintered ore, not more than 3% (absolute value) for pellet ore and the one for natural ore shall be agreed between the supplier and the purchaser. If the difference between the two results is within the above range, the test can be ended. If it is not within the above range, it shall be carried out according to the procedures specified in Annex C.
9.4 Expression of final results
The reduction index RI shall be reported according to the average number of experimental results as specified in Annex C, in %, to the nearest of one decimal place, rounded off according to GB/T 8170.
The value of the test result of reduction velocity index RVI is consistent with the value of reduction index RI and shall be reported by its average, in %/min, to the nearest of 0.01%/min.
Use the 3h reduction index RI as the evaluation index, the reduction velocity index RVI as a reference index.
10 Test report
The test results of this Standard shall be considered in conjunction with other tests, especially those indicating other metallurgical properties of iron ore during reduction. The test report shall contain the following information:
a) Test organization;
b) Date of test report;
c) Reference to this Standard;
d) Specimen description (including total iron and ferrous content before reduction);
e) Test material mass and number of particles;
Annex A
(informative)
Carbon monoxide generator
WARNING - Carbon monoxide is a colorless and odorless toxic gas that
can harm the human body. When using a carbon monoxide generator in
this experiment, carbon monoxide shall be used with production, and
storage is not allowed. After use, the test equipment and pipelines must be cleaned with nitrogen or air. Carbon monoxide alarm shall be installed indoors. The test is conducted in an environment with good ventilation. Indoor carbon monoxide concentration is not allowed to exceed 50??10-6.
A.1 Principle
Load charcoal into the metal reactor. Heat to 900??C and access with nitrogen. Through retorting, the charcoal is dehydrated, dehydrogenated and other volatiles are removed. Then access with CO2 gas. React with charcoal to produce CO gas.
A.2 Raw material
N2, CO2, charcoal;
N2: purity 99.99%;
CO2: purity 99.5%;
Charcoal: ash content is ???5.0%; fixed carbon is ???70%; particle less than 10mm is ???10%.
A.3 Equipment
The process flow chart of the CO generator is shown in Figure A.1, including: a) Reaction tank:
Material is GH3044, with soda separator.
b) Heating furnace:
Working temperature: 1000??C.
c) Temperature control device:
Temperature control range: room temperature to 1000??C.
16 - Gas mixing tank;
17 - Switching valve;
18 - CO exit;
19 - Evacuation exit.
Figure A.1 -- Flow chart of CO generator
A.4 CO occurrence steps
A.4.1 Charcoal retorting
CO generator starts. At 200??C, access with nitrogen at a flow rate of 5L/min into the furnace. When it is heated to 950??C, start isothermal retorting, to remove water and volatiles from charcoal. After a constant temperature of 60min, stop the dry distillation process.
A.4.2 CO generation, scrubbing and gas distribution
Access with 2.25L/min??0.01L/min CO2 into the furnace. After dehydration, CO2 removal, and dust removal, CO enters the CO flow detector. By adjusting the CO2 flow, the CO flow can reach 4.50L/min??0.01L/min. CO gas enters the mixer and mixes with N2 (10.5L/min??0.01L/min). The test starts.
A.4.3 Gas line cleaning
After the test, CO2 is switched to N2, and the flow rate is 5L/min. Drain the CO in the reaction tank, pipeline and scrubbing system then the test is over.

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