ISO 4696-2:2015 pdf download – Iron ores for blast furnace feedstocks – Determination of low- temperature reduction-disintegration indices by static method
6.5 Tumble drum, made of steel, at least 5 mm thick, having an internal diameter of 130 mm and an inside length of 200 mm. Two equally spaced steel lifters (200 mm long, 20 mm high, and 2 mm thick) shall be mounted longitudinally inside the drum. These can be mounted on a frame that can be inserted inside the vessel from one end. One end of the drum shall be closed and the other open. A close-fitting lid shall be held in place on the opening to ensure a dust-tight seal. The drum shall be replaced in any case when the thickness of the vessel wall is reduced to 3 mm in any area, and the lifters when their height is reduced to less than 18 mm. Figure 3 shows an example of a tumble drum.
6.6 Rotation equipment, capable of ensuring that the drum attains full speed in one revolution, rotates at a constant speed of 30 r/min ± 1 r/min and stops within one revolution. The equipment shall be fitted with a revolution counter and with an automatic device for stopping the drum after a predetermined number of revolutions.
8.2 Reduction
Take, at random, one of the test portions prepared in 5.2. Place it in the reduction tube (6.2) and level its surface. NOTE In order to achieve a more uniform gas flow, a double-layer bed of porcelain balls can be placed between the perforated plate and the test portion. Close the top of the reduction tube. Connect the thermocouple, ensuring that its tip is in the centre of the test portion. Insert the reduction tube into the furnace (6.3). Connect the gas-supply system (6.4). Pass a flow of N 2 through the test portion at a rate of at least 5 L/min and commence heating. When the temperature of the test portion approaches 550 °C, increase the flow rate to 15 L/min. Continue heating while maintaining the flow of N 2 until the test portion reaches 550 °C ± 10 °C. Allow a period of 15 min for temperature equilibration at 550 °C. DANGER — Carbon monoxide and the reducing gas, which contains carbon monoxide, are toxic and therefore hazardous. Testing shall be carried out in a well-ventilated area or under a hood. Precautions should be taken for the safety of the operator, in accordance with the safety codes of each country. Introduce the reducing gas at a flow rate of 15 L/min ± 0,5 L/min to replace the N 2 . After 30 min of reduction, turn off the power. Replace the reducing gas with N 2 at a flow rate of 5 L/min and cool the test portion to a temperature below 100 °C.
8.4 Sieving
Remove all material from the drum, determine and record the mass and hand sieve with care on 2,8 mm sieve. Determine and record the mass retained on this sieve (m 1 ). Material lost during tumbling and sieving shall be considered to be part of the –2,8 mm fraction. NOTE Equivalent mechanical sieving can be used provided that preliminary test programme is carried out according to ISO 3086, being the hand sieving the reference method. Sieving results are influenced by the sieve shaker characteristics. Therefore, in cases in which two or more laboratories need to compare their results for commercial or research purposes, they should adjust the sieving conditions until they obtain identical results for the same test sample.