ISO 4695:2015 pdf free

ISO 4695:2015 pdf free.Iron ores for blast furnace feedstocks – Determination of the reducibility by the rate of reduction index
The test portion is isothermally reduced in a fixed bed, at 950 °C, using a reducing gas consisting of CO and N2, 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.
The test apparatus shall comprise the following:
a) ordinary laboratory equipment, such as an oven, hand tools, a time-control device and safety equipment;
b) reduction tube assembly;
c) furnace, equipped with a balance for permitting the mass loss of the test portion to be read at any time during the test;
d) system to supply the gases and regulate the flow rates;
e) weighing device.
Figure 1 shows an example of the test apparatus.
Reduction tube, made of non-scaling, heat-resistant metal to withstand temperatures higher than 950 °C and resistant to deformation. The internal diameter shall be 75 mm±1 mm. A removable perforated plate, made of non-scaling, heat-resistant metal to withstand temperatures higher than 950 °C, shall be mounted in the reduction tube to support the test portion and to ensure uniform gas flow through it. The perforated plate shall be 4 mm thick, with its diameter 1 mm less than the internal diameter of the tube. The holes in the plate shall be 2 mm to 3 mm in diameter at a pitch centre distance of 4 mm to 5 m.
Figure 2 shows an example of a reduction tube.
Take, at random, another portion prepared in 5.2 and record its mass (mo). 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 sized between 10,0 mm and 12,5 mm 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, as shown in Figure 1.
Insert the reduction tube into the furnace (6.3) and suspend it centrally from the balance (6.4) ensuring that there is no contact with the furnace wall or heating elements.ISO 4695 pdf free download.