ISO 4701:2019 pdf free.Iron ores and direct reduced iron-Determination of size distribution by sieving.
4 Principles and planning
4.1 General
The determination of size distribution of iron ores and direct reduced iron (DRI) may be carried out on a “dry” or “natural” (or “as-received”) basis. Before a particle size determination is carried out, it is necessary to plan the entire sequence of procedures to be followed.
The basis for determination and the sequence of procedures will depend on the following:
a) the purpose of the size analysis;
b) the properties of the iron ore and DRI to be evaluated;
c) the form in which the iron ore and DRI is received, e.g. gross sample, increments or partial samples;
d) the apparatus available.
A typical decision tree to determine the sequence of procedures necessary to perform size analysis is shown in Figure 1. The guidelines for practical application of this document are provided in Annex A. General principles of sieving are given in ISO 2591-1.
4.2 Purpose of the analysis
The principal purposes of particle size determination are as follows.
a) To measure the mass and calculate the percentage mass of an ore or DRI passing or retained on one or more specification sieves.
The choice of sieve aperture sizes shall be determined by the specification size(s) required together with the necessity for introducing intermediate aperture sizes to satisfy the maximum particle size and sieve loading constraints. See 4 and 42.
b) To generate an overall size distribution curve.
The choice of sieve apertures will depend on the resolution required for the curve and the need to satisfy sieve loading constraints.
4.3 Impact of ore and DRI properties
4.3.1 Effect of moisture content
The effect of the moisture content of the size sample on sample division and sieving should be assessed before the commencement of the size determination procedure.
When it is difficult to conduct sample division due to sample being adhesive or excessively wet, the sample shall be dried to constant mass in accordance with 71.
Partial drying of a sample for the purpose of size distribution analysis is not acceptable, as residual moisture might affect the effective separation of the individual size fractions.
4.3.2 Degradation of material
Certain iron ores, particularly lump ore, and DRI can be subject to significant degradation during the sampling and size analysis sequences. Furthermore, different sampling and size analysis processes can cause degradation of ores and DRI to different extents. Consequently, this could lead to significant variation in results for the same lot.
It is therefore essential that any degradation should be minimized through the correct design of handling, sampling and size analysis systems.
Sampling systems should be designed in accordance with the guidelines set out in ISO 3082 and
ISO 10835.
4.3.3 Magnetic ores
For iron ores with pronounced magnetic properties and DRI that has been handled by magnets, it is desirable to ensure that the size sample be demagnetized or that the sieves are non-magnetic.
4.4 Nature of sample
The sample may be received in the form of a gross sample, several partial samples or increments. The procedures for sampling of iron ores and direct reduced iron (see Iso 3082 and ISO 10835) will generally provide quantities of material in excess of the requirements for sieving.
lilt is undesirable to sieve the entire mass, division of the following is permissible:
a) gross sample; b) partial samples; c) increments; d) fractions obtained during sieving.
Methods governing the division and the mass of sample to be sieved are provided in Clause 6.ISO 4701 pdf dwonload.