BS 7312 specifies methods for the sampling and testing of magnetite for use in coal preparation. The test methods are intended primarily for the testing of milled magnetite, the largest particle size of which is usually less than 250 4m.
However, the tests are also applicable to unmilled magnetite with an upper particle size limit of about 500 4m.
Note: BS 7312 applies exclusively to the testing of magnetite and no attempt is made to recommend specific tests for the dense medium suspensions of which magnetite forms the solid phase.
BS 7312 on methods of test for magnetite for use in coal preparation is useful for:
The total moisture content of a consignment may be required for both commercial and safe shipment purposes. A knowledge of the total moisture content of samples prepared for laboratory analysis may also be required for subsequent conversion of the analytical results to the dry basis.
The total moisture content of a consignment is often required in order to comply with various maritime regulations as, when moisture is present in excess, it may result in stability problems during shipping.
The basic requirements for a material to be used in dense medium suspension are that it should be inert, have a high relative density and be easy to recover. In coal preparation, the mineral magnetite (FeO, Fe2O3) has become the most commonly used material, not only because it fulfils all the above criteria, but also because of its worldwide occurrence either as an iron ore or as a by-product of mining operations for other minerals. Like any mineral, magnetite rarely occurs in the pure state and the presence of gangue minerals may lower the relative density and affect the ferromagnetic properties.
These variations may seriously affect the efficiency of recovery operations and it is important when designing a coal preparation plant that the manufacturer of the magnetic separators be informed of the source of magnetite to be used and if possible be provided with a sample.
The purpose of BS 7312 is to provide a basis for the testing of magnetite for use in coal preparation. It is intended for use by contracting parties in the sale and purchase of magnetite and for coal preparation engineers engaged in the design and quality control fields.
The tests specified BS 7312 will assist the user in the selection of magnetite for use in dense medium suspension and provide a basis for quality control testing. No attempt is made to formulate the requirements for particular plant applications.
The tests specified in BS 7312 help ensure that the properties which make magnetite suitable for coal preparation purposes are simply and adequately tested.
These properties are
All the above tests may be required for the assessment of magnetite from a new source, but for routine checking of regular supplies, moisture, particle size distribution, total magnetics content and relative density should be sufficient.