Method for Monitoring the Efficiency of Raw Material Beneficiation Apparatus

In the beneficiation of raw materials such as various ores and coal it is known to employ a float-sink classification process and apparatus wherein separation of usable material, such as coal from rock and other heavier refuse mateials, is achieved by gravity separation. In operations of this type in the well known manner there is provided a bath which is usually water or water mixed with sand or finely ground magnetite, and the raw material in particle form is introduced to the surface of this bath. In the case of coal, which could have a specific gravity of separation of approximately 1.60, the coal will float on the water and the rock and other refuse materials will sink. Although various adjustments may be made to equipment of this type to alter the separating action, such as varying the pulp density of the said material, varying the quantity of the water and raising or lowering wiers, it is difficult to obtain an objective basis for making any such changes. Hence, the efficiency of float-sink separation operations is generally poor.

It is accordingly an object of the present invention to provide a method for monitoring the separating efficiency of float-sink separation apparatus on a continuous basis so that changes may be made to the equipment to improve the efficiency of separation. This is achieved in an efficient and economical manner.

Broadly in the practice of the invention application thereof is made to any float-sink separation process and apparatus for specific gravity separation of raw materials in particulate form, such as coal. Further, it is applicable to any said apparatus or process wherein the raw material in particulate form is introduced for separation into a liquid bath such as water and wherein the particles are separated within the liquid bath in accordance with the specific gravity of the particles, with particles of relatively higher specific gravity sinking within the liquid bath and particles with relatively lower specific gravity floating within said bath. In the case of coal it is the material to be recovered that will float since coal has a lower specific gravity than the refuse material with which it is mingled. It is to be understood, however, that the invention is also applicable to the float-sink separation of material such as various ores, wherein the material to be recovered is heavier than the associated refuse material, and thus the material to be recovered would sink in the liquid bath with the refuse material floating.

In accordance with the invention prepared particles are provided for introduction to the bath with the raw material particles to be separated. The prepared particles are of known and determined size and specific gravity. They are introduced individually with the particulate raw material to be separated and these prepared particles are detected at one or more of the separation locations of the sink-float classification apparatus. By determining the total number of detected prepared particles at each detection and separation location and dividing said total number by the total number of prepared particles introduced to the bath it is possible to achieve a determination with respect to the efficiency of separation of a particular float-sink classification unit.

Preferably the prepared particles of determined size and specific gravity would be within consecutive specific gravity ranges or limits. In the case of coal, for example, a known number of prepared particles with the specific gravity ranges of 1.30 to 1.32, 1.40 to 1.42, 1.50 to 1.52 and so forth could be provided. In this manner, by dividing the total number of prepared particles detected within each specific gravity range at a given separation location by the total number of prepared particles introduced for each said specific gravity range a fraction related to the separation efficiency of material within each specific gravity range can be obtained for each collection or separation location. By plotting each fraction for each specific gravity range against the average specific gravity of said range, e.g. mid-point, a series of points may be obtained and plotted for all of the ranges to result in a "partition curve" (Tromp curve). This partition curve will represent a percentage of the partition distribution that is in error from the particular specific gravity, sink-float separation being monitored.

In the preferred practice of the method of the invention in monitoring a conventional float-sink coal separation operation, the apparatus to which the method is applied would have two separation locations. The "clean separation" would constitute the float coal product to be recovered and the "tailings separation" which would constitute the heavier refuse material such as rock. A device for detecting prepared particles would be provided at each of the two collection and separation locations. During the operation of the separation apparatus and while the particles of raw material are being introduced thereto for separation a single prepared particle within one of the specific gravity ranges as described hereinabove would be introduced with the material for separation. When the prepared particle passes through the apparatus and is detected by one of the detectors, the separation location at which it is detected is recorded, as well as its specific gravity. A second prepared particle is then introduced and this sequence is repeated by sequentially introducing prepared particles to the apparatus until information sufficient to construct a partition curve is obtained.

The prepared particles are provided with means for actuating detection devices located at at least one separation location in the sink-float classification unit to be monitored and preferably at each location. For this purpose radiation producing or magnetic field producing material and the like may be introduced to the particles and a suitable detector provided. Any conventional material emitting a detectable substance or providing otherwise for detection may be used in accordance with the invention, and the detecting mechanism does not constitute a part of the invention. Furthermore, the prepared particles may be simulated particles rather than actual particles of the material being separated by the particular float-sink classification unit. More specifically, in the float-sink separation of coal, the prepared particles for detection may be coated with a radioactive substance, such as technetium (Tc), and detection thereof would be achieved by the use of a conventional Geiger counter provided at each separation location where detection of prepared particles is desired. Technetium is a fission product of uranium not occurring in nature. It is obtained by the extraction of neutron-irradiated molybdenum in methyl ethyl ketone.