DEVELOPMENT AND COMMERCIAL TEST OF SLON-O 00 VERTICAL RING AND PULSATING HIGH-GRADIENT MAGNETIC SEPARATOR

Slon-2000 vertical ring and pulsating high-gradient magnetic separator is an efficient industrial equipment for processing weakly magnetic minerals. It has been recently developed at the Ganzhou Non-Ferrous Metallurgy Research Institute. A six-month commercial testwork to process low-grade hematite ore was completed in Chong Changeling Mineral Processing Plant in 1995. compared with WHIMS-2000 wet high-intensity magnetic separator, the grade of the concentrate is by 7.21% higher t_he grade of the railings lower by 5.41% and the iron recovery higher by 7.36%. Particularly, the matrix is always clean so that the matrix clogging usual in the WHIMS 2000 machine has been overcome.


INTRODUCTION
As the mining scale of oxidised iron ore increases and reserves of rich iron ores decreases, the minerals processing industry is facing problems with treating low-grade and finely disseminated oxidised iron ores. High-intensity magnetic separation has a very important position in the processing of oxidised iron ore. Unfortunately, most high-intensity magnetic separators face a problem of matrix clogging. 90

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Such a problem is, for instance, serious in processing in beneficiation of the hematite ore in Gong Changeling Mineral Processing Plant of Anshan Iron and Steel Company. The grade of the mined ore was about 30% Fe in 1980s and has dropped to about 28% Fe in 1990s, with annual rate of decrease of about 0.2% Fe.
There are five wet high-intensity magnetic separator installed at the plant. Their ring diameter is 2000 mm (WHIMS-2000), with grooved plates as matrix. The separators are used as roughers for 2 mm hematite. Because the feed contains many coarse particles and some strongly magnetic particles such as magnetite and maghemite, the matrix can be very easily clogged. This happens even when the gaps between the grooved plates is set to 3.5 mm which results in unstable beneficiation results and in demanding maintenance.
In order to solve these problems, a contract was signed between Gong Changeling Mining Company and Ganzhou Nonferrous Metallurgy Research Institute (GNMRI). It was agreed that GNMRI designs and builds SLon-,O00 Vertical Ring and Pulsating High-Gradient Magnetic Separator. It was also agreed that GNMRI delivers the separator to Gong Changeling Mineral Processing Plant in order to carry out commercial tests for a period of six months. The aim of the tests was to compare the results with those obtained with WHIMS-2000. The target of the testwork was that SLon-$O00 must eliminate the matrix clogging and that the grade of the railings must be lower by 2% than the railings produced by WHIMS-2000.

STRUCTURE AND PRINCIPLES OF OPERATION OF SLON-P,O00
SLon-2000 magnetic separator consists of the pulsating mechanism, the energising coil, magnetic yoke separating ring, the feed and product boxes, as is shown in Fig.  1. Its operating principles are as follows: while the direct electric current flows through the energising coil, a magnetic field is built in the separating zone. Stainless steel 5 mm rods were used as a matrix in these commercial tests.
The ring with the magnetic matrix rotates around its horizontal axis. A slurry fed from the feed box enters the matrix located in the separating zone. Magnetic SLon-O00 vertical-ring and pulsating high-gradient magnetic separator brought to the top of the ring where the magnetic field is negligible. Magnetic particles are then flushed into the concentrate box. The non-magnetic particles pass through the matrix and enter the railings box under the combined force of the slurry pulsation, gravity and hydrodynamic drag.
Since the ring rotates in the vertical plane, direction of the flush is opposite to that of the feed, relative to each segment of the matrix. The pulsating mechanism drives the slurry in the separating zone up and down keeping particles in the matrix section in a loose state at the time. Magnetic particles can thus be more easily captured by the matrix and the non-magnetic particles can can be more easily dragged to the tailings box through the segment of the matrix.
Therefore, the opposite flushing and pulsation help to prevent the matrix dogging, and the pulsation help to purify the magnetic product. These measures guarantee 92 XIONG DAHE that the SLon-2000 separator possesses an advantage of higher ratio of beneficiation, higher efficiency and considerable flexibility. The main specifications of the SLon-$O00 separator and the plant operational data in this commercial testwork are summarised in Table 1. The electrical and magnetic specifications are listed in Table 2.  iron minerals is mainly from 0.037 mm to 0.125 mm, and the average size of quartz is about 0.13 mm. The grade of the mined ore is about 28.4% Fe.
As the mined ore contains low percentage of iron it is very important to discard as much gangue as possible, and as early in the process as possible. Since it contains very low concentrations of harmful elements, it is relatively easy to use magnetic and gravity methods to concentrate the iron minerals. Schematic diagram of the hematite beneficiation is shown in Fig. 2    As the background magnetic field increases, the recovery of iron increases while the grades of the mags and the railings decrease. Reasonable background magnetic field is 0.85 T for this type of an ore, and the corresponding energising current is  Table 5 shows that the slurry pulsation increases the grade of the mags by 4.84% Fe, and reduces both the grade of the railings by 0.36% and the mass of the mags by 8.22%, compared to a situation when no pulsation was used in the same SLon-2000 separator. The fact the the recovery with pulsation is slightly lower is a results of the fact that the grade of the mags is higher. The throughput tests demonstrated that the SLon-2000 separator can treat up to about 100 tons per hour of such a hematite ore, as can be seen in Table 6. To get better railings and consider its tonnage, it is more advantageous to set the throughput to 60 to 70 tons per hour.

Comparison Tests with WHIMS-2000
During the commercial tests the SLon-,O00 separator ran for six months in parallel with the WHIMS-2000 separator, from September 1, 1994 till February 28, 1995. Its installation on the plant is shown in Fig. 3. The efficiency of beneficiation, operating hours, water and electricity consumption were compared with WHIMS-2000. The employed operating parameters of SLon-,O00 are shown in Table 1 while the test results re summrised in Table 7.  Table 7 shows that the SLon-2000 separator can achieve a much higher grade and the recovery into the mags, much lower grade of the railings and lower mass yield into the mags than WHIMS-2000. A higher grade of the mags is mainly due to the contribution of its pulsating mechanism, a lower grade of the railings and a higher recovery of iron is mainly due to the fact that the matrix is always kept clean and that the magnetic force acting on the iron mineral particles is stronger. The lower mass yield into the mags is favourable for the subsequent processing procedure and the secondary ball mill. The operating time and the availability of SLon-,O00 are 4220 hours and 98.8%, respectively, in the 6-month commercial test, as is shown in Table 8. It is 869 hours and 20.3% higher than with WHIMS-2000 separator. The matrix clogging and the ring problem are the major problems affecting the operation of the WHIMS-2000 separator. It has been demonstrated that the magnetic matrix of the SLon-,O00 separator is always kept clean which is very important for maintaining high availability and for reducing the maintenance work.

CONCLUSIONS
The six-month commercial testwork in processing low-grade hematite ore in Gong Changeling Mineral Processing Plant demonstrated that the SLon-,O00 vertical ring and pulsating magnetic separator is a reliable and efficient equipment for processing weakly magnetic minerals. The separator increased the gade of the magnetic concentrate by 7.21% Fe and the recovezy of iron by 7.36.%. Its throughput is 50% higher compared to the WHIMS-2000 wet high-intensity magnetic separator.
Because the ring of the separator rotates vertically, allowing the magnetic fraction to be flushed in a direction opposite the that of the feed, and because the pulsating mechanism keeps the slurry in the separation zone pulsating, the matrix 100 XIONG DAHE is always kept dean. Onerous problem of matrix blockage that exists in wet high-intensity magnetic separators with a horizontal ring is thus eliminated. The maintenance work is thus considerably reduced and the availability of the separator increased.
The commercial tests fully satisfied the conditions of the contract signed between Gong Changeling Mining Company and Ganzhou Nonferrous Metallurgy Research Institute.