RESEARCH AND COMMERCIALISATION OF TREATMENT OF FINE ILMENITE WITH SLon MAGNETIC SEPARATORS

The fine ilmenite material finer than 0.045 mm at the Pang Zhi Hua Ilmenite Processing Plant was discarded for the lack of efficient processing equipment and method. The total recovery of ilmenite in the plant had been only about 17-20%. To increase the ilmenite recovery, numerous laboratory, pilot and commercial tests were conducted in 1995-1996. Finally, a magnetic separation-flotation flowsheet was chosen for the commercial test, in which the finefraction was fed into 125 mm diameter cyclones for desliming. The underflow of the cyclones was then fed into the magnetic separation-flotation flowsheet. A SLon- 1500 vertical ring and pulsating high gradientmagnetic separator was applied as a rougher and was followed by flotation as a cleaner. The overall results ofthe magnetic separation- flotation flowsheet in the commercial test were: feed 11.03% TiO2, concentrate 47.36% TiO2, recovery 44.79% TiO2. The flowsheet of the commercial test has been used as a production process since 1997. The recovery accounted for about 12% TiO2 of the feed into the ilmenite processing plant.


INTRODUCTION
The Pang Zhi Hua Ilmenite Processing Plant is the biggest producer of ilmenite in China. The deposit consists of vanadium, titanium and iron minerals and other gangues. Magnetite is the major iron mineral and vanadium exists in magnetite. Ilmenite is the major titanium mineral.
An iron processing plant recovers magnetite and vanadium before the ilmenite processing plant. The tails of the iron processing plant represent the feed into the ilmenite processing plant. 121 122 XIONG DA-HE The previous flowsheet of the ilmenite processing plant was based on classification into +0.1 mm (coarse), 0.1-0.045mm (middle) and -0.045 mm (fine) fractions. The coarse and the middle particle fractions were treated with spirals and electrical separators. The fine fraction was discarded as the final tails for the lack of efficient beneficiation technology. The overall recovery of ilmenite had been only 17-20% of the feed of the ilmenite processing plant.
The mass of the fine fraction is about 35% and the TiO2 grade is almost the same as that of the feed to the ilmenite plant. The recovery of ilmenite from the fine particle fraction is thus of great significance for increasing the overall recovery of the ilmenite plant.

MINERALOGICAL ANALYSIS
Major minerals and their physical properties in the feed into the ilmenite plant are shown in Table I Table I that magnetic susceptibilities of vanadium-titanium magnetite, ilmenite and pyrite are relatively stronger than the others. But magnetic susceptibility of titaniferous augite is close to that of ilmenite. It is possible to remove plagioclase and part of titaniferous augite by magnetic separation.
The fine particle fraction (-0.045 mm) of the ilmenite plant feed was used as the feed in our laboratory test. SLon-100 cyclic pulsating high gradient magnetic separator (SLon-100) was used as a rougher. In the test, the matrix type, the background magnetic induction, pulsating stroke and pulsating frequency were optimized. Typical results of the magnetic separation test are shown in Table II. Table II shows that with 4 mm dia. rod matrix in SLon-100 magnetic separation better results can be obtained than with 2 mm dia. rod matrix TREATMENT OF FINE ILMENITE 123 124 XIONG DA-HE TREATMENT OF FINE ILMENITE 125 or expanded mesh. When the feed is 9.25 % TiO2 and with 4 mm dia. rod matrix, the concentrate grade is 22.29% TiO2, the tails grade is 4.44% TiO2, recovery in the concentrate is 64.93% TiO2, the mass of the concentrate is only 26.95% and the mass of the tails is 73.05%. The importance of magnetic separation is that it can discard about 73% by mass of the low-grade tails and only about 27% by mass of the concentrate enters into next cleaning stage. For example, if flotation is used for the cleaning, a lot of flotation reagents can be saved.

Laboratory Tests with Flotation as a Cleaning Stage
In the laboratory flotation tests, several reagents as collectorswere tested and the flowsheet was optimized. Typical results are shown in Table III.
The Table shows    The laboratory tests-scale showed the direction for subsequent pilot and commercial tests.

Pilot-Plant Tests on Fine llmenite
In 1995, SLon-1000 vertical ring and pulsating high gradient magnetic separator [1] was moved to Pang Zhi Hua Ilmenite Procesing Plant for pilot-plant tests to recover ilmenite from the discarded -0.045 mm ilmenite slime. SLon-1000 was installed in the production flowsheet and a slurry stream of-0.045 mm ilmenite slime was used as its feed.
The magnetic product (the rougher concentrate) was used as the flotation feed in the cleaning stage. The flowsheet of the pilot test is shown in Fig. 1.
In the pilot-plant tests technical parameters were first optimized.
Then SLon-1000 ran continuously for 72 h to get more reliable results.
As is shown in Fig. 1  separator was installed in the production flowsheet as shown in Fig. 2. In order to increase the throughput of SLon-1500, 125 mm diameter cyclones were used to dewater and deslime the -0.01 mm slime fraction. The operational results of the cyclones, of SLon-1500 and of flotation are shown in Tables V-VII respectively. Table V shows that the cyclone operation is important because the solids concentration in the feed is only 5.42%. The solids concentration of the cyclone underflow is 28.32%. Most water and -0.01 mm slimes report into the cyclone overflow. This creates a much better condition for the SLon-1500 operation. As shown in Table VI, the capacity of SLon-1500 reaches 25.25 t/h with 76.24% TiO2 operational recovery. Figure 2 shows that the combined TiO2 recovery of the cyclone and SLon-1500 is 50.51%, almost the same compared with the pilot test shown in Fig. 1

THE PRODUCTION-SCALE APPLICATION
The commercial test shown in Fig. 2 was completed at the end of 1997, and the flowsheet was implemented on production scale. In 1998, about 10000 t of > 47% TiO2 ilmenite concentrate was recovered from the -0.045 mm fine fraction. After more than a one year-long production practice, it was demonstrated that the SLon-1500 VPHGMS magnetic separator works very reliably. In 1999, the production scale of the -0.045 mm fine fraction is expected to reach 15 000-20 000 t of the ilmenite concentrate as the flowsheet becomes more optimized.

CONCLUSIONS
A magnetic separation-flotation flowsheet is applied to the recovery of the -0.045 mm fine ilmenite minerals from the previous tails in the Pang Zhi Hua Ilmenite Processing Plant. SLon-1500 vertical ring and pulsating high gradient magnetic separator is used in the roughing stage. It is a key equipment for the flotation cleaning stage. The overall flowsheet is relatively simple and reliable. It has been put into production 130 XIONG DA-HE by the end of 1997. The overall results of the flowsheet are as follows: feed grade 11% TiO2, ilmenite concentrate grade > 47% TiO2 and TiO2 recovery 44%. Approximately 10 000-20 000 t of such ilmenite concentrate can be recovered from the previously abandoned tails. It is a significant technological innovation in the history of the Pang Zhi Hua Ilmenite Processing Plant.