Minerals Engineering 45 (2013) 1–3

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Min erals Engin eering

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Technical Note

Cyclonic-static micro-bubble flotation column

Haijun Zhang ⇑, Jiongtian Liu ⇑, Yongtian Wang, Yijun Cao, Zilong Ma, Xiaobing Li School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China

a r t i c l e i n f o a b s t r a c t

Article history:Received 14 October 2012 Accepted 4 January 2013 Available online 27 February 2013

Keywords:Cyclone separation Micro-bubble flotationMultiple mineralisation Flotation column

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⇑ Corresponding authors. Tel./fax: +86 516 8359009E-mail addresses: zhjcumt@163.com (H. Zhang), sc

A cyclonic-static micro-bubble flotation column (FCSMC) was developed for mineral separation, particu- larly for whole flotation circuits. The FCSMC featured multiple mineralisation steps, including counter- current mineralisatio n, cyclone mineralisation and pipe flow mineralisation in a single column,through which the mineralisation energy, mineralisation rate and dynamic turbulence intensity gradu- ally increased to compensate for the decrease in the floatability of mine ral particles. It thus led to highly efficient mineralisation as well as a sufficient retention time fine mineral recovery. The usability and per- formance of the FCSMC was assessed and further confirmed by lab-, pilot- and industrial-scale unit sbased on magnetite ore. The iron concentrate grade reached 69% with a recovery of 95%.

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1. Introduction

Since the flotation column was invented by Boutin and Tremb- lay (1964) in the early 1960s, the column flotation technique has developed rapidly and become an important mineral separation technology widely accepted by the mineral industry. Compared with conventional flotation machines , it features efficient self- cleaning and simple circuits (Ding et al., 2001; Finch and Dobby,1991; Flint et al., 1992; Honaker and Mohanty, 1996; Stonestreet and Franzidis, 1992; Xu et al., 1996; Yoon, 1988, 1993 ). However ,the current column flotation technique is mainly based on a single mineralisation step without an internal recycling separation pro- cess, resulting in low recovery in roughing and scavenging (Nak-haei et al., 2012; Goodall and O’Connor, 1991; Vashisth et al.,2011). To solve these problems, some flotation columns containing circulation or cyclone(s) have been investigated in laborator ies.However, they have not been successfully used in roughing and scavenging for the mineral flotation industry (Anderson et al.,2009; Finch, 1995; Gu and Yalcin, 2012; Tao et al., 2000 ). There- fore, a cyclonic-static micro-bubble flotation column (FCSMC) inte- grated with not only an internal recycling process but also multiple mineralisation steps was designed and tested in terms of lab-, pi- lot- and industrial-scal e performance.

2. Design of cyclonic-static micro-bub ble flotation column (FCSMC)

The FCSMC design, as shown in Fig. 1, employed column flota-tion separation, cyclone separation, high-turbul ence mineralisation

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and cyclone scavenging. For the column flotation separation, coun- tercurren t mineralisation was realised to generate a high-quality concentr ate from raw materials. Subseque ntly, cyclone mineralisa- tion in the cyclone separation step further separated flotationmiddling to obtain high-quality tailings. Finally, pipe flow minerali- sation was used for the separation of cyclone middling and the cir- culation of pulp.

The FCSMC device, as shown in Fig. 2, was in the form of a single column. As mentioned above, it consisted of column flotation zone,cyclone separation zone and pipe flow zone. The column flotationzone was packed with sieve plates and vertical tubes to provide the necessar y low-turbulence environment for roughing and cleaning.The cyclone separation zone was located immediately below the flotation zone, which incorporate d density separation and surface flotation, depending on the high-intens ity centrifugal force field.The pipe flow mineralisati on zone was connected perpendicularly to the cyclone separation in a tangent direction. An external bubble generato r based on the principle of a venturi sparger was installed at the pipe flow mineralisation zone to inhale and crush air into micro-bubb les. Pulp continuously flowed between the cyclone sep- aration zone and the pipe flow zone through a circulation pump.Addition ally, a washing water sprayer was placed at the top of the device to clean the flotation froth.

3. Experimen tal

3.1. Material

Magnetit e ore provided by the Gongchangl ing Concentr ation Plant, Liaoning, China purified by gravity and magnetic separation was used to test the FCSMC in this study. The ore mainly consisted of magnetite and quartz minerals. It had an average head grade of

Fig. 1. Schematic of mineralization and separation.

Fig. 2. Schematic of the cyclonic-static micro-bubble flotation column (FCSMC).

Fig. 3. Flowsheet of (a) FCSMC and (b) BF mechani

2 H. Zhang et al. / Minerals Engineering 45 (2013) 1–3

63.73% Fe. The size fraction of �74 lm was 88.76% with a head grade of 65.29% Fe, and the size fraction of �45 lm was 73.20%with a head grade of 66.05% Fe.

3.2. Methodolo gy

Reverse flotation was applied for magnetite ore separation,whereby the gangue mineral quartz was reported as the flotationfroth. Dodecylami ne hydrochlori de, supplied by the Gongchangl ing Concentr ation Plant, was used as a collector and frother. The tem- perature of the pulp was kept at �35 �C. All tests were performed at the natural pulp pH of �7.5.

The flowsheet included a one-stage rougher and two-stage scavenge r, as shown in Fig. 3. The middlings from the scavenge rwere separated by a magnetic separator. The tailings from the magnetic separator and the scavenge r flotation column were collected together as the final tailings.

Reverse flotation tests were first carried out in a laboratory sep- aration system. Subseque ntly, based on the lab test results, more tests were carried out in a semi-industria l separation system at the Gongchangl ing Concentr ation Plant. Finally, tests were carried out in an industrial separation system (FCSMC 3.6 m � 8 m, FCSMC 3 m � 7 m, FCSMC 2.6 m � 7 m) at the Gongchangli ng Concentr a- tion Plant.

4. Results and discussion

As shown in Table 1, similar results were obtained from these FCSMC systems using magnetite ore. By FCSMC separation, the iron concentr ate grades reached 69% with the recovery of 95%. Further- more, Table 2 compares the FCSMC and a BF mechanical flotationcell. The iron concentrate grade of produced by FCSMC system was almost the same as that produced by the BF mechanical flota-tion cell. However , the recovery increased from 94.54% to 95.82%,and the power consumptio n per ton decreased from 6.85 to 6.12 kW h/t. Moreover, the flowsheet of the FCSMC was simpler than that of the BF mechanical flotation cell, as shown in Fig. 3.In addition, the column flotation froth was transported by a self- sucking device located in the upper part of the column flotationzone.

The better performance of the FCSMC relative to that of the BF mechanical flotation cell was mainly attributed to the multiple mineralisati on steps, particularly the design of the countercurrent and cyclone zones. Because the floatability of mineral particles gradually decrease s with the delay in the flotation time, the

cal flotation cell for magnetite ore separation.

Table 1Results of replicate tests in different separation systems of FCSMC.

Test # Capacity (t/h) %Fe Wt.% Fe Rec (%)

Feed Conc. Tailings Conc. Tailings Conc. Tailings

1a – 63.70 69.95 20.04 87.48 12.52 96.06 3.94 2b 0.25 63.87 69.22 19.20 89.30 10.70 96.78 3.22 3c 70.61 63.59 69.15 22.37 88.11 11.89 95.82 4.18

a Laboratory separation system.b Semi-industrial separation system.c Industrial separation system.

Table 2Comparison of industrial systems betwe en FCSMC and BF mechanical flotation cell for magnetite ore separation.

Industrial separation system %Fe Conc. Power consumption per ton (kW h/t)

Flowsheet

Feed Conc. Tailings Wt.% Fe Rec (%)

BF mechanical flotation cell 63.59 69.23 26.37 86.84 94.54 6.85 One rougher two scavenger and magnetic separation process FCSMC flotation column 63.59 69.15 22.37 88.11 95.82 6.12 One rougher one cleaner magnetic separation and grinding process

H. Zhang et al. / Minerals Engineering 45 (2013) 1–3 3

mineralisation energy, mineralisati on rate and dynamic turbulence intensity gradually increased to overcome the decrease in mineral floatability. The countercurrent zone equipped with the sieve plates and the vertical tubes increased the probabilities of collision and adhesion between bubbles and particles. Hence, it provided awell-mixed reactor and solved the blocking problem of conven- tional packing. In the cyclone zone, density separation and surface flotation took place. In addition, the flotation rate was improved due to air lifting produced by the high-intens ity centrifugal force field.

5. Conclusions

The performanc e of an FCSMC was tested and verified by an industrial-s cale plant. The FCSMC was successfully industrialised for the whole flotation circuit of mineral separation in China. Be- cause the FCSMC combines countercurrent mineralisation , cyclone mineralisation and pipe flow mineralisation , highly efficient min- eralisation and a sufficient retention time for better mineral recov- ery can be achieved.

Acknowled gments

The authors would like to thank the National Key Basic Re- search Program of China (No. 2012CB2 14905), the National Natural Science Foundation of China (No. 51004107, 51074157) and the National Key Technology R&D Program for the 11th Five-Year Plan of China (No. 2008BAB 31B02). The authors would also like to thank the Gongchangli ng Concentration Plant.

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