Gravity Spiral Separator with Different Pitch

Mineral Processing Efficiency of the Spiral Separator with Different Pitches

Introduction

The mineral processing flow is consists of grinding, size classification, gravity separation, strong magnetic separation, flotation. In 2004, we carried out a gravity separation experimental that replacing 1200mm spiral separator with 1500mm one. The result shows that processing capability increased by 30%.

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In recent years, the serious silting problem of 1500mm spiral chute has reduced the mineral classification efficiency greatly of which doesn’t separate the concentrate, medium, and tailings ore accurately. Ore deposition not only influences efficiency but also reduce the spiral chute service life.

The observation found that the ore mainly piles in the middle-lower part of the chute body, and the middle part of the cross-section.
The reasons as follows, first of all, the placid chute curve and small inclination angle slow down the flow speed, and weak the fluidity, that easy to cause minerals deposition, especially in the middle-lower part of the spiral chute while mineral preliminary separating. Secondly, unreasonable parameter. The difference between longitudinal dip angles may be an important cause of silting. Thirdly, the determination of spiral chute pitch is key to improve the dressing efficiency of different spiral chute processing stages.
Therefore, it is necessary that carrying out the comparison experimental by different chute pitch, 800mm, 840mm, 900mm, 940mm, 980mm.

1 Mineral processing flow

In brief, grinding – size classification – gravity separation – magnetic separation -flotation.
Beneficiation processing machine: ball mill, cyclone, spiral separators, magnetic separator, thickener, flotation machine.

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2 Ore property

Fine hematite ore with poor iron and high silicon and a trace amount of phosphorus, sulfur and manganese.
Main iron mineral: hematite, hematite and magnetite.
Gangue mineral: main in quartz, few amounts of silicate minerals, such as tremolite, actinolite, chlorite, etc.

3 Experimental scheme and result

3.1 Rough dressing spiral concentrator

3.1.1 Experimental condition of concentrate ore

Putting the disposit ore of size grading cyclone into the rough dressing spiral concentrator machine, and it is required that the grade of concentrate of disposition ore is 50-60%, the distribution width of spiral concentrate( 840mm pitch ) is 250mm. Carry out the distribution width test for a different pitch.

It will be seen that when the same distribution width, the grade of concentrate increases with the increase of pitch. Ensuring reach the technology requirements, distribution width of 310mm for the 980mm spiral chute, distribution width of 290mm for the 940mm spiral chute, distribution width of 250mm for the 840mm spiral chute， distribution width of 240mm for the 800mm spiral chute.

3.1.2 Result of different pitch

The experimental results show, when the grade is the same, the spiral concentrator with 900mm pitch has the advantages of high recovery rate, low tailings loss, and best separation effect.
The rough dressing effect of 900mm pitch has an output of 7.97t/h, the productivity of 20.88%, grade of concentrate mineral 59.27%, recovery rate of 32.73%, and comprehensive efficiency of 25.19%. In summary, the 1500mm spiral separator with 900mm pitch is suited for the rough dressing task.

3.2 Scavenging spiral chute

3.2.1 Experimental condition of tailings ore

The tailings of roughing spiral concentrator then into the scavenging process, it is required that the grade of tailings is 15-20%, the distribution width is about 300mm. Take the distribution width test firstly.

As shown in the table, in the same distribution width cases, the grade of tailings is increased by the addition of pitch; distribution width is decreased by the addition of pitch.
In given conditions of meeting technical requirements, distribution width of 120mm for the 980mm spiral chute, distribution width of 180mm for the 940mm spiral chute, distribution width of 250mm for the 840mm spiral chute， distribution width of 300mm for the 840mm spiral chute, distribution width of 320mm for the 800mm spiral chute.

3.2.2 Result of different pitch

The result of that the 900mm spiral classifier has the best beneficiation effect in the cases of the same grade concentrate ore.
The scavenging effect of 900mm pitch spiral separator machine has the output of 3.42t/h, the productivity of 32.18%, the grade of concentrate mineral 17.46%, recovery rate 17.16%, and comprehensive efficiency of 27.74%. In summary, the 1500mm spiral gravity separator with 900mm pitch is suited for the scavenging task.

3.3 Concentration spiral chute

3.3.1 Experimental condition of concentrate ore

The concentrated mineral of roughing spiral concentrator then into the spiral gravity chutes of the concentration process, it is required that the grade of tailings is 65-67%, the distribution width is about 170mm. Take the distribution width test firstly.

As shown in the above table, in the same distribution width, the grade of concentrate is increased by increasing pitch.
In given conditions, distribution width of 250mm for the 980mm spiral chute, distribution width of 220mm for the 940mm spiral chute, distribution width of 200mm for the 900mm spiral chute， distribution width of 170mm for the 840mm spiral chute, distribution width of 140mm for the 800mm spiral chute.

3.3.2 Result of different pitch

The result of that the 900mm spiral classifier has the best beneficiation effect that with high recovery rate and low losing rate in the cases of same grade concentrate ore.
The concentration effect of 900mm pitch spiral separator machine has an output of 7012t/h, the productivity of 21.18%, the grade of concentrate mineral 66.96%, recovery rate 26.46%, and comprehensive efficiency of 20.75%. In summary, the 1500mm spiral gravity separator with 900mm pitch is suited for the concentration processing task.

In summary, the larger the pitch ratio is, the higher the concentrate grade is. The greater of chute surface dip angle can heighten the centrifugal force thus fasten thus flow speed.
The large-pitch ratio is advantageous because the major function is to improve concentrate rate, 900mm pitch is performed better than the 1500mm.
In addition, during the experimental none of the 5 sets of mineral spiral concentrator have disposition ore. it turns out that the disposition ore phenomenon is mainly owing to the deformation of spiral chute separator, and the coarse grain size of minerals. The spiral machine of 800mm pitch is the easiest to cause disposition.

4 Conclusion

As for the 1500mm spiral separator, the disposition width is greater with the increasing mineral weight; as for the same distribution width, the grade of concentrate is increased by the addition of pitch.
It is suggested that replacing the 1500mm with 900mm to optimize the gravity separation process.
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