TRIFLOW The New Generation Multistage Heavy Media Separation Technology For

High Ash Indian Coals

Authors

P.C.Bozzato Ecomin S.R.L. , Italy

Dr.- Ing. Heribert Breuer , Allmineral Gmbh & Co. K.G. , Germany

Sabyasachi Mishra , Allmineral Asia Pvt. Ltd. India

Introduction:-

Coal remains a vital source of energy worldwide and is essential for the power &steel industry.

High quality coal reserves are becoming scarce worldwide. Modern highly mechanized coal

mining technologies and their economical optimization reduce the clean coal yield and make it

more difficult to control the product quality.

When it becomes necessary to improve the quality of run-of-mine coal with a washing process,

the selection of the suitable technology is often paramount in achieving operational profitability.

For that many mining projects activity have been started in India to compensate the energy and

manufacturing industries. The run of mine ash percentage is typically in the range of 45-50%.

This coal is necessary due to the Ministry of Environment & Forests (MoEF) issuing to reduce

the ash up to a 35% level. The possible solutions available are heavy media, jigging, dry

washing, forth flotation etc. The Coal processing plant includes the latest technology in coal

processing to increase the yield at the specified quality. This paper will present the basis for

design for coal washing with: (a) two-density heavy medium separation (Tri-Flo).

Tri-Flo Heavy Media separation:-

The Tri-Flo™ is a compact multistage cylindrical separator applied in difficult heavy medium

separations or where a 3-product separation is required. Below Figure reports a schematic view.

The material is fed at atmospheric pressure separately from the medium. The first stage float

material directly enters the second stage for a second separation. In a difficult 2-product

separation, only one Correct Medium (CM) is used and the second stage further washes the float

material for improved separation sharpness. Two CMs are used in a 3-product separation and the

second stage operates the low gravity cut. Partition curves in Figure (illustrative only) show that

the overall separation of a rougher-cleaner circuit is improved if compared with a single stage

separation and that an abnormal load in the first stage causes some heavies to be misplaced in the

first stage float product but the second stage, which is workIng in more stable conditions since

the first stage smoothes out variations, can correct the situation.The Tri-Flo is a proven

technology as indicated by many Tri-Flo pilot plants and more than 30 Tri-Flo industrial plants

existing worldwide, mainly in mineral processing.

A new feeding system has been recently developed to further improve the separation sharpness

and the throughput capacity of cylindrical cyclones.

Figure:-A

Figure:-B

Advantage of Heavy Media Tri-Flow Technology

• The heavy medium Triflow is a multistage separator in one unit and the float stream is

rewashed.

• Multiple separation can be performed at the same density or at different densities to

produced final product, Middling & Reject.

• The separation sharpness of finer material is highly improved in the tri-Flow vessel due

to multiple processing.

• The system allows to operate a sharp separation in the first stage in all condition and can

also applied to single stage separation.

Highlights of Tri-Flo technology:-

Double washing in one vessel with

-Higher separation sharpness if washing discards 2 product mode.

-Production of clean, middling and reject if washing 3 product modes.

Compact layout

Low head point

Similar amount of CM pumped to equivalent capacity single stage DSM system.

High throughput capacity

Coarser top size accepted, sharp separation with variable speed.

High sink capacity up to 100m3/hr

No pumping of highly abrasive discard

Very forgiving of feed change, operator friendly.

Minimal vessel wear with on line cut point adjustment for minimal maintenance-longer

life

Multiple product from one vessel

It has a very high sink capacity and produced three product in one vessel, the results it reduced

capital cost (building, piping etc) and operating cost if compared with same traditional circuit.

The second or following stage can be :

-A final by product clean, middling(Power coal) & reject.

-Comminuted to improve the liberation and re-processed for increase recovery

-Re-circulated to head feed for sharper separation in difficult application.

-Energy cost of pumping is reduced by up to 50% if compared with traditional double stage

installation.

Larger feed top size

-The Tri-flow technology can accept larger particle than conical cyclone if comparing the

same vessel diameter.

- A single circuit (Tri-flow) can operate the separation saving on the coarse coal circuit.

As an Example:-Assuming a 200t/h application with good liberation at top size of 75mm,a single

Tri-flow can be installed, if a cyclone is installed for the capacity a 750mm should be chosen but

the feed material must be crushed at top size of 50mm.As an alternative ,to accommodate a top

size of 75mm a 1000mm should be installed. in both case ,the economical saving offered by the

Tri-flo® are significant.

Reprocessing the float material gives better results than reprocessing the heavy

material.

- In some case the second stage(middling) is fed with the first stage light material and the

majority of the heavy material has been already rejected, making the condition in the

second stage more stable and allowing to reject the misplaced material.

- Reprocessing the light material gives better overall performance because each size

fraction is separated at more or less the same density.

Improved hydrodynamic inside the vessel.

The flow pattern inside cylindrical vessel is improved in comparison with more uniform

centrifugal acceleration and wider region of zero axial velocity particularly useful for difficult

high near gravity separation(which is very common in Indian coal)

Minimal contact of the material with the separator wall.

Tri-Flo-the feed enters the separator at atmospheric Pressure along the center of the separator,

light material floats along with the central axe, highly abrasive heavy material quickly reports to

the wall and is discharged through the sink head positioned near the feed inlet.

Only the medium is pump.

Reduced wear of the heavy medium feed pump and following piping-typical life time is doubled

if feed is not pumped. Higher plant availability due to reduced blockage of piping and pump. The

feed material remains into the slurry for a very short time as opposed tom conical cyclone.

Lower degradation of the feed material and product with following saving in water treatment.

Tri-Flo Operating Data

Types Of coal Ash Cv(MJ/KG) Ep Organic

Efficiency

Feed 30-55 16-10

0.012

98.9 Clean 20-30 20-24

Reject 55-70 3-10

Conclusion:-

The Tri-Flo allows multistage separation in one unit, hence compact layout and

ultimately capital savings

All production specs have been met operating in the 2-product mode (for discards feed)

and 3-product mode (for ROM feed)

The modular and fully transportable plant is compact but designed for the operators,

maintenance is easy and operation settings are highly simplified also because

The Tri-Flo is very forgiving if feed characteristics and throughput capacity change

Elongated pieces up to 200 mm long (8-in) did not block the feed chute nor the separator

The new feeding system allows to operate at high throughput capacity without blockages

and within product specs

Allmineral | Asia having additionally dry jigging technology (Allair® ) and wet

jigging technology (Alljig® ), has already made deep in roads into the Indian Mineral

beneficiation market. With the Tri-Flo ® technology in its bag, it is the only company

in India to offer such a varied range of technologies to the Indian coal and minerals

industry.