BALAKRISHNAN.N,

1500mm wide belts running in excess of 5 m/s are being used to convey iron ore pellets in the US. Therefore, it is possible to run belts at over 4 m/s for iron ore pellets.

As far as the maximum capacity and incline angles are concerned for your application - the answer to that is best obtained from the belt manufacturer and conveyor designer of your choice. Alternatively, you can use one of the design programs available (see previous postings).

Regards, ■

Yes, iron ore pellets can be transported via belts running at greater than 4 m/s for a horizontally oriented flight. Belts width is only relevant to tonnage to be carried which you have not specified. The caveat to theabove is the chute.

The transfer/loading chute must be correctly designed. A curved hood and spoon must centralize the load and place it on the belt near the belt speed and in the same direction as the receiving belt.

Pellets can be pushed uphill on a very mild slope for a short length such as an elevated head pulley to transfer onto another belt. The problem will come when the tail end of the pellet feed goes up the incline and unsupported pellets rill back. The slope angle and length depends on the irregularity of the pelllet shape. If the pellets are near mable roundness then the ore will flow like water and virtually no incline greater than a few degrees is tolerable for more than a few meters. When the belt stops with pellets on the incline they will rill backward.

The incline slope can be increased by cleating, cheveroning or making a flexwall of the belt carry surface. The pattern, dimensions, and shape of the belt surface will dictate the slope angle. Pellets will stack on top of each other provided the base layer is held stationary by the cleat system. Conservatively, you could incline the belt 10 degrees depending on belt sag and idler alignment disturbance using the cleats. you can do better with the flexwall system.

The whole chute, belt surface, belt speed, material and incline slope selection process can be simulated using the Discrete Element (DEM) modeling.

All of these points have restrictions with respect to belt tensions, pulley arrangements, .......

We can provide the DEM design modeling of round or irregular shape pellets, chute and belt.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Iron ore pellets are not so difficult to handle. To facillitate handling is why iron ore is pelletized in the first place. Iron pellets can be, have been and are being conveyed at speeds above 4 m/s. Iron ore pellets also transfer well through chutework though wear is high and the pelletizing agglomerate (clay) can accumulate, cake up and compact in the valleys.

Conveying angle is a problem with conventional open troughed conveyors, limited to about 10 degrees. Conveying angle is not a problem with sandwich belt type high angle conveyors. These have elevated iron ore pellets continously at rates above 10000 t/h at angles to 90 degrees. Such a system, the DSI Snake Sandwich high-angle conveyor uses all and only conventional conveyor equipment and components, including smooth surfaced rubber belts, that can be continuously scraped clean (cleated and pocket belts cannot be discharged completely or cleaned).

I am surprised that previous commentators are not aware of the great success in elevating iron ore pellets from self-unloading ships with C-profiled sandwich belt conveyors.

Please visit our website to learn more about DSI Snakes.

Joseph A. Dos Santos, PE ■

Joeseph Dos Santos is correct in stating that sandwich belt systems (Robbins Loop system, Continental Conveyor HAC, and DSI Snake) are used for the vertical lifting of iron ore in self-unloading ships at rates in excess of 5m/s. He is wrong, however, in assuming that I or Mr. Nordell are unaware of these systems.

If the primary issue is one of conveyance angle over that normally available with flat belts, there are a number of options.

But, I believe that this is getting away from the original question. If Mr. BALAKRISHNAN would indicate what his needs are a more focused discussion may be possible.

Regards, ■

Mr. Miller,

My jab was prompted by Mr. Nordell's disertation on cleated belts and pocket belts while not mentioning the better solution.

However, indeed conveying angle is an issue as stated by Mr. BALAKRISHNAN. And, the lower the allowed conventional angle the more is the cost advantage of the Sandwich conveyor system.

I too am interested in the specifics so that they can be addressed with specific solutions rather than generalities.

Joseph A. Dos Santos, PE ■

Dear Joe,

Iron ore is pelletized to control the feed size to the furnace from finer and discordant size distribution which otherwise would not smelt properly.

Yes, I can be held accountable for not being through and mentioning the sandwich class of belts. I apologize.

Lawrence Nordell

Conveyor Dynamics Inc. ■

MR. Balakrishnan,

Our facility handles about 4.5 million short tons of iron ore pellets a year. Some of it is on a Continental conveyor HAC. Most of it is on conveyors of the size and speed you mention. We do have a conveyor that is steeper than 10 degrees and it does have a pellet spillage problem associated with it. It dates from the time when there was a sinter plant on the property, so it was not specifically designed for pellets. We run around 6000 to 8000 tons a day up that belt, and clean it up once per week. Key is to keep it running until it is empty, and not to stop it if possible with pellets on it.

I don't know what manufacture of pellets you are looking at. If they are from North America, it is likely we have handled them.

We currently operate 3 antiquated ore bridges with 15 ton buckets that pick up the pellets and drop them into hoppers over pan feeders. The pan feeders feed to a belt. They date from the days of raw ore. Yes, I know we should have replaced them years ago, that is why the US steel industry is going down the tubes, however, I am actively looking for a cost effective replacement to the pan feeders, due to high maintenance. It would seem to me that a vibratory feeder with a false bottom in the hopper would be a reasonable solution. We have had several suggestions for live feed belts to replace the pan feeder, but the prices seem far too high, ~$150,000 and more. Has anyone who is watching this forum ever done work like this before? ■

Dear Hcrosmun

Besides being the world's leading authority in sandwich belt high angle conveyors the writer has also designed belt feeders for the most severe applications including recieving face blasted copper ore and waste rock from 220 ton end dumptrucks and feeding this to the gyratory crusher. Traditionally such duties have been handled by apron feeders.

From an operating and maintenance stand point a belt feeder is likely the best choice for your application.

Call me if you are interested in pursuing this further.

Joseph A. Dos Santos, PE ■

From:

KS Dilip

Tecpro Systems (P) Ltd

Chennai

Sir,

Please send the conveyor requirements to us for us to submit detailed specifcations and submit our technical and commercial offer.

We have handled iropn ore pellets in many projects and can meet your requirements

Regards

KS Dilip

Manager- Marketing

Tecpro Systems (P) Ltd

Chennai- 600020

India

Ph: +91 44 2442 5886/ 2442 6027

Direct: +9144 2442 5965

Fax: +9144 2442 5922

Email: ksdilip@tecprosystems.com ■

Is it not possible to consider a Pipe conveyor system for this application ? Low material size, high speeds, steep angles - all indicate a potential pipe conveyor system.

Regards

Kayem ■

Kayman,

A pipe conveyor cannot convey at high angles, especially at the lower conveying rates. It may be able to contain the material that is rolling back. At higher rates, where the cross-section is half full or more, slightly higher (than conventional) angles may be achieved. In order to achieve high angles at a pipe conveyor the cross-section would have to plug causing the material to bridge. This would result in turbulance in the pipe, discontinuity of flow, high power consumption (due to plugging and bridging) and the material could never be fully purged at the end of operation.

Joe Dos Santos ■

Dear Mr. Balakrishnan,

The earlier respondents have already given useful information about the belt speeds that can be used for iron ore pellets. In this context, I would like to draw attention to following basic considerations.

The speed limitation is due to degradation of iron ore pellets during conveying / handling process. The degradation is consequence of dissipation of impact energy. The impact energy is proportional to the square of speed, and therefore degradation will increase according to the square of speed.

Also, in integrated system, how many times a pellet will pass through transfer / impact points before reaching the consumption point will also affect the speed to be selected. Suppose at each transfer point there is degradation by quantity x, with reference to velocity v. Suppose the system is made up of one very long conveyor, ten transfer points within the plant. By using uniform speed v for all transfer points the total degradation will be 11x. But if one uses 25% more speed for long conveyor, the total degradation in the system will amount to 10x + (1.25) . (1.25)x = 11.56x. Thus the percentage increase in degradation amounts to (100) . (0.56) / 11 = 5.09%. If this is acceptable to user and if there is sufficient saving by using higher speed for particular conveyor; one can do so.

Contrary, if one uses 25% higher speed for all conveyors, the degradation increase will be more than 50% compared to quantum of degradation occurring at velocity v. Therefore, the use of speed is subjective, and higher speed used in some installations may not be considered as a benchmark in every case. This need not be construed that I am suggesting the use of lower speed. This only narrates the method to analyze the subject issue.

In general, steel plant people / users are sensitive to fear of possible degradation and generally they prefer the normally used speed, instead of one step narrow belt, higher speed and some saving which may not be significant compared to the total risk involved for steel process and the cost of steel plant.

Few days back, I happened to meet an American expert with decades of experience in steel process. As per the information, the iron ore pellets from all sources need not to have the same mechanical strength, i.e. resistance to breakage / erosion. The pellet can be said as strong, average and less strong. Hence, the speed will also depend upon the characteristics of pellets.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

Dear Messrs. BALAKRISHNAN.N & Mulani:

I offer this additional response to clarify and correct Mr. Mulanii's claims on iron pellet breakage related to speed. One must factor all conditions that lead to pellet breakage handled in the transfer station.

1. We must consider a) type of impact at discharge, b) drop distance and handling during drop ( maybe on slope to reduce velocity), and c) type of impact as pellets are guided onto receiving belt.

2. Yes, simple physics tells you, as Mr. Mulani states, direct impact onto a plate 90 degrees to the discharge will produce kinetic energy proportional the speed squared. Most conveyor transfers would not be so configured.

3. Does not factor in the transfer height in total degradation. The drop distance and impact surface may be a multiple of the conveyor's belt velocity suggesting this too should be given far greater importance in the degradation equation.

4. Properly designed transfer chutes are geometrically developed to minimize breakage from all impact conditions and large changes in velocity gradients within the chute. The total impact index change from conventional to an optimal chute design can reduce impact breakage from 30 to 90%.

5. To acknowledge the total breakage index you need to know the particle(pellet) breaking strength due to both impact and shear (chipping) as noted by Mr. Mulani's reference to an American consultant.

6. Impact and shear degradation or comminution is an exponential function with properties solved in lab breakage testing. Pellets may be made strong enough resist direct (normal)impact breakage but still reasonably degrade from shear work (tangential) component of impact. A transfer chute may aggravate one over the other. This leads to the question - which produces the greatest degradation.

7. DEM, as I have stated many times in this forum, can resolve the differences between all types of transfer chutes and their geometric influences. No more speculation, misconception and myth is involved. DEM willl lead the engineer to the best geometry to meet the minimal breakage (comminution) index.

8. I claim a proper chute design will produce far less breakage than is implied by speed change alone. I further claim it is possible to design a 5m/s belt that can produce significantly less breakage than a 2 m/s belt speed taking advantage of narrower belt and smaller pulleys (lower belt strength) by using these geometries to lower the drop distance, internal impact and shear.

9. Thus, minimal belt speed should not be the ultimate constraint on minimizing pellet breakage.

With Regards,

Lawrence Nordell

Conveyor Dynamics, Inc.

website: www.conveyor-dynamics.com ■