Employ a materials handling consultant to visit your site, show him your problem areas, get him to prepare a report on the necessary remedial action. Obviously you'll have to pay him.

With the minimal information provided so far this is your only hope! ■

With the comparatively lesser rainfall in Western Europe the terrors of wet coal were once well appreciated. Asia, part of it, seems to be newly aware of the phenomenon.

In another recent parallel thread the originator was twice advised against blending outdoors & simply replied that he had to.

By all means employ a Consultant & then do something pioneeering & listen to what he has to say. Otherwise there is no hope.

PS There is no such thing as minimum investment. you get what you pay for; warts & all! ■

Dear Shri Banerjee,

In India, power generation is mainly by coal based thermal power stations. So, the people in this field (i.e. coal handling plants users, manufacturers, consultants) have sufficient experience about the remedial measures which can generally be adopted, to reduce the problem. Mostly, people opt for following features :

1) Chute valley angle around 60 degree.

2) Hopper valley angle around 65 degree.

3) In case of crushed coal, people also use UHMW liners, which have very low friction coefficient and are resistant to clogging.

4) Stainless steel liners have comparatively less friction coefficient. People sometimes use this liner for lumpy coal.

5) The most important aspect is also to make approximate / reasonable analysis of the material flow path and velocities within the chute. The chute layout should be done in such a manner that it should consistently maintain the speed for material. This means chute should not be such that material is falling with high velocity at a point but after impact, its velocity becomes nearly zero and material has to labor to acquire velocity and move further.

6) Chute vibrators have been also used in coal handling plants. The chutes should be constructed to suit the mounting and to respond to the vibrator. In general such chute vibrators would remain idle for most part of the year, but will be operated during very wet season or when needed.

7) Sheds are also used on certain portion of the stockpile, to use this coal during days of excessive rain. This is a monsoon feature in India when suddenly it continues to rain for a week or so. However, it may be also noted that for larger part of India there is no rain almost for 8 to 9 months.

Regards,

Ishwar G Mulani.

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

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

We simulate the behavior of coal in chutes and applly corrective designs for best outcome using granular flow physics. Your problem can be simulated including application of the specific coal internal rheology. ■

Hi there Banerjee..

We did alot of tests on the affect of moisture variation on the flowability of finer materials.

To put it simply:

If dry, it flows almost uncontrollably

If sloppy wey it flows like a slurry

If around 14 to 20% moisture (by mass) it sticks like crazy.

At 17% it sticks to the ceiling.

So.... make every effort to not have 15% moisture as part of your criteria. It should drain to about 11% reasonably quickly. That would be fine to handle.

As for the rain, you will have to ask Larry to control that for you!

Hope this helps

Regards

LSL Tekpro ■

LOL !! ■

Dear Mr. Banerjee

Moisture of Coal at Coal Handling Plants especially for Coke Ovens makes big problems, so we have many economic solutions

for each case..

However it is necessary to study your local situation since there are so many influencig technical and economical factors..

As recommended also by other authors , you have to prepare a basic engineering study for the solution, whereby you have to hire an expert as consultant.

As assumed, you must also pay for the consultants engineering hours..

With kind regards ■

Dear Sir,

We have been providing solutions for the clogging and sticking problems as you have mentioned here in your message.

We have utilized our systems for prevention of these problems on the silos, channels, bunkers and chutes for many years. As YUNEL, we have been awarded with the Contracts of clogging preventions, which are YUNEL Air Cannons, that are utilized more than 7000 pcs, most of which are operated in COAL Fired thermal power plants here in Turkey. For further helps, may be good to contact me via our e-mail. If we can have some technical informations from your end, such as the geometry of the chutes, etc. it will be really useful.

Thanks for bringing up such a problem in the forum.

Best Regards,

Ufuk YUNEL

(M.Sc. Mining Eng; M.B.A)

Sales Coordinator

YUNEL LTD., STI

Address: Ankara - Cankiri Karayolu 26. Km 06750 Akyurt Ankara / TURKEY

Tel:+90 312 847 5201

Fax: +90 312 847 5205

e-mail: sales@yunel.com

Web: www.yunel.com ■

We engineer and manufacture a saddle mount solution that holds a pneumatic vibrator that is ideal for coal pipes and we have many successful installations on coal pipes. it works well even on wet, sticky and frozen coal.

See a brochure here.

http://www.navco.org/files/1000.010 Vibs for Power.pdf

Also see why Pneumatic Vibrators are better and safer than Air Blasters for promoting coal flow:

http://www.navco.org/pneumaticvscannon.html

Contact us so we can discuss your application further.

NAVCO

www.navco.org

1(800)231-0164 x118

or 1(832)467-3636 x118 ■

Try vibrators by all means, but don't forget that vibrators are also used for compaction. Get a guarantee from the supplier that their solution will not result in compaction of the coal in your chutework. ■

We offer vibratory equipment for use with coal for both compaction and flow, our engineers are very knowledgeable of the differences and requirements for each method.

We are confident we can provide a solution to promote reliable flow of coal in your pipes, chutes, storage hoppers and railcar unloading(compaction in railcars too) as we have at many many other coal handling facilities in the US an worldwide.

We are waiting for you to call and discuss the application with us.

Or you can email us the details: sales@navco-jvi.com

NAVCO ■

Your problem is an old one requiring old solutions.

Keep the belt speed down use 90degree transfers only, keep transfer height to a minimum and have direct impact onto the belt from the head pulley or scraper system. Do this correctly and you will not have a run off problem.

In cases like your it is likely that the primary scrapers will do all of the discharge so they must be kept in good order. ■

A word of caution folks...

We have all but banned the use of primary scrapers for most stuff that sticks to the belt.

The reason is that you often get a built up between the scraper and the belt on the pulley. Larger lumps going round the pulley in the finer sticky stuff then get lodged in this gap and they damage the belt.

We now use a primary scraper type blade in the normal position of the secondary scraper, and put a secondary one behind it.

We have had far better results this way in practice.

Regards

LSL Tekpro ■

That may be so Graham but between 15 and 19% moisture on fine coal your not going to get any trajectory so the scrapers must do there job. ■

In practice the faster you go the more proper trajectory you get so you musn't go too slow.

But then we are also relying heavily on the two belt scrapers in the secondary position, so you musn't go too fast either.

We got this to a fine art on a number of conveyors conveying the dreaded sticky stuff.

(Still say try and keep material from being sticky in the first place though)

LSL Tekpro ■

I agree with most of you comments on the forum Graham but not this one. I make a habit of getting in and studying the material flows in just about every transfer that I come across with some startling results and one thing is for sure; if you have wet material you can through trajectory calcs out of the window. Really wet coal still has no trajectory at 2 to 2.5m/s and is anyones guess above that.

To give an example look at this very wet product (not coal) on the photo. I hope the photo is size large so that people can examine it closely. The chute is a 1980's design where the material is caught in the main chute and the scrapping fall into a separate chute. Both ending up on the same belt.

You can see from the photo that under these conditions ALL of the material is discharged down the scrapings chute and only water travels down the main chute. Addmittidly this is a rare occasion but it proves a point.

Attachments

dscf1403a (JPG)

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I too have been throught he traps as they say, Dave.

But please read what I said everso nicely though:

"In practice the faster you go the more proper trajectory you get so you musn't go too slow."

This is a fact

Now by putting the PRIMARY TYPE scraper in the secondary position, then if you do have a SLOWISH belt:

"ALL of the material is discharged down the scrapings chute and only water travels down the main chute."

(You wrote that, not me)

This is a fact too

All I am trying to do is warn the good people that I have found in practice that operating on sticky material the primary scraper can cause damage to the belt.

(Been there, done that....never again though)

I am also trying to provide the solution which I have found to actually work nicely in practice.

Feel free to disagree Dave (but please go easy on the belts)

Cheers

LSL Tekpro ■

I'm not arguing about your scraper comments Graham. In my book its horses for courses. Each transfer needs a specific design which may be excellent for that case be no good for another application. The likelyhood of these guys buying a design is pretty slim so we stick to the generalities.

Harping back to the 60's it was quite common to keep transfers as low as possible and belts as slow as possible. Look at recomended max speeds for that era. These worked pretty well when the material varied from dry to sloppy which is the case in question. You have to cater for both material conditions and slow belts do this best. The modern high tech chutes require lots of height and material training which is a no no for sticky stuff.

The photo was an example of what can be encountered. It was not one of my chutes. It has since been replaced by another company who never bothered to see what the problem was and therefore gave little improvement. You know the story. My difficult one was getting <6 wet coal mixed with tar to pass through 6 transfers without blocking.

I'm not sure everyone read the pic correctly. Anyway to clear any doubt. The outline of the main chute section is the white portion on the right and the yellowish stream from the top is the water. The shot is taken square on with the primary scraper much lower than the the norn but not as low as Graham suggests. In other conditions the material does go down the main chute. ■