Conveying Wet (25% moisture) Fly Ash

David Campbell
(not verified)
Posted in: , on 9. Mar. 2009 - 19:30

Can anyone advise me as to sucess in conveying wet fly ash (25% moisture). For every person who says it can be done, there is another who says you will clog hoppers, chutes, etc. Has anyone out there done this successfully and can you direct me to a solution? Thanks.

Re: Conveying Wet (25% Moisture) Fly Ash

Erstellt am 10. Mar. 2009 - 03:25

I have seen it done at a coal fired generating station, it is not a pretty sight. (I assume you mean coal ash) There were about 3 belts in series the first being loaded by from the wet conditioner, and the last discharging into a pit.

The material stuck to a vertical UHMW lined chute face. The open cross section of the chute narrowed daily. The return run was a mess as the belts were hard to clean. The chutes had to be cleaned out regularly. Imagine trying to convey wet plaster and you will have a good picture of what it will be like. Also a good degree of your success will depend on how good the conditioner works, usually you get slurry one minute and dust the next.

We have used centreless screws on a similar material with good success. We have also handled flyash mixed with bottom ash on a belt at an incinerator, but that is a different ash altogether.

David Campbell
(not verified)

Re: Conveying Wet (25% Moisture) Fly Ash

Erstellt am 10. Mar. 2009 - 07:10

thanks for your valauble assistance!

Re: Conveying Wet (25% Moisture) Fly Ash

Erstellt am 12. Mar. 2009 - 07:13

Hi David..

Conveying power station ash has been done for years, so fear not with the principle.

I went on a tour of power stations in UK (Drax etc) and in Europe to see how they got on with conveying ash, so I could do the same for the several power stations built here in South Africa way back in the 80's.

Power stations produce alot of fly ash and a bit of coarse bottom ash.

Fly ash is dry so we mix in some water to stop it blowing off the conveyors.

Bottom ash is sopping wet and is combined with the fly ash to convey it.

The trouble with conveying ash is that at between 15 and 20% moisture it becomes extremely sticky, so try and make it as dry as possible but not dusty.

Due to its nature you can drop the stuff directly onto a belt so go for vertical sided chutes, and use curved baffles at the top to direct the ash vertically downwards.

The client experimented here with curved hood and spoon chutes, but the bottom spoons clogged up. So they changed to a flexible hood and spoon arrangement with the bottom spoon being made as a flexible lobster back.

This did not not work so good though, and also blocked. The vertical sided chutes however are still going after 25 years.

Another ever present problem is what to do with the belt scrapings if you have an angled transfer station. Belt washing can solve this provided you have done it many times before and therefore know the pitfalls ...and.. ensure that it is maintained. Otherwise its a dead duck, and you need a separate scapings handling arrangement or a very well designed chute with the correct linings such as UHMWPE.

Good luck

LSL Tekpro

Graham Spriggs