From the description my opinion would be that the problem lies with the chute work into the feeder as a chain conveyor can't "reach up into the chute and pull material down", your material, in this case coal, has to flow into the chain conveyor to be conveyed.

You need to speak to your chute/bunker designer rather than the feeder supplier. If the chute and bunker won't flow then there's nothing the feeder can do. ■

Originally Posted by nemprr

Drag chain conveyor - coal clogging due to moisture

Dear Sirs,

I am a new member to the forum.

I need your expert advice on the below issue.

I am working on a 80MW indonesian coal based power plant in India. The boiler is in commissioning process. One of the major problem faced is, coal which has moisture content 32%, is getting clogged in the coal feeder inlet chute.

Below are the details about the system.

Coal feeder - inlet opening size - 750mm x 750mm

Chute height (bunker outlet to feeder inlet) - 1334mm

Feeder type - Drag chain - double strand

Chain speed - 0.15m/sec

coal size - 50mm

Presently the coal choke is being hammered manually to release the jam.

I am not sure whether feeder vendor has considered moisture content in his design calculation. Whether really it matters?. Could anyone help me in providing solution to solve the choking permenantly.

Advance Thanks for your suggestion.

Regards,

PR

Welcome to the forum, you are among friends who have many years of work

experience, and training in many fields involved with bulk handling of materials

and can help with solutions from past experience.

My experience as a mine mechanic involved mined Halite and both passive surge piles ( that were badly designed)and active drawdown bins using Apron Feeders and inverted cone silos with openings sized properly for the run of mine (minus six inch ore) halite which was 36 inches which were the screening plants belt sizes required for 450 TPH tertiary processing to make finished halite of minus 1 inch product.

I also worked as seasonal laborer in a pulverised coal steam station whch generated 230 mega watts and consumed 100 tons per hour of bituminous coal.

Assuming you are describing a double strand flight conveyor as the bed chain

conveyor used in this setting- rather than a double strand plow conveyor,

and as the chute is 29.5 inches by 29.5 inches by 53.5 roughly it brings up a

number of issues.

Do the chutes in question have a tapered design with the chute being narrower

at the bottom discharge end or is the 29.5 inch size the same size from the

hopper base to the chutes open mouth above the feeder?

Is it possble you are recieving broken run of mine coal that has not been sized?

Mosture content matters as it affects flowability to an extent where any mud or

clay will become a magnet for water.

Is the coal being loaded into a hopper used as a bunker with chutes that are fully

open to the chain conveyor?

1. Is the width of the double strand flight chain bed smaller or the same width as

the chutes opening-it sounds as if it is not as wide as the double strand flight

conveyor?

2. The chutes have to be designed to allow unrestricted mass flow where the

material being conveyed is not allowed to bridge and rathole and cannot

create a compacted mass creating a bridge of material that will continue support

itself.

Perhaps all that is needed is to spray an anti caking solution on the inbound coal entering the stockpile (if used) to keep it from sticking.

Sodium Ferro Cyananide-Yellow Prussiate of soda is used as an anti-caking agent

for Halite and many food stuffs and is easy to obtain and mix in quantity to spray

on hygroscopic materials that cake and clog like table salt, flour cake mixes etc..

Lining the chutes with a slippery liner material cut to size will aid in coal handling

as well.

But I believe you will gain more headway quickly with the anti caking agent as an aid in maintaining the flowability of the coal due to its moisture content as the spraying of the high concentration yellow prussiate of soda will be an quick fix if your incoming coal is sized per the specification.

As you are in the comissioning phase, obtaining some yellow prussiate of soda

YPS from a chemical house or a bakery supply house to experiment on the required amount of solution to acheve flowability is in order before anything else is done as spraying the stockpile bound coal with a solution of anti caking agent will solve these issue as yellow prussiate of soda is unaffected by moisture when it is used for stockpiling hygroscopic materials like halite and table salt.

A higher concentration of the YPS may be all you need in this case which will stop the coals ability to stick and clump.

Seimans manufactures YPS dispensing and mixing machineries and thier brand of YPS anti caking agent and mixing machinery is available world wide.

Taking a cubic meter of the steam coal and spraying it with a solution of YPS while it spread out in a thin layer and dumping quantities of it in a six by six inch piece of sheet metal duct 53 inches long used for air conditoning and secured to a vertical chain vise on a nearby work bench will represent 25 percent of the chutes cross section rough size would be a quick indicator/proof of how much YPS in solution you would need if that route is chosen.

The use of the YPS and possibly a properly sized air cannon could solve the issue

with no further modifications.

my thoughts anyway.

lzaharis ■

Namaskar, Asaalam Maalaikum,

I have an article from Power Magazine Oct 03 which I can e-mail to you that explains issues and problems involving funnel flow of coal and how it was remedied by Wisconsin Public Power at one of their power stations that was damaged due to an explosion when they were blending Powder River Basin coal and bituminous coal and how the problem was solved by the utility.

And as you are apparently dealing with funnel flow it will be very informative regarding your coal delivery problems.

If these intermediary chutes are really necessary to direct flow to the drag chain conveyor (if it is exposed and not in a hopper of its own) perhaps an air cannon in combination with the anti caking agent and systems from Siemans can solve the troubles on this muddy cricket pitch.

Heres a link for air cannons www.martin-engineering.com

they have a world wide presence and work in the power generation industry also.

Mr. Lyn Bates has an excellent thread regarding mass flow of materials here on the web site site which describes how it must be designed to provide mass flow and to avoid bridging and rat holes in bins.

If you have the opportunity the BNSF.com web site also has wealth of information regarding coal handling.

lzaharis ■