Hi Alex,

I found good document , please refer this . you can get some thing.

http://www.ckit.co.za/secure/conveyo...i1-paper02.htm

regards

uditha ■

The spillage could also be caused by an inadequate chute design. Send me your transfer GA drawings to my email below and I will review and respond with my opinions. I specialize in transfer design and flow simulation.

Regards,

Gary ■

Alumina is very prone to flooding. When does the spillage occur?

Examine the hopper opening and fit an electromagnetic feeder beneath. Dust can be contained by a hood and isolating the vibrator unit across a flexible membrane.

There is a proprietary feeder for this purpose 'aus Deutschland' but you can just as soon knock one together in house.

If the installation is in a pot-room then you had better consider a pneumatic vibrator unit. Take a clapped out ball bearing and remove all but one of the balls, and the cage; drill a hole tangentially through the outer race; braze a pipe fitting against the said hole; couple it to the utility air main and away you go. No stray electrics at all. ■

Originally Posted by alex-kaveh

Hi All,

We have got an existing conveyor system ( Two belt conveyors and Transfer chute ) and we have got a heavy spillage issue in the transfer point between two conveyors. I am investigating to find a solution for spillage issue however it seems to be not an easy one. The details of the system is as below.

Material conveyed : Calcinated Alumina Powder

Bulk Density of 1000 Kg/m3

Very free flowing – Surcharge of about 5 degrees or less

Size : about 20 microns

Feeding and Receiving conveyor details:

Belt : 750 mm

Idlers : 45 degrees

Receiving conveyor inclination angle at chute area : 16 degrees

Tonnage rate : 130 TPH

Belt Speed : 1.8 m/s ( fixed speed ) VVVF not available

Width between skirts 450 mm

Chute : Spoon type

Conveyors are perpendicular in transfer point

Chute height : 3.5 m

The intension is to INCREASE the conveyor capacity to 250TPH which will worsen the spillage issue.

Just wondering it might be the sealing system that does not seal properly – As I have done the calcs using Helix software and even for 250 TPH rate the percentage full of belt is 73%.

Do you know of any sealing system that works for very fine flowing materials , or if you recommend any other solutions ? (Other than increasing the belt width or changing the inclination angle of the conveyor as these type of solutions are major and not practical in this case)

Highly appreciate your comments

Regards,

Alireza

Hi Alex,

I am an Artisan with 17 years experience in maintenance, with my main focus on spillage control and finding solutions to eliminate transfer area spillages.

I am willing to assist you for free. If you are interest, please forward me your contact details and I will gladly show you what I have implemented and achieved.

For proven records, please don't hesitate to contact my references below:

Peter Gates – Port Maintenance Superintendent, Phone: + (27) 72 550 6226 | Email: petergates10@yahoo.com

Simion-Mircea Muresan – Maintenance Manager, Phone: + (40) 773 837 642 | Email: mirceam34@yahoo.com

Best regards

Ashwell Craig Stallenberg

Phone: + (27) 731 494 411

Email: ashwell.craig@gmail.com ■

Originally Posted by johngateley

Alumina is very prone to flooding. When does the spillage occur?

Examine the hopper opening and fit an electromagnetic feeder beneath. Dust can be contained by a hood and isolating the vibrator unit across a flexible membrane.

There is a proprietary feeder for this purpose 'aus Deutschland' but you can just as soon knock one together in house.

If the installation is in a pot-room then you had better consider a pneumatic vibrator unit. Take a clapped out ball bearing and remove all but one of the balls, and the cage; drill a hole tangentially through the outer race; braze a pipe fitting against the said hole; couple it to the utility air main and away you go. No stray electrics at all.

--------------------------------------------

As John says the fine granular material will be hard to control, especially when aerated. If you anticipate modeling the material flow consider the need for a model that can include the gas filling the interstitial space along with the alumina flow. You must find means to understand the change in bulk density by the infused gas and work towards driving the gas out of the granular stream. In the mean time, the skirt system must be designed to contain the gas and alumina mixture until the product density is controllable with a skirt extension.

Since we do not see you dilemma, we are talking through our hats. Not much more point in that. ■

Hi Alex,

Everyone is saying the same thing, it is poor flow control. The point Larry makes in regard to aeration is extremely important as the bulk density of this material based on my experience with alumina is more likely to be below 500 kg/m3 due to this. There are no difficulty designing transfers for alumina providing you start with an accurate trajectory calculation and then focus on very good flow control. The very good thing about alumina is that it flows very easily. The bad thing is that it will easily bulk up if the flow control is poor. We have designed many dustless transfers without installing any dust collection system with no spillage issues by following pretty straight forward design principles that are outlined in our book (referenced on the website below). Providing you have a good trajectory calculation methodology the principles are so simple you can achieve excellent results without any modelling.

Cheers

Colin Benjamin

Gulf Conveyor Systems P/L

www.conveyorsystemstechnology.com ■

Regardless of the transfer, how does a material with 5 degrees surcharge angle convey up a conveyor of 16 degrees incline? Just out of curiosity, what is the angle of repose for this material? ■

Dear Mr.Alireza,

Request to post the general arrangement drawing of these transfer points.

We do have such chutes for iron ore fines. The problem with iron ore fines is the flow-ability reduces drastically from summer to monsoon periods.

Having polymer liners may avoid this problem. But I am little nervous to use polymer liners, which may catch fire, if hot work is carried out nearby.

Thanks & Regards, ■

Hi Joseph,

The angle of repose of alumina depends on the ultra fines content. Some alumina with very high ultra fines has not only a very low surcharge angle but a very low angle of repose. Regardless if you load it correctly you can get the alumina up reasonable inclines. The key is to ensure you do not fluidise the alumina with air as one does if you want to transport it using an air slide when it is hot i.e. straight out of the calciners.

As for GA drawings of solutions, this does not help unless you also give out the design parameters and this is not in my opinion appropriate

Cheers

Colin Benjamin

Gulf Conveyor Systems P/L

www.conveyorsystemstechnology.com ■

Hi Alex,

Whilst DEM simulation and correct chute design will provide the desired result, it sounds like you need to work with what you have and try to reduce or eliminate the existing problem.

To do this with a free flowing material like alumina you need to deliver the material onto the receiving belt with the least possible energy. Ideally, this might involve a cascade type of feed chute, a choke feed chute, a separate feeder as suggested or a well-designed spoon chute.

In your case, the spoon exists and you need to try to get this working. The main things that you need to achieve are that the material joins the belt at the belt speed or less, with minimal drop height onto the belt and with the bulk of the load at belt centre and away from the skirts. The material will settle out to the skirts as it travels, but at least that will be low energy contact.

If the material is being delivered onto the belt at more than the belt speed, it will not be taken away quickly enough and the feed will be impacting on the belt load, causing spreading and loading of the skirt seals. In this case, you need to slow the feed material down and this might require some trial and error. I would suggest that you try an extension of the lower chute at a flat angle to keep the material in the feed chute longer. This will also allow you place the chute exit very close to the belt surface to minimise drop. You would also contour the plate with a vee shape and extended sides so that the bulk of the load is delivered at belt centre.

If the material is still too fast, you might try some baffles in the drop chute itself, but you will need to make them either adjustable or removable in case you start blocking the chute – trial and error!

Once you get the material feed right, you can look at belt support – either close spaced idlers or slider bars. Slider bars usually do not like light constant load type of materials, but the low belt speed will mean that you will not have a problem. Use a load cradle with rollers at the centre and bars on the wings.

Finally, get a good, efficient and easily adjusted skirt seal. Alumina is very abrasive and the seals will need to be adjusted regularly. Self-adjusting dual seals are not recommended unless the primary seal is doing a very good job. Excessive material escaping the primary seal will quickly fill the void between primary and secondary seal and form a brick!

One last thing – ensure that you have a very good rear chute seal. If the belt stops while loaded, the material will probably flow down the belt and will flood the rear chute seal. This can be the source of major spillage.

Best of luck.

Terry Thew

ESS Engineering, Queensland. ■

I suggest take a look on below book:

Martin Foundations™, the Practical Resource for Cleaner, Safer, More Productive Dust & Material Control.

http://www.martin-eng.com/page/foundations-book ■

Originally Posted by Colin Benjamin

Hi Joseph,

The angle of repose of alumina depends on the ultra fines content. Some alumina with very high ultra fines has not only a very low surcharge angle but a very low angle of repose. Regardless if you load it correctly you can get the alumina up reasonable inclines. The key is to ensure you do not fluidise the alumina with air as one does if you want to transport it using an air slide when it is hot i.e. straight out of the calciners.

As for GA drawings of solutions, this does not help unless you also give out the design parameters and this is not in my opinion appropriate

Cheers

Colin Benjamin

Gulf Conveyor Systems P/L

www.conveyorsystemstechnology.com

===========================================================================================

The present G/A drawings would be very helpful in determining whether the existing chute can be adequately fitted to achieve the goal of no spillage.

They obviously can get the alumina to flow as they have stated, albeit with spillage. Now they wish to double the capacity through the same drop height and orientation between discharge and receiving belt. The surcharge angle is indicative of free flowing action, but does not indicate whether typical geometries will solve the spillage. So the bigger question is can a geometry be developed to achieve their objective with guarantees of no spillage, that do not require other equipment modifications such as pulley location change, elevation change, belt speed change, idler arrangement change, etc.

It is presumptuous to argue such without seeing the present G/A. Although some may have knowledge of the installation.

A solution may exist, but, I claim it will take more than knowledge of alumina trajectory path. Making a right angle flow will introduce more air into the flow stream thereby exacerbating the aeration. I think it is possible to achieve the goal with some additional de-aeration scheme and possible belt speed change.

I would not offer a solution without modeling the condition to gage the degree of calamity the alumina is at the present. Based on the model results the proposed design should be able to demonstrate the improvement against spillage. Of course, the solution comes with a performance guarantee, as any proper design should. ■