3rd September 2002, 15:48
Conveyance of Residential Waste
Does anyone know where I can get information for sizing pipes for the pneumatic conveyance of residential waste? Right now I am just looking at the equilibrium equation to find pressure loss. Is that the correct equation to use?
Also, can anyone recommend friction factors to use?
Any help offered would be greatly appreciated. Where I am from this method is still under investigation so there is no literature on it.
5th December 2002, 8:33
Since it is residential waste I believe that you will have particles of widely varying size range ! Correct me if I am wrong !
For such varying particle sizes I guess no one will be able to give you any satisfactory answer for friction etc. Even for common bulk powders the assessment of friction factor varies widely as per the equations available in the literature !
In order to overcome this problem we have developed a set of equations for prediction of pressure drop.
We normally run a laboratory scale test in order to determine a coefficient in that equation and then based on the equation we can design any scaled up system. Till now we have tested the method with success for some materials and would be very much willing to help you with your product !
Do you have your own test laboratory where you run tests !
we shall be willing to collaborate with your organisation if you so desire! My email address is email@example.com
with best regards
10th January 2003, 9:17
Handling Residential Waste
The handling characteristics of residential waste is likely to depend much upon the location from which it is collected. Warren Spring Laboratories in UK did considerable experimental work in the late 70's on handling domestic waste and developed a 'plug flow' system based upon direct injection into the conveying pipe, (no rotary valves or other pressure barrier), from a supply hopper into a pipe approx. 200mm diameter by means of a screw feeder. This technique employed an air knife that separated a solid plug of the material and projected it as a coherent mass along the pipe with minimum dilatation. (Ajax equipment supplied the screw to deal with the difficult problem of promoting flow in the supply hopper and producing a compacted plug virtually impervious to the leakage of air)
This method is highly efficient on air consumption because it 'fires' the slug like a bullet. There are various design 'secrets' to the technology, such as (1), Using twin air knives to effect plug separation and the supply of the subsequent conveying air in two stages to prevent plug damage. (2) Relaxation of the tube diameter, (a) To avoid regenerative wall friction during the plug compaction process and (b) To relax wall contact to allow transfer on a Bingham layer in the conveying tube and negotiate bends without excess wall pressures. (3) design of the integrated hopper/screw feeder to overcome the strong arching tendencies of variable, elastic natured product and provide a powerful, balanced, end thrust to the delivery end of the screw.
Wall friction is easily measured. See www.ajax.co.uk.
One of the operating virtues of this method is the ability to handle virtually all the miscellaneous junk that is collected in domestic waste.
As with all conveying systems, the 'systems' aspect is crucial to effiecient performance. Probably the most difficult part in this system design is then geometry of the hopper/feeder element.
11th January 2003, 15:36
Conveyance of Residential Waste
We are manufacturers of Waste Recycling Equipment. Please visit our site at www.trommel.co.uk which may be helpful to you.
We certainly do not use pneumatic conveyance of waste material due to the unknown and varying characteristics of this material. Conventional belt conveying is used. Raw waste will go up a plain 15 degree conveyor - shred it and it won`t, a chevron belt has to be used.
Our Blowers are used to remove ligtweight contaminates from screened material, this is the nearest we get to using air.
If you have any questions we would be pleased to pass on our experiences.
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