If this is post consumer plastic, you will probably have to consider washing and drying the material after shredding and/or granulation. Flotation in a saline solution will do partial density separation for different types of plastic.

Colour separation is a different issue which may affect price received.

In the current market, does the price for the product justify the process? ■

Originally Posted by J D

Flotation in a saline solution will do partial density separation for different types of plastic.

This is very intriguing to this layman. Are there any references available, please?■

The flotation solution must have a specific gravity greater than the plastic which you want to float. A similar concept to coal cleaning operations.

I checked my job file for this project and did not record what the solution additive was. (We were doing material handling but not to do with the plastics washing process) It was not common salt, (sodium chloride), but was something similar which was highly soluable in water.

The floatation tank achieved two objectives, high density plastics and grit were dropped out, and low density plastics, now clean, were skimmed off the top. The tank was similar to a wastewater degritter, a slow speed screw dragged heavies out from the bottom into a waste bin. The surface was skimmed off into another screw which transferred the desirable plastic to a vibrating screen to mechanically shake off as much water as possible, then a pneumatic conveyor system with a dryer before going for extruding into pellets.

The supplier for the floatation tank depends on your budget and location. Where is the project located? Wastewater treatment firms might be interested, but their pricing may mean you will have to put it together on your own. ■

After you have perfomed initial seperation of the plastic by broad type you will still need to make the plastic more homogenous to reduce colour and melt flow index variation.

This means that prior to use the plastic will require some sort of blending I have included a hyperlink below to an article published in Solids and Bulk Handling magazine about making recycled plastic homogenous using Zeppelin blending silos.

http://viewer.zmags.com/showmag.php?mid=wprsrs#/page15/

Pages 15, 16 & 18 ■

eposadar

Your situation seems to require an economical solution without a lot of expensive process equipment. Email your mailing address to me at jim @ hanaar . com, and I will send you some handwritten notes & sketches on the process which may be of assistance.

Since your labour costs are a fraction of North American costs, you could likely do more hand sorting, then granulate, wash, dry and pelletize which will reduce your equipment costs and perhaps eliminate the need for large storage bins. Avoiding film plastic will also make the process more manageable. ■

Originally Posted by eposadar

We are helping a local community of about 20 recyclers to design a facility to handle the mixed plastic materials they gather in the streets and garbage sites in such a way that they can be classified, separated and transported to individual production units. Our idea is to mill the materials in some central units, taking them to silos and do pneumatic transporting of the materials from the silos to the individual production units. Do you know of experiences of this kind or manufacturing facilities applied to the handling of about 60 tons per day of these materials? Could you share with us this experiences? Could you comment on our idea? Thanks,

dear sir or madom

this is frieda from intco recycling . you said you have aproblem with the transport of the plastics . may i know , do you have some eps (styrofoam).

we need the compacted eps as the material to make new products if you have eps , why not have them compacted so that we can buy them . by the way , we can offer the recycling machine . our slogan is to make it environmental and profitable to recycl eps

for information about our company please visit www.itcorecycling.com .

my emai is friedali@intco.com.cn ■

There is a technique to homogenize the various types of post-consumer plastic wastes. The process does require pre-sorting and pre-sizing of the plastic types before processing. Then a ratio is put forth and the materials are fed to the process. The end result is a homogenized polymeric compound - without degradation - and with consistent properties, including color and melt flow index. This compound can then be tailored for reuse (reformed) in to specific end-use applications. A consistent supply of the post-consumer waste polymer types is a key criteria in the design for the final reformed product. ■

It's an interesting issue that looks to be affecting all sectors of the solid recycling industry. Plastics seperation, even in the UK's costly labour market still looks to require a large percentage of manual seperation. However, with labour costs being lower in South America, manual processing will far outweigh the use of a mechanical seperation process, which in turn would cut overheads associated with power, water, plant and space. ■