Practical Matters

The recycling of shredded plastics from electronics using dry separation technology can be done today. There is equipment available in the market for the identification of the different polymers in plastics from electronics using high-speed camera identification technology. This equipment is expensive and its results as of today are not that good, maybe 85 percent effective with the non-black material and not effective at all with black plastic. But there is another way.

EXAMINING THE NUMBERS
Shredded plastics from electronics is generally a mixture of at least 10 different  polymers  along with 1 percent to 2 percent metal. Currently, companies are getting zero to 4 cents per pound for these commingled plastics, but if the material is separated, you can sell metal-free polymers for more than 20 cents per pound. Depending on what you are shredding, CPUs contain about 15 percent plastic, while other electronics are close to 30 percent plastic on average. Using these numbers, you will have an average of 25 percent plastic by weight. (One-third CPUs to two-thirds electronic scrap.) Therefore, 100,000 pounds of mixed electronics will give you approximately 25,000 pounds of mixed plastic with metal. For this article we will work with these numbers.

The 25,000 pounds of mixed plastic with approximately 2 percent copper in it at a rate of 3 cents per pound will yield $750 dollars per day. With that product, you are losing the copper, or $450 dollars per day in additional revenue.
There is a better way. 

In light of environmental restrictions, we are going to work with a dry process to separate the various plastics. This will be done using different equipment and processes than in a flotation (wet processing) system.

NO WATER NEEDED
First, you want to take that 2-inch and smaller shredded plastic mix and grind it down to a size that is uniform and frees up any of the remaining metal in it. Next, you will run this material over a gravity separator or a screening system to remove the $450 worth of copper, giving you a clean metal-free mixed plastic product to work with. 

The next step is to separate the polymers. You are going to run the mixed ground plastic over a dry system gravity separator to remove the light plastics. These plastics have a specific gravity of less than one. This material includes polypropylene (PP), polyethylene (PE) and the high-density polyethylene (HDPE). These light plastics will account for roughly 6 percent of the total plastics. This material can be packaged in bulk-sized shipping sacks and sold for 3 cents to 4 cents per pound.

Next, you are going to run the remaining plastic mix through another gravity separation process to separate the heavier plastics with a specific gravity of more than 1.1. These plastics include polycarbonate (PC),  polyethylene terephthalate (PET), phenylene ether co-polymer (PEC) and CPVC (chlorinated polyvinyl chloride). These plastics make up about 15 percent of the total plastics from electronics. Again, this material can be loaded into bulk-sized shipping bags and sold as a mix for roughly 3 cents per pound.

The remaining material is regular and flame-retardant (FR) polystyrene (PS), acrylonitrile butadiene styrene (ABS) and high-impact polystyrene (HIPS). This is close to 80 percent of the plastic contained in electronics. It can be separated and sold for a decent price (more than 20 cents per pound).  This material will not be perfect, but will be more than 90 percent pure when separated.

The HIPS can be separated in two ways.  One method is to separate the black plastic by hand prior to shredding, but in some cases this is not practical.  The second method involves running the ground plastic through a high-speed color separator using a camera system. (This type of equipment is used in the food industry.)  This will separate all the black plastic, which is primarily HIPS. To be sure that it is HIPS, you could also keep the HIPS in the process until after you have separated all the other polymers except the ABS and PS. HIPS is just about the same specific gravity as the ABS and PS.  At this time it can be color separated.

 The remaining mixed PS, ABS, FRPS and FRABS have to be separated using specific gravity. Also at this stage you can separate the FR material from the non-FR material. Approximately 15 percent of the remaining material is flame retardant, the other 85 percent is not.

STATIC INTERVENTION
Now comes the hard part, separating the ABS from the PS and the FRABS from the FRPS. Both ABS and PS have almost the same specific gravity, so they cannot be separated from one other with a specific gravity system. This can be done with an electrostatic separator. This process will put a magnetic charge on one polymer and not on the other.  With one polymer being attracted and the other one not, they can be separated.

It sounds simple; it’s not, but it can be done by using proven equipment manufactured for other industries. Let’s go though the numbers.

1) A) 25,000 pounds of   shredded plastic  $750.00

2) A) 24,500 pounds of ground   clean plastic  $735.00

 B) 500 pounds of mostly   copper wire $450.00   

Total $1,185.00

3) A) Light plastic (6 percent,  or 1,500 pounds) $45.00

 B) 500 pounds of mostly copper wire $450.00

 C) Heavy plastic (15 percent, or 3,750 pounds) $112.50

 D) ABS, PS, FRABS, FRPS & HIPS (78 percent, or 19,500 pounds, at 20 cents per pound) $3,900.00

Total $4,507.50

As you can see there is a more than $3,000 increase per day for the complete processing of the shredded plastic. With the equipment cost of approximately $750,000, there can be a payback in a little more than one year when you are processing 100,000 pounds of electronics per day. At 50,000 pounds of electronic scrap per day, the payback would occur in a little more than two years. If you don’t want to spend that much money for the whole system, look at the gain by just grinding the plastic and removing all the metal.

 Now, there is a hitch in this process, and that is finding the market for 90 percent clean pure product. It is there in the recycled plastic extrusion business. You just have to find it. I am sure that this market also will expand.

The author is a consultant to the electronics recycling industry and can be reached at Pfmprinz@aol.com.