Classifying – separating – and assorting solids – With heat treatment
Patent
1993-04-09
1994-11-22
Bollinger, David H.
Classifying, separating, and assorting solids
With heat treatment
2091272, 2091274, B03C 700
Patent
active
053660919
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the separation of plastic particles of a plastic mixture of plastics of a chemically different type which, however, are in a density range overlapping itself, such as, for example, polyethylene terephthalate (PET) and polyvinyl chloride (PVC), by an electrostatic separation process by means of a free-fall separator.
Enormous quantities of mixed plastic wastes are collected in many countries. A known example thereof are used one-way plastic beverage bottles. Said bottles consist of PVC or PET. In addition, the bottles have, as a rule, a polyethylene screw cap, and the PET-bottles are provided with a bottom part made of polyethylene (PE). A mixed plastic waste consisting of PET, PVC and PE is collected in the collection of such bottles.
Direct recycling of the mixed bottle plastics is not possible because PET melts only at 260.degree. C., whereas PVC decomposes already above the softening temperature of 160.degree. C., and PE already at 105.degree. to 135.degree. C.
There are, therefore, no appreciable possibilities for recycling such mixed plastics, so that heretofore, the waste plastics have not been collected in most cases but eliminated via the household refuse, i.e., they are finally incinerated or deposited in dumps.
Due to the fact that the dumping space becomes scarce and because of the resistance of the population against the set-up of new refuse incineration plants, said type of elimination will be highly restricted in the future by government regulations on recycling, among other things.
Furthermore, as a rule, no profits can be achieved for mixed PVC-containing plastics; the fact is rather that the reuser frequently demands a credit oriented on the dumping cost saved.
As opposed to the above, there is since a long time a demand for sorted recycling plastics, whereby the prices for this are in line with the prices for the new materials. For recycling goods, up to 60% of the value of the new materials is achieved depending on the quality. There is, therefore, much interest in processes for the separation of PVC-containing mixed plastics. The use of hydrocyclones is already known for the separation of plastics of different density. However, said process fails if the plastics to be separated are in the same density range, as intended in the present case.
Furthermore, a process has become known which exploits the different melting points of the plastics of a mixture for the separation. The plastic mixture is ground and heated, whereby the PVC particles melting first adhere to a rotating roll and are removed from the mixture. Since the process of melting out takes place very slowly, said process is suitable only for low through-puts and, therefore, out of the question for application on a large technical scale.
Furthermore, a process operating with an X-ray detector has become known. According to said process, the PVC-bottles are identified spectroscopically and sorted mechanically.
Such plants have a low through-put. The process is limited to whole bottles.
A process of the type specified at the beginning is known from DE-PS 30 35 649.
In this connection, the plastic mixture is brought to a uniform particle size of 3 to 7 mm, then charged triboelectrically, and admitted into a free-fall separator, where an electrostatic field of 3 to 5 KV/cm is maintained between its electrodes.
In this connection, a portion of the material is deposited in accordance with the charge on the respective electrode, whereas another portion of the mixture falls as so-called medium material through the free-fall separator because it is not attracted by any electrode due to insufficient electrostatic charge. Furthermore, plastics of the same density have heretofore not been accessible to electrostatic separation.
It is disadvantageous with the known process that considerable amounts of medium material are collected.
Now, it has been found that an increase in the degree of separation can be achieved, or an effective separation is made possible at all with certain plastic mixtures by subje
REFERENCES:
patent: 4379748 (1983-04-01), Hoogendoorn
patent: 4570861 (1986-02-01), Zentgraf et al.
patent: 4797201 (1989-01-01), Kuppers et al.
patent: 4809854 (1989-03-01), Tomaszek
patent: 5115987 (1992-05-01), Mithal
patent: 5118407 (1992-06-01), Beck et al.
patent: 5234110 (1993-08-01), Kobler
patent: 5268074 (1993-12-01), Brooks et al.
Geisler Iring
Hollstein Axel
Kleine-Kleffmann Ulrich
Neitzel Ulrich
Stahl Ingo
Bollinger David H.
Kali und Salz Aktiengesellschaft
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