Classifying – separating – and assorting solids – Precedent preparation of items or materials to facilitate... – Selective differentiation
Patent
1995-08-09
1998-04-14
Terrell, William E.
Classifying, separating, and assorting solids
Precedent preparation of items or materials to facilitate...
Selective differentiation
209 121, 2091725, 209930, B03B 100
Patent
active
057382220
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for separating solids mixtures of differing density, a separating liquid and a device for implementing the process. The process is above all suitable for the analysis and technical separation of waste products belonging to the group of plastics, glass and electrical scrap.
2. The Prior Art
When recovering recyclable products from mixtures of waste, separation and grading are the first processing stages. Mixtures containing differing amounts of materials of the most diverse nature have to be classified in separation processes. Of all the problems which exist at the start of recycling processes, obtaining information regarding the separability of waste mixtures and determining the useful material content are basic prerequisites for cost-effective plant operation. For said reason, besides developing and refining separation processes it is just as essential to find a way of controlling the selectivity of separation and determining the concentration of useful materials throughout all of the processing stages. There are currently on the market no process-accompanying measuring methods or devices which allow recycling plants to be operated with a view to selectivity of separation and concentration of plastics materials.
Up till now, determining the useful material content in waste mixtures has been effected by manual separation followed by grading analysis in the case of waste assessment (Hardtle, G., Marek, K., Bilitewski, B., Kijewski, K., "Recycling of plastics waste" Berlin: E. Schmidt, 1991, supplement 27 of MULL UND ABFALL (Refuse and Waste), p.33) or by the costly method of manual separation and grading in the form of useful material assessment in the case of electrical and electronic scrap, car recycling (von Essen, U. "Plastics Recycling Practice", published by TUV Rheinland GmbH, Cologne 1993, chapter 8.2, p. 3-5).
The use of automatic sorting systems to separate PVC and PET bottles on the basis of X-ray fluorescent analysis (identification of PVC) in the USA (Gottesman, R. T., The Vinyl Institute, USA, IUPAC Internat. Sympos. Recycling of Polymers, Marbella 1991, Separation of PVC and PET and other plastic using automatic sortation devices). The degree of purity of PET is however unsatisfactory, so that after automatic sorting a flotation process is required to achieve separation into pure grades.
The previous analytical processes for the separation of plastics mixtures may be used only for input assessment prior to the comminution processing stage. The required process-accompanying analysis and evaluation of the useful material concentration cannot be effected in said manner because an isolation after comminution is technologically no longer possible to achieve and a sample cross-section is not meaningful unless the mass flows are known.
A method of separating materials according to their density, which has already been used in practice, involves the use of heavy and dense media. The principle of said method is that a heavy or dense medium is adjusted to a specific desired density. Aqueous solid suspensions are commonly used for said purpose. Such dense media are used to separate ore and gangue, the material to be separated being split into a floating and a sinking component. Adjustment of the density of the dense media is effected by introducing disperse solid additives into water. The solid additives used are ferrosilicon, also PbS (galenite), iron sulphate (magnetite), barium sulphate, quartz sand, pyrite.
From U.S. Pat. No. 2,266,840 a device and a method are known for determining the percentage of a mineral such as coal in a mineral product, which may contain coal and ash in differing amounts. The invention may also be translated to other minerals such as ores in a mineral mixture, with zinc chloride being mentioned as a separating liquid.
JP-A-59-196760 relates to the classification of seals made of polypropylene according to the degree of crystallization through density separation in alcohol solutions havi
REFERENCES:
patent: 1854107 (1932-09-01), Chance
patent: 2266840 (1941-12-01), Alexander et al.
patent: 5246115 (1993-09-01), Vezzoli et al.
patent: 5268128 (1993-12-01), Lahoda et al.
Hardtle et al, Mull und Abfall (Refuse and Waste), Supplement 27, Berlin 1991, p. 33.
von Essen, U. "Plastics Recycling Practice", published by TUV Rheinland GmbH, Cologne 1993, chap. 8.2, pp. 3-5.
Gottesman, R.T. The Vinyl Institute, USA IUPAC Internat. Sympos. Recycling of Polymers, Marbella 1991.
Allies Manfred
Pagenkopf Ingeborg
Nguyen Tuan N.
Pagenkopf Ingeborg
Terrell William E.
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