The invention relates to processes and apparatus for recycling. More particularly, the invention relates to processes and apparatus for recycling composite materials.
There are several types of packaging used for food products or for different industrial products in general. Most food and industrial product packaging is typically constructed in one of the following forms: a) paper board, for example, cardboard; b) plastic, for example, polyethylene terephtalatic (PET); c) paper/plastic, for example, beverage cartons; d) plastic/aluminum laminates, for example, packaging for coffee, dry soups, dog food, chocolates, cereals, etc.; and, e) paper/plastic/aluminum, for example, beverage cartons for orange juice, milk, etc.
When the food and industrial product packaging contains only paper (as in (a)) or paper/plastic (as in case (c)), the public has already discovered processes to recycle such packaging materials. For example, paper packaging is fed into hydro-pulping equipment to desegregate the paper fibers. The separated paper fibers are then removed with water and dried in a paper machine. The resulting recycled paper may then be reused, for example, to make cardboard boxes for instance. In the case where the food and industrial product is a composite material such as paper/plastic (as in case (c)), the plastic is separated automatically in the hydro-pulping, and normally discarded since the plastic is (1) rarely made of only one type of plastic and (2) contains contaminants, which makes it difficult to reuse the plastic rejects.
When the food and industrial product packaging contains only plastic such as bottles, the recycling process involves washing, drying and grinding the plastic packaging, and extruding and melting the ground plastic packaging in order to form a new, recycled plastic product.
The recycling of food or industrial packaging becomes challenging where plastic/aluminum laminates and paper/plastic/aluminum composite materials are concerned. For example, both types of packaging typically contain a very thin piece of aluminum foil, for example, less than 10 microns thick, intimately joined with a plastic component, for example, a plastic sheet less than 100 microns thick, and paper. The paper can be recycled using recycling processes already described. However, the plastic and aluminum rejects cannot be recycled.
There are no commercial recycling processes for recycling plastic and aluminum rejects from plastic/aluminum packaging and paper/plastic/aluminum packaging due to the difficulties associated with separating the plastic from the aluminum. Moreover, whereas paper/plastic/aluminum contains one type of plastic, plastic/aluminum packaging generally utilizes more than one type of plastic. For example, the plastic component typically contains polyethylene (PE), with minor amounts of polypropylene (PP) and polyethylene terephtalatic (PET) also present. These factors contribute to the present inability to effectively recycle plastic/aluminum and paper/plastic/aluminum packaging.
Plastic/aluminum food and industrial packaging and the plastic/aluminum rejects, for example, factory wastes, spent packaging, etc., are not being properly recycled; most of these materials are being dumped into landfills or incinerated. Although incineration sounds like an efficient process, incineration possesses some operating difficulties due to the presence of the aluminum. Aluminum does not “burn” and generate gas, rather aluminum oxidizes and generates aluminum oxide, a solid waste, which needs to be periodically removed from the incinerators.
At the present time, Corenso United Oy Ltd. of Finland utilizes a pyrolysis process to recycle paper/plastic/aluminum packaging once the paper component is removed. Pyrolysis is conducted for generating a combustible gas that can be used to generate energy. However, the remaining aluminum foil, in pieces, cannot be recycled or reused. During pyrolysis, the aluminum partially oxidizes and the oxidized aluminum becomes difficult to melt. Aluminum oxide will form from the outside to the inside of the aluminum foil. Aluminum oxide melts at temperatures above 1,700° C. and does not melt at temperatures of 700° C., the melting point of aluminum. Since the aluminum foil is very thin to begin with, even a thin oxide layer becomes a significant obstacle and prevents successfully melting the aluminum foil. In addition, the pyrolysis process creates aluminum/aluminum oxide residues and generates a considerable amount of burnt gases. Hence, pyrolysis is not an environmentally friendly process and fails to effectively recycle aluminum from paper/plastic/aluminum food and industrial packaging.