Distillation: apparatus – Apparatus – Systems
Patent
1995-09-06
1998-05-19
Bhat, Nina
Distillation: apparatus
Apparatus
Systems
202 94, 202 96, 202108, 202111, 196 98, 196116, 196123, C10B 900, B01D 100, C10G 700
Patent
active
057530866
DESCRIPTION:
BRIEF SUMMARY
This is a national stage application of PCT/US94/02433, filed Mar. 8, 1994.
I. TECHNICAL FIELD
The present invention relates generally to processes for low temperature thermal decomposition of waste plastics. Specifically, the invention focuses upon achieving decomposition of waste plastics at a lower temperature than was previously possible. In particular municipal, health and industrial waste plastics are processed such as (but not limited to) polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyurethane (PU), and polyvinyl chloride (PVC).
II. BACKGROUND ART
Waste plastics, that is synthetic polymer-containing substances, pose an environmental issue because of the problems associated with disposal: a large volume of non-biodegradable material. Because of the limits on landfill capacity, future recycling or decomposition is a necessity. Direct recycling back to the manufacture is not always feasible because such waste plastic is often mixed with respect to polymer type and separation is uneconomical. Economical considerations for processing waste plastic often require the use of the unseparated mixed waste plastic. Plastic recycling originated with the manufacture of synthetic thermoplastics. Rejected parts, trim, and flash from operations represented valuable materials that were ground and recycled with virgin material. This process was potentially repeated a number of times provided the percentage of regrinds remained low. As long as the plastic scrap generated by the industry was clean and uncontaminated with other plastics, reprocessing within the industry continued to expand, provided the price of virgin plastic remained high. After 1960 with a decrease in prices, profit margins for plastic scrap were squeezed, and disposal instead of reprocessing often occurred.
After 1970, plastic prices rose again due to OPEC raising the cost of petroleum feedstocks and recycling practices again increased. Interest increased not only in processes for reclaiming waste plastics, such as product evaluation for chemicals and fuels, but also in the necessary step of separation of plastics from other waste material. A review of this early history of plastics recycling is given by R. J. Ehrig in Plastics Recycling, Oxford University Press, N.Y., 1992, hereinafter referred to as Ehrig (1992). Some of the early operating plants for recycled plastic included a Department of Energy funded plant in LaPorte, Tex., which used a fluidized bed of sand and was designed for 17 million pounds per year of atactic polypropylene. It ran from 1980-82. In 1984 at Ebenhausen, Germany, a 20 million pound per year plant used molten salt with a fluidized bed reactor to process plastic wastes and tires.
In all cases economics governed whether such plants continued operation. Since 1985 plastics recycling has become more economically feasible due to continued plastics technological growth and increased environmental concern, however, significant cost impacts remain due to the level of the elevated temperatures previously required.
III DISCLOSURE OF INVENTION
The present invention relates to a process which overcomes the above-mentioned deficiencies in the prior art and to a process which achieves decomposition of waste plastic at a relatively low temperature. As one example, the process decomposes a mixed stream of waste plastic at a temperature generally less than 375.degree. C. in a hot oil medium. The process converts the polymeric structure of the waste plastic or plastics to smaller chemical molecules such as the monomeric units and related chemical structures at a relatively lower temperature. It also serves the market for the such products. Since this market is not a to-be-developed manufacturing process, but rather one for which existing plants in the refining and petrochemical industries already exist, the process is adaptable to existing facilities that are already experiencing limited supplies of low molecular weight, heteroatomic free feedstocks from petroleum crude oils. The low-m
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Barbour Floyd Alan
Guffey Frank D.
Bhat Nina
Santangelo Luke
The University of Wyoming Research Corp.
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