Chemistry of hydrocarbon compounds – Production of hydrocarbon mixture from refuse or vegetation – From synthetic resin or rubber
Patent
1997-03-21
1999-06-29
Yildirim, Bekir L.
Chemistry of hydrocarbon compounds
Production of hydrocarbon mixture from refuse or vegetation
From synthetic resin or rubber
585240, 208400, 208415, 208424, 208426, 201 25, 201 25, 4221841, 422198, 422203, 422232, 422235, 422236, C07C 100, B01J 1924
Patent
active
059171022
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for depolymerizing used and waste plastics, and also to an associated process.
2. Discussion of the Background
In a process for re-treating carbon-containing waste, EP 0 236 701-A1 describes a thermal pretreatment in the presence or absence of hydrogen of organic wastes of synthetic origin as a preliminary stage for a subsequent hyrdogenating treatment. From the description and also from the examples it emerges that such a pretreatment can be carried out in a stirred reactor.
EP 0 512 482 A2 describes a thermal treatment of such synthetic organic wastes in which no coke formation or only a small amount of coke formation occurs in the absence of hydrogen.
Used plastics such as those which have to be recycled, for example, as a result of the German Packaging Regulation, have an impurity content of up to 10% by weight. Some of these impurities are present as fine fillers and pigments which have virtually no settling rate in the liquefied used plastic. Other inert constituents are, for example, adhering metal parts, for example aluminium lids or thin aluminium layers made of composite foils.
In the preliminary sorting and ancillary processing, it is not possible, or possible only at extremely high expense, to extract these metal foils or to remove them mechanically/manually. At present, the ancillary processing of used plastics permits particle sizes of up to 10 mm. In the extreme case, even metal agglomerates up to this size are therefore possible. The metal parts entrained with the used plastic have, because of their density and sizes, a marked to high sedimentation rate in liquefied plastic. They can therefore erode pumps and other sensitive elements, which may result in their destruction.
In order to be able to depolymerize used and waste plastics thermally, it is necessary to introduce a large amount of energy at a high temperature level (about 400.degree. C.). Plastics are very sensitive to overheating. Such overheating results in uncontrolled decomposition with undesirable side reactions.
SUMMARY OF THE INVENTION
The object of the invention is to eliminate the disadvantages described in the prior art, in particular in regard to overheating and erosion problems.
It is therefore proposed, according to the invention, to convey the reactor contents via a circulation system connected to the reactor as a protection against overheating. Said circulation system comprises, in a preferred embodiment, an oven/heat exchanger and a high-output pump. The advantage of this process is that a high circulating flow via the external oven/heat exchanger achieves the result that, on the one hand, the necessary temperature overshoot of the material contained in the circulation system remains low and, on the other hand, favourable transfer conditions in the oven/heat exchanger make possible moderate wall temperatures. As a result, local overheating and, consequently, uncontrolled decomposition and coke formation are avoided to a very substantial extent. The reactor contents are thus heated under comparatively very mild conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a preferred embodiment of the device of the invention.
FIG. 2 shows a reactor with a similar construction to that in FIG. 1, with the difference that the riser section is not formed as a pipe, but by a reactor segment which is separated from the remaining reactor contents by a partition.
FIG. 3 shows a depolymerization system containing two containers which can be operated at a different temperature level.
FIG. 4 shows an enlarged detailed of the T-shaped arrangement of the downcomer section and branch of FIG. 3.
FIG. 5 shows a processing alternative in which a separating device is connected immediately downstream of the downcomer section.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A high circulation flow can preferably be achieved with high-output rotary pumps. However, just like other sensitive elements of the circulation system, these have the dis
Hecka Christian
Holighaus Rolf
Niemann Klaus
Strecker Klaus
Ullrich Dieter
Veba Oel Ag
Yildirim Bekir L.
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