Chemistry of hydrocarbon compounds – Production of hydrocarbon mixture from refuse or vegetation – From synthetic resin or rubber
Reexamination Certificate
1999-11-12
2001-01-09
Yildirim, Bekir L. (Department: 1764)
Chemistry of hydrocarbon compounds
Production of hydrocarbon mixture from refuse or vegetation
From synthetic resin or rubber
C201S002500, C201S025000, C202S084000, C202S152000, C202S158000, C196S098000
Reexamination Certificate
active
06172271
ABSTRACT:
TECHNICAL FIELD
This invention concerns a method and apparatus to extract oil from waste plastic using pyrolysis. More specifically, it concerns a method and apparatus to reclaim oil either from waste plastic which has been separately collected as a portion of municipal garbage or waste plastic which has been collected as an industrial waste product. The resulting oil can then be reused as fuel.
TECHNICAL BACKGROUND
Previously, oil has been extracted from plastic separately collected as a portion of municipal garbage or waste plastic collected as an industrial waste by severing the carbon frameworks at approximately 400° C. to reduce the molecular weight, resulting in liquified oil.
The energy required by this method is approximately 500 to 1,000 kcal/kg (of plastic). To deliver this energy, the liquified plastic is circulated by means of a pump and a furnace is provided on the path of circulation.
In order to prevent thermosetting resins or hard foreign materials from causing trouble in the pump circulation line, these substances must be completely removed through preprocessing. This drives up the cost and creates a problem of economy.
Furthermore, oil obtained solely pyrolyzing a plastic is unstable. This instability can result in coking on the walls inside the furnace pipes.
In the case of thermoplastic resins, some carbon residue is created in the process of thermal polycondensation, and these particles will be suspended in the pump circulation line. They can be separated from the liquid by passing the plastic through a filter or by centrifuging it, but there is no way to prevent some of the oil from combining with these particles and being lost. The carbon residue also could be a valuable source of energy; however, there is no way to use it efficiently.
Since this liquid oil will solidify at normal temperatures, the pump circulation line must be insulated with a steam jacket. A heavy oil lubricant is required in the processing line, which must be changed each time the line is started up or shut down. This increases the cost of operation.
DISCLOSURE OF THE INVENTION
Object of this Invention
This invention was developed in consideration of the problems which occur with the prior technology. It provides a method to extract oil from waste plastic comprising thermosetting resins and solid foreign matter without a problem. This method greatly reduces the burden of presorting the garbage or industrial waste.
Another objective of this invention is to provide a method and apparatus to extract oil which would reduce the incidence of coking during the process of applying energy to the waste plastic, and which would allow the solid residue of pyrolysis to be used efficiently as a heat source without having to separate it.
Yet another objective of this invention is to provide a method and apparatus to extract oil which is easier to start up and shut down the process in which the aforesaid waste plastic is pyrolyzed to extract its oil.
A further objective of this invention is to provide a method and apparatus to extract oil which can efficiently separate the gaseous component obtained from the pyrolyzed plastic into oils with high, and low boiling points and a low molecular-weight gas, and which can easily and efficiently yield high-quality oils with low boiling points.
Yet another objective of this invention is to provide a method and apparatus to extract oil which enables the size of the components involved in the process of pyrolyzing the aforesaid waste plastic to be reduced, and which can efficiently yield the gaseous products of pyrolysis.
Another objective of this invention is to design the pyrolysis process as discussed above using a horizontal agitation device such as a horizontal feed reactor in order to simplify and reduce the size of the pyrolysis device.
Another objective of this invention is to combine the aforesaid pyrolysis process with a dechlorination process in a single step by constructing a single mechanical agitation device to perform both processes. This will allow the size of the pyrolysis device to be greatly reduced.
Configuration
In order to achieve the objectives outlined above, this invention is designed as follows. Its first distinguishing feature is that it entails a dechlorination process prior to a pyrolysis process, which yields dechlorinated products comprising an admixture of waste plastic and sand. This process is used when oil is to be obtained by pyrolyzing waste plastics which may contain chloride compounds such as vinyl chloride. Prior to the pyrolysis process, while the waste plastic is being extruded and forced along, it is combined with heated sand and/or another additive agent. Heating the plastic to a temperature in the range between 250 and 350° C. results in a mixture of substantially dechlorinated waste plastic and sand.
The waste plastic which has been substantially dechlorinated by the aforesaid process is then subjected to the pyrolysis process. The second distinguishing feature of this invention is that this pyrolysis process entails applying heat directly to the mixture of plastic and heated sand, raising the temperature of the mixture to between
350
and 500° C., ideally between 400 and 480° C., and maintaining the mixture at this temperature to effect pyrolysis.
The third distinguishing feature of this invention is that it entails a residue incineration process to incinerate the residue of the pyrolyzed plastic. To make efficient use of the solid residue derivatives of pyrolysis, they are incinerated on a fluidized bed using pneumatically circulated sand as the medium, or on a high-speed circulation fluidized bed. Heated sand is produced, a portion of which is then returned to either the aforesaid pyrolysis process or to the dechlorination process which precedes pyrolysis. Thus the residue is incinerated through the use of recirculation.
The fourth distinguishing feature of this invention is that in order to obtain high-quality oil with a low boiling point, the product obtained from the aforesaid pyrolysis process is separated by a first separation device into a liquid oil fraction with a high boiling point, a gaseous oil fraction with a low boiling point and a low molecular-weight gas. A first process in which oils with high boiling points are returned to the aforesaid pyrolysis process is directly and serially connected to a second process in which a second separation device separates a liquid oil with a low boiling point from a low molecular-weight gas.
Another distinguishing feature of this invention is that the overall system for extracting oil by pyrolyzing waste plastics is as follows. The aforesaid processes of dechlorination, pyrolysis and incineration of residue are linked together. The first gas/liquid separation device separates the product obtained from the aforesaid pyrolysis process into a liquid oil with a high boiling point, a gaseous oil with a low boiling point and a low molecular-weight gas. After the pyrolysis process, two more processes occur: a recirculation process in which the oil with a high boiling point is recirculated to the pyrolysis process, and a separation process in which the second gas/liquid separation device separates the oil into a liquid with a low boiling point and a low molecular-weight gas.
At this point the product from the aforesaid pyrolysis process undergoes the first gas/liquid separation process, in which a cooling unit is installed above the gas/liquid interfacial unit. The product is separated into 1) a liquid with a high boiling point, 2) a gaseous oil with a low boiling point and a low molecular-weight gas. The oils with a high boiling point may be recirculated to the aforesaid pyrolysis process.
Ideally, the first and second gas/liquid separation processes should be connected in series. The aforesaid first gas/liquid separation process should entail a liquid dispersion unit which is placed above the gas/liquid interfacial unit. The liquid which is supplied to the aforesaid liquid dispersion unit should be the low-boiling point oil separated by the second separation process, pr
Amari Takeshi
Horizoe Hirotoshi
Kaihara Yuji
Kawami Yoshimasa
Matsukawa Yasumasa
Evenson, McKeown, Edwards & Lenshan, P.L.L.C.
Mitsubishi Heavy Industries Ltd.
Yildirim Bekir L.
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