METHOD OF RECYCLING WASTE PLASTIC MATERIAL

Abstract

In a method for thermal processing of catalytically active waste plastics mixture, the mixture is subjected in a receiving tank to a cracking temperature to undergo a cracking reaction. The mixture is transferred to a mixer pump to produce a reaction mixture which is directed into an outgassing chamber of an intermediate tank to produce an outgassed fraction and a non-outgassed liquid fraction. The outgassed fraction to produce fuel is cooled down, and a first portion of the non-outgassed liquid fraction is returned and subjected again to the cracking temperature in the receiving tank. A second portion of the non-outgassed liquid fraction is conducted in a bypass to the outgassing chamber of the intermediate tank for outgassing while fresh mixture is added. Residual matter settling in the intermediate tank is periodically removed.

Claims

1. A method of recycling plastic comprising the steps of: comminuting waste plastic together with an active biocatalyst containing catalytically effective inorganic residue suitable for cracking of waste plastic to form a catalytically active waste plastic mixture and feeding it into a receiving tank; heating the catalytically active waste plastic mixture in the feeding receiving tank to a cracking temperature to undergo a cracking reaction; transferring the catalytically active waste plastic mixture to a mixer pump to produce a reaction mixture; directing the reaction mixture into an outgassing chamber of an intermediate tank to produce an outgassed fraction and a non-outgassed liquid fraction; cooling down the outgassed fraction to produce fuel; returning a first portion of the non-outgassed liquid fraction and subjecting it again to the cracking temperature in the receiving tank; conducting a second portion of the non-outgassed liquid fraction in a bypass to the outgassing chamber of the intermediate tank for outgassing while fresh waste plastic mixture is added; and periodically removing from the intermediate tank settled residual matter.

2. The method of claim 1, wherein the transferring step includes the step of subjecting the catalytically active waste plastic mixture to a further cracking reaction in the mixer pump.

3. The method of claim 1, wherein the cracking temperature is in the a range of about 280 C to about 360 C.

4. The method of claim 1, further comprising the step of dewatering the fuel.

5. The method of claim 1, further comprising the steps of combusting the fuel In a turbine, and utilizing exhaust gas from the turbine for generating the cracking temperature.

6. The method of claim 5, wherein the exhaust gas of the turbine is used for drying fresh waste plastic mixture.

7. The method of claim 5, wherein the exhaust gas of the turbine is used for heat introduction in a thermal oil circulation which produces the cracking temperature.

8. The method of claim 1, wherein the active biocatalyst is a biological waste material.

9. The method of claim 8, wherein the biological waste material is rice husks.

10. The method of claim 1, further comprising the step of subjecting the waste plastics mixture with the biocatalyst to ultrasound.

11. The method of claim 1, further comprising the step of heating the second portion of the non-outgassed liquid fraction.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0032] Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which the sole FIGURE shows a schematic illustration of one embodiment of an apparatus for thermal processing of waste plastic mixture in accordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0033] The depicted embodiment is to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the FIGURE is not necessarily to scale. Details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

[0034] Turning now to the sole FIGURE, there is shown, by way of example, a schematic illustration of one embodiment of an apparatus for thermal processing of waste plastic mixture in accordance with the present invention.

[0035] The apparatus includes a reservoir 2 having a closeable inlet 4 for accepting finely particulate and rather dry and catalytically active waste plastic mixture P. The waste plastic mixture P is a mixture to contain about 70% waste plastic and about 25-30 % of rice husks as biocatalyst for producing as much diesel oil based fuel K as possible. Water content should be low, to approximately 5%. The mixture is comminuted to a granular size of approximately 2 mm.

[0036] Arranged at the lower end of the reservoir 2 is a metering valve 6, e.g. a controllable supply unit, which is connected to a transport device 7 or worm for routing the waste plastic mixture P from the reservoir 2 along a conduit 5. Inside the reservoir 2 above the waste plastic mixture P level is a nitrogen cushion 8 or a cushion of different inert gas under pressure. This prevents air, i.e. oxygen, from penetrating the apparatus. The introduction of catalytically active waste plastic P into the apparatus will be described further below. The catalytically active waste plastic mixture P is made from a mixture of waste plastic and biocatalyst.

[0037] The apparatus further includes a receiving tank 20 having a double-jacketed configuration so as to define a passageway 21 which is part of a thermal oil heat circulation for circulating thermal oil O and heating the plastic mixture P to a cracking temperature T ranging from about 280 C to about 360 C. Introduction of heat is indicated by arrows 22. The heat transfer to P is provided by thermal oil. An example of thermal oil includes Meganol 420. As a result of the elevated temperature T in the receiving tank 20, organic molecules of the plastic mixture P are subjected to a thermal cracking process. Substances in the, plastic mixture P in particular mineral fractions of the biocatalyst, act hereby as catalyst for the cracking reaction. After undergoing the thermal cracking process, a liquid reaction mixture N, in which the previously present substances have been broken down to a large extent as a consequence of the catalytic and thermal cracking process, exits the tank 20 via an outlet 23.

[0038] Connected to the lower end of the receiving tank 20 is a mixer pump 24 which subjects the liquid reaction mixture N from the receiving tank 20 to a further cracking reaction. The mixer pump 24 rotates counterclockwise, as indicated by the curved arrow, and has two functions: On one hand, the mixer pump 24 assists a thorough mixing of the reaction mixture N exiting the tank 20 and resulting from the plastic mass mixture P and on the other hand, the mixer pump 24 effects a shearing of particles in the reaction mixture N so that the surface is enlarged and efficiency increased.

[0039] The mixer pump 24 may be constructed as a heating unit. The added heating through shearing and/or friction is indicated by the wavy arrows.

[0040] The mixer pump 24 is connected to a feed line 26 which is part of a reaction circulation and leads to an outgassing device 28 which is accommodated in an outgassing chamber of an intermediate tank 31 and provided to separate water vapor and organic vapor D from a non-outgassed liquid residue R of the reaction mixture N. The intermediate tank 31 is arranged anteriorly of a distillation column 30 which receives the water vapor and the organic vapor D. The liquid residue R collects in a lower portion of the intermediate tank 31 and eventually settles upon the bottom of the intermediate tank 31 as residual matter A for discharge in a collecting vessel 32 and ultimate storage or optional use as combustible. Extending from the lower portion of the intermediate tank 31 is a conduit 34 for feeding a first portion of the liquid residues R that have not been distilled as of yet back to the receiving tank 20. The conduit 34 of the intermediate tank 31 thus represents a return line of the reaction circulation.

[0041] The mixer pump 24 thus repeatedly feeds liquid reaction mixture N, obtained from the plastic mass mixture P, in the reaction circulation comprised of mixer pump 24, feed line 26, outgassing device 28, intermediate tank 31, conduit 34, receiving tank 20, until substantially all organic substances have been thermally cracked and conducted upwards and until residual matter A has been separated out. In order to initiate the reaction circulation, a high-boiling product from the process or thermal oil should be introduced. In other words, the reaction process R commences when the product R from the intermediate tank 31 is in hot liquid form or when the thermal oil is added to the mixture N via the conduit 34.

[0042] To ensure a continuous operation, small amounts of plastic mixture P are transferred by the transport device 7 to a bypass 35. The presence of the bypass 35 is instrumental to prevent or at least reduce foam formation in the Intermediate tank 31. The bypass 35 includes a return line 35 which extends from the lower part of the intermediate tank 31, an optional double-jacketed post-heating unit 35b which defines a passageway for circulation of heated thermal oil P, a bypass pump 35, and a feed line 35d which ends in an outgassing device 35e disposed in the upper part of the intermediate tank 31 above the level of the product R, i.e. in the outgassing chamber. The outlet of the transport device 7 connects to a port 35f of the feed line 35d. The volume introduced per time unit from the transport device 7 is substantially smaller than the volume transported by the bypass pump 35c per time unit and amounts to only 5%, for example.

[0043] A second portion of the residue R is drawn via the return line 35a by the pump 35c. Plastic mass P, which is still relatively cold, is fed via the port 35f and heated by the residue R flowing in the feed line 35d to an elevated temperature, even up to the reaction temperature T. All water is hereby converted into water vapor which flows upwards in the intermediate tank 31 towards the distillation column 30 and then to the condenser 38 for subsequent discharge together with fuel K and optional separation from the fuel K by means of a centrifuge, for example.

[0044] Low-boiling organic vapor D is separated within the distillation column from atop the distillation column 30 and drained through a drain line 36 which connects to a condenser 38. The outgassed organic vapor fraction D is cooled down in the condenser 38 and discharged in the form of liquid fuel K through a fuel drain line 46. The fuel K maybe similar, e.g., to diesel oil. Reference numerals 40 and 42 designate coolant lines of the condenser 38, with coolant line 40 constituting a coolant feed line and coolant line 42 constituting a coolant drain line. The fuel drain line 46 connects the condenser 38 with a processing device 48 for processing the fuel K, e.g. for dewatering the fuel K and removal of water, or for desulphurization, and subsequently to a downstream storage tank 50. The storage tank 50 has an outlet line 52 via which the fuel K can be optionally supplied to a fuel-operated system, for example a drive motor.

[0045] In the non-limiting example of the FIGURE, the fuel-operated system involves a turbine generator which includes a turbine 54 and an electric generator 56 which is operatively connected to the turbine 54 by a shaft 55. The turbine generator is used for generating electricity as well as for generating the cracking temperature T via the thermal oil circulation. Fuel K is conducted via the fuel outlet line 52 from the storage tank 50 to the turbine 54 and combusted to thereby drive the electric generator 56. As the fuel K is combusted in the turbine 54, exhaust gas G is produced which is conducted via an exhaust line 58 to a heat exchanger 60 and cooled down as it interacts with thermal oil P of the thermal oil circulation. As a result, thermal oil Q is heated up and returned via a feed line 66 to the passageway 21 of the receiving tank 20 for heating the mixture P. The cooled down exhaust gas G leaves the heat exchanger 60 via outlet line 62 and may also be used for crying the Introduced waste plastic mixture.

[0046] The heat exchanger 60 is thus also part of the thermal oil circulation, shown only schematically A temperature controller 64 maintains the thermal oil P in the feed line 66 at a predefined temperature close to the cracking temperature T, e.g. to 360 C. As it enters the passageway 21 and flows there through, the thermal oil P cools slightly and is returned via a return line 68 to the heat exchanger 60 where the incoming exhaust gas G heats the thermal oil P. As an alternative, and in dependence on the temperature adjustment and actual temperature, the temperature controller 64 may control the flow of thermal oil O in such a way that the thermal oil Q sidesteps the heat exchanger 60 and flows via a bypass line 70 back to the feed line 66.

[0047] As further shown in the FIGURE, the electric generator 56 feeds electric energy via power lines 72 to the public power grid which is symbolized here by a power pole 74. Of course, the power lines 72 may also be electrically connected to a different consumer.

[0048] According to the present invention, the apparatus for fuel production is thus able to produce fuel and/or energy from the plastic components with biocatalyst as starting substances, which together form the catalytically active waste plastic mixture P. This is realized while reducing mass at the same time. As a result, the apparatus is operative in the absence of addition of external catalysts.

[0049] While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.