METHOD AND SYSTEM FOR TRANSFERRING PLASTIC WASTE INTO A FUEL HAVING PROPERTIES OF DIESEL/HEATING OIL

Abstract

The invention relates to a method for recovering hydrocarbons from plastic wastes, in particular polyolefin-rich waste, by means of purely thermolytic cracking without the use of catalysts, comprising melting the plastic waste in two heating devices (3) and (4), wherein a recycle stream derived from the cracking reactor (5) and purified in a separator system (8, 9) is admixed with the molten plastic waste from the heating device (3). The mixed plastic stream is further heated in the second heating device (4), and from there is guided into the cracking reactor (5), where the plastic materials are cracked, and by means of subsequent distillation are separated into diesel and low boilers. A special entry system allows the prior separation of water and acidic gases, and the saving of inert gas. The invention further relates to a system for carrying out the method.

Claims

1. A method for recovering hydrocarbons from plastic-containing waste and organic liquids based on crude oil, denoted overall as reusable plastic materials, preferably from polyolefin-rich reusable plastic materials, by means of purely thermolytic cracking in a cracking reactor (5), with a first heating device (3) and a second heating device (4) situated upstream therefrom, without using catalysts, wherein (b1) the reusable plastic materials, which are optionally and preferably already partially melted, are supplied to a first heating device (3) in which they are (further) melted at a temperature of 300° C. to 380° C., (b2) the melted reusable plastic materials together with the recycle stream which have been pumped out of the cracking reactor are supplied to a second heating device (4), in which they are further heated to temperatures of 380° C. to 400° C., (b3) the melted reusable plastic materials together with already formed hydrocarbon-containing vapors are supplied from the second heating device (4) to the cracking reactor (5), in which the melted reusable plastic materials are further cracked at approximately 400° C., wherein the gaseous hydrocarbons are supplied to a partial condenser (11) in which long-chain hydrocarbons condense, and are returned to the cracking reactor (5). (b4) short-chain hydrocarbons exit from the cracking reactor (5) and are supplied to a distillation unit in which they are fractionated into a gaseous fraction and a liquid fraction, (b5) high-energy pitch- and tar-like substances that have not assumed the gaseous state, and excess carbon that results during the thermolytic cracking of polymers, together with the recycle stream are pumped out of the cracking reactor (5) and separated into the recycle stream and the residue by means of a separator system (8, 9), and the recycle stream between the first heating device (3) and the second heating device (4) is admixed with the melted reusable plastic materials melted in the first heating device (3), and the residue is led into a collection tank.

2. A method for recovering hydrocarbons from plastic-containing waste and organic liquids based on crude oil, denoted overall as reusable plastic materials preferably from polyolefin-rich reusable plastic materials, by means of purely thermolytic cracking in a cracking reactor (5), with a first heating device (3) and a second heating device (4) situated upstream therefrom, without using catalysts, in particular according to claim 1, wherein the supplying of the plastic waste to the first heating device takes place via a feed system (1, 2) in which (a2) in a first stage, water vapor is discharged in a mechanical compactor at 120 to 150° C., and compaction and drying take place, (a3) in a second stage, at least partial melting and removal of acidic gases, in particular HCl and H.sub.2S, take place under vacuum in an extruder (2) at 250 to 300° C., optionally followed by gas scrubbing.

3. The method according to claim 2, wherein the compaction in the first stage (a2) takes place by means of a screw compactor.

4. The method according to claim 2 or 3, wherein (a1) the reusable plastic materials are introduced into the feed system (1, 2) via a system of at least two, and preferably two, buffer tanks that are optionally flushed with inert gas, in particular nitrogen, wherein at least one, and preferably one, buffer tank is filled while at leak one other, and preferably one other, buffer tank is emptied into the feed system (1, 2), and all (both) buffer tanks are connected to a weighing system that allows metered filling of the charging system with plastic waste.

5. The method according to any one of the preceding claims, wherein the recycle stream is obtained by pumping melted reusable plastic materials, high-energy pitch- and tar-like substances that have not assumed the gaseous state, and excess carbon that results during the cracking of polymers out of the bottom of the cracking reactor (5) by means of a high-temperature pump (7) and supplying them to a separator system (8, 9), the separator system (8, 9) including a cyclone separator (8) and a sedimentation/settling tank (9).

6. The method according to one of the preceding claims, wherein the gaseous hydrocarbons from the cracking reactor (5) are supplied to the partial condenser (11) via a packed column (12).

7. The method according to one of the preceding claims, wherein the gases from the cracking reactor (5), downstream from the partial condenser (11), are supplied to a distillation unit (13, 14, 15, 16) having a reboiler (13) and a distillation column (14), the distillation column (14) having a packed column (15) and an intermediate tray (16), and the gases from the cracking reactor (5) are fractionated into a gaseous fraction and a liquid fraction in the distillation unit (13, 14, 15, 16), and the liquid fraction is stripped off at the intermediate tray (16) as diesel product, and of the stripped-off gaseous fraction, the light boilers (C5-C7, for example) are condensed and separated from the uncondensed gases (C1-C4, for example).

8. The method according to one of the preceding claims, wherein the facility is continuously operated.

9. The method according to one of the preceding claims, wherein the first heating device (3) and the second heating device (4) are in each case a tube heat exchanger that is flushed with thermal oil.

10. The method according to one of the preceding claims, wherein the partial condenser (11) is settable to a temperature of 150° C. to 350° C., preferably 300° C., as the result of which the chain length of the molecules that are able to pass through the partial condenser may also be set.

11. The method according to one of the preceding claims, wherein the thermal fine separation of the gas exiting from the cracking reactor (5) is carried out in the distillation column (14) by means of counterflow distillation, in such a way that a portion of the diesel product stripped off at the intermediate tray (16) is returned to the top of the distillation column via a recycle stream line (17), preferably after cooling, and preferably combined with a radical inhibitor.

12. The method according to claim 10 or 11, wherein the nature of the hydrocarbon mixtures is defined via the temperature setting in the distillation column (14) and/or in the condenser, in which a portion of the gaseous fraction is condensed.

13. The method according to one of the preceding claims, wherein impurities possibly still present in the diesel product and/or in the light boilers, in particular sulfur-containing compounds, haloacids, and organic acids, are removed by absorption and/or filtration.

14. The method according to one of the preceding claims, wherein short-chain gaseous hydrocarbons (C1-C4, for example) that are present downstream from the condenser, optionally after compression and intermediate storage, are used as fuel for a source of energy.

15. A device for processing plastic-containing waste and organic liquids based on crude oil, denoted overall as reusable plastic materials, comprising a first heating device (3), a second heating device (4), a cracking reactor (5), and a recycle stream line (10) that leads from a lower area of the cracking reactor via a separator system (8, 9) into the feed line of the melted reusable plastic materials from the first heating device (3) into the second heating device (4).

16. The device according to claim 15, wherein the first heating device (3) and the second heating device (4) are in each case a tube heat exchanger that is flushed with thermal oil.

17. The device according to claim 15 or 16, wherein the heating devices (3, 4) and the cracking reactor (5) have independently controllable heaters.

18. The device according to one of claims 15 to 17, wherein the heating devices (3, 4) are heat exchangers designed as tube heat exchangers, the tubes being filled with the melted reusable plastic materials and flushed with thermal oil.

19. The device according to one of claims 15 to 18, wherein the separator system (8, 9) includes a cyclone separator (8).

20. The device according to claim 19, wherein the separator system (8, 9) has, in addition to the cyclone separator (8), a sedimentation/settling tank (9) which is situated outside the recycle stream line (10) but connected to the cyclone separator, and which is connected to the recycle stream line (10) via a bypass on the heating device side.

21. The device according to one of claims 15 to 20, wherein the cracking reactor (5) includes a partial condenser (11) having a cooling/heating device that is designed in such a way that a defined temperature is settable in the partial condenser (11), in particular a cooling/heating device having a heat carrier, which by means of a temperature control unit may be brought to a temperature that is necessary to set the defined temperature, a thermal oil being a preferred heat carrier.

22. The device according to one of claims 15 to 21, wherein in the cracking reactor (5) a packed column (12) is situated upstream from the partial condenser (11).

23. The device according to one of claims 15 to 22, wherein a distillation unit (13, 14, 15, 16) that includes a reboiler and a distillation column (14) is situated downstream from the cracking reactor (5), the distillation column (14) having an intermediate tray (16) such that the liquid fraction may be stripped off at the intermediate tray, and the gaseous fraction may be stripped off at the top of the column.

24. The device according to one of claims 15 to 23, wherein a cooler for cooling the liquid fraction, and/or a condenser for partially condensing the gaseous fraction, are/is situated downstream from the distillation column (14), the cooler and/or the condenser having a heating/cooling device via which a defined temperature is settable in the cooler and/or in the condenser.

25. The device according to one of claims 15 to 24, wherein the distillation column (14) is designed, at least in part, as a packed column (15).

26. The device according to one of claims 15 to 25, wherein the distillation column (14) is provided with a recycle stream line (17) in such a way that a portion of the liquid fraction stripped off from the distillation column (14) may be returned to the distillation column (14) above the intermediate tray (16), which is the withdrawal point.

27. The device according to one of claims 15 to 26, having least one adsorption or filtration unit for adsorbing impurities from the liquid fraction or the condensed portion of the gaseous fraction.

28. The device according to claim 27, wherein the adsorption or filtration unit has multiple adsorbers or filters, respectively, which may be connected or disconnected in alternation for adsorption or regeneration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Further embodiments, advantages, and applications of the invention result from the dependent claims, and the following description with reference to the FIGURE.

[0088] The FIGURE schematically shows the design of a preferred facility according to the invention. The reference numerals in the FIGURE have the meanings given below:

[0089] 1 compactor

[0090] 2 extruder

[0091] 3 first heating device (first heat exchanger)

[0092] 4 second heating device (second heat exchanger)

[0093] 5 cracking reactor

[0094] 6 heater for cracking reactor (heat exchanger)

[0095] 7 high-temperature pump

[0096] 8 cyclone separator

[0097] 9 sedimentation tank/settling tank

[0098] 10 recycle stream line

[0099] 11 partial condenser

[0100] 12 packed column

[0101] 13 reboiler (evaporator)

[0102] 14 distillation column

[0103] 15 packed column

[0104] 16 intermediate tray

[0105] 17 recycle stream line

APPROACH(ES) FOR CARRYING OUT THE INVENTION

[0106] The method for recovering hydrocarbons, in particular individual fractions of hydrocarbons, from plastic waste, in particular polyolefin waste, by means of pyrolytic cracking is now described in greater detail with reference to the facility diagram illustrated in the FIGURE.

[0107] The compactor 1 is preferably filled via two buffer systems (not shown) which are acted on or flushed with nitrogen and which may be weighed to allow accurate determination and control of the quantity of reusable plastic materials introduced. Due to the two buffer systems, the facility may be continuously operated due to the fact that one buffer system is filled while the other buffer system is emptied.

[0108] The reusable plastic materials are homogenized, compacted, and heated essentially by friction in the compactor 1, assisted if necessary by a thermal oil heater, preferably in the outer wall of the compactor, in particular a screw compactor. Heating in this compactor to 120-150° C. allows removal of the majority of the contained water. The removal of water may be assisted by applying a vacuum, and is preferably assisted by applying a vacuum.

[0109] From the compactor 1, the dried, compacted reusable plastic materials are conveyed into an extruder 2 that is preferably heated with thermal oil, and further heated to approximately 250-300° C., so that at least a portion of the reusable plastic materials is melted. At the extruder 2 a vacuum pump draws off the pollutant gases, in particular the acidic gases HCl and H.sub.2S. This feed system 1, 2, formed from the compactor 1 and the extruder 2, and this feed technique also have the advantage that continuous flushing with inert gas (nitrogen) may be dispensed with during filling of the melting zones and the cracking reactor, since the system filled with melted plastic represents an airtight closure.

[0110] From this feed system 1, 2, the at least partially melted plastic passes into a first heating device, which is a first tube heat exchanger 3, in which the reusable plastic materials are heated to a temperature of 300° C. to 380° C., so that all plastic is present in melted form.

[0111] Downstream from the heat exchanger 3, the reusable plastic materials exiting from same are mixed with a recycle stream. This recycle stream is removed from the cracking reactor 5 by means of the high-temperature pump 7 and led in the recycle stream line 10, via the cyclone separator 8, into the stream of reusable plastic materials exiting from the heat exchanger 3.

[0112] The liquid phase, formed from the melted reusable plastic materials originating from the heat exchanger 3 and the recycle stream, is further melted, if necessary, in a second heating device, a second heat exchanger 4, at a temperature of 380° C. to 400° C., where thermal cracking may possibly already begin. The melted reusable plastic materials, together with hydrocarbon-containing vapors that have already formed, are subsequently supplied to the cracking reactor 5, which may optionally be heated by means of the heat exchanger 6, and in which the melted hydrocarbons are cracked at approximately 400° C. The entire plastic melt that is present in the cracking reactor 5 and in the second heat exchanger 4 is continuously circulated by means of the high-temperature pump 7. As a result, on the one hand good intermixing is achieved, and on the other hand the pump is simultaneously used for pumping the dross from the cracking reactor into the separator system 8, 9, formed from the cyclone separator 8 and the sedimentation tank 9, from which it may be discharged. This dross for the most part consists of high-energy pitch- and tar-like substances that have not assumed the gaseous state, and excess carbon that results during the cracking of polymers.

[0113] The gaseous hydrocarbons leaving the cracking reactor are supplied to a packed column having a connected partial condenser 10 [sic; 11], in which long-chain hydrocarbons (longer than C22, for example) condense, are returned to the cracking reactor 5, and cracked until they have a maximum chain length of C20 to C22, depending on the setting.

[0114] The gases that do not condense (C1-C20/C22) in the customarily unheated packed column 12 or in the partial condenser 11 are supplied to a distillation unit 13, 14, 15, 16, in which they are fractionated into a gaseous fraction and a liquid fraction, and from which the liquid fraction is stripped off as middle distillate, and the gaseous fraction is stripped off as light boilers and uncondensed gases, from the distillation unit 13, 14, 15, 16.

[0115] The distillation unit 13, 14, 15, 16 includes a reboiler 13 and a distillation column 14. The distillation column 14 preferably has a region designed as a packed column 15, and optionally within this region containing packing or preferably above this region, an intermediate tray 16 on which the liquid fraction (diesel product) is collected and may be discharged. The diesel product discharged from the distillation unit 13, 14, 15, 16 is preferably cooled by means of a heat exchanger, and a portion of this cooled diesel product may be recirculated to the distillation unit via the recycle stream line 17 in order to set optimal temperature conditions. The recirculation, i.e., reflux, usually takes place at the top of the distillation device, but in any case, above the intermediate tray 16, which is the withdrawal point of the diesel product.

[0116] A radical inhibitor that prevents the formation of long-chain paraffins, etc., is preferably added to the diesel product used as reflux. This addition suitably takes place downstream from the heat exchanger and downstream from the branch point of the reflux stream.

[0117] The discharged liquids may be purified in adsorption and/or filtration systems, and any interfering components (organic acids, for example) may be removed, before the hydrocarbons are transferred into a storage tank.

[0118] At least a stabilizer is preferably added to the diesel product before it is stored.

[0119] Those skilled in the art are familiar with radical inhibitors, as well as stabilizers and antioxidants. A suitable radical inhibitor is butylhydroxytoluene (BHT), for example, suitable stabilizers are strongly basic amines, for example, and a suitable antioxidant is phenyl diamine, for example.

[0120] Although preferred embodiments of the invention are described in the present patent application, it is expressly pointed out that the invention is not limited thereto, and may be carried out in some other way within the scope of the following claims.