EP3247775B1 - Method and system for transferring plastic waste into a fuel having properties of diesel/heating oil - Google Patents

Description

Field of the Invention

The invention relates to a method and a plant for processing plastic waste, in particular plastic waste based on (i) polyolefins and / or (ii) organic liquids based on petroleum, converting such plastic waste into hydrocarbons with 1 carbon atom (methane). up to hydrocarbons with more than 22 carbon atoms.

background

In view of the finite oil reserves, the increasing consumption of plastics and the increasingly restrictive government regulations with regard to the treatment of waste and the recycling of valuable materials, the treatment of plastic waste, which is sorted out of residual waste, for example, is becoming increasingly important.

There are already some methods for processing plastic waste known, but they still have various disadvantages.

From the WO 2005/071043 A1 A processing method is known in which plastic waste is processed into oil.

Fractionated hydrocarbons are obtained from plastic waste and / or from oil-containing residues, the plastic waste and / or residues being sorted first and compressed using an entry system to exclude air. The compacted mass is fed to a melting tank and heated therein, so that a separation into a first liquid phase, a first gas phase and a residue takes place, after which the first liquid phase and the first gas phase are transported into an evaporation tank, in which a second liquid phase with further heat input and a second gas phase arise, the second liquid phase being transferred to a post-heater and further heated there with further heat input, so that a third gas phase is formed, after which the second gas phase from the evaporation container and the third gas phase from the post-heater are fed to a cracking reactor, where further cracking of the long-chain hydrocarbons into short-chain hydrocarbons takes place and the resulting oil gas is then fed to a condenser in which the oil gas is condensed to liquid oil, the oil being the target product.

This process does not meet today's environmental requirements in terms of sulfur and chlorine levels, leads to a high proportion of carbon-rich residues and has shortcomings in terms of flexibility and quality of the end product.

• Eintragen des Stoffgemischs in einen Reaktor, der in eine Schmelz- und eine Crackzone unterteilt ist, oder in zwei hintereinander geschaltete Reaktoren,
• Aufschmelzen des Stoffgemischs in einer Schmelzzone des Reaktors bei 250°C bis 350°C,
• Austragen von Störstoffen aus der Schmelze,
• Cracken von in der Schmelze enthaltenen langkettigen Polymeren in einer Crackzone des Reaktors bei 420°C bis 450°C bis diese in den gasförmigen Zustand übergehen,
• Austragen der Gasphase aus dem Reaktor,
• Kondensieren der Gasphase in einem Kühler,
• Entfernen von Verunreinigungen aus der nach dem Kühlen (Quenchen) vorliegenden Leichtflüssigkeit und
• Speichern der Leichtflüssigkeit.

WO 2008/022790 describes a method for processing plastic-containing waste and organic liquids based on petroleum, cooking oil, fats or the like, with the steps:

• Introducing the substance mixture into a reactor which is divided into a melting and a cracking zone, or into two reactors connected in series,
• Melting the mixture of substances in a melting zone of the reactor at 250 ° C to 350 ° C,
• Discharge of contaminants from the melt,
• Cracking of long-chain polymers contained in the melt in a cracking zone of the reactor at 420 ° C. to 450 ° C. until they change into the gaseous state,
• Discharge of the gas phase from the reactor,
• Condensing the gas phase in a cooler,
• Removal of impurities from the light liquid and after cooling (quenching)
• Save the light fluid.

The gas phase present after the cracking zone of the reactor is, for example, fed to a distillation device which is operated in such a way that long-chain polymers condense and are fed back to the cracking zone of the reactor. Relatively short-chain hydrocarbons (C1-C4) present in gaseous form after the distillation device and a cooler connected to it can be used as fuel for energy.

In the prior art processes, relatively large amounts of slag are produced and the end products are only moderately adaptable to the needs and of moderate purity.

WO 2012/149590 A1 describes a process for the depolymerization of plastic material, in particular old or waste plastics, by means of heat input, the plastic material being melted and degassed into a plastic melt before it is fed to a depolymerization reactor, the plastic melt being added as a solvent from crude oil, so that the viscosity of the plastic melt solution supplied to the depolymerization reactor (3) is reduced compared to the viscosity of the plastic melt.

Summary of the invention

While the invention is defined in the independent claims, further aspects of the invention result from the dependent claims, the drawings and the description below.

• (b1) die gegebenenfalls und vorzugsweise bereits teilweise geschmolzenen Kunststoffwertstoffe einer ersten Heizvorrichtung zugeführt werden, in der sie bei einer Temperatur von 300°C bis 380°C (weiter) aufgeschmolzen werden,
• (b2) die geschmolzenen Kunststoffwertstoffe zusammen mit Rückführstrom, welcher aus dem Crackreaktor abgepumpt wurde, einer zweiten Heizvorrichtung zugeleitet werden, in der sie weiter erhitzt werden auf Temperaturen von 380°C bis 400°C,
• (b3) die geschmolzenen Kunststoffwertstoffe zusammen mit bereits gebildeten kohlenwasserstoffhaltigen Dämpfen aus der zweiten Heizvorrichtung dem Crackreaktor zugeführt werden, in dem die geschmolzenen Kunststoffwertstoffe bei ca. 400°C weiter aufgespalten (gecrackt) werden, wobei die gasförmigen Kohlenwasserstoffe einem Partialkondensator zugeführt werden, in dem langkettige Kohlenwasserstoffe kondensieren und in den Crackreaktor zurückgeführt werden, vorzugsweise einem Kondensator, dem eine Füllkörperkolonne vorgeschaltet ist,
• (b4) kurzkettige Kohlenwasserstoffe aus dem Crackreaktor austreten und einer Destillationseinrichtung zugeführt werden, in der sie in eine gasförmige und eine flüssige Fraktion zerlegt werden und aus der die flüssige Fraktion als Produkt-Diesel abgezogen wird, und die gasförmige Fraktion über einen Kühler geleitet wird, in dem sie aufgespalten wird in Leichtsieder (C5-C7), die gelagert werden, und in die nicht kondensierten Gase (C1-C4), die vorzugsweise als Brennstoff zum Heizen des Thermoöls verwendet werden,
• (b5) hochenergetische aber nicht in den gasförmigen Zustand übergehende pech- und teerartige Substanzen, sowie beim thermolytischen Cracken von Polymeren entstehender Kohlenstoffüberschuss zusammen mit dem Rückführstrom aus dem Crackreaktor abgepumpt und mittels einer Separiervorrichtung in Rückführstrom und Rückstand aufgetrennt werden, wobei der Rückführstrom zwischen der ersten Heizvorrichtung und der zweiten Heizvorrichtung den geschmolzenen Kunststoffwertstoffen beigemischt und der Rückstand in einen Auffangbehälter geleitet wird.

The aim of the present invention was to provide an improved process for the treatment of plastic waste (hereinafter also referred to as plastic waste) and a plant for carrying out this process. The improvements include reduction of slag formation and / or more flexible product control and / or optimized product purity. In one embodiment, the invention relates to the provision of a process for the recovery of hydrocarbons from preferably polyolefin waste by means of purely thermolytic cracking in a cracking reactor, which is preceded by a first heating device and a second heating device, without the use of catalysts, wherein

• (b1) the optionally and preferably already partially melted plastic materials first heating device are supplied, in which they are melted at a temperature of 300 ° C to 380 ° C (further),
• (b2) the molten plastic materials, together with the recycle stream which has been pumped out of the cracking reactor, are fed to a second heating device in which they are further heated to temperatures of 380 ° C. to 400 ° C.,
• (b3) the molten plastic materials together with the already formed hydrocarbon-containing vapors are fed from the second heating device to the cracking reactor, in which the molten plastic materials are further cracked at about 400 ° C, the gaseous hydrocarbons being fed to a partial condenser in which condense long-chain hydrocarbons and return them to the cracking reactor, preferably a condenser preceded by a packed column,
• (b4) short-chain hydrocarbons emerge from the cracking reactor and are fed to a distillation unit in which they are broken down into a gaseous and a liquid fraction and from which the liquid fraction is withdrawn as product diesel and the gaseous fraction is passed over a cooler, in which it is broken down into low boilers (C5-C7) which are stored and into the uncondensed gases (C1-C4) which are preferably used as fuel for heating the thermal oil,
• (b5) high-energy pitch-like and tar-like substances which do not change into the gaseous state, and excess carbon formed during the thermolytic cracking of polymers, are pumped out of the cracking reactor together with the recycle stream and separated into recycle stream and residue by means of a separating device, the recycle stream being between the first Heater and the second heater mixed with the molten plastic materials and the residue is fed into a collecting container.

The withdrawn liquids (product diesel and low boilers) can be cleaned in special adsorption and / or filter systems before being transferred to storage tanks and any interfering components (e.g. organic acids) that may have been removed can be removed.

• (a2) in einer ersten Stufe in einem mechanischen Verdichtersystem bei 120 bis 150°C Wasserdampf abgeführt wird und eine Verdichtung und Trocknung erfolgt,
• (a3) in einer zweiten Stufe, in einem Extruder, bei 250 bis 300°C zumindest partielles Aufschmelzen und Entfernung saurer Gase, insbesondere von HCl und H₂S, mittels Vakuum erfolgt.

A feed system preferred for the system according to the invention comprises feeding the plastic waste to the first heating device via a feed system in which

• (a2) water vapor is removed in a first stage in a mechanical compressor system at 120 to 150 ° C. and compression and drying take place,
• (a3) in a second stage, in an extruder, at 250 to 300 ° C. at least partial melting and removal of acid gases, in particular of HCl and H ₂ S, is carried out by means of a vacuum.

These acidic exhaust gases are preferably subjected to gas scrubbing with an alkali, such as sodium hydroxide solution, whereupon the scrubbing liquor, which contains practically no hydrocarbons, can be disposed of uncritically.

The compression in the first stage (a2) is suitably carried out by means of a screw compressor and the second stage (a3) by means of an extruder, the compressor as well as the extruder should be heatable. A preferred heating medium is thermal oil.

The supply of the plastic materials in a stage (a1) upstream of stage (a2) is suitably carried out via a system of at least two and preferably two buffer containers, which are preferably pressurized and / or flushed with nitrogen, and one of which is filled while the another is emptied, and both are connected to a weighing system, which allows a metered filling of the feeding system with plastic waste.

The recycle stream mentioned in (b5) above is obtained by pumping down plastic recyclables melted from the cracking reactor by means of a high-temperature pump, high-energy pitch and tar-like substances that do not convert into the gaseous state, and pumping excess carbon from the cracking of polymers and feeding them to a separator system . This separator system is preferably a cyclone separator, optionally and preferably connected to a sedimentation tank (settling tank).

The gaseous hydrocarbons from the cracking reactor are preferably fed to the partial condenser via a packed column, so that the path for the separation of the hydrocarbons which have not yet been sufficiently cracked (usually more than 22 carbon atoms) becomes longer. This has the positive effect that the partial condenser can be operated at a higher temperature without a substantial proportion of excessively long hydrocarbons being able to leave the cracking reactor, or that the temperature in the partial condenser does not have to be set so low that a substantial proportion of hydrocarbons also have 22 or fewer carbon atoms are returned to the cracking reactor and further cracked there, which would reduce the proportion of longer-chain hydrocarbons in the product diesel.

The gases / vapors emerging from the cracking reactor after the packed column and the condenser are fed to a distillation device with a reboiler and distillation column, which is at least partially designed as a packed column and with an intermediate plate. In this device, the gases / vapors are broken down into a gaseous and a liquid fraction. The liquid fraction is drawn off at the intermediate plate as product diesel and the gaseous fraction at the top of the distillation column. The gaseous fraction is cooled so that low boilers (C5-C7 / C8) condense and can be drawn off as a liquid fraction. The Uncondensed gases (C1-C4) are preferably used as fuel for heating the thermal oil.

The lengths of the hydrocarbons in the individual fractions can be controlled well, on the one hand by the temperature of the partial condenser, then by the length of the distillation column and the temperature in this and in the cooler.

The system can be operated continuously thanks to the entry of the recyclable plastics via two buffer systems.

Preferred first and second heating devices in the context of this invention are tubular heat exchangers which are flushed with thermal oil.

So that the chain length can be adapted to the respective requirements, it is preferred if the temperature of the partial capacitor is adjustable, for example in a range from 150 ° C. to 350 ° C., for chain lengths of a maximum of 22 carbon atoms, preferably to 300 ° C.

The thermal fine separation of the gas emerging from the cracking reactor is preferably carried out by countercurrent distillation, in which part of the product diesel is returned to the distillation column above the removal point, in particular sprayed. By returning product diesel to the distillation column, the temperature in this column can be varied or adjusted, e.g. in such a way that - depending on the setting - hydrocarbons with 8-9 to 20-22 carbon atoms are removed from the intermediate floor as product diesel. The type of hydrocarbon mixture of the low boilers or the uncondensed gases can also be varied or determined via the temperature setting during cooling.

The product diesel and / or the low boilers are usually drawn off and stored for later use, while the uncondensed gases (C1-C4) are used directly as fuel for heating the thermal oil.

Any impurities present in the product diesel and / or the low boilers, in particular sulfur-containing compounds, halogen acids and organic acids can be removed by absorption and / or filtration.

A device for processing plastic-containing waste and organic liquids based on petroleum, which is particularly suitable for carrying out the method described above, comprises a first heating device, a second heating device, a cracking reactor, and a return flow line leading from a lower region of the cracking reactor via a separator system into the feed of the molten plastic waste from the first heating device into the second heating device.

In a preferred embodiment, the first and the second heating device are each a tube heat exchanger which is flushed with thermal oil. The first and / or the second heating device can also consist of a plurality of heating devices connected in series or in parallel, but as a whole they have the properties of the first and second heating devices.

For optimal flexibility, the first and second heating devices and the cracking reactor have independently controllable heaters.

Preferred heating devices are heat exchangers which are designed as tubular heat exchangers, the tubes being filled with the melt and being washed around by thermal oil. This ensures the largest possible heat transfer area, which has the advantage that it is possible to work with a small temperature difference (usually max. 20 ° C) between the desired temperature in the melt and the temperature of the heat transfer medium, the thermal oil.

In addition to plastic melt, the recycle stream includes carbon-rich particles and non-meltable ones Contaminants that accumulate in the bottom of the cracking reactor. This recycle stream is pumped out continuously from the cracking reactor and passed through a separator system in which particles are separated, whereupon the residual stream is fed back to the plastic melt before the second heating device. The separator system includes a cyclone separator. This cyclone separator comprises a cylindrical part with a centrally arranged tube. As a result of the centrifugal force, larger particles are moved outward, so that primarily plastic melt and possibly small particles are returned to the cracking reactor via the second heating device via the centrally arranged tube.

This cycle, in particular the continuous pumping-out, brings about continuous mixing in the cracking reactor, which in many cases makes additional stirring unnecessary.

In a further preferred embodiment, in addition to the cyclone separator, the separator system has a sedimentation tank which is arranged outside the recycle stream line but is connected to the cyclone separator, but can optionally be connected to the recycle stream line via the heater device bypass and is preferably connected .

The cracking reactor is equipped with a partial condenser which has a cooling / heating device which is designed such that a defined temperature can be set in the partial condenser. A preferred cooling / heating device contains as a heat transfer medium a heat carrier which can be brought to a temperature by means of a temperature control unit which is required to set the temperature required within the partial condenser. A preferred heat transfer medium is a thermal oil.

Upstream of this partial capacitor, ie arranged between the cracking reactor and the partial capacitor, can be a packed column which is usually not heated. This packed column is used for better separation in the partial condenser.

The partial capacitor, in particular in combination with a packed column, has the effect that only - or at least predominantly - molecules of a defined chain length emerge from the cracking reactor.

Downstream of the cracking reactor or the partial condenser is a distillation device which can be operated in such a way that long-chain molecules condense (product diesel) and from which short-chain molecules emerge as a gas phase. This gas phase can be partially condensed in a cooler downstream of the distillation column (low boilers and uncondensed gases).

The distillation device comprises a reboiler and a distillation column, which preferably has an area designed as a packed column and also preferably an intermediate plate at which the liquid fraction, e.g. condensed product diesel, is withdrawn. Part of this liquid fraction, this product diesel, can be returned to the distillation column to optimize the temperature above the removal point, which serves for better separation of the hydrocarbon fractions.

The cooler intended for further separation of the gas phase into low boilers and non-condensed gases has a heating / cooling device with which a defined temperature - and thus the composition of the hydrocarbon fractions - can be set in the cooler.

Downstream of the distillation column or the cooler, adsorption and / or filter units can be provided for adsorbing impurities from the light liquid and / or the product diesel. These adsorption or filter units can comprise several adsorbers or filters, which alternate can be switched on or off for adsorbing or regenerating.

An overall process from the delivered waste to the end products will now be described in detail.

Cleaned and pre-sorted polyolefin-rich waste, hereinafter also referred to as plastic waste, is stored in a bunker. The pre-sorting can be carried out using standard methods. The plastics, e.g. PVC, PET recognized on the basis of their IR spectra or other characteristics and foreign substances e.g. removed by means of a selectively placeable air flow. Despite this pre-sorting, the plastic materials may still contain small amounts of contaminants, e.g. chlorine and / or sulfur containing compounds, rubber, metals, sand etc. which will be removed later in the process.

Since the preparation process for preventing undesired oxidation must be carried out with a substantial exclusion of oxygen, the plastics materials are preferably fed to the plant with the aid of the introduction system described below. This system has the advantage that a permanent purging with inert gas (nitrogen) can be dispensed with when filling the melting zones and the cracking reactor, since the introduction system filled with at least partially melted plastic materials represents an airtight seal. In principle, the system can also be filled with another delivery system.

The exact and reproducible dosing in the introduction system according to the invention takes place with the aid of two buffer containers which are weighed. These buffer containers can optionally be pressurized with nitrogen or flushed. The system is filled from the respective buffer tank with the help of a mechanical feeding system.

This delivery system itself is divided into at least two zones that perform different tasks. The plastic mixture to be processed is continuously fed to the introduction system from the buffer containers, which are alternately filled or emptied, first in a compressor, in which it is homogenized and essentially heated by friction. If necessary, the heating can be supported by additional heating, in particular via the outer wall of the compressor, which, e.g. with thermal oil, can be heated. In the compressor, the material should be heated to a temperature of 120 to 150 ° C so that water vapor can be evaporated and extracted in this stage, especially by applying a slight vacuum.

The material is then conveyed into an extruder, preferably heated with thermal oil, and heated there to about 250-300 ° C. At these temperatures, sulfur-containing and chlorine-containing plastic parts are destroyed. HCl and H ₂ S are drawn off from the extruder with a vacuum pump. The acidic pollutants are preferably neutralized with sodium hydroxide solution as part of a gas wash and disposed of. At max. The exhaust gas contains only small amounts of hydrocarbons at 300 ° C. In addition to the removal of water, HCl and H ₂ S at relatively low temperatures, this technology also has the advantage that the heating devices (melting zones) and the cracking reactor are permanently flushed with inert gas (nitrogen) can be dispensed with, since the feed system or the extruder, which is already filled with partially melted plastic, is an airtight seal.

The extruder compresses and transports the plastic materials into a first heating device, a first tubular heat exchanger, in which the plastic materials flow through the tubes, which are washed with thermal oil as the heating medium. The entire heating surface of the Tubes are chosen so large that the smallest possible temperature difference between the heating medium and plastic materials can be used. This minimizes the deposition of coke by cracking processes on the tube walls. An additional advantage of tubular heat exchangers is that they are easy to clean. In order to melt the plastic materials completely, they are heated to approx. 380 ° C.

The output of the first heating device, the first heat exchanger, is connected to a return flow line. Through this recycle stream line, recycle stream, which was passed out of the cracking reactor via a cyclone separator functioning as a slag discharge system, is mixed into the plastic melt from the first heating device. The mixed stream flows into a second heating device, a second tubular heat exchanger, in which the plastic melt is heated to 400 ° C. From this second heat exchanger, the molten plastic materials, together with the cracking gases already generated at this temperature, enter the cracking reactor. In this reactor, the plastic molecules become purely thermolytic at approx. 400 ° C, i.e. without the use of catalysts, broken down into an essentially gaseous hydrocarbon mixture (cracked).

For example, a method has proven to be very suitable which works with large heat exchange surfaces, so that despite good throughput, it is possible to work with heat transfer medium at a temperature which is at most about 20 ° C. above the desired temperature. This temperature limitation largely prevents coke formation or at least greatly reduces it.

To avoid pyrolytic decomposition reactions, the heat transfer in the cracking reactor is preferably not carried out or not only through the reactor wall (boiler principle). The heat input preferably takes place over a large area with the smallest possible temperature difference, as a result of which baking and coke formation can be avoided or at least greatly reduced. A suitable heating medium is a plurality of tubular heat exchangers or bundles of heating tubes which are arranged within the cracking reactor and which are filled with heat transfer medium, in particular heat transfer oil, or through which heat transfer medium flows.

The tube heat exchangers or heating pipes can easily be arranged within the cracking reactor in such a way that, even when they are present, a conventional, centrally located agitator can be dispensed with, i.e. that sufficient mixing of the melt is achieved solely due to the continuously pumped and recirculated recycle stream.

Because of the large heat transfer surfaces, the heat transfer medium that is used to heat the plastic melt in the cracking reactor can be kept at a comparatively low temperature of preferably 405 ° C. to a maximum of 420 ° C.

At the bottom of the cracking reactor there is an outlet leading to a high temperature liquid pump. This pump is able to pump fluids with a temperature of 400 ° C and is not affected by possible abrasive components in the plastic melt. High-energy pitch-like and tar-like substances that do not change into the gaseous state, as well as the excess carbon that results from the cracking of polymers, are pumped through a separator system, in particular a cylindrical cyclone separator with a sedimentation container connected to it. When entering the cyclone separator, the tangential velocity of the fluid is increased due to the dimensions of the cyclone separator.

The increase in the speed of the plastic melt in combination with the cylindrical shape of the cyclone separator leads to a centrifugal effect. Higher density particles are swung to the outside of the cyclone, while lighter particles find their way into find the center of the cyclone separator. These lighter particles are passed through a tube out of the cyclone together with most of the molten plastic. This tube is advantageously arranged parallel to the cylinder axis and concentrically around it. This stream, which is conducted from the cyclone separator, is again mixed with molten plastic, which comes from the first heating device, and is returned to the cracking reactor via the second heating device.

The heavier parts flow downwards in the cyclone separator, preferably into a settling basin, since these still contain large amounts of molten plastic. The flow rate in the settling tank is very low, so that an additional separation between high and low density parts, or solid particles and molten plastic can be achieved.

A phase obtained in the settling tank, which is rich in molten plastic, can be bypassed back into the recycle stream line, the separated phase of higher density, which comprises the solids, is removed and can be used as a high-energy fuel.

The gaseous hydrocarbon mixture formed in the cracking reactor flows from the cracking reactor into a partial condenser, and preferably first through a packed column and only then into a partial condenser. This partial condenser is preferably actively heatable and / or coolable, in particular coolable and also preferably set such that hydrocarbons which do not correspond to the desired product character, e.g. diesel / heating oil character, condense and flow back into the cracking reactor, where they are cracked further until they are cracked are shorter than hydrocarbons with a maximum of 22 carbon atoms and can pass through the condenser.

With this technology it is possible to largely or completely avoid the formation of long-chain hydrocarbons (wax / paraffins).

The part boiling at lower temperatures (for example less than C20 or C22) is not retained by the condenser and is sent from it to a quench / distillation unit in which the low boilers and gases (C1-C7 / C8) are separated from the middle distillate (C8 / C9 - C20 / C22) is carried out. This quench / distillation device comprises a reboiler (evaporator) and a distillation column.

The bottom temperature in this quench / distillation device is preferably controlled by an evaporator, a so-called reboiler, which can be heated up to 400 ° C. Hydrocarbons with more than 22 carbon atoms are accumulated in the reboiler and pumped back out of the reboiler into the cracking reactor.

The distillation column is at least partially designed as a packed column. In a central region, for example in the middle of the distillation column, a tray is preferably also provided, in which at least a portion of the liquid hydrocarbons is collected. These liquid hydrocarbons are drawn off and - preferably in a heat exchanger - cooled. Part of the cooled liquid is returned as a recycling stream (reflux) for temperature control at the top of the distillation column, preferably after adding a radical inhibitor which acts as a stabilizer and prevents the formation of new paraffins in the product diesel.

The product diesel, which is removed from the distillation step and preferably contains a radical inhibitor (as a result of the reflux mixed with such an inhibitor), is - as already mentioned above - preferably finally cooled in a further heat exchanger and, if appropriate, filtered and processed by means of an adsorption and / or filtering device. After this Filtration step or before being placed in a storage container, an antioxidant is preferably added to prevent the degradation of the product diesel.

The steam that emerges from the top of the still includes the lower boiling components (gasoline hydrocarbons, e.g. C1 to C8). This steam is cooled in an actively coolable condenser. The condensate, a low boiler (e.g. C5-C8), is drained into a storage container. The part that is not condensed at room temperature, C1 to C4 or methane to butane is - optionally after cleaning, e.g. by means of adsorption / desorption processes - either placed in a storage container by means of a compressor, from which it can later be used in a burner for heating the heat transfer medium, or it is fed directly to such a burner.

1. (i) Eintrag der Kunststoffwertstoffe über das spezielle Eintragssystem. Dieses Eintragssystem ermöglicht Prozessführung ohne bzw. mit geringen Mengen Inertgas (Stickstoff), was die Brennbarkeit der aus dem System abgeführten kohlenwasserstoffhaltigen Gase (C1-C4) verbessert.
2. (ii) Durch die Verwendung des speziellen Eintragssystems, das in der ersten Zone, dem Verdichter, bei Temperaturen von 120°C - 150°C arbeitet, wird der Anteil an Wasserdampf stark reduziert, was zu einer Optimierung des Gasvolumens führt.
3. (iii) Durch die Anordnung des Extruders vor den Heizvorrichtungen und vor dem Crackreaktor und durch dessen Betrieb bei 250-300°C werden Schadstoffgase, wie HCl und H₂S, ausgetrieben, ohne dass bereits merkbare Mengen an Kohlenwasserstoffen verloren gingen. Diese frühe Abtrennung von sauren Gasen führt zu einer stark verminderten Korrosion der nachfolgenden, bei höheren Temperaturen betriebenen Vorrichtungen.
4. (iv) Durch den Partialkondensator, insbesondere mit vorgeschalteter Füllstoffkolonne, wird verhindert, dass Kohlenwasserstoffe, die eine gewünschte Länge überschreiten, ins Destillationssystem gelangen.
5. (v) Die Destillationseinrichtung ermöglicht eine sehr genaue Auftrennung der Kohlenwasserstoff-Fraktionen in eine flüssige Fraktion, z.B. Produkt-Diesel, und eine gasförmige Fraktion, z.B. Leichtsieder/nicht-kondensierte Gase. Durch die Einstellung der Sumpftemperatur im Reboiler einerseits, und durch die Einstellung der Temperatur bzw. des Temperaturprofils in der Destillationskolonne durch Anpassung des Refluxes an Produkt-Diesel lässt sich die Auftrennung des aus dem Crackreaktor direkt stammenden Gasstroms in kurzkettige und langkettige Fraktionen gezielt steuern.
6. (vi) Ein Teil der geschmolzenen Kunststoffmischung wird aus dem Crackreaktor und durch einen Zyklon-Separator gepumpt, wo die Teilchen mit hoher Dichte abgetrennt werden. Um eine bessere Trennung zu erzielen, wird die Fraktion mit hoher Dichte aus dem Zyklon in einen Sedimentations-/Absetztank geführt, in dem die Flüssigkeit genügend Zeit hat, um ein stabiles Gleichgewicht zwischen leichteren und schwereren Teilchen zu erreichen, so dass ein weiterer Anteil an Kunststoffschmelze zurückgeführt werden kann. Durch dieses Abpumpen von Bodenmaterial aus dem Crackreaktor und Abscheiden von Feststoffen bzw. Produkten hoher Dichte im Separatorsystem wird einerseits die Bildung von Ablagerungen im Crackreaktor vermindert oder gar verhindert, andererseits wird durch die im Kreislauf geführte Kunststoffschmelze eine Durchmischung im Crackreaktor erzielt, die ein zusätzliches Mischen oft überflüssig macht.

Although an overall process is described here, it contains individual inventive aspects that can also be used to improve existing systems. Such aspects are:

1. (i) Entry of plastic materials via the special entry system. This entry system enables process control without or with small amounts of inert gas (nitrogen), which improves the flammability of the hydrocarbon-containing gases (C1-C4) discharged from the system.
2. (ii) By using the special entry system, which works in the first zone, the compressor, at temperatures of 120 ° C - 150 ° C, the proportion of water vapor is greatly reduced, which leads to an optimization of the gas volume.
3. (iii) By placing the extruder in front of the heating devices and in front of the cracking reactor and by operating it at 250-300 ° C., pollutant gases such as HCl and H ₂ S are driven off without any noticeable amounts of hydrocarbons being lost went. This early separation of acid gases leads to a greatly reduced corrosion of the subsequent devices operated at higher temperatures.
4. (iv) The partial condenser, in particular with an upstream filler column, prevents hydrocarbons which exceed a desired length from entering the distillation system.
5. (v) The distillation device enables a very precise separation of the hydrocarbon fractions into a liquid fraction, for example product diesel, and a gaseous fraction, for example low boilers / non-condensed gases. By setting the bottom temperature in the reboiler on the one hand, and by setting the temperature or the temperature profile in the distillation column by adapting the reflux to product diesel, the separation of the gas stream directly from the cracking reactor into short-chain and long-chain fractions can be controlled in a targeted manner.
6. (vi) A portion of the molten plastic mixture is pumped out of the cracking reactor and through a cyclone separator where the particles are separated with high density. In order to achieve a better separation, the high-density fraction is fed from the cyclone into a sedimentation / settling tank, in which the liquid has enough time to achieve a stable balance between lighter and heavier particles, so that a further proportion of Plastic melt can be recycled. This pumping of soil material out of the cracking reactor and separation of solids or high-density products in the separator system on the one hand reduces or even prevents the formation of deposits in the cracking reactor, on the other hand the circulation of the plastic melt results in thorough mixing in the cracking reactor, which often makes additional mixing unnecessary.

Brief description of the drawings

Further refinements, advantages and applications of the invention result from the dependent claims and from the following description with reference to the figure.

1. 1 Verdichter
2. 2 Extruder
3. 3 erste Heizvorrichtung (erster Wärmetauscher)
4. 4 zweite Heizvorrichtung (zweiter Wärmetauscher)
5. 5 Crackreaktor
6. 6 Heizung für Crackreaktor (Wärmetauscher)
7. 7 Hochtemperaturpumpe
8. 8 Zyklon-Separator
9. 9 Sedimentationsbehälter/Absetzbehälter
10. 10 Rückführstrom-Leitung
11. 11 Partialkondensator
12. 12 Füllkörperkolonne
13. 13 Reboiler (Verdampfer)
14. 14 Destillationskolonne
15. 15 Füllkörperkolonne
16. 16 Zwischenboden
17. 17 Rezyklierstrom-Leitung

The figure shows schematically the structure of a system preferred according to the invention. The reference symbols have the following meanings:

1. 1 compressor
2. 2 extruders
3. 3 first heating device (first heat exchanger)
4. 4 second heating device (second heat exchanger)
5. 5 crack reactor
6. 6 heating for crack reactor (heat exchanger)
7. 7 high temperature pump
8. 8 cyclone separator
9. 9 sedimentation tank / settling tank
10. 10 return current line
11. 11 partial capacitor
12. 12 packed column
13. 13 reboiler (evaporator)
14. 14 distillation column
15. 15 packed column
16. 16 mezzanine
17. 17 Recycling current line

Way (s) of carrying out the invention

The process for the recovery of hydrocarbons, in particular individual fractions of hydrocarbons, from plastic wastes, in particular polyolefin wastes, by means of pyrolytic cracking, will now be described in more detail with reference to the plant scheme shown in the figure.

The compressor 1 is preferably filled via two buffer systems (not shown) which are pressurized or flushed with nitrogen and which can be weighed in order to be able to precisely determine and regulate the quantity of plastic materials introduced. Thanks to the two buffer systems, the system can be operated continuously, since one buffer system is filled while the other buffer system is being emptied.

In the compressor 1, the plastic materials are homogenized, compressed and essentially heated by friction, if necessary supported by a thermal oil heater, preferably in the outer wall of the compressor, in particular a screw compressor. Heating in this compressor to 120-150 ° C allows the removal of most of the water it contains. The water removal can be supported by applying a vacuum and is preferably supported by applying a vacuum.

The dried, compressed plastic materials are conveyed from the compressor 1 into an extruder 2, preferably heated with thermal oil, and further heated to approximately 250-300 ° C., so that at least some of the plastic materials are melted. At the extruder 2, a vacuum pump sucks off the harmful gases, in particular the acidic gases HCl and H ₂ S. This entry system 1, 2 formed from compressor 1 and extruder 2, or this entry technique also has the advantage that when filling the melting zones and the cracking reactor to one permanent purging with inert gas (nitrogen) can be dispensed with, since the system filled with molten plastic is an airtight seal.

From this entry system 1, 2, the at least partially melted plastic reaches a first heating device, a first tubular heat exchanger, 3 in which the plastic materials are heated to a temperature of 300 ° C. to 380 ° C., so that all plastic is melted.

After the heat exchanger 3, the plastic materials emerging from it are mixed with a recycle stream. This recycle stream is withdrawn from the cracking reactor 5 by means of the high-temperature pump 7 and conducted in the recycle stream line 10 via the cyclone separator 8 into the stream of plastic materials emerging from the heat exchanger 3.

The liquid phase, formed from the molten plastic materials originating from heat exchanger 3 and the recycle stream, is melted further in a second heating device, a second heat exchanger, 4 at a temperature of 380 ° C. to 400 ° C., if necessary, whereby already a thermal one Can use cracking. The molten plastic materials, together with vapors already containing hydrocarbons, are then fed to the cracking reactor 5, which can optionally be heated by means of a heat exchanger 6 and in which the molten hydrocarbons are broken down (cracked) at approx. 400 ° C. The entire plastic melt, which is located 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, thorough mixing is achieved on the one hand, and on the other hand it serves to pump the slag from the cracking reactor into the separator system 8.9, formed from the cyclone separator 8 and the sedimentation tank 9, from which it can be discharged. The majority of this slag is high-energy but not pitch-like and tar-like substances that change into the gaseous state, as well as the carbon excess that arises when polymers are cracked.

The gaseous hydrocarbons leaving the cracking reactor are fed to a filler column with a subsequent partial condenser 10 in which long-chain hydrocarbons (longer than e.g. C22) condense, returned to the cracking reactor 5 and cracked until they have a chain length of - depending on the setting - a maximum of C20 to Have C22.

The gases which do not condense in the usually unheated packed column 12 or in the partial condenser 11 (C1-C20 / C22) are fed to a distillation device 13, 14, 15, 16, in which they are broken down into a gaseous and a liquid fraction and from which the liquid fraction as middle distillate, the gaseous fraction as low boilers and uncondensed gases are withdrawn from the distillation device 13, 14, 15, 16.

The distillation device 13, 14, 15, 16 comprises a reboiler 13 and a distillation column 14. The distillation column 14 preferably has an area designed as a packed column 15 and, if appropriate within this area containing the packed body or preferably above this area, an intermediate plate 16 on the liquid fraction (Product diesel) is collected and can be derived. The product diesel derived from the distillation device 13, 14, 15, 16 is preferably cooled by means of a heat exchanger and part of this cooled product diesel can be returned to the distillation device via recycle stream line 17 in order to set optimal temperature conditions. The return, the reflux, usually takes place at the top of the distillation apparatus, but in any case above the intermediate base 16, the removal point of the product diesel.

A radical inhibitor which prevents the formation of long-chain paraffins etc. is preferably added to the product diesel serving as reflux. This addition is suitably carried out after the heat exchanger and after the reflux stream has branched off.

The removed liquids can be cleaned in adsorption and / or filter systems and any interfering components (e.g. organic acids) can be removed before the hydrocarbons are transferred to a storage tank.

Before storing the product diesel, it is preferred to add at least one stabilizer to it.

Free radical inhibitors as well as stabilizers and antioxidants are known to the person skilled in the art. A suitable radical inhibitor is e.g. BHT (Butylhydroxitoluol), suitable stabilizers are e.g. strongly basic amines and a suitable antioxidant is e.g. Phenyldiamine.

While preferred embodiments of the invention are described in the present application, it should be clearly pointed out that the invention is not limited to these and can also be carried out in other ways within the scope of the following claims.

Claims (20)

1. Method for recovering hydrocarbons from plastic-containing waste and organic liquids based on oil, collectively referred to as recyclable plastic materials, preferably from polyolefin-rich recyclable 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) being arranged upstream thereof, without the use of catalysts, wherein

   (b1) the optionally and preferably already partially melted recyclable plastic materials are fed to a first heating device (3) in which they are (further) melted at a temperature of from 300°C to 380°C,

   (b2) the melted recyclable plastic materials together with the recycle stream which has been pumped out of the cracking reactor (5) are supplied to a second heating device (4) in which they are further heated to temperatures of from 380°C to 400°C, (b3) the melted recyclable plastic materials together with already formed hydrocarbon-containing vapors are fed from the second heating device (4) to the cracking reactor (5), in which the melted recyclable plastic materials are further split (cracked) at approx. 400°C, wherein the gaseous hydrocarbons are fed to a partial condenser (11) in which long-chain hydrocarbons condense and are returned to the cracking reactor (5),

   (b4) short-chain hydrocarbons exit the cracking reactor (5) and are fed to a distillation apparatus in which they are broken down into a gaseous fraction and a liquid fraction,

   (b5) high-energy pitch-like and tar-like substances which do not change into the gaseous state and excess carbon which results during the thermolytic cracking of polymers are pumped out of the cracking reactor (5) together with the recycle stream and are separated into recycle stream and residue by means of a separator system (8, 9), wherein the recycle stream, between the first heating device (3) and the second heating device (4), is admixed with the recyclable plastic materials melted in the heating device (3) and the residue is conducted into a collecting tank.
2. Method according to claim 1, wherein the plastic waste is fed to the first heating device via an entry system (1, 2) in which

   (a2) in a first stage, water vapor is removed in a mechanical compressor (1) at 120 to 150°C and is compressed and dried,

   (a3) in a second stage, in an extruder (2), acidic gases, in particular HCl and H₂S, are at least partially melted and removed at 250 to 300°C by means of a vacuum, optionally followed by gas scrubbing.
3. Method according to claim 2, wherein the compression in the first stage (a2) is carried out by means of a screw compressor.
4. Method according to either claim 2 or claim 3, wherein (a1) the recyclable plastic materials are introduced into the entry system (1, 2) via a system of at least two, and preferably two, buffer tanks which are optionally flushed with inert gas, in particular nitrogen, wherein at least one, and preferably one, buffer tank is filled while the at least one other, and preferably one other, buffer tank is emptied into the entry system (1, 2), and wherein all (both) buffer tanks are connected to a weighing system which allows the introduction system to be filled with plastic waste in a metered manner.
5. Method according to any of the preceding claims, wherein the recycle stream is obtained by melted recyclable plastic materials, high-energy pitch-like and tar-like substances which do not change into the gaseous state and excess carbon which results during the cracking of polymers being pumped out from the bottom of the cracking reactor (5) by means of a high-temperature pump (7) and being supplied to a separator system (8, 9), wherein the separator system (8, 9) comprises a cyclone separator (8) and a sedimentation/settling tank (9).
6. Method according to any of the preceding claims, wherein the gaseous hydrocarbons are fed from the cracking reactor (5) to the partial condenser (11) via a packed column (12).
7. Method according to any of the preceding claims, wherein the gases are fed from the cracking reactor (5), after the partial condenser (11), to a distillation apparatus (13, 14, 15, 16) comprising a re-boiler (13) and a distillation column (14), wherein the distillation column (14) has a packed column (15) and an intermediate bottom (16), wherein the gases from the cracking reactor (5) are broken down in the distillation apparatus (13, 14, 15, 16) into a gaseous fraction and into a liquid fraction, wherein the liquid fraction is removed at the intermediate bottom (16) as a diesel product and the gaseous fraction is removed at the top of the column, wherein the low-boiling component (e.g. C5-C7) is condensed from the removed gaseous fraction and separated from the non-condensed gases (e.g. C1-C4).
8. Method according to any of the preceding claims, wherein the system is operated continuously.
9. Method according to any of the preceding claims, wherein the first heating device (3) and the second heating device (4) are each tube heat exchangers flushed with thermal oil.
10. Method according to any of the preceding claims, wherein the partial condenser (11) can be set at a temperature of from 150°C to 350°C, preferably at 300°C, as a result of which the chain length of the molecules which can pass through the partial condenser can be determined, wherein the type of the hydrocarbon mixtures is preferably defined via temperature setting in the partial condenser in which some of the gaseous fraction is condensed.
11. Method according to any of the preceding claims, wherein the thermal fine separation of the gas exiting the cracking reactor (5) is carried out in the distillation column (14) by means of counter-current distillation such that some of the diesel product removed at the intermediate bottom (16) is returned to the top of the distillation column via a recycling stream line (17), preferably after cooling and preferably mixed with a radical inhibitor, wherein the type of the hydrocarbon mixtures is preferably defined via temperature setting in the distillation column (14).
12. Method according to any of the preceding claims, wherein any impurities, in particular sulfur-containing compounds, halogen acids and organic acids, still present in the diesel product and/or in the low-boiling component are removed by adsorption and/or filtration.
13. Method according to any of the preceding claims, wherein short-chain hydrocarbons (e.g. C1-C4) present as a gas downstream of the condenser, optionally after compression and intermediate storage, are used as fuel for energy.
14. Method according to any of the preceding claims, wherein heat exchange surfaces for setting the temperature are dimensioned such that it is possible to work with a heat transfer medium which is at a temperature which is at most 20°C above the desired temperature.
15. Device for processing plastic-containing waste and organic liquids based on oil, collectively referred to as recyclable plastic materials, comprising a first heating device (3), a second heating device (4), a cracking reactor (5), and a recycle stream line (10) which leads from a lower region of the cracking reactor via a separator system (8, 9) into the supply of the melted recyclable plastic materials from the first heating device (3) into the second heating device (4), wherein the cracking reactor (5) has a partial condenser (11) which has a cooling/heating device which is designed such that a defined temperature can be set in the partial condenser (11), and wherein the separator system (8, 9) comprises a cyclone separator (8).
16. Device according to claim 15, wherein the first heating device (3) and the second heating device (4) are each tube heat exchangers flushed with thermal oil, wherein the heating devices (3, 4) and the cracking reactor (5) have independently controllable heaters, and/or wherein the heating devices (3, 4) are heat exchangers which are designed as tube heat exchangers, wherein the tubes are filled with the melted recyclable plastic materials and are flushed with thermal oil.
17. Device according to either claim 15 or claim 16, wherein, in addition to the cyclone separator (8), the separator system (8, 9) has a sedimentation/settling tank (9) which is outside the recycle stream line (10) but connected to the cyclone separator, and which is connected to the recycle stream line (10) via the bypass on the heating-device side.
18. Device according to any of claims 15 to 17, wherein the cooling/heating device comprises a heat transfer medium which can be brought to a temperature necessary for setting the defined temperature by means of a temperature control unit, wherein a preferred heat transfer medium is a thermal oil, wherein a packed column (12) is preferably arranged upstream of the partial condenser (11) in the cracking reactor (5).
19. Device according to any of claims 15 to 18, wherein a distillation unit (13, 14, 15, 16) comprising a re-boiler and a distillation column (14) is arranged downstream of the cracking reactor (5), wherein the distillation column (14) has an intermediate bottom (16) such that liquid fraction can be removed at the intermediate bottom and gaseous fraction can be removed at the top of the column, wherein a cooler for cooling the liquid fraction and/or a condenser for partially condensing the gaseous fraction is arranged preferably downstream of the distillation column (14), wherein the cooler and/or the condenser has a heating/cooling device by means of which a defined temperature can be set in the cooler and/or in the condenser, wherein the distillation column (14) is preferably at least partially designed as a packed column (15), and wherein the distillation column (14) is preferably provided with a recycling stream line (17) such that some of the liquid fraction removed from the distillation column (14) can be returned to the distillation column (14) above the intermediate bottom (16), which is the removal point.
20. Device according to any of claims 15 to 20, comprising at least one adsorption or filter unit for adsorbing impurities from the liquid fraction or the condensed part of the gaseous fraction, wherein the adsorption or filter unit preferably has a plurality of adsorbers or filters which can be switched on or off alternately for adsorbing or regenerating.

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