HK1238611B - Plasma exhaust purification - Google Patents

Description

Plasma exhaust gas purification

Technical Field

The present invention relates to a method for degassing a polymer melt and rendering harmless the waste gases generated thereby, and a system for degassing a polymer melt and rendering harmless the waste gases generated thereby.

Background Art

In the production of polymer products, extruders are often used to melt plastic granules, add one or more liquid or solid additives (such as softeners, lubricants, antistatic agents, etc.) (if appropriate properties of the resulting plastic product are desired), and feed the melt to an extrusion nozzle. The temperature of the melt is in the range of 200°C to 300°C.

After melting, the resulting polymer melt contains gaseous inclusions and liquid substances in solution. This can negatively impact the quality of the finished product when the melt is processed in a mold. Inclusions can be particularly detrimental in the production of plastic films. Therefore, in the plasticizing unit, melting the plastic and mixing it with one or more additives is usually followed by a degassing process in one or more vacuum zones before the melt is discharged via a discharge unit.

For this purpose, a vacuum system is used, which is connected to a degassing zone (vacuum zone). In the vacuum system, a vacuum pump station generates a negative pressure, which can act on the vacuum zone via corresponding lines and thus ensure that interfering gases, polymers, decomposition products of additives and contaminants are extracted from the melt.

The purpose of degassing is, inter alia, to remove water (in the form of water vapor) and non-crosslinked plastic molecules (residual monomers) from the melt.

These gaseous and, in some cases, liquid components removed from the plasticizing unit by the negative pressure can damage the vacuum unit over time, significantly shortening the service life and availability of various components. This significantly increases cleaning and maintenance costs, and machine breakdowns are inevitable. This ultimately leads to the problem of disposing of these substances and machine components.

The cause of damage and contamination of the vacuum unit and components connected thereto, such as lines, valves and sensors, is that the separated substances react with one another and separate thermodynamically at the surface.

To achieve the best possible quality for products manufactured from plastic melts, these products should contain only low levels of moisture. Furthermore, volatile decay products of the plastic, such as oligomers or undesirable additive components, should be removed from the finished product. Therefore, efforts are made to remove water vapor, hydrocarbons, and other sublimable components from the melt in the extruder area. In addition to leaking air and water vapor, these accompanying substances require a vacuum that is unaffected by them. Previous systems for this purpose use an operating medium that is conveyed along with the accompanying substances, or use separation systems that operate in a vacuum.

For this purpose, systems are used in the prior art which essentially comprise a melt catcher, a separation device or a gas cleaning system and a vacuum system.

In a separation device or gas purification system according to the prior art, the following method is used:

1) Condensation

Condensable contaminants, such as oligomers, condense out of the mixture of water vapor, hydrocarbons, and air.

Separation is performed in a vacuum using dry-running vacuum pumps, such as Roots pumps, screw pumps, claw pumps or the like, or combinations thereof. Methods based on condensers/sublimators (cold traps) are also commonly used, often in combination with particle filters.

Due to the vapor pressure curve of water, complete condensation is impossible. At very low pressures, it is possible to separate the ice below the freezing point (resublimation). Because other deposits and ice can also form on the cold trap, cleaning systems for the cooling surfaces are also common. Alternating operation of redundant systems (freeze-locking and defrosting) is also conceivable.

Since continuous operation is to be ensured, a redundant system is usually sufficient. This allows one separation chain to be cleaned while another is in production, see EP 2 209 604 and DE 10 2013 000 316.

2) Gas scrubber

Gas scrubbers are also used. Here, the gas exiting the extruder comes into contact with a scrubbing liquid over a large area. Such equipment is also used to absorb gaseous pollutants in such a gas mixture in the scrubbing liquid or to filter out solid components of such a drawn-out gas mixture and/or dissolve them in the scrubbing liquid.

The scrubbing liquid should absorb or adsorb substances contained in the gas in such a way that these substances, along with the liquid, can be removed (continuously or discontinuously) from the vacuum system. With suitable selection of the scrubbing liquid, the water vapor content (hygroscopic liquid) in the gas stream can also be reduced. In the device previously known from DE 10 2011 082 769, ethylene glycol, for example, is used as the hygroscopic scrubbing liquid in conjunction with a regeneration device.

For example, US 2008/0207868 A1 discloses another gas purification system which uses a scrubbing liquid (but without a vacuum device). Ethylene glycol is used as the scrubbing liquid.

DE 10 2008 031 834 A1 shows a gas purification device comprising an integrated filter and condenser.

According to DE 44 24 779 A1, it is proposed to extract, in particular, softened oil from the existing vacuum. The gas emerging from the extrusion process and to be condensed is directed via a pipe to a solids separator, where coarse contaminants and residual monomers (oligomers) are separated. In the condensate separator, the vaporous components of the gas condense and are subsequently collected in a condensate collection vessel. Valves are provided at appropriate locations and are automatically controlled, if necessary, to ensure proper operation.

WO 2009/065384 A2 further proposes cooling the gas mixture to a temperature below 10°C in a degassing system and resubliming the sublimable gas onto a cooled horizontal plate, from which the gas is blown. Thermodynamically, this prior publication describes a process in which the solid is directly converted into gas and resublimed as a solid onto the cooling plate by cooling. According to this prior publication, resublimation can be performed not only in a sublimator in the form of a cooling plate, but also in a downstream bag filter known from the prior art.

3) Liquid ring pump

The operating medium pump can be implemented as a liquid ring pump. If water is used as the operating medium, an additional booster pump, such as a single-stage or multi-stage Roots blower (i.e., a rotary piston blower without internal compression), is usually required because the vapor pressure of the operating medium affects the achievable ultimate vacuum and the pump's suction capacity (which depends on the specified temperature). Therefore, glycol or other liquids are also used here. The liquid must be purified during operation or replaced as needed.

Furthermore, it should be mentioned that, quite generally, redundant systems belong to the prior art, which, for example, allow the repair of individual components, while the system can continue to be operated as such.

Despite these measures, increased contamination of the vacuum pump occurs, resulting in a high maintenance outlay for the system.

Thus, in the cold trap area, even at very low operating pressures (<=3 mbar, cooling water temperature 1°C), weakly cohesive powders are often separated, and at higher pressures (3-10 mbar, cooling water temperature -4°C to +5°C), liquid or multiphase substances with solid components are separated. Dust-like deposits form in the particle filter, which can sometimes cause cohesive failure. These separation products, in addition to the aforementioned parameters of pressure and cold trap temperature, also depend on the cold trap design, air leakage and leaks, the processed substance, and the extrusion parameters.

Monoethylene glycol is identified as the main enabler of the bonded filter element.

Pump stations known from the prior art (e.g., DE 10 2013 000 316 A1) typically include a combination of a Roots pump and a screw pump. Because exhaust gas residues remain in the gas flow, which can cause deposits on contacting surfaces such as the pump housing and pump rotor, flushing devices are provided. These flushing devices allow liquid to be sprayed over the Roots pump during operation.

The basic design for such an extrusion system known from the prior art comprises an extruder or an extruder arrangement, downstream of which a separator and one or more vacuum pumps are arranged.

The extruder can be a single-screw or multi-screw extruder. A condensation system according to the prior art, such as that shown and described in DE 10 2013 000 316 A1, can be used as a separator. Such a condensation system can also include a filter or a combination of a separator and a filter. The associated vacuum pump station is also known from the prior art.

Summary of the Invention

Against this background, the object of the present invention is to provide an improved method and an improved system for degassing melts, in particular polymer melts.

This object is achieved with respect to the method and with respect to the system according to the concept of the invention.

The present invention provides a significantly improved method and a significantly improved system for degassing melts, ie, in particular polymer melts. This is made possible by an improved exhaust gas purification device.

The present invention relates to a method for degassing a polymer melt and for rendering harmless the harmful substances produced thereby, comprising the following method steps:

- Create negative pressure or vacuum with the help of vacuum equipment,

- introducing negative pressure or vacuum to the degassing zone in which the polymer melt is located,

- the exhaust gas removed or sucked out of the degassing zone by means of a vacuum device or the exhaust gas is separated from pollutants in the form of liquid and/or solid components in subsequent filter stages and/or separators,

in:

After removal from the degassing zone and before being fed to the filter stage or separator, the pollutants are fed to a plasma source which is designed and/or constructed such that the pollutants are completely or partially converted into a plasma aggregate in the plasma source.

Furthermore, the present invention relates to a system for degassing a polymer melt and for harmlessly treating the waste gases generated thereby, having the following characteristics:

A vacuum device is provided, by which a negative pressure or vacuum can be generated,

a conduit and/or a conduit system is provided, via which negative pressure and/or vacuum can be supplied to a degassing zone for degassing the polymer melt located in the degassing zone,

at least one filter stage and/or separator stage is provided, by means of which the waste gases or pollutants in the form of gaseous and/or liquid and/or solid components which can be removed or sucked out of the degassing zone by means of a vacuum device can be separated,

in:

At least one plasma source is arranged downstream of the degassing zone, in which plasma source the harmful substances that can be removed from the degassing zone can be converted into a plasma aggregate state.

The exhaust gas is rendered largely harmless in the exhaust gas purification system, so that no further purification is necessary, or remaining waste can be removed with minimal effort, and undesirable solid/liquid components can be easily filtered out before the pump.

Plasma devices are used as important components of exhaust gas purification systems.

A method is proposed which enables the virtually residue-free detoxification of exhaust gases.

With the activated plasma source, no increase in the differential pressure across the filter can be seen.

It preferably has the following steps:

By controlling the temperature of the corresponding feed lines, condensates, resublimates, deposits, coke and impurities are avoided in order to prevent their formation until an effective plasma is established.

The supply line is designed as a heated line and can be heated within an adjustable, defined temperature range.

The process is controlled in such a way that an explosive atmosphere in the pump area is avoided by permanent oxidation. For this purpose, a control device can be provided which preferably feeds ambient air or water vapor or another process gas such as oxygen, nitrogen, carbon dioxide, or argon to the process. In principle, all available gases useful for the desired reaction are conceivable.

The method described yields the following advantages:

Using a dry-running pump without flushing the equipment.

After the LUTZ pump, the water is separated in a higher pressure range; the water vapor is thus separated better (condensed).

The screw pump can be selected in a smaller size.

In known solutions, contaminated components can be repaired economically only within longer periods. Regardless of how the deposits appear, a reduction in the effectiveness of a separator, such as a solids separator, condensate separator, or sublimation separator, is achieved within these periods.

To reduce equipment costs, maintenance intervals can be increased.

Furthermore, within the scope of the present invention, the cost-effectiveness of a process to be carried out using the system according to the present invention can also be significantly improved.

Furthermore, the invention also makes it possible to increase the service life of the vacuum system and in particular the vacuum pump provided therein, and to eliminate the cleaning problems existing in the prior art.

Waste material that has accumulated so far is eliminated and does not need to be disposed of additionally.

The present invention generally provides for supplying energy, such as heat, to exhaust gases and/or pollutants and/or converting them into a plasma state in some other way. When the exhaust gases or pollutants are excited for conversion into a plasma state, the molecules present are completely or partially ionized. After the gas no longer remains in the plasma state, the particles can react to form energetically favorable compounds. This primarily involves gases that can be extracted without further filtering.

Different types of plasma are generated according to various methods and used, for example, to modify substrates (see, for example, PlasTEPConference Proceedings, Tartu, 2012). Plasma treatment is used, for example, for coating, cleaning, and etching substrates, in medicine for treating implants, and in technology for exhaust gas purification. The workpiece geometries to be treated range from flat substrates, fiber bundles, or web-shaped materials to any desired structural shapes. Microwave plasma has gained significant importance due to the high efficiency and good availability of microwave generators.

Various sources are known for plasma treatments, such as microwaves (MPS microwave plasma sources), corona (DC and RF), high-voltage devices (US 2009146349), and RF sources (up to the GHz range). Examples of known manufacturers of microwave plasma sources include: Muegge (http://www.muegge.de/de/produkte/); CSClean Systems, Piranha, EP 885455 and EP 992052, EP 872164; for RF sources: DryScrub; Advanced Energy, Litmas Blue; ASTeX, ASTRON. See also the PlaSTEP Conference Proceedings, Tartu, 2012. This prior art also mentions or differentiates, for example, between cold or non-thermodynamic plasmas, hot non-thermodynamic plasmas (so-called transition plasmas), and thermodynamic plasmas.

In the context of the present invention, microwave plasma is preferably used as a purification device, but other plasma generation methods should not be excluded in principle. According to the prior art, these microwave plasma sources are automated, allowing the microwave coupling to be self-adapted (Automatischer Tuner, Automatic-Tuner TRISTAN (Muegge GmbH)). Glow discharge plasma can also be used in a pressure range of 1 mbar to 50 mbar.

Plasma involves another type of aggregation state. By increasing the temperature (e.g., by supplying heat), the solid, liquid, and gaseous states are gradually transitioned to these aggregation states. This also applies to plasmas in principle. If the temperature of the gas is continuously increased, at some point the atoms and nuclei will separate from each other as ions. This state is called a hot plasma. However, plasma can also be generated in a similar manner by exciting only electrons. This is referred to as a non-thermodynamic or non-uniform plasma.

Plasma is used in various areas of industry. Such hot plasmas are used for welding, separation, and gas processing. Plasma is used for coating or surface modification at atmospheric pressure or in a high vacuum. Toxic fluorinated compounds or those with a high climate potential also need to be decomposed and, in other cases, removed from the exhaust gas after the vacuum pump using other separation methods (gas scrubbers, adsorbers, etc.). Weapons have also been destroyed at atmospheric pressure using GlidArc systems. The decomposition of refrigerants is also described.

A large number of different structural types of devices are used to generate microwave plasma. According to the prior art, the system comprises a plasma chamber, a receiver or active space located therein, and a guided hollow conductor coupled thereto, which is often implemented as an enclosed hollow conductor resonator.

The microwaves are introduced into the plasma chamber via feed lines and, if necessary, coupling devices. Different plasmas are used for different applications. Hollow conductors and coaxial cables are often used for microwave feed lines, while antennas and slots are often used for coupling (DE 42 35 914 A1).

In other words, it can be summarized that the present invention relates in particular to a method for degassing a polymer melt and harmlessly treating the waste gases generated therein before continuous further processing to form a stretched polymer film, wherein preferably

The solid plastic to be processed is melted in the form of granules by a plasticizing unit (extruder), and

One or more liquid or solid additives (such as softeners, lubricants, antistatic agents, etc.) are added to the plastic, and

The mixture of molten plastic and additives is degassed in one or more vacuum zones of the plasticizing unit which are connected to a vacuum device;

And these waste gases are rendered harmless in separation devices or purification equipment, and

The entire system should be designed in such a way that condensates, resublimates and impurities due to organic deposits and coking are avoided.

For example, when processing undried PET, vacuum degassing of the liquid melt is necessary. Pre-drying can be saved by using a twin-screw extruder. This avoids the complex dryer/crystallizer process, which requires a significant amount of energy and requires maintaining several tons of material at a sufficiently high temperature. To maintain consistent melt quality, the residence time, as well as the temperature and humidity in the dryer, must be kept constant.

The system according to the invention, comprising a twin-screw extruder, a purification or decontamination device, and a vacuum system, can reduce the moisture content of the material (possibly up to 4000 ppm) to below the indicated limit without pre-drying. To this end, one or more degassing zones are provided in the moving parts of the extruder, which, aided by the material transport in the extruder, allow for large-scale degassing.

The following degassing is set up, since the contained moisture is converted into the gas phase at normal extrusion temperatures (260° C.-300° C.) and normal vacuum pressures (0 mbar-100 mbar) (vapor pressure specification: water 260° C.-42 bar, 280° C.-55 bar, (see also Antoine equation).

In addition, other organic residues enter the vacuum system. These residues are generated partly by the back reaction of PET to monoethylene glycol and terephthalic acid, but also by thermal and hydrolytic damage to the material during melting. In addition to polymers, air, and water, cyclic and linear oligomers, acetaldehyde, and, in the case of PET 1.2, ethylene glycol, in the case of PET 1.4, phenylenedicarboxylic acid, 2-methyldioxolane, and other unidentified decomposition products are also present. In PP, in addition to oligomers, esters, amines, and volatile components such as glycerol monostearate and erucamide, which are derived from the addition of additives (antistatic agents, lubricants, slip), are also present. Hydrocarbons adhere to the wall if heating is insufficient and react to form long-chain molecules, which can usually only be removed with high maintenance costs.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further explained below with the aid of examples. Herein, it is shown in detail:

FIG1 shows a schematic diagram of a first embodiment of the present invention;

FIG2 shows a schematic test device with which the advantages of the solution according to the invention over devices used according to the prior art can be implemented;

FIG3 shows an alternative embodiment with a simplified construction;

FIG4 shows an example of a device with serial and parallel multiple redundant configurations, comprising four plasma regions or plasma sources and an additional redundant conduit system;

FIG5 shows a simplified configuration of the apparatus, comprising only a degassing conduit and a redundantly designed separator arrangement;

FIG6 shows a device which is simplified again with respect to FIG5 , without redundant splitter branches; and

FIG7 shows a further modified embodiment comprising two degassing ducts connected in parallel, wherein only one plasma source is present in one degassing duct and two plasma sources are connected in series in a second degassing duct extending parallel thereto, wherein this branch can be connected to a suction station using an additional redundant duct system.

DETAILED DESCRIPTION

The basic principle of the present invention is further explained below with reference to FIG1 .

1 shows in a schematic diagram a plasticizing unit 1, for example in the form of an extruder or, for example, in the form of a twin extruder 1.1', a plasma source 2 connected downstream, and a further vacuum device 5 connected downstream of the plasma source 2, which is also partially referred to as a vacuum device 5. The entire arrangement is connected to one another via a conduit 11 (pipe).

FIG. 1 thus again shows the simplest conceivable embodiment of the arrangement according to the invention, in which the aforementioned plasma source 2 can be used directly downstream of the extruder 1 , 1 ′ and any separation becomes superfluous.

The corresponding plasticizing unit 1 according to the first embodiment shown in FIG1 comprises, for example, an extruder 1, 1', which, as is known, generally has at least one or two (or more) plasticizing screws. The at least one plasticizing screw of the plasticizing unit 1 (not shown in FIG1 ) can, if necessary, be mixed with a heating device or heating belt by means of a heating device or heating belt to mix the plastic supplied to the plasticizing unit 1 and, if necessary, with supplied additives. Simultaneously, the plastic melts. The plastic melt enters the area of influence of one or more vacuum zones 5 of the overall system.

In this case, for example, two vacuum domes of a twin screw are used to prevent condensate from depositing. The guide tubes are combined and the gas temperature is determined by thermocouples.

In principle, the solution of the present invention can be used in all types of extruder vacuum degassing, that is, also in lateral degassing. Generally speaking, the melt-filled interior of the plasticizing unit 1 is connected to the aforementioned vacuum zone 5 via corresponding openings in the housing. Finally, the plastic supplied to the plasticizing unit, for example at the aforementioned inlet Eg, is then discharged in molten form at the outlet Ag.

Extruders are also known, to which the melt is fed and where degassing also takes place in the draw-in shaft.

More precisely, it is already known in principle to use plasma sources, for example in the semiconductor industry, for exhaust gas treatment. In this case, the plasma source is used upstream of a vacuum pump, but at a maximum pressure of 1 mbar. All other applications have so far been carried out at atmospheric pressure (~1000 mbar) or under high vacuum (<1 mbar).

However, what is completely new is the first use of a plasma source in a machine or system for processing plastics, namely, in the vacuum system of an extruder (single-screw and multi-screw extruder), as described within the scope of the present invention, and the direct treatment of the exhaust gas at the point of generation. Furthermore, the pressure range in the extruder is not comparable to that in other applications. The pressures required during extrusion, such as 5-10 mbar for BOPET, 10-15 mbar for MOPET, 80-120 mbar for BOPP, and 200-300 mbar for BOPA, have not been developed to date.

2, which shows a test setup for determining the effectiveness of the solution according to the invention. Plastic granules are melted in a schematically illustrated extruder 1, 1' and fed to the plasticizing unit 1, 1' via an input E, for example in the form of an injection funnel 1.1.

The melt (plastic melt) is degassed in the vacuum zone or zones, here VD1 and VD2, as appropriate. For this purpose, a vacuum and/or degassing line 11, also referred to below as a degassing line 11a, is provided. For this purpose, a connection is established between the vacuum zone VD (here, vacuum zones VD1 and VD2) via the plasma source 2 (discussed below) and possibly other cold traps 3 and filters or separators 4, as well as via other line sections to vacuum systems 5 and 6, which preferably include multiple vacuum pumps. To quantify the effectiveness of the plasma separation, a bypass line 11b is also provided, along with a shutoff valve D held therein. By opening the bypass valve D in the bypass line 11b and closing the valves A.1, A.2, and B in the degassing line 11a, which includes the plasma source 2, the situation according to the prior art, in which the exhaust gas is separated in the cold trap 3 and the particle filter 4, can be reset.

The effectiveness of the plasma source can be demonstrated by comparative measurements of the separation quantity and separation rate on separators 3 , 4 with and without the plasma source 2 .

Thus, the embodiment of the test device according to FIG. 2 shows that the two vacuum zones VD1 and VD2 provided there, where degassing takes place within the extruder, are alternatively connected to subsequent processing stages via a degassing conduit 11 a or a bypass conduit 11 b extending therefrom, by opening or closing a switching valve provided in each of the conduits.

The subsequent treatment stage comprises a line 12a in which, for example, shutoff valves G.1 and G.2 with a larger flow cross section and a smaller flow cross section are connected in parallel. Connected to this, for example, are a cold trap 3 and a separator or filter 4 (particle filter). Connected in series thereto is another switching valve arrangement comprising a larger switching valve H.1 with a larger flow cross section and a smaller switching valve H.2 with a smaller flow cross section, connected in parallel.

A further line 13 is connected to the line section 12a, which includes the aforementioned devices, and leads to the vacuum devices 5, 6. In the illustrated embodiment 3, the vacuum devices have three parallel branches 16a, 16b, 16c, each comprising two consecutively connected vacuum stages or vacuum pumps 5, 6. At the input end, these vacuum devices can be disconnected or connected to the line 13 via a switching valve K.1, K.2, or K.3, respectively, so that the corresponding vacuum is not applied as far as the degassing zone VD, i.e., as far as the degassing zone VD1 or VD2.

The further process stage described above (and more precisely valves 1.1 and 1.2 as well as J.1 and J.2) is additionally arranged in line 12b, which is connected in parallel with respect to first line 12a. This further process stage comprises valves G.1 and G.2, which are connected in parallel with a larger and a smaller flow cross section, as well as a cold trap 3 and a filter or separator 4 (for example in the form of a particle filter) connected thereto, and a switching valve combination connected thereto, which comprises switching valves H.1 and H.2, which are connected in parallel with respect to a larger and a smaller flow cross section.

For the test, a bypass line 11 b is provided which is connected in parallel with the line 11 a and which does not comprise a plasma stage 2 but instead has, for example, only one switching valve D.

As can also be seen from the diagram according to FIG. 2 , the two degassing zones VD1 and VD2 are connected to one another via a connecting line 15a. Similarly, the two end sections of the bypass lines 11a and 11b, which are respectively connected downstream of the switching valves D and B in the flow direction, are connected to one another via a connecting line 15b. Finally, the sections of the lines or tubes 12a and 12b, which are downstream of the switching valves H.1 and H.2 on the one hand and J.1 and J.2 on the other hand in the flow direction, are also connected to one another via a connecting line 15c.

This creates a further, parallel bypass line 12b with respect to the line section 12a containing the devices 3 and 4. This bypass line 12b is constructed identically to the components arranged in line 12a. In other words, line 12b also includes two switching valves 1.1 and 1.2 connected in parallel, a cold trap 3 arranged downstream, and a separator or particle filter 4 arranged downstream of the cold trap 3. Two parallel-connected shutoff valves J.1 and J.2 are then provided at the output end. The output lines of these shutoff valves are connected to the output of the first line section 12a via a connecting line 15c and merge into an output line 13, via which the vacuum system is connected.

Furthermore, within the scope of the invention, the lines 11, 11a, 11b are heated upstream of the separator 4 to avoid contamination. This occurs in the PET processing range of 200-300° C. In addition, a large cross section and a well-accessible cleaning flange are provided.

In the exemplary embodiment shown in FIG2 , the vacuum and/or degassing lines 11a, 11b and 12a, 12b leading to the two cold traps 3 are temperature-controlled to, for example, 150° C. to 300° C., so that condensation (and/or sublimation) of the exhaust gases in these lines is largely eliminated. This is important for the maintenance-free operation of the production system. Every surface in the vacuum system upstream of the plasma source, separator, or filter must be heated to a sufficient degree. The plasma source must be adapted as follows.

The vacuum line is further characterized in that a special device (melt catcher) prevents the melt from penetrating from the plasticizing unit into the vacuum line.

The plasma source arranged in the bypass line 11 a is a device which completely or partially ionizes the gas flowing through and thus initiates a chemical reaction.

The fundamental suitability of the plasma source for treating extrusion exhaust gases was demonstrated by detailed comparative tests on a production plant.

The plasma source is powered by a microwave generator. The plasma source can be used as a tube component through which a flow flows. The diameter of the plasma source's inlet and outlet openings is determined by the microwave frequency used. With larger diameters, microwaves can also be coupled into the tube or directed out of the plasma source. This prevents functionality (this only applies to embodiments using a microwave plasma source).

According to various embodiments, a quartz tube, for example, is located in the plasma source and is sealed toward the housing with a polymer seal. The quartz tube serves as a microwave window and provides a separation between the pressure of the surrounding atmosphere and the vacuum on the process gas side. The component surrounding the process space is a "ring resonator" and ensures a uniform distribution of microwaves around the circumference of the process chamber and a uniform coupling of energy into the process chamber via the coupling gap (functioning as an antenna).

According to the prior art, a "vortex nozzle" or waveguide nozzle can be used on the inlet side, for example. This involves, for example, a thick-walled aluminum tube with tangentially introduced holes. The process gas is thus forced onto a spiral path. Consequently, at high flow rates, the particle density near the process chamber wall is higher, which should prevent direct plasma contact with the wall and damage to the wall. Furthermore, the residence time and mixing in the process chamber are improved. The plasma source itself can be equipped with a water cooler to cool the inlet area and also to keep the polymer seal on the quartz glass at a controlled temperature. Small holes are introduced into the ring resonator, which allow observation of the plasma but are primarily used to cool the quartz glass. An external blower is preferably used, and a cooling air flow is also drawn through the quartz glass.

The preferred embodiment is a flow through the process chamber from bottom to top. This flow through direction prevents any solids or condensates from passing through the plasma source untreated.

The cold trap 3 is understood to be a device for cooling the gas flow and, if appropriate, for condensing corresponding internal materials, such as water or hydrocarbons. A possible embodiment according to the prior art is a cooling cross with a small surface or a tube bundle heat exchanger. The housing is also cooled, and the heat exchanger can be partially cleaned during operation, as is generally known from the already mentioned DE 10 2013 000 316 A1 or EP 2 209 694 B1.

A separator, filter, or particle filter 4 is understood to be an apparatus for separating particles from an air flow when using a large-area material filter. Hydrocarbons, which initially form from the gas phase via dust-like deposits, are often also separated on the filter. Also known are dynamic separation devices that separate particles relative to the air flow via density differences, such as cyclones and centrifuges.

The vacuum system mentioned can be designed such that in each of the three branches shown in FIG. 2 , a Roots blower 5 is arranged on the line 13 (after passing through the shutoff valve) and a screw pump 6 is arranged connected thereto.

The Roots blower may be a high-capacity vacuum pump that can only create a small pressure differential.

The aforementioned screw pump 6 can be, for example, a backing vacuum pump for a LUTZ blower.

2, a plurality of pressure gauges p are connected at different positions so that the current pressure can be measured at the relevant positions or zones. Similarly, temperature measuring devices T can also be connected at different positions.

For testing purposes, valve D can be closed once and valves A.1, A.2 and B opened, but also the subsequent valves together with line 12a or 12b, in order to operate the system with plasma source 2 connected and determine corresponding measurements regarding the result of the performed degassing.

The valve in the degassing line 11a containing the plasma source 2 can then be closed and the valve D in the bypass line 11b opened to carry out normal operation and then perform the corresponding measurements. This comparison directly shows the clear advantages of using a plasma source.

It should be noted that a connecting line 15b between the two lines 11a, 11b or 12a, 12b is not absolutely necessary. Preferably, the test is carried out with the plasma source 2 connected, using only the line chain, for example, the cold trap 3 and separator 4 in line chain 12a, while the valves are locked and shut off in the bypass line 12b, similarly to how valve D closes the bypass line 11b. To comparatively test the shutoff of the valves in the degassing line 11a and, if necessary, the subsequent line 12a, conventional operation can then be carried out using the cold trap 3 and separator 4 arranged in the second line 12a, so that the test can be analyzed separately. Alternatively, instead of two parallel lines 12a, 12b, only one line system 12 can be provided, so that the exhaust gas is always routed through the same cold trap 3 and separator 4, regardless of whether the plasma source 2 is switched on or off.

Reference is now made to Figure 3, which illustrates and describes the apparatus according to the invention, which is designed in principle similarly to the test apparatus according to Figure 2. Furthermore, the apparatus according to Figure 3 has the possibility of also feeding in other co-reactants.

In the device according to FIG3 , the gas cold trap 3 shown in FIG2 is connected directly downstream of the plasma source 2, i.e., in the conduit section 11a. Therefore, only a separator or filter, in particular in the form of a particle filter 4, is provided in the subsequent conduits 12, 12a. In the conduit branch 12a, a valve G is connected upstream of the particle filter 4 and another valve H is connected downstream of the particle filter 4, so that the corresponding branch can be opened and closed in the flow direction, as is also the case with the other valves or switching valves mentioned. In the bypass conduit 12b provided for this purpose, two switching valves I and J are also connected in series, although in principle only one switching valve is required. In the illustrated embodiment, the connecting conduit 12 extends between a connection point X and a branching point Y at the input end, at which the degassing conduit 11a and the bypass conduit 11b are connected to each other, and at which the two subsequent conduit systems 12a and 12b extending in parallel branch off. At the output end, the two branch or bypass lines 12a, 12b meet again at a connection point Z and are connected via a line 13 to the pump stations 5, 6, which in turn can be equipped in one or more stages with parallel and/or series connected pumps or the like.

Thus, the degassing line 11a, which is connected to the vacuum zones VD1 and VD2 via connecting lines 11, 11a (similar to the other exemplary embodiments), has valves (shutoff or switching valves) A and B at the input and output, respectively. A plasma source 2 is arranged between the two valves, and a cold trap 3 is arranged downstream of the plasma source in the flow direction. In the bypass line 11b connected in parallel thereto, in the illustrated embodiment, not just one valve D is provided, but two valves D.1 and D.2, connected in series, are provided to open and close the line.

3 , pressure gauges p, for example _p1 and _p2 , and temperature measuring devices T, in particular _T1 , _T2 and _T3 , are also connected at various locations. These measuring devices can also be provided additionally or alternatively at other locations.

3 shows that the following possibility is provided before the plasma source 2: in the event of a possible lack of co-reactants (incomplete oxidation, formation of carbon black), water vapor and/or air or other gases (plasma-based depollution) can be additionally introduced through the accessible connections _N1 and _N2 . The co-reactants here are in particular the water contained in the material and the leaking gas conveyed therewith. This stimulates the oxidation process. Existing leaks can also be charged with other gases in a targeted manner, so that the reaction can be influenced in a targeted manner, for example, by charging the inlet with carbon dioxide or argon. An additional advantage here is that a reduction in the oxidation of the melt is avoided. The disadvantage is the additional cost for the gas. For the two mentioned connections 31a and 31b, preferably controllable regulating valves 33a and 33b in terms of their flow rate are used to meter the co-reactants.

In addition to this transport, particles or additives can also be cleaned with a gas or gas mixture, which likewise has an advantageous effect on the reaction in the plasma source (this will be described in detail later).

As mentioned above, a gas cold trap can optionally be installed downstream of the plasma source in order to cool down the gas which may be heated in the plasma source.

A variant of a redundant and serially connected production plant is described below with reference to FIG. 4 .

4 shows an extruder 1 including a vacuum system. This vacuum system is designed to be redundant. For example, the corresponding plasma source chains 2.1 and 2.2 as well as 2.3 and 2.4 are present in duplicate, as are the separators 4.1 and 4.2.

That is, the multiple redundant construction is obtained as follows, namely, on the one hand, two parallel-connected branches are provided, comprising a conduit system 11a, 12a and a conduit arrangement 11b, 12b connected in parallel therewith, wherein in each of the two parallel-connected chains, which can be operated together or alternatively with each other, two plasma sources 2.1 and 2.2 or 2.3 and 2.4 are respectively arranged in series.

In each of the two treatment chains, comprising a line system 11a, 12a or a pipe system or a line arrangement with line sections 11b and 12b connected in parallel therewith, a second plasma source is connected in series with the plasma sources 2.1 and 2.2 already mentioned and present in each chain, namely plasma source 2.2 in line arrangement 11a, 12a and plasma source 2.4 in line arrangement 11b, 12b connected in parallel therewith. Corresponding switching valves are connected upstream and downstream of the plasma sources, preferably also in the form of parallel switching valves (which may have different flow cross sections), in order to enable particularly metered and precise switching or changeover or particularly sensitive opening and closing processes.

Furthermore, three pump chains 16a to 16c are shown. The number of parallel systems is for informational purposes only. Other pump chains connected in parallel are also conceivable to increase reliability. The series arrangement of the plasma sources allows for higher power, which can be introduced into the gas via the plasma sources and, through the two-stage embodiment, stimulates the reaction in a targeted manner. The reduced power in the first plasma source can thus be used for partial oxidation and, after the addition of any process gas (e.g., oxygen), for complete oxidation in a subsequent plasma source.

The inlet funnel 1.1 of the extruder 1 is fed via an adjustable gas feed valve N.0. This valve allows the material to be processed in the extruder to be purged with a gas or gas mixture that is preferably advantageous for material processing and reaction in the plasma, such as argon, nitrogen, carbon dioxide, oxygen, water vapor.

Adjustable devices or valves N.1 to N.4 are likewise located upstream of the plasma sources 2 . 1 to 2 . 4 , via which gases and/or water vapor can be introduced in a targeted manner into the vacuum system upstream of the plasma source 2 .

Ignition devices 23.1 to 23.4, each connected upstream of a respective plasma source 2 in the flow direction R, allow ignition of the plasma source even under optimized ignition conditions with the aid of auxiliary energy. The goal is to provide ions (charge carriers) that reduce the required ignition energy. This allows the plasma source to form and maintain a plasma even under non-optimized conditions.

The plasma sources 2.1 and 2.2 connected in series and the plasma sources 2.3 and 2.4 connected in series are preferably directly separated from one another by valves B.1 and B.2 and E.1 and E.2 and can be closed independently of the rest of the vacuum system (for the arrangement and switching of the further switching valves A.1, A.2, C.1, C.2, D.1, D.2, F.1, F.2, G.1, G.2, H.1, H.2, J.1, J.2 and valves K.1 to K.3 and N.1 to N.3, see in particular the illustration according to FIG. 4 . This shows where the corresponding valves are arranged in the flow direction. This arrangement applies not only to the embodiment according to FIG. 4 , but also to any variants thereof).

These valves can each preferably open or close lines or pipe sections upstream and/or downstream of components such as the plasma source 2 with or without an upstream ignition device, filters and/or cold traps 3 which are generally not required within the scope of the invention.

Separators 4.1 and 4.2 also each contain a gas cold trap (as described further above). These separators can also be completely separated from the system via valves H and G or J and I and can be controlled separately.

The provided pumps (here 8.1 to 8.3) are separated from the vacuum system by valves K.1 to K.3 and can be connected or disconnected from the process control system, depending on the required suction capacity or any disturbances that occur.

The continuous operation of the system can be implemented such that, for example, two plasma sources 2.1 and 2.2 connected in series are opened by correspondingly controlling a regulating and/or switching valve provided in the process chain or process line 11a, and a corresponding regulating and/or switching valve in the line 11b or pipeline connected in parallel therewith is closed. If a problem should occur during operation with one or both of the active plasma sources 2.1 and/or 2.2, the redundant design allows switching to the plasma sources 2.3 and 2.4 in the second process branch 11b by opening the regulating and/or switching valve provided there and closing the switching and/or regulating valve provided in the first line system 11a. In this case, the two plasma sources 2.3 and 2.4 connected in series are also active in the redundant design.

However, if, for example, a problem were to occur in second plasma sources 2 . 2 and/or 2 . 4 and one or both of these plasma sources were to be switched off, the configuration according to FIG. 4 would also be designed redundantly here.

To this end, valves M.1 to M.3, which are additionally attached to the vacuum pump, and valves L.1 to L.4, which are attached to the plasma source, are connected via a separate conduit system Z2 and form an auxiliary system. This conduit system Z2 is connected to the input of the vacuum station, that is, to the pump chain 16a to 16c provided in the illustrated embodiment, and more specifically, via the valves M.1 to M.3, for generating a vacuum or negative pressure. This conduit system Z2 branches off and leads to branching points 41.1, 41.2, 41.3, or 41.4, respectively, downstream of the respective plasma source 2.1 to 2.4 in the flow direction, more specifically, via valves L.1, L.2, L.3, or L.4, each of which is additionally switched in the conduit system Z2 before reaching these branching points.

By closing valves K.1, K.2 or K.3 (or, for example, valves connected directly upstream and downstream of separators 4.1 and 4.2) and opening valves M.1, M.2 and/or M.3 as well as the valves assigned to the plasma sources, for example, by opening valves L.1 and L.3 and closing valves L.2 and L.4, it can be ensured that, for example, only plasma sources 2.1 and 2.3 are active during the degassing process, while plasma sources 2.2 and 2.4 are switched off and locked.

In an extreme case, valve L.1 can also be opened or closed as an alternative to valve L.3 or vice versa, so that only one plasma source is active for the intended purpose, ie, plasma source 2.1 or 2.3, for example. This also further increases the overall redundant design of the system.

This allows the pressure of a plasma source separated from the main vacuum system to be specifically regulated using a pump separate from the main vacuum system. Thus, the plasma source can be started, for example, at a reduced pressure level compared to the main vacuum system. Subsequently, the ion source can be operated at a higher pressure level in the main vacuum system Z1. However, this state can also be used for functional testing of the plasma source.

For example, valves A, B, C, G, H, K, M, and L (designed as individual switching valves or as parallel-connected double valves, as shown in the figure according to FIG. 4 together with valves A.1, A.2, B.1, B.2, etc.), K.1, and K.2 are opened in the main vacuum system and ensure suction at, for example, 10 mbar on the extruder. Exhaust gas purification is carried out using active plasma sources 2.1 and 2.2. All other valves are closed. If a second plasma chain is now to be put into operation, this part of the system is evacuated using a separate pump. To this end, valves L.3, L.4, and M.3 are opened, and the plasma sources are evacuated independently of the main vacuum system to, for example, 1 mbar, since the critical field strength for plasma ignition is lower at lower pressures. Plasma sources 2.3 and 2.4 are ignited. After successful ignition, valves L.3, L.4, and M.3 are closed, and valves D.2, E.2, and F.2 are opened. When the pressures p2.2 and p3.2 largely correspond to the pressures p1.1, p1.2 and p4.1, the main valves D.1, E.1 and F.1 are also opened. The gas flows are thus processed in parallel by the two plasma source chains.

A variant of the transformation is described below with reference to FIG. 5 , which shows and explains a simpler, non-redundant system for separation.

The exemplary embodiment shown in FIG5 comprises an extrusion system 1 including a plasma source 2, a separator system 4, and a vacuum pump 5. The plasma source 2 is simple in design. The separation is redundant to ensure protection of the vacuum pump in the event of a plasma source failure. The plasma source 2 is autonomously capable of igniting and maintaining a plasma. Several suction chains are provided, each of which can be switched on or off depending on the suction power.

The composition of the extruder offgas allows direct treatment, thereby carrying out the total oxidation of the hydrocarbons contained, or carrying out a partial oxidation thereof. In partial oxidation or similar reactions, waste materials may remain, which can be removed from the gas stream by means of a separator.

In other words, this embodiment is implemented similarly to the other variants, but only includes the conduit branches 11, 12, and 13, in which the plasma source 2 and the separators 4.1 and 4.2 are arranged, along with the corresponding valves. Not included in this variant is the cold trap 3 described in the other embodiments, which, if required, can also be connected in the variant according to FIG. 5 , for example, directly after the respective separators 4.1 and 4.2 in the conduit sections 12 a and 12 b and directly before the filter 4.1 or 4.2 between valves G and H or I and J. At the output end, one, two, or more (in the example shown, three) branches can be provided, in which corresponding vacuum arrangements are provided for parallel operation or individual connection. Instead of the aforementioned valves G and H or I and J, respectively, a parallel-connected dual valve arrangement can also be used, as in all other exemplary embodiments. For example, instead of valve G shown in FIG. 5 , two parallel-connected valves G.1 and G.2 can be provided, instead of valve H, two parallel-connected valves H.1 and H.2 can be provided, and correspondingly instead of the aforementioned valves I and J, parallel-connected valves I.1 and I.2 or J.1 and J.2 can be provided. No restrictions or limitations regarding such variations exist in any of the exemplary embodiments or in other deviating device types.

To start the vacuum system, proceed similarly to the previous description. During operation, only one separator chain is used in each case. If the pressure difference increases across the filter (difference p_3.1 and p_4) and exceeds, for example, 7 mbar (PET), then switch to the other separator.

Another variant is described below with reference to FIG. 6 , which includes an embodiment with a simple plasma cleaning device and a simple separator system 4 .

This means that, similar to the previous exemplary embodiment, some of the devices explained with reference to the previous exemplary embodiment are omitted. The exhaust gas from the extruder 1 is treated in the plasma source 2 and passed through the separator 4 .

By using a plasma source, it is no longer necessary to purify the gas in the separator 4. The separator remains as a gas cold trap and failsafe. In addition, it is possible to partially separate water from the gas at the correct cold trap temperature (depending on the pressure) and thus reduce the required suction power.

Finally, FIG7 shows another variant in which the device is also designed in parallel to increase redundancy, i.e., it comprises two line branches 11a and 11b and one line branch 11b connected in parallel, which are further connected to one another in the two vacuum zones VD1 and VD2 via an intermediate line 15a. By disconnecting one branch in each case (by closing a valve provided there) and opening the parallel branch, a connection to each of the provided degassing zones VD1, VD2 can be established via the connected branch, which includes at least one plasma source.

If maintenance work is carried out on a plasma station or system in a branch, operation can be continued by switching in a second degassing branch connected in parallel.

At the ends, both branches are connected via a connecting line 15 b comprising a common discharge line to the separator/filter 4 , unless a separate filter is provided in each branch.

As already mentioned, it is also possible to connect a cooling filter 3 and/or an ignition device 3 ′ upstream, one at a time or separately in each branch.

FIG. 7 also illustrates that the overall treatment of the exhaust gas flowing through can be further improved and enhanced by additionally connecting two plasma stations in series (or in parallel) in the corresponding branch 11 b (shown in the right-hand branch 11 b in FIG. 7 ). However, this serial connection or series connection can also be arranged in two branches, deviating from FIG. 7 . As already discussed several times, here again, corresponding single valves or parallel-connected double valves are connected at least upstream and/or downstream of the respective components, such as the respective plasma source 2 , separator 4 , etc., or preferably upstream and downstream thereof, respectively. The corresponding single valves or double valves can also be connected upstream of the respective suction stations. The same arrangement also applies to the additionally provided conduit system Z2, which establishes a connecting conduit from the inlet of the suction station, for example, via switching valves M.1 to M.3, at least to a degassing conduit (e.g., degassing conduit 11 b). The connection is made via a branched line arrangement, the connection point of which is provided at a connection point 41 . 3 or 41 . 4 of the degassing line 11 , which is arranged downstream of the respective plasma source 2 in the flow direction.

The following is a detailed description of the method process corresponding to the device.

In order to ensure that all extruder exhaust gases are treated during automatic operation, the plasma source 2 should be inserted directly after the extruder 1 in the direction of gas flow. When the vacuum system is started, the vacuum system, including the plasma source 2, is evacuated. To avoid large pressure shocks, the valves in the system of the present invention are designed in two stages. Initially, the bypass valves with reduced cross-sections (valves B.2 and F.2) are opened until the adjacent ducts have approximately the same pressure level, and only then are the main valves (valves B.1 and F.1) opened. The use of a bypass with a pipe diameter of, for example, 15 mm allows for a slower equalization of the pressures of the two adjacent volumes. This avoids strong pressure shocks that could occur if a main valve with a diameter of, for example, 100 mm was suddenly opened. When the extruder starts operating, the plasma source is ignited. The bypass valve A.2 is then opened to evacuate the vacuum dome. If the pressure on the dome is approximately the same as the vacuum system pressure, the main valve A.1 opens.

During operation, the function of the plasma source 2 must be monitored in order to be able to react in the event of a possible malfunction. The plasma is monitored by means of a yellow sheet of the plasma source or by means of an additional system. To ensure ignition, it may be necessary to utilize an additional ignition system 3'. This ignition system should provide the ignition conditions in the plasma source 2. Additional vacuum lines are conceivable here, which allow for independent pressure levels (K.1-K.3 and M.1-M.3) in the plasma source compared to the remaining systems. If pre-ionization of the gas in the plasma source is difficult, this can be accomplished by means of high-voltage ignition or another auxiliary energy source (e.g., an ignition plug 23 in the gas flow upstream of the plasma source).

Excessive pressure or temperature is considered a shutdown condition. These pressures or temperatures are monitored directly downstream of the plasma source. Excessive pressure at the plasma source can occur due to defects in the vacuum system, such as leaks, incorrect supply of additional process gas, clogged filters, or a defective vacuum pump. Increased temperatures can also occur due to increased gas flow.

The extruder is also switched off as soon as, for example, the pressure p ₁ at the vacuum dome is well outside the production-typical limit values (eg ≧30 mbar).

By connecting a plurality of plasma sources in series, the conversion of the exhaust gas flowing through can be increased again, or the course of the reaction can be influenced at any point before or after the plasma source by adding additional gases (see co-reactants).

For degassing in the extruder, the pressure at the vacuum dome is crucial and can be predetermined as a process variable. The process control system ensures sufficient pump suction power and regulates the vacuum pressure to the desired value. The plasma source must be adapted to these ambient conditions to ensure proper operation (for example, in microwave plasma sources, the frequency modulator can be adapted mechanically or manually). Power adaptation of the energy introduced into the gas flow can be beneficial for the energy consumption of the system and for stimulating specific reactions, and should be implemented. The power requirement also depends on the gas flow and, therefore, on the extruder output and the state of the material being processed.

As control criteria for the course of the method, the pressures at the vacuum dome (before the filter p ₁ ) and at the pump (after the filter p ₂ ) are detected.

Additionally, it is important for automated operation that the plasma source adapts independently to changing environmental variables.

According to the present invention, the frequency modulator in the microwave system is automatically adjusted according to the vacuum pressure. The pressure measurement value is transmitted to the plasma source by the PPS system.

Claims (30)

1. A method for degassing a polymer melt and for rendering harmless substances generated therefrom, comprising the following method steps: -Use vacuum equipment to generate negative pressure or vacuum. - Negative pressure or vacuum is supplied to the degassing zone, where the polymer melt is located. - Waste gas removed or extracted from the degassing zone (VD; VD1, VD2) by vacuum equipment, or waste gas and harmful substances in liquid and/or solid form are separated in subsequent filter stages and/or separators (4; 4.1, 4.2). - After the hazardous substances are removed from the degassing zone (VD; VD1, VD2) and before being conveyed to the filter stage or separator (4; 4.1, 4.2), they are conveyed to a plasma source (2; 2.1, 2.2, 2.3, 2.4), said plasma source being constructed and/or configured such that, in the plasma source (2; 2.1, 2.2, 2.3, 2.4), the hazardous substances are completely or partially transformed into a plasma aggregate state. - To supply the hazardous substance with process gases, said process gases including oxygen, nitrogen, carbon dioxide, argon, ambient air, and/or water vapor. It is characterized by the following other features: - Harmful substances removed from the degassing zones (VD; VD1, VD2) and transported to the plasma sources (2; 2.1, 2.2, 2.3, 2.4) move forward through a conduit system heated to at least 150°C to prevent deposition. - One or more plasma sources (2; 2.1, 2.2, 2.3, 2.4) can be switched on or off via valves (A, A.1, A.2, B, B.1, B.2, C, C.1, C.2, D, D.1, D.2, E, E.1, E.2, F, F.1, F.2) located in conduits (11, 11a, 11b, 12, 12a, 12b, 13), and - Switching valves with different flow cross sections, in the form of parallel switching valves, are connected upstream and downstream of the plasma source. 2. The method according to claim 1, characterized in that the process gas is additionally supplied to the hazardous substance before or during delivery to the plasma source (2; 2.1, 2.2, 2.3, 2.4). 3. The method according to claim 1 or 2, characterized in that the harmful substances are transformed into a plasma aggregate state in the plasma source (2; 2.1, 2.2, 2.3, 2.4) under the condition of energy supply. 4. The method according to claim 3, characterized in that the harmful substance is transformed into a plasma aggregate state in the plasma source (2; 2.1, 2.2, 2.3, 2.4) by thermal excitation, electromagnetic radiation including laser radiation, electrostatic field and/or electromagnetic field and/or alternating electric field, inductive excitation and/or with the aid of microwaves. 5. The method according to claim 1, wherein the conduit system is heated to at least 200°C to avoid deposition. 6. The method according to claim 1, characterized in that the harmful substances are heated to a temperature range of 150°C to 300°C between the degassing zone (VD; VD1, VD2) and the plasma source (2; 2.1, 2.2, 2.3, 2.4). 7. The method according to claim 6, characterized in that the harmful substances are heated to 200°C to 300°C between the degassing zone (VD; VD1, VD2) and the plasma source (2; 2.1, 2.2, 2.3, 2.4). 8. The method according to claim 1 or 2, characterized in that the harmful substance is delivered to a plurality of successively connected plasma sources (2; 2.1, 2.2, 2.3, 2.4) to generate a plasma state. 9. The method according to claim 1 or 2, characterized in that a plurality of plasma sources (2; 2.1, 2.2, 2.3, 2.4) are connected in parallel to each other so as to implement a conversion from one plasma source (2; 2.1, 2.2, 2.3, 2.4) to a separate second plasma source (2; 2.1, 2.2, 2.3, 2.4) during operation. 10. The method according to claim 1 or 2, characterized in that a plurality of plasma sources (2; 2.1, 2.2, 2.3, 2.4) are provided, the plasma sources being partially connected in series and partially connected in parallel with each other. 11. The method according to claim 1 or 2, characterized in that a plasma source (2; 2.1, 2.2, 2.3, 2.4) is used, said plasma source being configured such that at least 20% of the harmful substances are converted into a plasma aggregate state therein. 12. The method according to claim 11, characterized in that a plasma source (2; 2.1, 2.2, 2.3, 2.4) is used, said plasma source being configured such that at least 30%, 40%, 50%, 60%, 70%, or at least 80% or at least 90% of the harmful substances are converted into a plasma aggregate state. 13. A system for degassing polymer melts and for rendering the waste gases generated therefrom harmless, having the following characteristics: Vacuum devices (5, 6) are provided, which can generate negative pressure or vacuum. A conduit system is provided through which negative pressure and/or vacuum can be delivered to degassing zones (VD; VD1, VD2), which are used to degas the polymer melt within them. The system includes at least one filter stage or separator (4; 4.1, 4.2) that can separate harmful substances in gaseous and/or liquid and/or solid form from the degassing zone (VD; VD1, VD2) via vacuum equipment. At least one plasma source (2; 2.1, 2.2, 2.3, 2.4) is disposed downstream of the degassing zone (VD; VD1, VD2), in which harmful substances removable from the degassing zone (VD; VD1, VD2) can be transformed into a plasma aggregate state. - A filter stage or separator (4; 4.1, 4.2) is installed downstream of the plasma source (2; 2.1, 2.2, 2.3, 2.4). - The system has a connection device upstream of the plasma source (2; 2.1, 2.2, 2.3, 2.4) for conveying process gas along the direction of exhaust gas flow. - A conduit or container is connected upstream of at least one connector (N1, N2), the conduit or container being used to deliver process gases, specifically process gases in the form of oxygen, nitrogen, carbon dioxide, argon, ambient air, and/or water vapor. It is characterized by the following other features: - The conduits leading from the degassing zones (VD; VD1, VD2) to the plasma source (2; 2.1, 2.2, 2.3, 2.4) or the conduits transferring hazardous substances to the plasma source are equipped with heat insulation and/or heating devices, through which the conduit system can be heated to at least 150°C. - Switching valves with different flow cross sections, in the form of parallel switching valves, are connected upstream and downstream of the plasma source. 14. The system according to claim 13, characterized in that the at least one plasma source (2; 2.1, 2.2, 2.3, 2.4) is constructed such that harmful substances flowing through it can be transformed into a plasma aggregate state when energy is supplied. 15. The system according to claim 14, characterized in that the at least one plasma source (2; 2.1, 2.2, 2.3, 2.4) is configured such that harmful substances flowing through it can be transformed into a plasma aggregate state by means of thermal excitation, electromagnetic radiation including laser radiation, electrostatic field and/or electromagnetic field and/or alternating electric field, inductive excitation and/or microwaves. 16. The system according to claim 13, characterized in that the conduit system can be heated to at least 200°C by the heat insulation device and/or heating device. 17. The system according to claim 13, characterized in that the conduit through which harmful substances can flow from the degassing zone (VD; VD1, VD2) to the at least one plasma source (2; 2.1, 2.2, 2.3, 2.4) is provided with and/or encased with a heating system for heating the conduit to a temperature range of 150°C to 300°C. 18. The system according to claim 17, characterized in that the conduit through which harmful substances can flow from the degassing zone (VD; VD1, VD2) to the at least one plasma source (2; 2.1, 2.2, 2.3, 2.4) is provided with and/or encased with a heating system for heating the conduit to 200°C to 300°C. 19. The system according to claim 13 or 14, characterized in that it is provided with a plurality of plasma sources (2; 2.1, 2.2, 2.3, 2.4) connected in series. 20. The system according to claim 13 or 14, characterized in that a plurality of plasma sources (2; 2.1, 2.2, 2.3, 2.4) are connected in parallel with each other. 21. The system according to claim 13 or 14, characterized in that at least one additional conduit (Z2) branches off from at least one conduit (11a, 11b; 12a, 12b; 13) extending between at least one degassing zone (VD; VD1, VD2) and at least one suction station, together with plasma sources (2; 2.1, 2.2, 2.3, 2.4) connected here in a series arrangement. 22. The system according to claim 21, characterized in that the at least one additional conduit (Z2) branches off from a branch location (41.1, 41.2, 41.3, 41.4) between two series-connected plasma sources (2; 2.1, 2.2, 2.3, 2.4), wherein the branch location (41.1, 41.2, 41.3, 41.4) is connected to the input and/or suction side of the at least one suction station via the switching valve (L.1 to L.4; M.1 to M.3). 23. The system according to claim 13 or 14, characterized in that the initiation device (23; 23.1, 23.2, 23.3, 23.4) is connected upstream of the corresponding plasma source (2; 2.1, 2.2, 2.3, 2.4). 24. The system according to claim 13 or 14, characterized in that one or more melt traps are provided in the conduits (11; 11a, 11b; 12; 12a, 12b; 13) to prevent melt from entering the vacuum unit from the plasticizing unit. 25. The system according to claim 13 or 14, characterized in that the process gas can be delivered to at least one or more plasma sources (2; 2.1, 2.2, 2.3, 2.4) through a vortex nozzle or a waveguide nozzle. 26. The system according to claim 13 or 14, characterized in that the vacuum equipment (5, 6) has at least one vacuum pump, at least one Roots blower and/or at least one spiral pump. 27. The system according to claim 13 or 14, characterized in that the valve disposed in the conduit (11, 11a, 11b, 12, 12a, 12b, 13) is configured as a simple switching valve or as a pair of valves (A.1, A.2 to K.1, K.2) connected in parallel. 28. The system according to claim 13 or 14, characterized in that the system is constructed without a cold trap. 29. The system according to claim 13 or 14, characterized in that the plasma source (2; 2.1, 2.2, 2.3, 2.4) is configured such that at least 20% of the harmful substances delivered to the plasma source (2; 2.1, 2.2, 2.3, 2.4) can be converted into a plasma aggregate state. 30. The system according to claim 29, characterized in that the plasma source (2; 2.1, 2.2, 2.3, 2.4) is configured such that at least 30%, 40%, 50%, 60%, 70%, 80%, or at least 90% of the harmful substances delivered to the plasma source (2; 2.1, 2.2, 2.3, 2.4) can be converted into a plasma aggregate state.