Patent Application
20150083572
The invention relates to a reactor for gasifying and/or cleaning, especially for the depolymerizing of plastic material, with (a) a reactor vessel for receiving a starting material, especially the plastic material, (b) a metal bath which is arranged in the reactor vessel and includes a liquid metallic material having a metal bath melting temperature, (c) a heating system for heating the plastic material in the reactor vessel and (d) a residual material-removal device for at least partially removing residual material which are produced during the gasification and/or cleaning of the starting material.
A reactor of this sort is described in WO 2010/130 404 and is used to gasify plastic materials, in particular polymers. To this end, the plastic material is introduced into the reactor vessel of the reactor, for example by extruder, where it comes into contact with a metal bath. The high temperatures and, where applicable, the present catalytic effect of the metal bath cause the depolymerization of the plastic material.
The starting material may comprise materials, which are either completely inert or not fully gasified, such that residual material is deposited. This residual material must be removed from the reactor vessel so that it remains in constant operation. It has been proven that the removal of the residual material is a restrictive factor with regards to enabling an economic operation of the reactor.
The invention aims to improve the removal of residual material from the reactor vessel.
DE 197 35 153 A1 describes a method and a device for gasifying of residual material. For this purpose, the starting material to be gasified is preferably introduced into a heated reactor, which has previously been filled with liquid slag, in such a way that an impulse causes the slag to rotate. The organic elements of the starting material are gasified and the mineral elements are fused and absorbed by the slag. This results in an increase in the volume of the slag. Should the slag volume exceed a particular limit, part of the slag runs through a side opening of a centrally located pipe in the reactor into a water bath, where it then solidifies.
DE 196 29 544 C2 describes a method for processing polyvinylchloride. In this method, the PVC is also added to a rotating slag bath, in which a gaseous part is separated off and the remaining material is absorbed by the slag. The resulting slag is also directed through a central outflow into a water bath.
The invention aims to improve the removal of the residual material from the reactor vessel.
The invention solves the problem by means of a reactor in accordance with the preamble, wherein the residual material-removal device comprises an overflow which is centrally arranged in the reactor vessel so that residual material that floating on the metal bath can be removed via the overflow. According to a second aspect, the invention solves the problem by means of an operation method for a reactor of this sort that includes the following steps: (i) raising a gauge of a metal bath so that the residual material enters the overflow, and (ii) removing the residual material through the overflow.
It has been proven that a centrally situated overflow is particularly well suited for the effective removal of residual material from the reactor vessel. It is thus advantageous if the overflow is always at the same temperature as the metal bath surrounding it. This eliminates the possibility of the residual material cooling down and clumping together upon removal.
A further advantage is that the gas development that occurs during the operation of the reactor enhances the removal of the residual material. It is a surprising revelation that the gas development on the radial outer edge of the inner space of the reactor vessel is particularly large. The rising gas bubbles slightly raise the gauge of the metal bath over a period of time, such that the residual material floating on the metal bath experience a force acting radially inwards. This results in a radially inward flow of residual material, which can be removed particularly effectively through the centrally located overflow.
The surprising realisation that the residual material has a preferred direction of flow, namely radially inwards, also contributes to a relatively rapid movement of the residual material into the overflow. If the overflow is arranged radially outwards, it may result in the formation of areas on the surface of the metal bath in which the residual material residence time is so high that the residual material clumps together. This results in the difficult removal of the residual material from the reactor vessel.
The central location of the overflow does have the disadvantage that it is more difficult to exert an external influence, for example to remove residual material that has stuck together. However, the above advantages more than compensate for this disadvantage.
The term reactor vessel should be understood in particular to mean a device which, during operation, accommodates the metal bath, the filling element and the starting material.
The term metal bath should be understood to mean a concentration of liquid metal, in particular molten metal, which takes the form of a liquid at an operating temperature of the reactor.
In particular, the metal bath comprises Wood's metal, the Lipowitz alloy, the Newton alloy, the Lichtenberg alloy and/or an alloy which contains gallium and indium. In principle, the metal bath has a density of more than 9 grams per cubic centimetre, so that the starting material experiences a strong buoyant force. The metallic material has a particular melting temperature of at least 300° C.
However, lower melting points are possible. The melting temperature preferably has a maximum value of 600° C. During operation of the reactor, the metal bath has a temperature of T from 300° C. to 600° C.
According to a preferred embodiment, the overflow consists of a removal pipe that is in thermal contact with the metal bath. This ensures that the removal pipe is of the same temperature as the metal bath, thereby avoiding the possibility of the materials clumping together when they cool down. The removal pipe is preferably a metal pipe, in particular a ferromagnetic metal pipe.
The term heater should be understood in particular to mean a device by means of which the plastic material can be directly or indirectly heated. In particular, the heater is an induction heater by means of which one component of the reactor can be heated. For example, the filling elements are ferromagnetic, so they can be heated by induction. However, it is conceivable that, in addition or alternatively to the filling elements, the overflow and/or the reactor vessel are ferromagnetic.
The starting material in particular is heated such that the filling elements are heated, which in turn heat the metal bath. The metal bath then transfers the heat to the starting material.
The residual material removal device is in particular a device by means of which the solid, fluid and/or paste-like matter that occurs during gasification and/or cleaning can be removed.
According to a preferred embodiment, a residual material support device is arranged inside the removal pipe, which is designed to use a mechanical impact to move residual material. For example, this may refer to a screw conveyor that can scrape along the inside of the removal pipe so as to prevent or remove blockages.
The removal pipe preferably has an inner pipe diameter that is at least a tenth of an inner reactor vessel diameter of the reactor vessel. This enables the efficient removal of the residual material.
It is beneficial if the residual material removal device comprises a storage vessel and a gas-tight lock, such that the storage vessel can be detached from the reactor vessel, while remaining gas-proof in the process. In other words, it is possible to detach the storage vessel from the reactor vessel without allowing the gas to infiltrate the reactor vessel and escaping out of the storage vessel. This reduces the risk of fire, as otherwise flammable gases can escape.
In the following, the invention will be explained in more detail with the aid of a drawing. It shows
The reactor 10 comprises a heater, for example an induction heater 18, which has a number of coils 20.1, 20.2, . . . , 20.4, by means of which an alternating magnetic field is created in an inner space 22 of the reactor vessel 14. The coils 20 (reference numbers without a numerical suffix refer to all respective object) are connected with a power supply unit, not depicted, which induces an alternating current on the coils. The frequency f of the alternating current is, for example, in the region of 4 to 50 kHz. Higher frequencies are possible, but they lead to an increase in the so-called skin effect, which is undesirable.
A deceleration device 24 is arranged in the inner space 22 of the reactor vessel 14, by means of which the upward flow of liquefied plastic material 12 in the reactor vessel 14 can be slowed down. The deceleration device 24 comprises a number of movable filling elements 25.1, 25.2, . . . arranged in the inner space 22. These elements are made of ferromagnetic material and in the present invention take the form of spheres with a radius R. The sphere radius R may be between 0.5 and 50 millimetres, for example.
As a result of their ferromagnetic properties, the filling elements 25 are heated by the induction heater 18 and thereby heat a metal melt 26, i.e. molten metal, present in the reactor vessel 14. The specification that an object such as the filling elements 25 is made of ferromagnetic material means that the object is ferromagnetic at a room temperature of 23° C.
The filling elements 25 have a Curie temperature TC,25, above which the magnetic susceptibility χ sinks abruptly. The connection to the electromagnetic field emitted by the induction heater suddenly becomes smaller and the filling element's 25 heat emission reduces dramatically. The heat input created by the induction heater is thus lower with hot filling elements than cold filling elements.
The metal melt 26 has a melting point of TSchmelz=300° C. and is introduced into the reactor vessel 14 to a filling level of Hfüll. Along with the plastic material, it fills the spaces of the filling elements 25. For example, the metal melt 26 is made of Wood's metal, the Lipowitz alloy, the Newton alloy, the Lichtenberg alloy and/or an alloy that comprises gallium and indium. In principle, the metal melt 26 has a density of at least 9 grams per cubic centimetre, so that the plastic material 12 experiences a strong buoyant force. This buoyancy accelerates the plastic material 12. The filling elements 25 counteract this acceleration.
A temperature T prevails in the reactor vessel 14: this temperature is above a reaction temperature TR at which the plastic material 12 gradually disintegrates. In this process, gas bubbles 28 are formed, which move upwards. The metal melt 26 can have a catalytic effect on the disintegration process, such that the reactor 10 may refer to a thermo catalytic depolymerisation reactor. The plastic material 12 introduced via the extruder 16 enters the inner space 22 through an entry opening 30, which is preferably located on the base of the reactor vessel 14.
The deceleration device 24 may comprise restraint devices, such as a grid stretched across a frame, whose mesh is so small that the filling elements 25 cannot move upwards through it. However, this is not necessary. For example, a filling of spheres is sufficient, as depicted here. The distribution of the filling elements 25, in the present case the spheres, is schematically depicted in
As a result of their buoyancy, one part of the filling elements 25 floats in the metal melt 26 and another part is pressed into the metal melt 26 by filling elements 25 that are positioned further up. The filling elements 25 are also depicted in
In addition to this,
The removal pipe 36 can be made of ferromagnetic pipe material with a pipe Curie temperature TC,36. As a result, the removal pipe 36 heats up to TC,36 when the induction heater 18 is driven with a sufficiently high power. The pipe material Curie temperature TC,36 may, for example, correspond to the filling element Curie temperature TC,25, 1: it may also be lower or higher. However, it is also possible that the removal pipe 36 is constructed using a non-ferromagnetic material, such as an austenitic steel or titan.
The reactor vessel 14 is constructed of a wall material on at least the side facing the inner space 22. The wall material may be ferromagnetic, for example iron or magnetic steel. Alternatively, the wall material may also be non-magnetic.
If the wall material is ferromagnetic, it has a wall material Curie temperature TC,14. This may be lower than the filling element Curie temperature TC,25. In this case, the wall of the reactor vessel 14 is colder during operation than the filling elements 25.
The removal pipe 36 is part of a pollutant removal system 40. As typical residual material impurities 38, such as sand, have a lower density than the metal bath 26, they float and can be removed at the top. In addition, the pollutant removal system 40 comprises a storage vessel, which may also be referred to as a settling tank 48, that collects residual material. The residual material 38 may contain not entirely depolymerized organic material, alongside inorganic material. The organic material floats on the inorganic material and can be lead back into the reactor vessel 14 through a recycling pipeline 50 on the bottom of the container.
The reactor 10 comprises a gas outlet 42 that flows into a condenser 44 and removes the resulting gas. The fluid material leaving the condenser 44 lands in a collector 46.
The reactor described can be operated with, for example, waste oil as a starting material instead of plastic material, and then be used for recycling and processing.
A method according to the invention is conducted by initially raising the gauge Hfüll, for example, by introducing the metal bath 26 to the reactor vessel 14. This may occur by introducing solid metal spheres made of the metallic material into the reactor vessel 14 so that they melt. It is also possible to increase the flow of plastic material 12, in particular by operating the extruder at a higher power. This increases the volume of both gasified and non-gasified plastic material present in the reactor vessel 14, so that the gauge Hfüll rises, for example in the form of the removal pipe 36. The residual material 38 are then removed: this means that they either automatically flow through the removal pipe or they are transported through the removal device by a corresponding device, in the present case the removal pipe 36.
It can be advantageous to lower the supply of plastic material prior to raising the metal gauge so as to reduce the formation of gas bubbles. This has the advantage that less gas bubbles form, thereby decreasing losses in the metal bath caused by splattering.
The gauge will preferably be lowered again after raising the gauge in the metal bath and removing the residual material through the overflow, for example by draining the metal bath.
It is preferable if a gauge of the metal bath is set such that the residual material layer is set at a thickness H38 of at least 10 cm, whereby the thickness H38 may fall below this value when the metal bath gauge is raised for the removal of the residual material through the overflow.
In other words, the fact that the residual material layer has a thickness H38 of at least 10 cm should be understood to mean that this thickness is achieved and exceeded at least 75% of the time. The thickness H38 is the distance from the boundary layer between the metal bath and residual material layer to the upper edge of the residual material layer on the other. The thickness is preferably regulated by means of a feedback control system. This means that the reactor 10 has a thickness registration device, which is not depicted, by means of which the thickness Has can be recorded. Should a maximum thickness Has be exceeded, the above described method for the removal of residual material is conducted.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102012008457.9 | Apr 2012 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/001221 | 4/23/2013 | WO | 00 |
