Patent Publication Number: US-2015087874-A1

Title: Reactor and Method for Gasifying and/or Cleaning a Starting Material

Description:
The invention relates to a reactor for gasifying and/or cleaning a starting material, especially for depolymerizing plastic material, wherein the reactor comprises: (a) a reactor vessel for receiving the 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; a plurality of filling elements which are at least partially arranged in the metal bath; and (d) a heater, especially an induction heater for heating the starting material in the reactor vessel. The invention also relates to a method for operating such a reactor. 
     WO 2010/130404 describes a reactor of this sort and a corresponding method: the purpose of the reactor is to depolymerize plastic material so it is easier to recycle. 
     DE 10 2010 002 704 A1 describes a device for the continuous pyrolysis of organic starting materials. The organic starting materials are transported through a tin bath, which has a temperature of around 480° C., thereby triggering the endothermic pyrolysis reaction. In order to prevent the liquid level in the tin bath from declining, the metal that has been transported out of the reactor with the solid materials may be transported back into the reactor by means of a metal feedback device. The device also has an opening for supplying additional external metals. 
     Residual materials are deposited during gasification or depolymerization, which stick to the filling elements. Therefore, it is generally necessary to clean the filling elements at regular intervals. With previous reactors, the removal of filling elements has been complex. 
     The invention aims to facilitate the cleaning of the filling elements. 
     The invention solves the problem by means of a reactor in accordance with the preamble with a metal bath intermediate storage device, which is connected to the reactor vessel and is designed to remove at least part of the metal bath from the reactor and to return the metal bath to the reactor vessel, and comprises a delivery device for delivering the metal bath, the delivery device having a pressure increasing unit by means of which the metal bath can be delivered by applying the gas pressure. Furthermore, the invention solves the problem by means of a method for operating such a reactor with the steps: (i) raising a metal bath gauge located in the metal bath, so that residual materials floating on the metal bath enter an overflow, (ii) removing the residual materials through the overflow and (iii) lowering the metal bath gauge of the metal bath. 
     The invention is advantageous in that only a small amount of structural elements of the reactor come into contact with the metal bath. Contrary to when pumps are used, it is not possible for any components to be damaged by solidifying metal. The simple structure of the metal bath intermediate storage device is also an advantage, as the energy required to deliver the metal bath can be supplied using gas pressure. 
     Within the scope of the present description, the term reactor should be understood in particular to mean a thermo-catalytic depolymerization reactor. This refers to a reactor which is designed to thermally and/or catalytically depolymerize polymers that have been introduced into the reactor, and/or to break them down into materials with a lower melting or boiling point. However, the reactor can also be designed to clean plastic material. The temperature in the reactor is then preferably selected such that the impurity disintegrates, but the plastic material remains unaffected. 
     The term heater should be understood to mean any device that is designed to supply the plastic material in the reactor vessel with heat energy. This may occur indirectly via the filling elements, preferably by means of induction. 
     It is preferable if the reactor vessel contains a starting material that it be gasified and/or cleaned which has a reaction temperature from which the starting material at least partially depolymerizes and/or vaporizes, the starting material having a carbonization temperature at which the starting material at least partially carbonizes, and wherein the metal bath melting temperature is higher than the reaction temperature and below the carbonization temperature. The reaction temperature should be especially understood to mean the temperature above which the starting material is gasified by at least 25% of its mass within one hour. 
     The carbonization temperature should be understood in particular to mean the temperature above which at least 3% of the starting mass remains at a reaction time of one day. This means that it is solid at the relevant temperature and therefore must be removed from the reactor as a solid. 
     The metal bath temperature of the metal bath is preferably above the reaction temperature and below the carbonization temperature, in particular between 350° C. and 600° C. 
     The term delivery device should be especially understood to mean any device by means of which the metal bath can be fully or partially removed from the reactor vessel and led back into it. 
     The term pressure increasing unit should be particularly understood to mean a device by means of which gas can be emitted, which is pressurized to such a degree that the metal bath can be delivered out of the reactor vessel and/or into the reactor vessel. The pressure increasing unit may, for example, have a pressurized gas store, as well as a gas cylinder. However, it is also possible that the pressure increasing unit has a pump which compresses gas. This aids the delivery process. In addition to this, it is conceivable that the pressure increasing unit comprises two chemical materials that react with one another during the development of gas. 
     In particular, the metal bath is made of Wood&#39;s metal, the Lipowitz alloy, the Newton alloy, the Lichtenberg alloy and/or an alloy that contains gallium and indium. In principle, the metal bath has a density of at least 9 grams per cubic centimetre, so that the starting material experiences a strong buoyant force. The metallic material has a melting temperature of at least 300° C. The melting temperature is preferably a maximum of 600° C. 
     It is preferable if the metal bath intermediate storage device comprises a metal bath vessel that is located at a distance from the reactor vessel. This metal bath vessel is designed such that it does not react with the metal bath and is not affected by the metal bath. 
     The reactor preferably comprises a removal pipe that is arranged centrally in the reactor vessel, through which the residual materials floating on the metal bath can be removed, the removal pipe comprising in particular a ferromagnetic pipe material. Residual materials may refer to organic or inorganic impurities of the starting material, for example, or reaction products, which must pass through the reactor vessel before they are fully gasified. 
     Due to the fact that residual material of this sort often has a higher melting temperature, it is advantageous if the removal pipe is warmer than the metal bath surrounding it. This can be achieved by using a ferromagnetic removal pipe. In particular, the pipe material may have a pipe material Curie temperature which is different by at least 10 Kelvins to a wall material Curie temperature of the reactor vessel and/or the filling element Curie temperature of the filling elements. In particular, the pipe material Curie temperature may be higher than the wall material Curie temperature and/or the filling element Curie temperature. 
     According to a preferred embodiment, the metal bath vessel is at least partially arranged underneath the reactor vessel, such that the metal bath can be at least partially drained. In this way, the metal bath can be easily removed from the reactor vessel. 
     It is especially beneficial if the pressure increasing unit is set up to increase the pressure, in particular the gas pressure, in the metal bath vessel, so that the metal bath can be pushed back into the reactor vessel. In this process, it is possible, but not necessary, that the metal bath can be pushed directly back into the reactor vessel. It is also possible that the metal bath intermediate storage device has a second or several more metal bath vessels into which the metal bath can be delivered. It is possible, but not necessary, that the metal bath vessel has a heater by means of which the metal bath can be heated. In principle, the duration of the metal bath&#39;s residence in the metal bath vessel is so short that it does not solidify. 
     The metal bath intermediate storage device preferably comprises a metal bath vessel that is initially partially arranged above the reactor vessel, such that the metal bath can be drained into the reactor vessel. In this case it is especially beneficial if the pressure increasing unit is set up to increase the pressure in the reactor vessel, so that the metal bath can be pressed into the metal bath vessel. However, it is also possible that the metal bath intermediate storage device has two metal bath vessels, one metal bath vessel being arranged in such a way that the metal bath can be drained from the reactor vessel into this first metal bath vessel, the metal bath intermediate storage device comprising at least a second metal bath vessel from which the metal bath can be drained into the reactor vessel. In this case, the pressure increasing unit is designed to increase the pressure in the first metal bath vessel, so that the metal bath can be pushed from the lower metal bath vessel into the upper metal bath vessel by means of gas pressure. 
     It is beneficial, but not necessary, if the volume of the at least one metal bath vessel is designed to completely receive the metal bath. 
    
    
     
       In the following, the invention will be explained in more detail with the aid of drawings. They show 
         FIG. 1  a reactor according to the invention for conducting a method according to the invention according to a first embodiment and 
         FIG. 2  a second embodiment of a reactor according to the invention for conducting a method according to the invention. 
     
    
    
       FIG. 1  shows a reactor  10  for gasifying a starting material in the form of plastic material  12 , in particular polyolefin polymers. The reactor comprises, for example, an essentially cylindrical reactor vessel  14  for heating the plastic material  12 , which is introduced into the reactor vessel  14  via an extruder  16 . 
     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 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 affect, 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 bath  26  made of liquid metal present in the reactor vessel  14 . The specification that an object such as the filling elements is made of ferromagnetic material means that the object is ferromagnetic at a room temperature of 23° C. 
     The metal bath  26  has a melting point of T Schmelz =300° C. and is introduced into the reactor vessel  14  to a metal bath gauge of H füll . Along with the plastic material  12 , the metal bath  26  fills at least part of the spaces of the filling elements  25 . In principle, the metal bath  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 T R  at which the plastic material  12  gradually disintegrates. In this process, gas bubbles  28  are formed, which move upwards. The metal bath  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: in principle, the filling elements  25  are enough to produce a sufficiently large deceleration effect. The distribution of the filling elements  25 , in the present case the spheres, is schematically depicted in  FIG. 1 . 
     As a result of their buoyancy, one part of the filling elements  25  floats in the metal bath  26  and another part is pressed into the metal bath  26  by filling elements  25  that are positioned further up. The filling elements  25  are also depicted in  FIG. 1  in a constant radius R. It is possible that the filling elements have variable radii, wherein, for example, the radius R decreases in an upward direction. 
     In addition to this,  FIG. 1  depicts a removal pipe  36  arranged in the reactor vessel  14 , via which the residual material  38  floating on the metal bath can be removed. In the present case, the removal pipe  36  runs coaxially to a longitudinal axis L of the reactor vessel  14 . The residual material  38  is, for example, impurities of the plastic material  12  and/or the additional catalyst  32  which can be introduced along with the plastic material  12 . 
     The removal pipe  36  can be made of ferromagnetic pipe material with a pipe material Curie temperature T C,36 . As a result, the removal pipe  36  heats up to T C,36  when the induction heater  18  is driven with a sufficiently high power. The pipe material Curie temperature T C,36  may, for example, correspond to the filling element Curie temperature T C,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 T C,14 . This may be lower than the filling element Curie temperature T C,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 impurities of the plastic material  12 , such as sand, are lighter than the metal bath  26 , they float and can be removed at the top. In addition, the pollutant removal system  40  comprises a settling tank  48  that collects residual material  38 . 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  also comprises a gas outlet  42  that flows into a condenser  44  and removes the resulting gas. The liquid 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 waste oil recycling. 
       FIG. 1  also depicts a metal bath intermediate storage device  52  that comprises a metal bath vessel  54 . The metal bath intermediate storage device  52  is connected to the reactor vessel  14  via a removal lead  56  on the bottom of the latter. Fundamentally, the metal bath  26  can be completely drained by opening a valve  58 . This should be understood to mean that certain residues of the metal bath  26  remain in the reactor vessel  14 , but that these residues only constitute a small fraction of the entire metal bath, for example less than 5%. 
     In addition, the metal bath intermediate storage device  52  comprises a pressure increasing unit  60 , which has a gas canister  62  and a gas valve  63  in the present case. The gas valve  63  can be controlled electronically by means of a control unit, not depicted, so that the pressure p in the metal bath vessel  54  can be adjusted. 
     In the present case, the pressure increasing unit  60  and the removal lead  56  form a delivery device  64 . In order to conduct a method according to the invention, a metal bath gauge, which is defined by the filling height H füll , is raised, for example, by supplying the reactor vessel  14  with an increased flow of plastic material via an extruder  16 . Alternatively, the pressure increasing unit  60  is activated, so that liquid metallic material is pushed through the removal lead  56  from the metal bath vessel  54  into the reactor vessel  14 . 
     As a result of this, the metal bath gauge H füll  rises and residual material  38  floating on the metal bath  26  land in the overflow, which is made up of the removal pipe  36  in the current case. The metal bath gauge of the metal bath  26  is subsequently lowered, for example by opening a drain valve  66 , such that the gas pressure p in the metal bath vessel sinks. If the valve  58  is opened, part of the metal bath  26  flows into the metal bath vessel  54 . 
     In addition to his, a method according to the invention is conducted by initially directing the metal bath  26 —this means the entire metal bath or only a part of it—from the reactor vessel  14  into the metal bath intermediate storage device  52 , especially into the metal bath vessel  54 . This is achieved by opening the valve  54 , wherein the gas pressure p in the metal bath vessel  54  is lower than a pressure p 26  of the metal bath  26  at the bottom of the reactor vessel  14 . The filling elements  25  are then removed and cleaned, or cleaned in the reactor vessel  14 , without being removed. The metal bath  26  is then directed back from the metal bath vessel into the reactor vessel  14  by closing the drain valve  66 , keeping the valve  58  open and applying gas pressure to the metal bath vessel  54 . If a predetermined metal bath gauge is reached, the valve  58  is closed. 
       FIG. 2  depicts a further embodiment of a reactor according to the invention  10 , wherein the metal bath vessel  54  is arranged above the reactor vessel  14 , so that the metal bath  26  can be drained into the reactor container  14 . It should also be recognised that the pressure increasing unit  60  is set up to increase the pressure p 14  in the reactor container  14  by opening a gas valve  68 . Gas pressure can also be applied to the metal bath vessel  54  by opening the gas valve  62 , such that the metal bath  26  present in the metal bath vessel  54  can be fully delivered into the reactor container  14  by raising the gas pressure p. 
     
       
         
           
               
             
               
                   
               
               
                 Reference list 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 10 
                 Reactor 
               
               
                 12 
                 Plastic material 
               
               
                 14 
                 Reactor vessel 
               
               
                 16 
                 Extruder 
               
               
                 18 
                 Induction heater 
               
               
                 20 
                 Coil 
               
               
                 22 
                 Inner space 
               
               
                 24 
                 Deceleration device 
               
               
                 25 
                 Filling elements 
               
               
                 26 
                 Metal bath 
               
               
                 28 
                 Gas bubble 
               
               
                 30 
                 Entry opening 
               
               
                 32 
                 Catalyst 
               
               
                 34 
                 Outer wall 
               
               
                 36 
                 Removal pipe/overflow 
               
               
                 38 
                 Residual material 
               
               
                 40 
                 Pollutant removal system 
               
               
                 42 
                 Gas outlet 
               
               
                 44 
                 Condenser 
               
               
                 46 
                 Collector 
               
               
                 48 
                 Settling tank 
               
               
                 50 
                 Recycling pipe 
               
               
                 52 
                 Metal bath intermediate 
               
               
                   
                 storage device 
               
               
                 54 
                 Metal bath vessel 
               
               
                 56 
                 Removal pipe 
               
               
                 58 
                 Valve 
               
               
                 60 
                 Pressure increasing unit 
               
               
                 62 
                 Gas canister 
               
               
                 63 
                 Gas valve 
               
               
                 64 
                 Delivery device 
               
               
                 66 
                 Drain valve 
               
               
                 68 
                 Gas valve 
               
               
                 χ 
                 Magnetic susceptibility 
               
               
                 f 
                 Frequency 
               
               
                 p 
                 Gas pressure 
               
               
                 L 
                 Longitudinal axis 
               
               
                 R 
                 Sphere radius 
               
               
                 H füll   
                 Flling height 
               
               
                 T Schmelz   
                 Metal bath melting temperature