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

Abstract

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

1 . A method for recovering hydrocarbons from plastic-containing waste and organic liquids based on crude oil, denoted overall as reusable plastic materials, preferably from polyolefin-rich reusable plastic materials, by means of purely thermolytic cracking in a cracking reactor ( 5 ), with a first heating device ( 3 ) and a second heating device ( 4 ) situated upstream therefrom, without using catalysts, wherein
 (b1) the reusable plastic materials, which are optionally and preferably already partially melted, are supplied to a first heating device ( 3 ) in which they are (further) melted at a temperature of 300° C. to 380° C.,   (b2) the melted reusable plastic materials together with the recycle stream which have been pumped out of the cracking reactor are supplied to a second heating device ( 4 ), in which they are further heated to temperatures of 380° C. to 400° C.,   (b3) the melted reusable plastic materials together with already formed hydrocarbon-containing vapors are supplied from the second heating device ( 4 ) to the cracking reactor ( 5 ), in which the melted reusable plastic materials are further cracked at approximately 400° C., wherein the gaseous hydrocarbons are supplied to a partial condenser ( 11 ) in which long-chain hydrocarbons condense, and are returned to the cracking reactor ( 5 ).   (b4) short-chain hydrocarbons exit from the cracking reactor ( 5 ) and are supplied to a distillation unit in which they are fractionated into a gaseous fraction and a liquid fraction,   (b5) high-energy pitch- and tar-like substances that have not assumed the gaseous state, and excess carbon that results during the thermolytic cracking of polymers, together with the recycle stream are pumped out of the cracking reactor ( 5 ) and separated into the recycle stream and the residue by means of a separator system ( 8 ,  9 ), and the recycle stream between the first heating device ( 3 ) and the second heating device ( 4 ) is admixed with the melted reusable plastic materials melted in the first heating device ( 3 ), and the residue is led into a collection tank.   
     
     
         2 . A method for recovering hydrocarbons from plastic-containing waste and organic liquids based on crude oil, denoted overall as reusable plastic materials preferably from polyolefin-rich reusable plastic materials, by means of purely thermolytic cracking in a cracking reactor ( 5 ), with a first heating device ( 3 ) and a second heating device ( 4 ) situated upstream therefrom, without using catalysts, in particular according to  claim 1 , wherein the supplying of the plastic waste to the first heating device takes place via a feed system ( 1 ,  2 ) in which
 (a2) in a first stage, water vapor is discharged in a mechanical compactor at 120 to 150° C., and compaction and drying take place,   (a3) in a second stage, at least partial melting and removal of acidic gases, in particular HCl and H 2 S, take place under vacuum in an extruder ( 2 ) at 250 to 300° C., optionally followed by gas scrubbing.   
     
     
         3 . The method according to  claim 2 , wherein the compaction in the first stage (a2) takes place by means of a screw compactor. 
     
     
         4 . The method according to  claim 2  or  3 , wherein
 (a1) the reusable plastic materials are introduced into the feed system ( 1 ,  2 ) via a system of at least two, and preferably two, buffer tanks that are optionally flushed with inert gas, in particular nitrogen, wherein at least one, and preferably one, buffer tank is filled while at leak one other, and preferably one other, buffer tank is emptied into the feed system ( 1 ,  2 ), and all (both) buffer tanks are connected to a weighing system that allows metered filling of the charging system with plastic waste. 
 
     
     
         5 . The method according to any one of the preceding claims, wherein the recycle stream is obtained by pumping melted reusable plastic materials, high-energy pitch- and tar-like substances that have not assumed the gaseous state, and excess carbon that results during the cracking of polymers out of the bottom of the cracking reactor ( 5 ) by means of a high-temperature pump ( 7 ) and supplying them to a separator system ( 8 ,  9 ), the separator system ( 8 ,  9 ) including a cyclone separator ( 8 ) and a sedimentation/settling tank ( 9 ). 
     
     
         6 . The method according to one of the preceding claims, wherein the gaseous hydrocarbons from the cracking reactor ( 5 ) are supplied to the partial condenser ( 11 ) via a packed column ( 12 ). 
     
     
         7 . The method according to one of the preceding claims, wherein the gases from the cracking reactor ( 5 ), downstream from the partial condenser ( 11 ), are supplied to a distillation unit ( 13 ,  14 ,  15 ,  16 ) having a reboiler ( 13 ) and a distillation column ( 14 ), the distillation column ( 14 ) having a packed column ( 15 ) and an intermediate tray ( 16 ), and the gases from the cracking reactor ( 5 ) are fractionated into a gaseous fraction and a liquid fraction in the distillation unit ( 13 ,  14 ,  15 ,  16 ), and the liquid fraction is stripped off at the intermediate tray ( 16 ) as diesel product, and of the stripped-off gaseous fraction, the light boilers (C5-C7, for example) are condensed and separated from the uncondensed gases (C1-C4, for example). 
     
     
         8 . The method according to one of the preceding claims, wherein the facility is continuously operated. 
     
     
         9 . The method according to one of the preceding claims, wherein the first heating device ( 3 ) and the second heating device ( 4 ) are in each case a tube heat exchanger that is flushed with thermal oil. 
     
     
         10 . The method according to one of the preceding claims, wherein the partial condenser ( 11 ) is settable to a temperature of 150° C. to 350° C., preferably 300° C., as the result of which the chain length of the molecules that are able to pass through the partial condenser may also be set. 
     
     
         11 . The method according to one of the preceding claims, wherein the thermal fine separation of the gas exiting from the cracking reactor ( 5 ) is carried out in the distillation column ( 14 ) by means of counterflow distillation, in such a way that a portion of the diesel product stripped off at the intermediate tray ( 16 ) is returned to the top of the distillation column via a recycle stream line ( 17 ), preferably after cooling, and preferably combined with a radical inhibitor. 
     
     
         12 . The method according to  claim 10  or  11 , wherein the nature of the hydrocarbon mixtures is defined via the temperature setting in the distillation column ( 14 ) and/or in the condenser, in which a portion of the gaseous fraction is condensed. 
     
     
         13 . The method according to one of the preceding claims, wherein impurities possibly still present in the diesel product and/or in the light boilers, in particular sulfur-containing compounds, haloacids, and organic acids, are removed by absorption and/or filtration. 
     
     
         14 . The method according to one of the preceding claims, wherein short-chain gaseous hydrocarbons (C1-C4, for example) that are present downstream from the condenser, optionally after compression and intermediate storage, are used as fuel for a source of energy. 
     
     
         15 . A device for processing plastic-containing waste and organic liquids based on crude oil, denoted overall as reusable plastic materials, comprising a first heating device ( 3 ), a second heating device ( 4 ), a cracking reactor ( 5 ), and a recycle stream line ( 10 ) that leads from a lower area of the cracking reactor via a separator system ( 8 ,  9 ) into the feed line of the melted reusable plastic materials from the first heating device ( 3 ) into the second heating device ( 4 ). 
     
     
         16 . The device according to  claim 15 , wherein the first heating device ( 3 ) and the second heating device ( 4 ) are in each case a tube heat exchanger that is flushed with thermal oil. 
     
     
         17 . The device according to  claim 15  or  16 , wherein the heating devices ( 3 ,  4 ) and the cracking reactor ( 5 ) have independently controllable heaters. 
     
     
         18 . The device according to one of  claims 15  to  17 , wherein the heating devices ( 3 ,  4 ) are heat exchangers designed as tube heat exchangers, the tubes being filled with the melted reusable plastic materials and flushed with thermal oil. 
     
     
         19 . The device according to one of  claims 15  to  18 , wherein the separator system ( 8 ,  9 ) includes a cyclone separator ( 8 ). 
     
     
         20 . The device according to  claim 19 , wherein the separator system ( 8 ,  9 ) has, in addition to the cyclone separator ( 8 ), a sedimentation/settling tank ( 9 ) which is situated outside the recycle stream line ( 10 ) but connected to the cyclone separator, and which is connected to the recycle stream line ( 10 ) via a bypass on the heating device side. 
     
     
         21 . The device according to one of  claims 15  to  20 , wherein the cracking reactor ( 5 ) includes a partial condenser ( 11 ) having a cooling/heating device that is designed in such a way that a defined temperature is settable in the partial condenser ( 11 ), in particular a cooling/heating device having a heat carrier, which by means of a temperature control unit may be brought to a temperature that is necessary to set the defined temperature, a thermal oil being a preferred heat carrier. 
     
     
         22 . The device according to one of  claims 15  to  21 , wherein in the cracking reactor ( 5 ) a packed column ( 12 ) is situated upstream from the partial condenser ( 11 ). 
     
     
         23 . The device according to one of  claims 15  to  22 , wherein a distillation unit ( 13 ,  14 ,  15 ,  16 ) that includes a reboiler and a distillation column ( 14 ) is situated downstream from the cracking reactor ( 5 ), the distillation column ( 14 ) having an intermediate tray ( 16 ) such that the liquid fraction may be stripped off at the intermediate tray, and the gaseous fraction may be stripped off at the top of the column. 
     
     
         24 . The device according to one of  claims 15  to  23 , wherein a cooler for cooling the liquid fraction, and/or a condenser for partially condensing the gaseous fraction, are/is situated downstream from the distillation column ( 14 ), the cooler and/or the condenser having a heating/cooling device via which a defined temperature is settable in the cooler and/or in the condenser. 
     
     
         25 . The device according to one of  claims 15  to  24 , wherein the distillation column ( 14 ) is designed, at least in part, as a packed column ( 15 ). 
     
     
         26 . The device according to one of  claims 15  to  25 , wherein the distillation column ( 14 ) is provided with a recycle stream line ( 17 ) in such a way that a portion of the liquid fraction stripped off from the distillation column ( 14 ) may be returned to the distillation column ( 14 ) above the intermediate tray ( 16 ), which is the withdrawal point. 
     
     
         27 . The device according to one of  claims 15  to  26 , having least one adsorption or filtration unit for adsorbing impurities from the liquid fraction or the condensed portion of the gaseous fraction. 
     
     
         28 . The device according to  claim 27 , wherein the adsorption or filtration unit has multiple adsorbers or filters, respectively, which may be connected or disconnected in alternation for adsorption or regeneration.