Auger reactor for melting waste plastic and waste plastic pyrolysis

Abstract

It has been discovered that use of a single reactor for melting waste plastics and pyrolyzing the melted waste plastics can lower the carbon footprint of a chemical recycling facility. More particularly, by melting and pyrolyzing in the same reactor vessel, one may mitigate the need for additional heat sources, thereby decreasing the potential need to combust additional fossil fuels for heating purposes. Consequently, by utilizing the plastic liquification and pyrolysis reactor described herein, one can lower the carbon footprint of the chemical recycling facility described herein.

1 . A chemical recycling process comprising:
 (a) introducing a solid waste plastic into a melting and pyrolysis reactor;   (b) melting and pyrolyzing at least a portion of the solid waste plastic in the melting and pyrolysis reactor with heat from a common heat source to thereby produce a pyrolysis gas stream and a pyrolysis oil stream; and   (c) combining at least a portion of the pyrolysis oil stream with the solid waste plastic either—
 (i) prior to the introducing in the melting and pyrolysis reactor, or 
 (ii) within the melting and pyrolysis reactor at a location upstream of a last off-take of pyrolysis gas from the melting and pyrolysis reactor. 
   
     
     
         2 . The process according to  claim 1 , wherein the melting and pyrolysis reactor comprises at least 2 reaction stages separated from one another by an upright weir and/or a vertical drop. 
     
     
         3 . The process according to  claim 2 , wherein each of the reaction stages comprises an impeller, a paddle, or an auger system. 
     
     
         4 . The process according to  claim 2 , wherein the melting and pyrolysis reactor comprises not more than 20 reaction stages, wherein each of the reaction stages comprises a gas outlet for removing gases that evolve in each of the reaction stages. 
     
     
         5 . The process according to  claim 2 , wherein the reaction stages comprise an initial reaction stage and at least one successive reaction stage downstream of the initial reaction stage, wherein the initial reaction stage is where the solid waste plastic is at least partially melted to form a liquefied plastic stream. 
     
     
         6 . The process according to  claim 5 , further comprising introducing the liquefied plastic stream into the successive reaction stage, wherein the viscosity of the liquefied plastic stream is increased within the successive reaction stage, and wherein the successive reaction stage has a higher temperature relative to the initial reaction stage. 
     
     
         7 . The process according to  claim 5 , wherein the reaction stages comprise at least at least 2, at least 3, or at least 4 successive reaction stages downstream of the initial reaction stage, wherein the temperatures within the melting and pyrolysis reactor increase with each successive reaction stage. 
     
     
         8 . The process according to  claim 1 , wherein the melting and pyrolysis reactor comprises a feed inlet for receiving the solid waste plastic and at least one gas outlet for discharging a pyrolysis vapor stream comprising the pyrolysis gas stream, wherein the temperature of the gas outlet of the melting and pyrolysis reactor is at least 525° C., as measured within the interior of the gas outlet. 
     
     
         9 . The process according to  claim 1 , wherein the solid waste plastic flows horizontality through the melting and pyrolysis reactor, and the melting and pyrolysis reactor comprises a plurality of gas outlets for discharging a pyrolysis vapor stream. 
     
     
         10 . A chemical recycling process comprising:
 (a) introducing a solid waste plastic into a melting and pyrolysis reactor;   (b) melting and pyrolyzing at least a portion of the solid waste plastic in the melting and pyrolysis reactor to thereby produce a pyrolysis gas stream and a pyrolysis oil stream, wherein the melting and pyrolysis reactor comprises at least one auger for transporting the solid waste plastic and/or a liquefied waste plastic through at least a portion of the melting and pyrolysis reactor; and   (c) combining at least a portion of the pyrolysis oil stream with the solid waste plastic either—
 (i) prior to the introducing in the melting and pyrolysis reactor, or 
 (ii) within the melting and pyrolysis reactor at a location upstream of a last off-take of pyrolysis gas from the melting and pyrolysis reactor. 
   
     
     
         11 . The process according to  claim 10 , wherein the melting and pyrolysis reactor comprises at least 2 reaction stages separated from one another by an upright weir and/or a vertical drop, and each of the reaction stages comprises an agitator comprising an impeller, a paddle, or an auger system, wherein at least one of the reaction stages comprises the auger as the agitator. 
     
     
         12 . The process according to  claim 10 , wherein the reaction stages comprise an initial reaction stage and at least one successive reaction stage downstream of the initial reaction stage, wherein the initial reaction stage is where the solid waste plastic is at least partially melted to form a liquefied plastic stream. 
     
     
         13 . The process according to  claim 12 , wherein the reaction stages comprise at least at least 2 successive reaction stages downstream of the initial reaction stage, wherein the temperatures within the melting and pyrolysis reactor increase with each successive reaction stage. 
     
     
         14 . The process according to  claim 10 , wherein the melting and pyrolysis reactor comprises a feed inlet for receiving the solid waste plastic and a gas outlet for discharging a pyrolysis vapor stream comprising the pyrolysis gas stream, wherein the temperature of the gas outlet of the melting and pyrolysis reactor is at least 500° C., as measured within the interior of the gas outlet. 
     
     
         15 . The process according to  claim 14 , wherein the temperature of the gas outlet of the melting and pyrolysis reactor is not more than 1,000, not more than 950, not more than 900, not more than 850, or not more than 800° C., as measured within the interior of the gas outlet. 
     
     
         16 . The process according to  claim 10 , wherein the combining of step (c) occurs within the melting and pyrolysis reactor at a location upstream of a last off-take of pyrolysis gas from the melting and pyrolysis reactor. 
     
     
         17 . A chemical recycling system comprising:
 (a) a plastic feed mechanism for receiving and metering plastic particles;   (b) a pyrolysis reactor having a plastic feed inlet for receiving the plastic particles from the feed mechanism, a gas outlet for discharging pyrolysis vapors, and a liquid outlet for discharging pyrolysis liquids; and   (c) a heater for providing heat to the pyrolysis reactor,   
       wherein the pyrolysis reactor comprises at least two stages separated from one another by an upright weir and/or a vertical drop, 
       wherein each stage of the pyrolysis reactor includes an agitator for promoting mixing of a reaction medium and/or horizontal movement of the reaction medium through each stage of the pyrolysis reactor. 
     
     
         18 . The system according  claim 17 , wherein the agitator comprises an impeller, a paddle, or an auger system. 
     
     
         19 . The system according to  claim 17 , wherein the pyrolysis reactor further comprises a waste outlet for discharging a halogen-containing off-gas, wherein the waste outlet is upstream of the gas outlet. 
     
     
         20 . The system according to  claim 17 , further comprising a separator for separating at least a portion of the pyrolysis liquids into a pyrolysis oil stream and a pyrolysis residue.