Pyrolysis reactor apparatus with injection system and method for modification of pyrolyzed feedstock

Abstract

An apparatus and method suitable for pyrolysis of alternative feedstocks, such as waste plastics, biomass, waste oils, and the like, wherein the pyrolysis reactor apparatus includes an injection system that selectively adds solid, liquid, or vapor injectants to a headspace or vapor space of the pyrolysis reactor and a feedstream located upstream from the pyrolysis reactor during use that react with or otherwise influence pyrolysis reaction products in the headspace or vapor space in order to produce desirable products and/or control formation of undesirable compounds for example by preventing certain headspace reactions from occurring or reducing the frequency of such reactions.

What is claimed is: 
     
         1 . A pyrolysis reactor apparatus for polymer feedstock, comprising:
 a pyrolysis reactor vessel having a longitudinal length running from a first end to a second end downstream from the first end in a longitudinal direction of the vessel; wherein the vessel has a free volume headspace of at least 60% of the total volume of the vessel when the vessel has feedstock therein;   a conveyor located in the vessel that agitates at least one portion of the feedstock and transports the at least one portion in the longitudinal direction through the vessel from a first zone to a second zone, wherein the first zone is upstream from the second zone in a process flow direction;   an injection system comprising:
 a first injection port located in the free volume headspace of the vessel that can supply at least one injectant that is one or more of a solid, vapor and liquid into the free volume headspace, whereby the at least one injectant participates in a vapor phase chemical reaction with a reaction product of the feedstock, or otherwise influences a pyrolysis reaction product in the free volume headspace; 
 a second injection port located in the free volume headspace of the vessel that can supply at least one second injectant that is one or more of a solid, vapor or liquid injectant into free volume headspace downstream from the first injection port, whereby the at least one second injectant participates in a vapor phase chemical reaction with a reaction product of the feedstock, or otherwise influences the pyrolysis reaction product in the free volume headspace; and 
 a conduit system connected to the injection ports, wherein the injection system selectively distributes the at least one injectant to the first injection port and the at least one second injectant to the second injection port through the conduit system during pyrolysis of the feedstock, 
   wherein the at least one injectant and the at least one second injectant are the same or different.   
     
     
         2 . The apparatus according to  claim 1 , wherein the at least one injectant is one or more of steam, an alcohol, an acid, a chain terminator, and radical scavenger, and wherein the at least one second injectant is one or more of steam, an alcohol, an acid, a chain terminator, and radical scavenger. 
     
     
         3 . The apparatus according to  claim 2 , wherein the at least one injectant is one or more of an alcohol, an acid, a chain terminator, and radical scavenger, and wherein the at least one second injectant is one or more of an alcohol, an acid, a chain terminator, and radical scavenger. 
     
     
         4 . The apparatus according to  claim 1 , wherein the injection system further includes a supply container that houses the at least one injectant, and wherein the conduit system is connected between the supply container and the first injection port. 
     
     
         5 . The apparatus according to  claim 1 , wherein the pressure in the reaction vessel is less than 25 psi, and wherein the first zone and the second zone have a temperature less than 1,200°F. 
     
     
         6 . The apparatus according to  claim 1 , wherein the headspace is at least present above an uppermost surface of the conveyor. 
     
     
         7 . The apparatus according to  claim 1 , wherein the pyrolysis reactor vessel includes at least one outlet in the headspace for pyrolytic product gases to exit the pyrolysis reactor vessel located between the first injection port and the second injection port. 
     
     
         8 . The apparatus according to  claim 7 , wherein at least a second outlet is present in the headspace downstream in the pyrolytic reactor vessel from the second injection port. 
     
     
         9 . The apparatus according to  claim 1 , wherein the pyrolysis reactor vessel, the at least one injectant and the at least one second injectant are free of a catalyst other than a catalyst inherently present in the feedstock. 
     
     
         10 . The apparatus according to  claim 1 , further including an injection port located in a feedstream conduit for the feedstock that can supply a third injectant into the feedstream prior to the feedstock entering the vessel. 
     
     
         11 . A pyrolysis reactor apparatus for polymer feedstock, comprising:
 a pyrolysis reactor vessel having a longitudinal length running from a first end to a second end downstream from the first end in a longitudinal direction of the vessel; wherein the vessel has a free volume headspace of at least 60% of the total volume of the vessel when the vessel has feedstock therein;   a conveyor located in the vessel that agitates at least one portion of the feedstock and transports the at least one portion in the longitudinal direction through the vessel from the first zone to the second zone;   an injection system comprising:
 a first injection port located in a feedstream conduit for the feedstock that can supply a first injectant into the feedstream conduit prior to the feedstock entering the vessel from the feedstream conduit; and 
 a second injection port located in the free volume headspace of the vessel that can supply a second injectant into the free volume headspace, whereby the second injectant participates in a vapor phase chemical reaction with a reaction product of the feedstock, or otherwise influence pyrolysis reaction products in the free volume headspace; 
 a conduit system connected to the injection ports, and 
 wherein the injection system selectively distributes the first injectant to the first injection port and the second injectant to the second injection port through the conduit system during pyrolysis of the feedstock. 
   
     
     
         12 . The pyrolysis reactor apparatus according to  claim 11 , wherein steam is injected through the first injection port to assist in preventing vapor from the reactor vessel moving upstream towards a feed hopper through the feedstream conduit. 
     
     
         13 . The pyrolysis reactor apparatus according to  claim 11 , wherein the second injectant is one or more of steam, an alcohol, an acid, a chain terminator, and radical scavenger, and wherein the second injectant is one or more of steam, an alcohol, an acid, a chain terminator, and radical scavenger. 
     
     
         14 . The pyrolysis reactor apparatus according to  claim 12 , wherein the second injectant is one or more of an alcohol, an acid, a chain terminator, and radical scavenger. 
     
     
         15 . A method for influencing pyrolysis reaction products in a headspace of a pyrolysis reactor apparatus, comprising the steps of:
 obtaining pyrolysis reactor apparatus of  claim 1 ,   supplying the at least one injectant into the free volume headspace of the pyrolytic reactor vessel from the first injection port, whereby the injectant participates in a vapor phase chemical reaction with a reaction product of the feedstock or otherwise influences a pyrolysis reaction product in the free volume headspace;   supplying at least one second injectant into the free volume headspace of the pyrolytic reactor vessel from the second injection port whereby the injectant participates in a vapor phase chemical reaction product of the feedstock or otherwise influences a pyrolysis reaction product in the free volume headspace.   
     
     
         16 . The method according to  claim 15 , further including the step of injecting the at least one injectant and the at least one second injectant into the free volume headspace simultaneously. 
     
     
         17 . The method according to  claim 15 , further including the step of injecting the at least one injectant and the at least one second injectant into the free volume headspace sequentially. 
     
     
         18 . The method according to  claim 15 , wherein the injection is performed for a period of time greater than 30 seconds but less than 5 minutes, continuously. 
     
     
         19 . The method according to  claim 18 , wherein the period of time ranges from 2 to 4 minutes. 
     
     
         20 . The method according to  claim 15 , wherein the feedstock has a residence time in the vessel of at least 40 minutes.