Process for production of useful hydrocarbon materials from plastic waste and reaction system therefor

Abstract

A process for production of useful hydrocarbon materials from plastic waste and reaction system therefor is provided. The process includes frequentatively thermolyzing of high molecular weight hydrocarbons such as plastic waste to produce useful medium molecular weight hydrocarbons and low molecular weight hydrocarbons. The process utilizes low molecular weight hydrocarbons as solution reactants which helps in reducing the viscosity of the material for more effective heat transfer. The process also includes addition of one or more low molecular weight olefins and solution reactants to high molecular weight hydrocarbons to augment the free radical environment. The process also includes hydrogenating and oxidizing the high molecular weight hydrocarbons. The process enables production of the useful, predominantly hydrocarbon materials such as waxes, lube oil base-stocks, refinery feedstocks, intermediates or fuel additives. The present invention also provides a reaction system comprising thermolysis reactor including a primary zone and an optional secondary zone for production of useful hydrocarbon materials from plastic waste.

1 . A process for production of hydrocarbon materials from at least one of plastic waste and high boiling hydrocarbons or combination thereof comprising:
 a. mixing high molecular weight hydrocarbons, and lower molecular weight hydrocarbons to obtain a uniform mixture representative of low viscosity dissolved polymer phase,
 wherein the high molecular weight hydrocarbons being selected from a group consisting shredded waste plastic, un-shredded waste plastic, high boiling hydrocarbons, other similar materials such as ethers and substituted hydrocarbons, and combinations thereof, 
 wherein the uniform mixture comprises 70% wt-30% wt of the high molecular weight hydrocarbons, and 30% wt-70% wt of the lower molecular weight hydrocarbons; 
   b. heating the uniform mixture to obtain a molten state;   c. separating heavy contaminants and light contaminants from molten uniform mixture prior to thermolysis reaction;   d. frequentatively thermolyzing the molten uniform mixture at a predefined temperature, pressure and duration to initiate free radical chemical reactions and causing breakdown of the uniform mixture,
 wherein the predefined temperature ranges from 350° C. to 425° C., the predefined pressure ranges from 3-20 bar, and predefined duration ranges from 1 to 4 hours; and 
 separating thermolyzed uniform mixture into at least three streams, wherein the at least three streams comprises dissolved hydrocarbon gases including light naphtha range material, naphtha through light wax material, and a crude thermolyzed product material. 
   
     
     
         2 . The process as claimed in  claim 1 , wherein the lower molecular weight hydrocarbons are selected from a group consisting naphtha/distillate range material, n-paraffin, decalin, coker gas oils and diesel. 
     
     
         3 . The process as claimed in  claim 1 , wherein the uniform mixture comprises 40% wt of the high molecular weight hydrocarbons, and 60% wt of the low molecular weight hydrocarbons. 
     
     
         4 . The process as claimed in  claim 1 , wherein the uniform mixture being heated at temperature ranging from 180° C. to 250° C. 
     
     
         5 . The process as claimed in  claim 1 , wherein the frequentatively thermolyzing of the molten uniform mixture is carried out at 15 bar pressure. 
     
     
         6 . The process as claimed in  claim 1 , wherein the crude thermolyzed product material from the at least three streams comprises heavy waxes with molecular weight ranging from 1,500 to 6,000 Dalton. 
     
     
         7 . The process as claimed in  claim 1 , wherein the steps (a) to (e) are operated intermittently in a batch mode. 
     
     
         8 . The process as claimed in  claim 7 , wherein the batch mode is configured to convert medium molecular weight hydrocarbons to low molecular weight hydrocarbons. 
     
     
         9 . The process as claimed in  claim 1 , wherein the steps (a) to (e) are operated in a continuous mode. 
     
     
         10 . The process as claimed in  claim 1 , further comprises recycling the three streams by supplying back to at least one step of the mixing of high molecular weight hydrocarbons and lower molecular weight, the heating of the uniform mixture, and the frequentatively thermolyzing molten uniform mixture. 
     
     
         11 . The process as claimed in  claim 10 , wherein the recycling of the three streams by supplying back comprises supplying the light naphtha range material as fuel for one of the heating the uniform mixture and the thermolyzing the molten uniform mixture. 
     
     
         12 . The process as claimed in  claim 10 , wherein the recycling of the three streams by supplying back comprises supplying back the stream of naphtha through light wax as solution reactant to the mixing step. 
     
     
         13 . The process as claimed in  claim 1 , further comprises adding one or more low molecular weight olefins selected from a group comprising 1 octene and 1-hexene to the step (a) to undergo supplementary reactions in the free radical environment. 
     
     
         14 . The process as claimed in  claim 1 , further comprises adding a solution reactants after the thermolysis and before hydrotreating process to reduce viscosity of the product to accelerate a hydrogenation process, wherein the adding of the solution reactants after the thermolysis enables separation of waxy molecules from non-waxy molecules by differential solidification, wherein the solution reactants comprise the lower molecular weight hydrocarbons. 
     
     
         15 . The process as claimed in  claim 1 , further comprises carrying out short path distillation (SPD) to separate the crude thermolyzed product into fractions. 
     
     
         16 . The process as claimed in  claim 15 , wherein the SPD is carried out at temperature 360° C. 
     
     
         17 . The process as claimed in  claim 1 , further comprises hydrogenating the high molecular weight hydrocarbons. 
     
     
         18 . The process as claimed in  claim 1 , further comprises oxidizing the high molecular weight hydrocarbons. 
     
     
         19 . A reaction system, comprising:
 at least one surge hopper adapted to receive high molecular weight hydrocarbons, wherein the high molecular weight hydrocarbons being selected from a group consisting shredded waste plastic and un-shredded waste plastic;   a melter fluidically connected to the at least one surge hopper via first set of one or more valves,
 wherein the melter is adapted to mix the high molecular weight hydrocarbons and the lower molecular weight hydrocarbons, via mixing means, to obtain a uniform mixture representative of low viscosity dissolved polymer phase, and heat the uniform mixture to yield a molten state, and 
 wherein the melter comprises one or more openings to receive at least one of low molecular weight hydrocarbons as solution reactant and heavy wax, and one or more openings to release dissolved hydrocarbon gases including light naphtha range material, and a molten uniform mixture of the high molecular weight hydrocarbons and the low molecular weight hydrocarbons; 
   a thermolysis reactor fluidically connected to the melter via second set of one or more valves and adapted to produce hydrocarbon materials comprising medium molecular weight hydrocarbons to low molecular weight hydrocarbons, wherein the thermolysis reactor comprises a primary zone, an optional secondary zone, one or more openings to receive hydrocarbon liquids, and one or more openings to release at least one of a vapour phase of the thermolysis reactor and a thermolyzed material,
 wherein the primary zone being adapted to convert the molten mixture into a condensed phase at a moderate temperature with a relatively long residence time, and the optional secondary zone being adapted to convert the molten mixture into a vapor phase at high temperature with a short residence time, and 
 wherein the optional secondary zone is adapted to receive vapors circulated from the primary zone. 
   
     
     
         20 . The reaction system as claimed in  claim 19 , wherein the melter is adapted to melt the uniform mixture at a temperature ranging from 180° C. to 250° C. 
     
     
         21 . The reaction system as claimed in  claim 19 , wherein the low molecular weight hydrocarbons are selected from a group consisting naphtha/distillate range, n-paraffin, decalin, diphenyl ether, coker gas oils and diesel. 
     
     
         22 . The reaction system as claimed in  claim 19 , wherein the mixing means comprises at least one of an agitator and an impeller. 
     
     
         23 . The reaction system as claimed in  claim 19 , wherein the mixing means comprises an external pump circuit which circulates liquid for effective mixing. 
     
     
         24 . The reaction system as claimed in  claim 19 , wherein the optional secondary zone is adapted to have a surface temperature between 500° C. and 1000° C., preferably between 600° C. and 750° C. 
     
     
         25 . The reaction system as claimed in  claim 19 , wherein the optional secondary zone is adapted to produce low molecular weight olefins from low molecular weight hydrocarbons, where the low molecular weight olefins comprise ethylene and propylene. 
     
     
         26 . The reaction system as claimed in  claim 19 , wherein the thermolyzed material comprises dissolved hydrocarbon gases including light naphtha range material, naphtha through light wax material, and a crude thermolyzed product material. 
     
     
         27 . The reaction system as claimed in  claim 19 , wherein the thermolysis reactor being operated at isothermal condition by soft heating by circulating hot oil. 
     
     
         28 . The reaction system as claimed in  claim 19 , further comprises a riser and a downcommer fluidically connected to the melter via third set of one or more valves, wherein the riser and downcommer combination operates as a trap, and adapted to receive the molten uniform mixture and automatically separate heavy contaminant and light contaminants from the molten mixture.