Process for conversion of waste plastics into hydrocarbons

Abstract

A process for production of chemical feedstocks from waste plastics, the process comprising providing a process configuration comprising a fractionation tower ( 1 ), a furnace ( 2 ), one or more coke drum(s) ( 3 ), and a pre-reactor ( 4 ), configured so that a bottoms stream (A) from the fractionation tower is mixed with an oligomeric stream (L) and supplied to the furnace, the product stream from the furnace (C) is supplied to a coke drum, and an overhead stream (D) from the coke drum is supplied back to the fractionation tower; wherein the oligomeric stream (L) is obtained as product stream from conversion of a waste plastics stream (B) in the pre-reactor, and has a weight average molecular weight of between 5,000 and 10,000 g/mol. Such process allows for the conversion of a wide variety of waste plastics into valuable chemical products.

1 . A process for production of chemical feedstocks from waste plastics, the process comprising providing a process configuration comprising a fractionation tower ( 1 ), a furnace ( 2 ), one or more coke drum(s) ( 3 ), and a pre-reactor ( 4 ), configured so that a bottoms stream (A) from the fractionation tower is mixed with a stream originating from waste plastics (L), and supplied to the furnace, the product stream from the furnace (C) is supplied to a coke drum, and an overhead stream (D) from the coke drum is supplied back to the fractionation tower;
 wherein the stream (L) is obtained as product stream from conversion of a waste plastics stream (B) in the pre-reactor;   wherein the stream (L) is supplied in molten condition.   
     
     
         2 . The process according to  claim 1 , wherein in the fractionation tower a fractionation of a mixture comprising the overhead stream (D) and a residual oil (K) is performed to result in a gaseous output stream (F) obtained as overhead stream from the fractionation tower, a naphtha-range stream (G), a light gas oil stream (J), a heavy gas oil stream (H), and a bottoms stream (A). 
     
     
         3 . The process according to  claim 1 , wherein the stream (L) is supplied at a temperature of ≥300 and ≤450° C. 
     
     
         4 . The process according to  claim 1 , wherein the bottoms stream (A) is supplied at a temperature of ≥300 and ≤400° C. 
     
     
         5 . The process according to  claim 1 , wherein the combined feed (A) and (B) are heated in the furnace by passing the feed through heating tubes and subjecting it to external heat energy to obtain a furnace product stream (C) having a temperature of >450° C. and ≤550° C. 
     
     
         6 . The process according to  claim 1 , wherein the bottoms stream (A) has a boiling point of ≥400° C. 
     
     
         7 . The process according to  claim 1 , wherein the pre-reactor ( 4 ) is a melt extruder. 
     
     
         8 . The process according to  claim 1 , wherein the pre-reactor ( 4 ) is operated at a temperature of ≥350 and ≤450° C., and/or wherein the waste plastic is subjected to a residence time in the pre-reactor of ≥10 min. 
     
     
         9 . The process according to  claim 2 , wherein the residual oil (K) is a residual oil obtained from atmospheric distillation of crude oil, or a residual oil obtained from vacuum distillation of the residual oil obtained from atmospheric distillation of crude oil. 
     
     
         10 . The process according to  claim 1 , wherein the coke drum is operated at a pressure of between 100 and 600 kPa. 
     
     
         11 . The process according to  claim 1 , wherein the fractionation tower operated so that the temperature in the bottom section of the tower is between 340° C. and 385° C. 
     
     
         12 . The process according to  claim 1 , wherein the furnace product stream (C) comprises ≥0.1 and ≤50.0 wt % of the stream (L), with regard to the total weight of the stream (C). 
     
     
         13 . The process according to  claim 1 , wherein a gaseous stream (M) comprising HCl that is formed from decomposition of chlorine-containing polymers, is removed from the pre-reactor ( 4 ), wherein the pre-reactor ( 4 ) is operated at a temperature where decomposition of the chlorine-containing polymers that are present in the waste plastics stream (B) occurs. 
     
     
         14 . The process according to  claim 1 , wherein the pre-reactor ( 4 ) comprises a first pre-reactor ( 4 A) and a second pre-reactor ( 4 B), wherein in the first pre-reactor ( 4 A), which may for example be a melt extruder such as a twin-screw melt extruder, the solid mixed waste plastics stream (B), which may for example comprise 80-90 wt % of polyolefins, and 1-5 wt % of chlorine-containing polymers such as polyvinylchloride (PVC), is heated to such temperature, where the chlorine-containing polymers are molten and decompose to form a gaseous HCl product that is removed as stream (M), so that a molten, dechlorinated plastic stream (B′) is formed, which then is supplied to a second pre-reactor ( 4 B), which may for example be a melt extruder such as a twin-screw melt extruder, wherein stream (B′) is processed at a temperature of ≥350 and ≤450° C., during a residence time of >10 min to form the oligomeric stream (L). 
     
     
         15 . The process according to  claim 13 , wherein the stream (M) is further contacted with an aqueous stream (R) containing a base to neutralise the HCl and thereby produce an aqueous stream (S).