Process for continuously converting mixed waste plastic into waxes and liquid fuels by cracking

Abstract

The present invention relates to a process for continuously converting mixed waste plastic into waxes and liquid fuels by cracking. The process comprises the steps of feeding a mixed waste plastic stream to a cracking reactor where the mixed waste plastic is catalytically cracked in the presence of a catalyst and circulating the catalyst between the cracking reactor and a regenerator where the catalyst received from the cracking reactor is regenerated and heated by burning coke and/or other combustible material deposited on or mixed with the catalyst.

1 . A process for continuously converting mixed waste plastic into waxes and liquid fuels by cracking, the process comprising the steps of:
 feeding a mixed waste plastic stream to a cracking reactor where the mixed waste plastic is catalytically cracked in the presence of a catalyst;   circulating the catalyst between the cracking reactor and a regenerator where the catalyst received from the cracking reactor is regenerated and heated by burning coke and/or other combustible material deposited on or mixed with the catalyst;   
       wherein the heat balance between the cracking reactor and the regenerator is adjusted depending on changes in the chemical composition of the mixed waste plastic. 
     
     
         2 . The process according to  claim 1  wherein the catalyst is a mixture of at least two different catalysts having different catalytic activity and the heat balance between the cracking reactor and the regenerator is adjusted by adjusting the ratio of the at least two different catalysts in the mixture of catalysts. 
     
     
         3 . The process according to  claim 1  wherein the heat balance between the cracking reactor and the regenerator is adjusted by diluting the mixed waste plastic with a diluent. 
     
     
         4 . The process according to  claim 3  wherein the mixed waste plastic in the feed stream is diluted with waxes and/or liquid fuels. 
     
     
         5 . The process according to  claim 4  wherein the waxes and liquid fuels are obtained from the cracking process. 
     
     
         6 . The process according to  claim 1  wherein the heat balance between the cracking reactor and the regenerator is adjusted by introducing a combustible stream into the regenerator. 
     
     
         7 . The process according to  claim 1  wherein the heat balance between the cracking reactor and the regenerator is adjusted such that the cracking reactor and the regenerator are maintained in a steady state heat balance. 
     
     
         8 . The process according to  claim 1  wherein the heat balance between the cracking reactor and the regenerator is adjusted such that a predetermined ratio of waxes to liquid fuels is obtained from the cracking reactor. 
     
     
         9 . The process according to  claim 1  wherein temperature and flow of the circulating catalyst are adjusted to maintain a pre-selected temperature in the cracking reactor. 
     
     
         10 . The process according to  claim 1  wherein the chemical composition of the mixed waste plastic changes over time. 
     
     
         11 . The process according to  claim 1  wherein the mixed waste plastic comprises more than 50% by weight of polyolefin and polystyrene based on the total weight of the mixed waste plastic. 
     
     
         12 . The process according to  claim 1  wherein the mixed waste plastic is subjected to a dry pretreatment prior to subjecting it to the cracking reactor. 
     
     
         13 . The process according to  claim 1  wherein the mixed waste plastic prior to feeding it to the cracking reactor has a water content of less than 20% by weight, based on the total weight of the mixed waste plastic. 
     
     
         14 . The process according to  claim 1 , further comprising the step of reducing the content of air and/or oxygen in the mixed waste plastic prior to feeding it to the cracking reactor. 
     
     
         15 . The process according to  claim 1  wherein the oxygen content in the cracking reactor is lower than 10 vol. % of the gas phase in the reactor. 
     
     
         16 . The process according to  claim 13  wherein the mixed waste plastic prior to feeding it to the cracking reactor has a water content of less than 10% by weight, based on the total weight of the mixed waste plastic. 
     
     
         17 . The process according to  claim 15  wherein the oxygen content in the cracking reactor is lower than 5 vol. % of the gas phase in the reactor.