In situ coking of heavy pitch and other feedstocks with high fouling tendency

Abstract

Processes and systems for in situ heating of a heavy pitch within a coking drum are disclosed. The in situ heating may provide for processing of neat pitch, improving coking operations and increasing liquid yield.

What is claimed: 
     
         1 . A process for producing coke, the process comprising:
 heating a heavy pitch to an incipient coking temperature to produce a heated coker feedstock;   feeding the heated coker feedstock to a coking drum;   further heating the heated coker feedstock in situ within the coking drum via direct heat exchange; and   subjecting the heated coker feedstock in the coking drum to thermal cracking to crack a portion of the heavy pitch to produce a cracked vapor product and a coke product.   
     
     
         2 . The process of  claim 1 , wherein the direct heat exchange is via contact of the heated coker feedstock with a superheating medium. 
     
     
         3 . The process of  claim 1 , wherein the steps of heating via direct heat exchange and subjecting occur concurrently. 
     
     
         4 . The process of  claim 1 , wherein the incipient coking temperature is between 500° F. and 750° F. 
     
     
         5 . The process of  claim 1 , further comprising feeding the cracked vapor product to a coker separator for recovery of one or more light hydrocarbon fractions. 
     
     
         6 . The process of  claim 1 , further comprising stopping the feed of heated coker feedstock to the coking drum and removal of the coke product from the coking drum. 
     
     
         7 . The process of  claim 2 , wherein the superheating medium is contacted with the heated coker feedstock via one or more of a feed inlet upstream of the coking drum, a superheating medium heater upstream of the coking drum, or a feed inlet introducing the superheating medium directly into the coking drum. 
     
     
         8 . The process of  claim 2 , wherein the superheating medium does not condense at coke drum operating conditions during a coking cycle. 
     
     
         9 . The process of  claim 8 , wherein the superheating medium is one or more of steam, carbon dioxide, nitrogen and other inert gases, or one or more light hydrocarbons. 
     
     
         10 . The process of  claim 2 , wherein the superheating medium is fed to the coking drum during a filling cycle, during a coking cycle, or both. 
     
     
         11 . The process of  claim 1 , wherein the heating of the heated coker feedstock in situ continues for a length of time required for the thermal cracking to approach completion. 
     
     
         12 . The process of  claim 1 , wherein the heavy pitch is 100% heavy pitch. 
     
     
         13 . The process of  claim 1 , wherein the heavy pitch comprises up to 10 wt % of a diluent. 
     
     
         14 . The process of  claim 1 , wherein the heavy pitch has a Conradson carbon content of 35 wt % or more, and an asphaltene content of 15 wt % or more. 
     
     
         15 . A process for producing coke, the process comprising:
 heating a heavy pitch to an incipient coking temperature to produce a heated coker feedstock;   mixing the heated coker feedstock with a superheating medium;   feeding the mixture to a coking drum;   heating the mixture in situ within the coking drum via direct heat exchange with the superheating medium; and   subjecting the mixture to thermal cracking in the coking drum to crack a portion of the heavy pitch to produce a cracked vapor product and a coke product.   
     
     
         16 . The process of  claim 15 ; wherein the superheating medium is one or more of steam, carbon dioxide, nitrogen and other inert gases, or one or more light hydrocarbons. 
     
     
         17 . The process of  claim 15 , wherein the heating of the heated coker feedstock in situ continues for a length of time required for the thermal cracking to approach completion. 
     
     
         18 . The process of  claim 15 , wherein the heavy pitch is 100% heavy pitch. 
     
     
         19 . The process of  claim 15 , wherein the heavy pitch comprises up to 10 wt % of a diluent. 
     
     
         20 . The process of  claim 15 , wherein the heavy pitch has a Conradson carbon content of 35 wt % or more, and an asphaltene content of 15 wt % or more. 
     
     
         21 . A system for producing coke, the system comprising:
 a heater for heating a heavy pitch to an incipient coking temperature to produce a heated coker feedstock;   a flow line for feeding the heated coker feedstock to a coking drum;   a heater for heating a superheating medium to produce a heated superheating medium;   a flow line for supplying the heated superheating medium for heating the heated coker feedstock in situ within the coking drum via direct heat exchange with the superheating medium;   a flow line for recovering a cracked vapor product from the coking drum.   
     
     
         22 . The system of  claim 21 , further comprising a mixer for mixing the heated coker feedstock with the superheating medium and a flow line for feeding the mixture to the coking drum. 
     
     
         23 . The system of  claim 21 , wherein the flow line for supplying the heated superheating medium is connected to the coking drum. 
     
     
         24 . The system of  claim 21 , wherein the heater for heating the heavy pitch and the heater for heating the superheating medium are disposed in different zones of a common heater. 
     
     
         25 . The system of  claim 21 , further comprising a control system for controlling the in situ heating of the heated coker feedstock within the coking drum.