Controlling coke morphology with sulfur

Abstract

Systems and methods are provided for controlling the morphology of coke produced during delayed coking. The morphology control is achieved in part by introducing elemental sulfur into the coker feedstock prior to coking. The elemental sulfur can be introduced into the feed under conditions so that the sulfur is well-dispersed within the feed for a sufficient period of time. This can allow for relatively even reaction of sulfur with components throughout the feed, resulting in a relatively small, uniform domain size distribution for the coke produced during delayed coking. This coke can correspond to shot coke. By producing coke with a small and relatively uniform domain size distribution, the risk of uneven heating within the coke can be reduced or minimized.

1 . A method for controlling coke morphology during delayed coking, comprising:
 providing a coker feedstock that forms transition coke under standard delayed coking conditions;   mixing the coker feedstock with 0.5 wt % to 5.0 wt % of elemental sulfur to form a mixed coker feedstock;   maintaining the mixed coker feedstock at a temperature of 160° C. to 260° C. for 2.0 hours to 5 days to form a treated coker feedstock; and   exposing the treated coker feedstock to second delayed coking conditions to form a coker effluent and treated coke comprising shot coke.   
     
     
         2 . The method of  claim 1 , wherein the treated coke further comprises a lognormal domain size distribution having a value of a shape parameter σ of 0.30 or less and a value of a location parameter μ of 1.85 or less. 
     
     
         3 . The method of  claim 1 , wherein the provided coker feedstock forms transition coke under standard delayed coking conditions comprising a lognormal domain size distribution having a value of a location parameter μ between 1.85 and 2.10. 
     
     
         4 . The method of  claim 1 , wherein the standard delayed coking conditions comprise a temperature of 475° C. and 150 kPa-g. 
     
     
         5 . The method of  claim 1 , wherein the second delayed coking conditions comprise a temperature of 400° C. to 475° C. and a pressure of 100 kPa-g to 500 kPa-g. 
     
     
         6 . The method of  claim 1 , wherein the second delayed coking conditions comprise standard delayed coking conditions. 
     
     
         7 . The method of  claim 1 , wherein the coker feedstock and the elemental sulfur are mixed in a holding volume, or wherein the mixed coker feedstock is maintained at the temperature of 160° C. to 260° C. for at least a portion of the 2.0 hours to 5 days in a holding volume, or a combination thereof. 
     
     
         8 . The method of  claim 1 , wherein the mixed coker feedstock is maintained at the temperature of 160° C. to 260° C. for at least a portion of the 2.0 hours to 5 days in one or more conduits in fluid communication with a coker furnace, or wherein the mixed coker feedstock is maintained at the temperature of 160° C. to 260° C. for at least a portion of the 2.0 hours to 5 days by passing the mixed coker feedstock into a vacuum fractionator, or a combination thereof. 
     
     
         9 . The method of  claim 8 , wherein the coker effluent is passed into the vacuum fractionator. 
     
     
         10 . The method of  claim 1 , further comprising separating the coker effluent to form at least an unconverted bottoms fraction, wherein at least a portion of the unconverted bottoms are exposed to the delayed coking conditions. 
     
     
         11 . A method for controlling coke morphology during delayed coking, comprising:
 providing a coker feedstock that forms sponge coke under standard delayed coking conditions;   mixing the coker feedstock with 8.0 wt % or more of elemental sulfur to form a mixed coker feedstock;   maintaining the mixed coker feedstock at a temperature of 160° C. to 260° C. for 2.0 hours to 5 days to form a treated coker feedstock; and   exposing the treated coker feedstock to delayed coking conditions to form a coker effluent and coke comprising shot coke.   
     
     
         12 . The method of  claim 11 , wherein the treated coke further comprises a lognormal domain size distribution having a value of a shape parameter σ of 0.30 or less and a value of a location parameter μ of 1.85 or less. 
     
     
         13 . The method of  claim 11 , wherein the provided coker feedstock forms sponge coke under standard delayed coking conditions comprising a lognormal domain size distribution having a value of a shape parameter σ greater than 0.32 and a value of a location parameter μ greater than 2.10. 
     
     
         14 . The method of  claim 11 , wherein the standard delayed coking conditions comprise a temperature of 475° C. and 150 kPa-g. 
     
     
         15 . The method of  claim 11 , wherein the second delayed coking conditions comprise a temperature of 400° C. to 475° C. and a pressure of 100 kPa-g to 500 kPa-g, or wherein the second delayed coking conditions comprise standard delayed coking conditions. 
     
     
         16 . The method of  claim 11 , wherein the coker feedstock and the elemental sulfur are mixed in a holding volume, or wherein the mixed coker feedstock is maintained at the temperature of 160° C. to 260° C. for at least a portion of the 2.0 hours to 5 days in a holding volume, or a combination thereof. 
     
     
         17 . The method of  claim 11 , wherein the mixed coker feedstock is maintained at the temperature of 160° C. to 260° C. for at least a portion of the 2.0 hours to 5 days in one or more conduits in fluid communication with a coker furnace, or wherein the mixed coker feedstock is maintained at the temperature of 160° C. to 260° C. for at least a portion of the 2.0 hours to 5 days by passing the mixed coker feedstock into a vacuum fractionator, or a combination thereof. 
     
     
         18 . The method of  claim 17 , wherein the coker effluent is passed into the vacuum fractionator. 
     
     
         19 . The method of  claim 11 , further comprising separating the coker effluent to form at least an unconverted bottoms fraction, wherein at least a portion of the unconverted bottoms are exposed to the delayed coking conditions. 
     
     
         20 . (canceled)