Patent Publication Number: US-10316253-B2

Title: Co-production of anode and fuel grade petroleum coke in a delayed coker unit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application takes priority from provisional patent application No. 62/192,132, filed: Jul. 14, 2015, and titled, “Co-Production of Anode and Fuel Grade petroleum coke in a Delayed Coker Unit,” the contents of which are incorporated by reference for all purposes. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure generally relates co-producing two different grades of coke. In certain aspects, the disclosure is directed to co-producing anode grade and fuel grade coke. 
     2. Description of the Related Art 
     There are several grades of coke used in industry. The predominant grades are fuel grade and anode grade. Systems and related methods for producing various grades of coke are known in the art. For instance, U.S. Pat. Nos. 4,919,793 and 6,332,975, the disclosures of which are incorporated for all purposes, describe processes related to delayed coking and anode grade coke production, respectively. The present disclosure addresses the continuing need for enhanced coke production. 
     SUMMARY 
     In aspects, the present disclosure provides processes and related systems for the co-production of fuel grade and anode grade coke. These processes may use two separate and different liquid feeds: an anode grade coke feed and a fuel grade coke feed. These two liquid feeds may be handled in two separate processors: an anode coker feed tower and a fractionator, respectively. The anode coker feed tower receives product vapors from only the drums making the product anode grade coke. However, the fractionator combines the product vapors from the coke drums making product anode grade coke and the drums making product fuel grade coke to produce a fresh and recycled fuel grade feed and various coker products such as coker off-gas, coker LPG, coker naphtha, coker diesel, coker heavy gas oil, etc. 
     The source that provides the feed for the anode grade coking section may include a complete redundant feed supply and preparation facility to ensure the availability of the feed for the anode grade coking section. Also, the anode grade and fuel grade coke section may each have a dedicated coke handling system or share a common coke handling system. 
     One non-limiting method according to the present disclosure includes the steps of: directing an anode grade coker charge material from a tower to a first coke drum set; generating a product anode grade coke using the first coke drum set while directing a first vapor stream from the first coke drum set to the tower; directing a fuel grade coker charge material from a fractionator to a second coke drum set; generating a product fuel grade coke using the second coke drum set while directing a second vapor stream from the second coke
         drum set to the fractionator; and directing vapor a stream from the tower to the fractionator while generating the product anode grade coke using the first coke drum set and generating the product fuel grade coke using the second coke drum set.       

     In further aspects, the present disclosure provides a system for co-production a product anode grade coke and a product fuel grade coke. The system may include a tower, a first coke drum set, a fractionator, and a second coke drum set. The first coke drum set receives an anode grade coker charge material from the tower and is configured to generate the product anode grade coke while directing a first vapor stream to the tower. The second drum set receives a fuel grade coker charge material from the fractionator and is configured to generate the product fuel grade coke while directing a second vapor stream to the fractionator. The tower is configured to direct a third vapor stream to the fractionator while the first drum set generates the product anode grade coke and while the second coke drum set generates the product fuel grade coke. 
     It should be understood that examples of certain features of the disclosure have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will in some cases form the subject of the claims appended thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For detailed understanding of the present disclosure, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein: 
       The Figure depicts a system for co-production of fuel grade and anode grade coke according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , there is shown a system  10  for the co-production of fuel grade and anode grade coke. In the non-limiting embodiment shown, the system  10  includes a fuel grade coking section  20 , an anode grade coking section  30 , and a common fractionator  40 . The system  10  enables anode grade and fuel grade coke to be produced simultaneously by using the shared fractionator  40 . 
     During operation, the fractionator  40  receives the vapors from the fuel grade coking section  20 , the vapors from the anode grade coking section  30 , and a raw fuel grade vacuum residue (VR) feed  42 . The VR feed  42  may have relatively high levels of impurities, such as sulfur and metals and be from a source  12 , e.g., a vacuum distillation unit. The products of the fractionator  40  include overhead vapor (coker gas and coker naphtha)  93 , light coker gas oil (LCGO)  95 , heavy coker gas oil (HCGO)  97 , heavier HCGO (HHCGO) outputs  99 , and bottoms liquids that comprise a recycled and raw fuel grade feed (hereafter “fuel grade coker charge material”)  101 . 
     In one embodiment, the fuel grade coking section  20  includes two coke drum sets  50 ,  52  that are fed the fuel grade coker charge material by a common charge pump  54  via a line  56 . Each coke drum set  50 ,  52  includes a pair of coke drums  60 ,  62 , each of which is connected to an associated heater  58  via lines  64 ,  66 , respectively. The coke drums  60 ,  62  are configured for a conventional batch operation wherein solidified product fuel grade coke is removed from one drum while cracking, condensation and phase separation occurs in the other drum. Vapor streams from the coke drum sets  50 ,  52  are passed to the fractionator  40  via lines  68 ,  70 , respectively. 
     In one embodiment, the anode grade coking section  30  includes a coke drum set  80 , a tower  86 , a charge pump  88 , and a coker heater  90 . Liquid bottoms from the tower  86 , which include recycled and raw anode grade feed (hereafter “anode grade coker charge material”), is pressurized and pumped by the charge pump  88  to the coker heater  90  via a line  89 . The coker heater  90  feeds the anode grade coker charge material to the coke drum set  80  via a line  92 . In one arrangement, the coke drum set  80  includes a pair of coke drums  82 ,  84  that generate product anode grade coke in a conventional batch operation. The coke drum set  80  further includes a line  94  that conveys a vapor stream from the drum set  80  to the tower  86 . 
     The tower  86  enables the separation of two feeds to allow the co-production of fuel grade and anode grade coke. In one arrangement, the tower  86  receives an anode grade vacuum residue (VR) feed  91  from a source  14  and generates product streams that include an overhead vapor and liquid bottoms, which is the anode grade coker charge material. The anode grade VR feed  91  has lower impurities than the fuel grade VR feed  42 . The lower impurities may be due to the use of an additional processing step such as hydrotreating to remove impurities or the source  14  processing a different crude oil than the source  12 . The overhead vapors from the tower  86  are conveyed to the fractionator  40  via a line  100 . 
     In certain arrangements, the source  14 , which provides the feed for the anode grade coking section  30 , may include a complete redundant feed supply and preparation facility. To ensure the availability of the feed for the anode grade coking section  30 , such a facility may include a suitable import, storage, and heating system; a second crude distillation unit (CDU) or a second vacuum distillation unit (VDU) for processing low sulfur low metal feed; and/or a residue treating unit. 
     Various arrangements may be used for coke handling during operation of the system  10  and transport of the produced coke products. Conventionally, coke handling systems include sluices, railcars, cranes, and other like conveyance mechanisms. In some arrangements, each section  20 ,  30 , may have a dedicated coke handling system that can operate independently of one another. In other arrangements, the sections  20 ,  30  may share a common coke handling system. Considerations such as the need for parallel operations may dictate which arrangement is suitable. 
     In an exemplary mode of operation, the system  10  simultaneously receives two separate coke feeds  42 ,  91  having different levels of impurities from two separate sources  12 ,  14 , respectively. The fuel grade coke feed  42  is directed into the fractionator  40  and the anode grade coke feed  91  is directed into the tower  86 . 
     The fuel grade coker charge material  101  from the fractionator  40  is pressurized to about 350 to 550 PSIG by the charge pump  54  and passed to coke heaters  58  via the line  56 . After being heated to about 920-950 degrees F., the fuel grade coker charge material is passed to appropriate drums of the drum set  50 ,  52 . Thereafter, product fuel grade coke is generated in a conventional batch process while a product vapor stream is directed back to the fractionator  40  via lines  68 ,  70 . 
     In a largely similar and concurrent process, the anode grade coker charge material from the tower  86  is pressurized to about 350 to 550 PSIG by the charge pump  88  and passed to coke heater  90  via the line  89 . After being heated to about 920-950 degrees F., the anode grade coker charge material is passed to appropriate drum of the drum set  80 . Thereafter, product anode grade coke is generated in a conventional batch process while product vapors are directed back to the tower  86  via the line  94 . The overhead vapors from the tower  86  flow to the fractionator  40  via line  100 . Thus, the fractionator  40  simultaneously receives vapor from the fuel grade coke section  20  and the anode grade coke section  30 . 
     In some variants, systems according to the present disclosure may be switched from simultaneous production of fuel grade coke and anode grade coke to production of only fuel grade coke. For instance, a line  110  and associated isolation valve  112  may be used to selectively connect the feed line  56  with feed line  89 . Additionally, a line  114  and associated isolation valve  116  may be used to selectively connect the vapor line  70  with the vapor line  94 . During co-production, the isolation valves  112 ,  116  are set to block flow and thereby isolate the fuel grade coke section  20  from the anode grade coke section  30 . To produce only fuel grade coke, the isolation valves  112 ,  116  are opened. Thus, the anode grade coke section  30  receives the fuel grade raw feed via line  110  and the vapors from the drum set  80  are passed directly to the fractionator  40  via line  114 . In this configuration, only fuel grade coke is generated. Also, only one coke feed, the fuel grade VR feed  42 , is used. The anode grade VR feed  91  is terminated. 
     It should be noted that the teachings of the present disclosure are not limited to only the described embodiments. For example, the number of drum sets and the number of individual drums within each drum set may be modified as desired. Also, in some applications, an anode grade coke is a coke with a sponge structure having a sulfur level between 0.5-4.0%, vanadium level of 50-300 ppm, and nickel level of 50-200 ppm and a fuel grade coke is a coke that has sulfur, vanadium, and/or nickel not in such ranges. More generally, a fuel grade coke has measurably more impurities than an anode grade coke. 
     From the above, it should be appreciated that what has been disclosed includes a method of co-production a product anode grade coke and a product fuel grade coke. The method may include directing an anode grade coker charge material from a tower to a first coke drum set; generating the product anode grade coke using the first coker drum set while directing a first vapor stream from the first coke drum set to the tower; directing a fuel grade coker charge material from a fractionator to a second coke drum set; generating the product fuel grade coke using the second coke drum set while directing a second vapor stream from the second coker drum set to the fractionator; and directing a third vapor stream from the tower to the fractionator while generating the product anode grade coke using the first coke drum set and while generating the product fuel grade coke using the second coke drum set. 
     The method may also include steps such as pressurizing and heating the anode grade coker charge material being directed to the first coke drum set, directing an anode grade vacuum residue feed into the tower; pressurizing and heating the anode grade coker charge material being directed to the second coke drum set; directing a fuel grade coke feed into the fractionator; and/or directing an anode grade vacuum residue feed from a first source into the tower while simultaneously directing a fuel grade coke feed from a second source into the fractionator, wherein anode grade vacuum residue feed and the fuel grade coke feed have different levels of impurities. The product anode grade coke and/or the product fuel grade coke may be generated using a batch operation. 
     The method may also include terminating an anode grade vacuum residue feed into the tower; directing a fuel grade coke feed to the first and the second coke drum set; and generating the product fuel grade coke using the first coker drum set while directing the first vapor stream from the first coke drum set to the fractionator. 
     From the above, it should be also appreciated that what has been disclosed includes a system for co-production a product anode grade coke and a product fuel grade coke. The system may include a tower; a first coke drum set receiving an anode grade coker charge material from the tower, the first coke drum set being configured to generate the product anode grade coke while directing a first vapor stream to the tower; a fractionator; and a second drum set receiving a fuel grade coker charge material from the fractionator, the second drum set being configured to generate the product fuel grade coke while directing a second vapor stream to the fractionator. The tower may be configured to direct a third vapor stream to the fractionator while the first drum set generates the product anode grade coke and while the second coke drum set generates the product fuel grade coke. 
     The system may also include a serially arranged first pump and first heater pressurizing and heating the anode grade coker charge material being directed to the first coke drum set; a serially arranged second pump and second heater pressurizing and heating the fuel grade coker charge material being directed to the second coke drum set; a first source directing an anode grade vacuum residue feed into the tower; and/or a second source directing a fuel grade coke feed into the fractionator. The first source and the second source ma be configured for simultaneous operation. The first drum set and/or the second drum set may be configured for batch operation. 
     The system may also include a first line selectively directing a fuel grade coke feed to the first and the second coke drum set; and a second line selectively directing the first vapor stream from the first coke drum set to the fractionator while generating the product fuel grade coke using the first coker drum set. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.