Abstract:
One exemplary embodiment can be a process for initializing hydroprocessing. Generally, the process can include providing a hydrocarbon feed to a hydrotreating zone within which the hydrotreating temperature is catalytically limited, passing an effluent from the hydrotreating zone to a hydrocracking zone, and adding a gas to the effluent that has a higher temperature than the effluent. Thus, the temperature of the effluent may be raised, facilitating hydrocracking reactions within the hydrocracking zone.

Description:
FIELD OF THE INVENTION 
     This invention generally relates to an initializing process and an apparatus relating thereto. 
     DESCRIPTION OF THE RELATED ART 
     A hydroprocessing unit can be comprised of a hydrotreating zone followed by a hydrocracking zone. During initializing of the hydroprocessing unit, the temperature of the catalyst bed or beds in the hydrotreating zone can be increased until impurities, such as organic nitrogen, passing through the zone may be eliminated or reduced to an acceptable level. 
     During initialization, the hydrotreating catalyst is very active. Often, the temperature of the hydrotreating zone has to be limited to about 390° C. or less to avoid alteration of the catalyst at least until the catalyst has established equilibrium. However, the hydrocracking zone may require a higher temperature for operation, so that this heat limitation can result in an operating and outlet temperature of the hydrotreating zone that may be lower than the required inlet temperature for the hydrocracking zone. A low hydrocracking inlet temperature may restrict the conversion of the hydrocracking zone and lower yield as the initial heat input for the hydrocracking beds is typically derived from the upstream hydrotreatment beds. 
     Eventually, the hydrotreatment catalyst bed temperature may be increased until the temperature of the downstream hydrocracking catalyst bed or beds in the hydrocracking zone may be increased to improve conversion. However, it can take a long time for some catalyst to reach equilibrium so the outlet temperature of the hydrotreating zone is no longer limited. This period is often about 21 days, and can be as long as 30-60 days. During this time the hydrocracking zone is prone to poor conversion and yield loss. 
     Sometimes, the hydrocracking reactor is run at severe conditions to overcome these problems; however, this is not a satisfactory solution as it can reduce the life of the hydrocracking reactor. Further, this start up restriction apparently has not yet been solved by catalyst design or selection. 
     To facilitate the heating of the hydrocracking catalyst beds due to the low hydrotreatment effluent temperatures, sometimes the quench to the hydrocracking beds is either reduced to a minimum or cut off during this initializing period. Operating the hydrocracking reactor without active quench, however, is not inherently safe with respect to the process and can lead to over conversion of catalyst activity loss. Accordingly, there is generally a need in the art for a method and apparatus that can adjust and maintain the hydrocracking zone to a higher temperature during initializing. 
     SUMMARY OF THE INVENTION 
     One exemplary embodiment can be a process for initializing hydroprocessing. Generally, the process can include providing a hydrocarbon feed to a hydrotreating zone within which the hydrotreating temperature is catalytically limited, passing an effluent from the hydrotreating zone to a hydrocracking zone, and adding a gas to the effluent that has a higher temperature than the effluent. Thus, the temperature of the effluent may be raised, facilitating hydrocracking reactions within the hydrocracking zone. 
     Another exemplary embodiment can be a process for hydroprocessing within about 60 days of initializing operations. The process can include providing a hydrocarbon feed to a hydrotreating zone to produce a hydrotreated effluent, and adding a hydrogen gas to the hydrotreated effluent. The hydrogen gas can raise the temperature of the hydrotreated effluent to a temperature sufficient to facilitate hydrocracking operations. 
     A further exemplary embodiment can be a process for initializing hydroprocessing. The process can include controlling an amount of hydrogen at a temperature of about 420-about 470° C. that may be added to a hydrotreated effluent depending on a temperature in a hydrocracking zone. 
     The embodiments disclosed herein can modify a hydrogen quench of the hydrocracking catalyst beds so that rather than only adding hydrogen at a cooler temperature after operation has been initialized, heated hydrogen can be added at a higher temperature. This heated hydrogen can help raise the cracking bed temperatures to obtain suitable conversion, so that generally the beds are not solely reliant on the upstream heat from the hydrotreating zone. This can prevent yield loss in the hydrocracking zone due to low feed temperatures. Thus, severe operations in the hydrocracking zone are usually not required. Operating the hydrocracking beds at a suitable severity can prolong catalyst life. Also, the quench stream can remain active enhancing safety. It can also maintain a desired hydrogen to hydrocarbon ratio, which can also prolong catalyst life. 
     DEFINITIONS 
     As used herein, the term “stream” can include various hydrocarbon molecules, such as straight-chain, branched, or cyclic alkanes, alkenes, alkadienes, and alkynes, and optionally other substances, such as gases, e.g., hydrogen, or impurities, such as heavy metals, and sulfur and nitrogen compounds. The stream can also include aromatic and nonaromatic hydrocarbons. Moreover, the hydrocarbon molecules may be abbreviated C1, C2, C3 . . . Cn where “n” represents the number of carbon atoms in the one or more hydrocarbon molecules. Furthermore, a superscript “+” or “−” may be used with an abbreviated one or more hydrocarbons notation, e.g., C3 +  or C3 − , which is inclusive of the abbreviated one or more hydrocarbons. As an example, the abbreviation “C3 + ” means one or more hydrocarbon molecules of three carbon atoms and/or more. Also, the term “stream” can include or consist of other fluids, such as a hydrogen. 
     As used herein, the term “rich” can mean an amount of at least generally about 50%, and preferably about 70%, by mole, of a compound or class of compounds in a stream. 
     As used herein, the term “zone” can refer to an area including one or more equipment items and/or one or more sub-zones. Equipment items can include one or more reactors or reactor vessels, heaters, exchangers, pipes, pumps, compressors, and controllers. Additionally, an equipment item, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones. 
     As used herein, the term “hydroprocessing” can refer to processing one or more hydrocarbons in the presence of hydrogen, and can include hydrotreating and/or hydrocracking. 
     As used herein, the term “hydrocracking” can refer to a process breaking or cracking bonds of at least one long-chain hydrocarbon in the presence of hydrogen and at least one catalyst into lower molecular weight hydrocarbons. 
     As used herein, the term “hydrotreating” can refer to a process including contacting a hydrocarbon feedstock with hydrogen gas in the presence of one or more suitable catalysts for the removal of heteroatoms, such as sulfur, nitrogen and metals from a hydrocarbon feedstock. In hydrotreating, hydrocarbons with double and triple bonds may be saturated, and aromatics may also be saturated, as some hydrotreating processes are specifically designed to saturate aromatics. 
     As used herein, the term “catalytically limited” can refer to a process, such as hydrotreating, having one or more parameters limited by, e.g., the catalyst utilized. As an example, typically new or regenerated catalyst placed in a hydrotreating zone may change characteristics if a temperature in the hydrotreating zone is exceeded. Hence, the hydrotreating zone may be operated not to exceed this temperature until the catalyst reaches equilibrium. After reaching equilibrium, the temperature may be raised although the process may be limited at a higher temperature or other process parameter. 
     As used herein, the term “cascade control” can refer to a control system used to maintain a proper temperature. A cascade control generally makes use of multiple control loops that involve multiple inputs to manipulate and control a single variable, such as, herein, temperature. Use of cascade control as disclosed herein can allow a system to be more responsive to disturbances in temperature. 
     As depicted, the process flow lines in the figures can be referred to interchangeably as, e.g., lines, pipes, feeds, branches, effluents, portions, products, or streams. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The FIGURE is a schematic, cross-sectional depiction of an exemplary apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the FIGURE, an exemplary hydroprocessing apparatus  10  can include a hydrotreating zone  100 , a hydrocracking zone  200 , and an effluent line  140  communicating the hydrotreating zone  100  to the hydrocracking zone  200 . Hydrogen can also be provided to the effluent line  140  by a recycled gas heater hydrogen stream  300  and/or a recycled gas compressor hydrogen stream  350 , as discussed hereinafter. 
     Usually, a hydrocarbon feed  30  is provided to the hydrotreating zone  100 . The hydrocarbon feed may have components boiling above about 285° C., such as an atmospheric gas oil, a vacuum gas oil boiling between about 315-about 565° C., a deasphalted oil, a coker distillate, a straight run distillate, a pyrolysis-derived oil, a high boiling synthetic oil, a cycle oil, a hydrocracked feed, a catalytic cracker distillate, an atmospheric residue boiling at or above about 340° C., and a vacuum residue boiling above about 510° C. Often, hydrogen can be combined with the hydrocarbon feed  30  before entering the hydrotreating zone  100 . Often, the hydrotreating zone  100  is comprised of a hydrotreating reactor  110 , which contains one or more hydrotreating catalyst beds  120 , which in this exemplary embodiment can be a single bed  120 . 
     Suitable hydrotreating catalyst for the catalyst bed  120  can be conventional hydrotreating catalyst and include those that may be comprised of at least one metal of groups 8-10 of the periodic table, preferably iron, cobalt and nickel, and at least one metal of group 6 of the periodic table, preferably molybdenum and tungsten, on a high surface area support material, such as at least one of silica, alumina, silica-alumina, magnesia, zirconia, boria, and titania, preferably alumina. 
     Other suitable hydrotreating catalysts can include zeolitic catalysts, as well as noble metal catalysts where the noble metal may be selected from palladium and platinum. More than one type of hydrotreating catalyst can be used in the hydrotreating reactor  110 . The metal of groups 8-10 is typically present in an amount ranging from about 2-about 20%, by weight, and the metal of group 6 is typically in an amount ranging from about 1-about 25%, by weight. 
     During initializing, the operating temperature of the catalyst bed  120  is typically limited to a temperature of no more than about 390° C. until catalytic equilibrium is reached, so that the temperature of the effluent stream  140  is also limited. This catalytic limitation can be up to about 21 days from the beginning of initializing, and further can be up to about 60 days from initializing. 
     Generally, the hydrocracking zone  200  operates at a higher temperature than the effluent stream  140 , typically a temperature exceeding about 400° C. The hydrocracking zone  200  may have a hydrocracking reactor  210 , which can operate under any suitable set of conditions and contain one or more hydrocracking catalyst beds  220 , which in this exemplary embodiment can be a single bed  220 . 
     The hydrocracking catalyst bed  220  can contain a catalyst including at least one metal component, such as a metal of groups 8-10, e.g., iron, cobalt, nickel, and/or platinum, and a group 6 metal, such as molybdenum, and/or other metals such as magnesium, and a suitable refractory inorganic oxide carrier, such as alumina and/or silica. A suitable hydrocracking catalyst is disclosed in, e.g., U.S. Pat. No. 8,062,509. 
     After undergoing hydrocracking, a product stream  230  can exit the hydrocracking zone  200 . The temperature of the effluent stream  140  can be adjusted, during initialization and operation, by at least one of a pair of gas streams and accompanying equipment. 
     At least one of the recycled gas heater hydrogen stream  300  (may be referred to herein as “stream  300 ” or “heated hydrogen stream  300 ”) and recycled gas compressor hydrogen stream  350  (may be referred to herein as “stream  350 ” or “cooler hydrogen stream  350 ”) can be provided to the effluent. Both streams may include hydrogen and be preferably rich in hydrogen. The stream  300  can be obtained from a recycled gas heater and provided to the suction of a recycled gas heater compressor  310 . The stream  300  can be at a temperature of about 420-about 470° C., and typically not exceeding about 470° C. The stream  350  can be derived from a recycled gas compressor  360 . The stream  350  can be a hydrogen stream adjusted to a temperature of about 40-about 110° C. Respective pressure indicators  330  and  370  can measure the pressure from the discharge of respective compressors. Generally the stream  300  is hotter than the stream  350 , and optionally these streams  300  and  350  may be combined as a stream  160  before being provided to the effluent stream  140 . A pressure indicator  390  can measure the pressure of the combined stream  160 . Generally, the pressure of the combined stream  160  may range from about 7,800-about 15,000 KPa and the hydrogen to hydrocarbon ratio with respect to the effluent stream  140  can be about 500-about 1,800 Nm 3 /m 3 . 
     During the operations of the hydroprocessing apparatus  10  while the hydrotreating catalyst is still limited, typically within 60 days from restarting operations, both streams  300  and  350  may be provided to the effluent stream  140 . The amounts of each stream may be regulated by a control system including a control valve  340  for the stream  300 , a control valve  380  for the stream  350 , a cascade controller  400 , and a temperature indicator controller  410  in the hydrocracking catalyst bed  220 . A sufficient amount of the combined gas stream  160  can be provided and added to the effluent stream  140  to raise the temperature of the effluent to at least about 400° C. before the effluent stream  140  enters the hydrocracking zone  200 . The relative amounts of each stream  300  and  350  can be regulated by the cascade controller  400 . The temperature indicator controller  410  can be in communication with the cascade controller  400 , and in turn in communication with the control valves  340  and  380 . The cascade controller  400  can be the master controller regulating the temperature of the hydrocracking catalyst bed  220  by changing the respective set points for the flow of streams  300  and  350 . Secondary loops correspond to the change in set points by opening and closing valves  340  and  380  for changing the amounts of hydrogen flowing in respective streams  300  and  350 . As each stream  300  and  350  is at a different temperature, the combined stream temperature  160  can be changed depending on the temperature in the hydrocracking catalyst bed  220  so that a sufficient amount of hydrogen can be added at the desired temperature to raise the hydrocracking temperature. 
     The additional heat can facilitate hydrocracking reactions by helping raise the temperature of the hydrocracking catalyst bed  220  to a suitable level to reach conversion without relying on the upstream heat from the hydrotreating zone  100  as the sole source of heat. Facilitation of the hydrocracking reactions within the hydrocracking catalyst bed  220  can safely eliminate poor conversion and yield loss in the hydrocracking zone  200  until hydrotreatment catalyst is no longer limited and reaches equilibrium. Once the hydrotreatment catalyst reaches equilibrium and the temperature of the hydrotreating zone  100  is no longer limited, a motor operated valve  320  can close blocking the flow of the heated hydrogen stream  300 . The cooler hydrogen stream  350  may continue to be provided to the hydrocracking zone  200  as a quench. As such, the heat required to heat the effluent stream  140  from the hydrotreating zone  100  over about 400° C. to facilitate reactions in the hydrocracking zone  200  can be provided by the hydrotreating zone  100 . Hence, the cooler hydrogen stream  350  may act as a quench for the hydrocracking zone  200  to prevent excessive temperature in the hydrocracking zone  200 . The temperature indicator controller  410  via the cascade controller  400  can regulate the flow of quench gas by opening and closing the control valve  380 . Continuing the quench can allow the hydrocracking catalyst bed  220  to operate at a correct level of severity that can lengthen the service life of the hydrocracking reactor  210 . 
     Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. 
     In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated. 
     From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.